for Plant and Soil Sience
Plant diseases, pests and weeds in Denmark 1985
102nd annual report Compiled by
The Research Centre for Plant Protection
Lyngby 1988
for Plant and Soil Sience
Plant diseases, pests and weeds in Denmark 1985
102nd annual report Compiled by
The Research Centre for Plant Protection
Lyngby 1988
A. Institute of P lant Pathology, L y n g b y ... 3
I. G en eral Survey of P lant Pathology Subjects 1985 ... 3
II. A dvisory work in L yngby... 9
1. D iseases in agricultural plants 1985 ... 14
2. P ests in agricultural plants 1985 ... 22
3. D iseases and pests in horticultural plants 1 9 8 5 . ... 30
III. B otany D e p a r tm e n t...35
IV. Virology D e p a r t m e n t ...41
1. E xperim ental w o r k ...41
2. N ew attacks of virus diseases 1985... 51
V. Zoology D e p a r t m e n t ...52
B. Pesticide R esearch Institute, L y n g b y ... 62
I. G en eral S u rv ey ... 62
II. E xperim ental w o r k ... 64
1. A griculture...64
a. Fungal d ise a se s... 64
b. P e s t s ...68
2. H o r tic u ltu r e ... 73
a. F ruit grow ing... I ... 73
b. Soft fruit, nursery and glasshouse c r o p s . ...76
c. R educed application o f p e s tic id e s ...79
3. N ew pesticides tested in 1 9 8 5 ... 81
C. P lant Protection Advisory D epartm ent, G o d th å b ...85
D. Institute of W eed C ontrol, F la k k e b je rg ... 87
I. Field o f activ ity ... 87
II. A griculture...87
1. Field e x p e rim en ts... 87
2. T esting o f c o m p o u n d s ... 92
3. R e-evaluation and evaluation of e ffic a c y ... 93
III. H o r tic u ltu r e ...94
IV. Forestry, w i n d b r e a k s ...95
V. W eed b i o l o g y ... 96
VI. T he persistence o f herbicides in s o i l ... 97
VII. C ontrolled environm ent d e p a rtm e n t... 98
VII. A dvisory w o r k ... 101
E. L aboratory for Pesticide an aly sis...102
F. P u b licatio n s... 107
C ontents P ag e
A. INSTITUTE OF PLANT PATHOLOGY
I. GENERAL STJRVEY OF PLANT PATHOLOGY SUBJECTS 1985. H. Rande Kristensen
In 1985 32 rese a rc h w orkers and a technical and adm inistrative staff o f 35 people were employed at th e Institute of Plant Pathology.
Besides, 7 stu d en ts w orking on their theses, 8 laboratory apprentices and 1 craftsman, th e la tte r working under the governm ent em ploym ent scheme, participated in th e w ork o f the institute.
A t the Botany D ep artm en t, M ogens H oum øller was em ployed from th e beginning o f 1985 (a p ro ject initiated by the Joint C om m ittee for A gricultural R esearch and Experim ents). A t th e sam e tim e Lilian K loster was em ployed on a p art tim e basis (as a biologist w orking u nder the governm ent em ploym ent schem e) a t the B otany D epartm ent.
Henning M ygind e n tered his resignation by the end of the year after 34 years of employment at th e State P lant Pathology Institute (later the Institute of Plant Pathology).
A t the Virology D ep artm en t, M orten H eide was em ployed from the 1st o f F ebruary (a project in itiated by the Joint C om m ittee for A gricultural R esearch and Experim ents) and from the 1st of July Lise H e rtz Jørgensen was em ployed as a biologist w orking u n d er the governm ent em ploym ent schem e also at the samis departm ent.
From the 1st o f F ebruary, F ritjof Lind was on the perm anent staff o f the Zoology D epartm ent as a research w orker. M ogens Juhl, who was em ployed at the Zoology D epartm ent since 1960, died in D ecem ber.
A t the Advisory Service, O le Bagger resigned on the 1st of M arch after 23 years of employment; h e was replaced by G hita C ordsen N ielsen on the 1st of June.
A t the B otany D ep artm en t, the investigations of bacterial ringrot in potatoes have aim ed at securing that the potato m eristem program m e should be free of this disease.
Experim ents concerning the spread o f bacterial ring ro t (in p o tato fields) have been finished.
bacteriological exam inations o f several im portant pot plant cultures have been continued in connection with the production o f healthy nuclear plants.
A s was the case in previous years num erous plant and stubble samples from cereals w ere exam ined for attacks by take-all and eyespot, and m o re than 1000 isolates o f the eyespot fungus w ere exam ined for carbendazim resistance.
T he com puter program m es E pidan and C erco have been developed further, so th a t reliable prognoses are w ithin the range o f possibility (after additional testing).
O bservations concerning frost dam age in w inter barley an d th e spread o f m ildew from w inter barley to spring barley are currently perform ed.
Investigations concerning the injury threshold criteria for m ildew and other p ests in cereals also continued.
In 1985, investigations on th e virulensgene spectrum o f pow dery mildew on w heat and barley in this country w ere started (a project initiated by th e Joint C om m ittee for A gricultural R esearch and Experim ents).
P o tato w art tests, which are m ade for the po tato b reed in g station at V andel an d for the G overnm ent Plant Protection Service, continued.
In the crucifers, experim ents regarding correct tim ing o f control for the m ost im portant fungal diseases in rap e have been finished. F u rth e rm o re a m ethod for the testing o f variety susceptibility to stem rot fungus has been c arrie d out.
W ithin th e greenhouse sphere the work carried out by th e Botany D ep artm en t has com prised, am ong o th er things, a registration o f the physiological strains o f downy mildew o f lettuce, and, as was the case in previous years, a considerable work has b ee n done testing for vascular fungi in connection w ith the establishm ent of healthy nuclear plants.
D eterm ination o f serious pests in sour cherry (a project initiated by the Jo in t C om m ittee fo r A gricultural R esearch and E xperim ents) was continued.
A t the Z oology D ep artm en t, the usual routine exam inations for potato cyst nem atodes continued. T hese exam inations are mainly carried o u t on samples ta k e n by the G overnm ent P lant Protection Service - mainly from seed potato fields, b u t also from fields grown w ith o th e r crops.
Several soil sam ples from th e experim ental and advisory activities were exam ined for cereal and b eet cyst nem atodes.
By m eans o f special exam inations, efforts have been m ade to try to throw light
on the im portance o f the cereal cyst nem atode as a grow th inhibitor in spring w heat and on its population dynamics in fields with cereals grown in m onoculture.
Investigations concerning biological control o f pests in greenhouses w ere continued and the sam e applies to the developm ent of testing m ethods for the dem onstration o f the effects o f pesticides on pests and beneficial arthropods.
A s a basis fo r a control guidance an d for the p rep aratio n of "Plant P rotection Bulletins" registrations have been m ade o f aphids, rust and mildew in the spring barley fields o f a large num ber of growers. W ith a view to the d eterm ination of injury thresholds for aphid attacks, regular registrations o f the density of aphids in experiments w ith w inter w heat and spring barley have been carried out.
In order to b e ab le to give advice as to a determ ination of the correct tim e for haulm desiccation, aphids registrations have also b ee n m ade in potatoes (by m eans of yellow traps).
In rape a nation-w ide registration of the occurrence o f various pests has been m ade - based p artly on traps, partly on plant samples.
A t the Zoology D e p artm en t various investigations have been m ade of pests in peas, seed grass, carrots, cabbage and straw berries.
A t the Virology D ep a rtm en t, as was the case in previous years, num erous electron microscopic exam inations have been carried out - m ost of them using the ISE M - method.
Thanks to th e em ploym ent o f a new research w orker it has been possible to expand and intensify the serological and biochem ical work. T he serological m ethods used com prise precipitation, agglutination, gel diffusion, ELISA, and "Dot Im m uno Binding".
W hen serology cannot b e used, electrophoresis (agarose electrophoresis and polyacrylamide electrophoresis) is applied.
In 1985, the seru m bank at the d epartm ent was com puterized.
In co-operation w ith the Institute o f Seed Pathology efforts have been m ade to develop m ethods fo r a virus testing of seeds.
A t the V irology D ep artm e n t, exam inations for possible virus attacks in rye grass, maize, peas an d w heat have been m ade in co-operation with the Advisory Service.
F u rth erm o re, efforts have been m ade to register th e distribution of cocksfoot m ottle virus.
In 1985, m any w inter barley fields and beet fields w ere examined fo r the occurrence of barley yellow m osaic and rhizom ania, respectively, and fo r the vectors of these diseases (Polym yxa spp.).
In connection with the production o f healthy p o ta to m eristem cultures extensive testings for virus diseases have b een m ade, and the possibilities of preserving foundation m aterial in test tubes have been examined.
Exam inations also continued o f the susceptibility o f different potato varieties to rattle virus.
W ithin the field of horticultural plants a substantial p art o f th e work focused on th e establishm ent o f virus free nuclear m aterial (by m eans o f therm otherapy an d tissue culture) o f a g reat num ber of plant species - herbaceous as well as ligneous.
In this work, exam inations are m ade to find the grow th m edia which are m ost suitable for the various plant species, especially w ith a view to the content o f cytokinin and auxin.
F u rth erm o re, tem p e ratu re experim ents were carried out w ith m eristem cultures in the rooting phase, and also experim ents with preservation o f ligneous plan ts in test tubes w ere m ade.
D uring 1985, FA O and m em bers of the staff o f th e V irology D epartm ent have collaborated on the production o f a video on th e D an ish potato m eristem program m e.
T h e video program m e, which is to be used for educational purposes in developing countries, has a playing tim e o f 21/2 hours (divided into sections).
A s an innovation at the Institute of Plant Pathology a new unit was established in 1985, a biotechnological project with Ib D inesen as th e day-to-day h e a d of d epartm ent.
T h e project has em ployed 4 research w orkers and 3 laboratory assistants in 1985.
T he p rogram m e com prises the developm ent of m ethods for th e production of disease free and resistant horticultural and agricultural plants, and for the time b ein g it deals w ith tissue cultures in barley and rape, cell suspension cultures of pot plan ts and acclim atization o f tissue cultures and the isolation o f fungal toxins.
Advisory work
In 1985, th e staff at the Institute o f Plant Pathology p repared 143 publications and gave 166 lectures.
International co-operation.
In 1985 the staff at the Institute o f Plant Pathology m ade 51 journeys to the following countries: Belgium , England, Finland, France, G erm any, G reece, H olland, Hungary, Israel, Italy, M arocco, Norway, Sweden, and the U .S A .
The following subjects w ere treated during these travels: B acterial ringrot in potatoes and o th er bacterial diseases, resistance biology o f cereals, seed bacteriology, in teg rated plant protection of field-grown vegetables, cyst nem atodes, integrated an d biological control of greenhouse crops, leafm iners and their parasites, pesticides an d beneficial arthropodes, electron microscopy, resently developed methods of diagnosis of viruses, diagnosis o f plant diseases, barley yellow m osaic and R hizom ania, virus in fruit trees and bushes, propagation and health control, fruit tree virus and tissue culture and in-vitro problem s in connection with m ass production o f horticultural plants.
In 1985 guests from the following countries have visited the In titu te o f Plant Pathology:
Australia, Belgium , B urm a, Canada, China, C uba, Czechoslovakia, Egypt, England, France, G erm any, G reece, Holland, India, Indonesia, Ireland, Israel, Jugoslavia, Marocco, N ew Z ealand, N igeria, N orth K orea, Norway, Pakistan, P eru, Poland, Somalia, Sudan, Sweden, Switzerland, Taiwan, Tanzania, U.S A ., Zim babw e.
The Plant Health Control and propagation of healthy plants.
In 1985, as in previous years, the Plant H ealth Council dealt with a g reat num ber of pests and diseases and their prevention/control, legislatively and through o ther measures.
During the past year the C olorado beetle was found in one place only, viz. in a private garden, w here 22 beetles and 1000 larvae w ere found. T h e favourable situation in 1985 m ust be seen as a reflection o f the com prehensive control efforts made by the G ov ern m en t Plant Protection Service in 1983 and 1984.
Dutch elm disease spread m ore rapidly in 1985 than the year before. T h e situation was most severe in the areas o f the cities of Vejle and Å rhus, and from th ere the disease sp re a d west and north as far as the region o f H im m erland. T he disease did not sp read so rapidly in the islands o f Funen and Sealand. It is considered impossible to e rad icate the disease, but the spreading m ay be delayed considerably by removing th e attacked trees immediately.
A t the sam e tim e, advisory work concerning the disease will still be done, e.g.
by m eans o f inform ation about which trees can replace elm s in the case of replantation and afforestation.
T he p o tato m eristem program m e has in 1985 continued satisfactorily. W ith few exceptions all potatoes, which w ere used for th e p ropagation of seed potatoes, originated from the m eristem program m e, and from 1986 all seed potatoes u sed for com m ercial agriculture (for the production of seed potatoes, potatoes for consum ption and potatoes for industrial use) should b e "m eristem potatoes".
T he P lant H ealth Council has also discussed drafts for a new legislation concerning the fungus-borne virus barley yellow mosaic and R hizom ania: negotiations on th ese diseases are awaiting results from EEC-discussions on R hizom ania and have th erefo re not concluded.
F u rth erm o re, a draft for a G overnm ent o rd er on re d core in straw berries (.Phytophthora fragariae) and health control regulations for tissue culture an d changes in the G overnm ent ord ers on w inter barley have been discussed.
W ithin th e N ursery C ontrol Com m ission certain changes o f structure have ta k e n place in 1985. T he num ber of contact groups was red u ced to two, viz. a propagation com m ittee for field-grown plants an d a propagation com m ittee fo r g reenhouse plants: T he two com m ittees have the sam e chairm an (for the tim e being: T h e D irecto r o f the Institute o f P lant Pathology), and there a re representatives from the institutes o f horticulture and from th e Institute o f P la n t Pathology on the com m ittees.
In 1985, the statutory h ealth control com prised 2285 en terp rises to which th e G overnm ent P lant Protection Service m ade 6571 inspection visits.
M ost of th e attacks found via the growth inspections w ere o f pests (68% of th e attacks), b u t the total num ber o f attacks have declined considerably.
New proposals forw arded to the com m ittees on p ropagation during the year com prise a to tal of 48 propagation tasks (in 32 plant genera).
In E P P O (the E u ro p e an P lant Protection O rganization) th e deputy director g en eral D r. G . M athys, resigned by th e 31st of D ecem ber 1985, a fter 17 years, and vice m anaging director, I. Sm ith, was tem porarily appointed to th e post until he w as elected director general at the council m eeting in S eptem ber 1986, carrying a g re a t m ajority.
II. ADVISORY WORK AT LYNGBY.
O le Bagger (till 1st o f M arch), H ellfried Schulz (till 1st of June) and G hita C ordsen Nielsen (from 1st o f Ju n e )
Main tasks
T he plant pathological advisory service, including telephone inquiries, diagnoses of diseases in p lan t sam ples, preparation o f forecasts and warnings and o f the Monthly Survey o f P lant D iseases. T he work also includes participation in all re levant sem inars, m eetings, symposia, etc..
Information in 1985
T he advisers received th e following bulletins and warnings:
6th February C o n tro l of mildew and rust in w inter barley 6th February Inform ation on staff changes
21st M arch A bn o rm al sprouts in w inter barley 21st M arch B e aw are of cereal cyst nem atodes
17th April C o n tro l of mildew and rust in w inter barley 30th April E yespot in w inter rye
14th May T h e m igration of frit flies 14th May E yespot in w inter wheat
20th May E xam ination o f peach potato aphids in b eet pits 23rd May C ontrol of mildew and rust in w inter rye 24th May T h e egglaying of the cabbage root fly
28th May T h e m igration of the 1st generation o f the brassica pod midge 29th May F o recast of attacks by sclerotinia disease in w inter rape 29th May M ildew in cereals
14th June L e af diseases and aphids in cereals, etc.
20th June A phids and mildew in spring barley 25th June C utw orm s
25th June F o recast o f attacks by sclerotinia disease in spring rape 25th June P e a m oths
27th June T h e m igration of the 2nd generation of the brassica pod midge 1st July W arning against late blight
3rd July F o recast o f attacks by sclerotinia in spring rape 4th July A phids in beets
10th July T h e 2nd generation of the frit fly 10th July P ea m oths
10th July T h e effect o f pyrethroids on aphids in barley 10th July T h e egglaying o f the cabbage root fly 11th July A phids in beet
16th July C utw orm s 18th July A phids in beet
19th July T h e 2nd warning against late blight 25th July A phids in beet
14th A ugust T h e m igration o f frit flies
9th S eptem ber T he m igration of the 3rd generation o f the frit fly 23th A ugust Inquiry form concerning the Plant Protection B ulletins 28th O ctober A ttacks by slugs in w inter crops
5th N ovem ber F u tu re use of benzim idazoles 8th N ovem ber F orecast of eyespot in w inter cereals
W ith a view to th e M onthly Survey o f Plant D iseases a collection was organized in cooperation with th e o th e r departm ents of 150 pea and ra p e samples fo r an exam ination for sclerotinia and other fungal diseases.
In 1985, as an innovation, the M onthly Surveys o f P lant D iseases were sent out as Plant P rotection Bulletins on the following dates: 7th May, 7th June, 5th July, 7th A ugust, 5th S eptem ber, 4th O ctober, and 5th N ovem ber.
T hese m onthly surveys w ere sent to 341 colleagues and 26 professional jo u rn als and new spapers. Besides, the M onthly Surveys w ere sent to 195 subscribers in D enm ark and th e rest o f th e world.
A s for titles and authors see the list o f publications.
522 persons participated in 11 plant pathological excursions. A total of 7 lectures w ere given at m eetings and sem inars.
W eath er conditions (Jørgen O lesen. A eral M eteorological Service-).
In Jan u ary the w eather was very cold with m ean te m p e ra tu res 5.4 degrees below norm al. A t the beginning of January there was snowfall an d very cold air invaded the country from north-east, so that the m ean te m p eratu re was -26 degrees in N orth-w estern Jutland around the 7th. The cold continued w ith m inor interruptions until th e end of th e m onth.
A t th e beginning o f F ebruary the w eather was m ild and rainy. A cold p erio d sta rte d around the 7th w ith large parts of the country w ithout snow cover. W h en the cold p eriod was ending around the 23rd, the frost p e n e tra te d deeply into the ground.
M arch was very wet with only little sun. T he num ber o f h o u rs with sun was less th an half norm al. T h e cloudy and not very sunny w eather gave rise to considerably
smaller 24-hours variations of the tem p eratu re than usual.
In April the changable and not very sunny w eather continued. A b o u t th e 15th, however, the w e a th er becam e som ew hat m ilder and dry with sunshine. O n the 26th - 27th a depression followed by sleet and snow invaded the country from the north. D u rin g th e last days of the m onth the w eather was very cold with some sunshine.
The first 5 days o f M av w ere very cold with changable w eather and local snowfall.
During the re st o f the m onth the w eather was sunny and m ostly dry, so th a t the m ean tem p eratu re for the m onth as a whole was a little above average and the rainfall som ew hat below average. In coastal areas low tem peratures w ere registered during the day o n several occasions because of cool sea water.
In June the w eath er was mostly cool and som ew hat changable w ith rainfall a little above n o rm al. T he tem perature was 1.2 degrees below norm al. G enuine summer te m p eratu res occurred only during the first 5 days of the m onth.
The changeable w eath er continued in July. However, the first half of the m onth was relatively dry w ith few sum m er days, b u t the last p art was rainy and relatively cool.
The w eather in A ugust was also m ostly changeable with rain and thunderstorm s from south-w est. O nly for a few days around the 14th and the 30th sum m er weather occurred w ith tem p eratu res around 25 degrees.
In Septem ber th e w eather was mostly cool and not very sunny with tem p eratu res for the m onth as a w hole 1.0 degree below average. In Jutland the rainfall was above average, w hereas precipitation was norm al in the rest o f the country.
O ctober was relatively w arm and dry with tem p eratu res for the m onth as a whole 1.4 degrees above average. Genuinely rainy w eather occurred only a few days around the 8th. T h u s rainfall was m uch below average. By the end of the m onth widespread night frost was registered.
In November th e w eather was mostly cool and cold with genuine w inter w eather in the last p a rt o f the m onth. The m ean tem p era tu re of the m onth was 3 degrees below norm al. A ro u n d the 24th - 25th dry and cold air invaded the country from the north follow ed by snow showers. D uring the rest of the m onth the w eather was dom inated by snow and frost. D ue to a clear, windless w eather and snow cover very low te m p e ra tu res w ere registered by the end of the m onth.
In D ecem ber th e w eather was mostly mild with record rainfall. T he average rainfall
in Jutland and the Islands was 140 m m , the norm al average being 55 mm. G en u in e w inter w eather with frost occurred only during the first and the last days o f the m onth.
F o r th e p reparation of this survey I have used weekly re p o rts on precipitation, etc. sent out by the M eteorological Office.
T em p eratu re °C No. of sunny hours
1985 N orm al 1985 N orm al
Ja n u ary ... . . .-5.5 -0.1 58 41
February . . . . .-4.1 -0.4 85 65
M a r c h ... . . . 1.2 1.6 60 127 A p ril... . . . 5.0 6.1 109 181 M a y ... . . .11.4 11.1 240 256 J u n e ... . . .13.2 14.4 212 257 J u l y ... . . .15.8 16.5 217 247 A u g u s t... . . .15.6 16.2 202 221
S eptem ber . . . . . .12.0 13.0 125 166
October. . . . . . . .10.0 8.6 102 98
November. . . . . . . 1.9 4.9 58 42
D ecem ber. . . . . . . 2.6 2.1 16 28
Annual average H ours in all . . .
. . . 6.6 7.8
1484 1729
Precipitation in mm Deviations from norm al
1985 norm al Jutland Island B ornholm
Jan u a ry ... . . . 46 55 -10 -7 27
February . . . . . . . 23 39 -17 -14 -17
M a r c h ... . . . 55 34 19 27 2
A p ril... . . . 59 39 21 18 6
May 32 38 -7 -3 21
J u n e ... . . . 54 48 3 11 -10
J u l y ... . . . 82 74 6 13 -8
A u g u s t... . . . 95 81 18 6 7
S eptem ber . . . . . . 81 72 14 -3 0
October. . . . . . . . 35 70 -35 -34 -45
Novem ber. . . . . . . 62 60 0 7 3
D ecem ber. . . . 140 55 92 85 62
T otal
precipitation... 764 665 104 106 48
1. D iseases in a g ric u ltu ra l p la n ts 1985 G hita C ordsen N ielsen
C ereals a n d G rasses
O verw intering of w inter crops a n d grasses. T he m ost w idespread frost d am ag e in recent years occurred. T he cause was severe black frost an d no isolating snow- cover. Especially in the period 7th - 19th February, black frost occurred, which lasted for several days.
W inter barley suffered the m ost severe dam age and about 80% of the area h a d to b e resown, especially on the light soils. From several localities, W estern S ealand am ong others, th e re w ere reports of a total resowing o f a whole region. T h e best overw intering was seen in Lolland-Falster and in E a ste rn Jutland. T h e six- row cultivars did well, including ’H asso ’, ’M am m ut’ and ’T a p ir’, whereas th e two- row cultivars, ’Igri’ and ’P an d a’ cam e out badly. Snow r o t (Typhula in ca m a ta ) and snow m ould ( G erlachia n ivalis) m ust be considered as secondary diseases.
T h e overw intering o f w inter w heat was satisfactory. H ow ever, a total o f 10% o f th e area had to b e resown, b u t w ith great variations. Generally, the cultivar
’K raka’ overw intered satisfactorily, b u t a few localities w ere completely destroyed by frost, especially on light soils and on soils, with w inter w heat following grass.
Especially the English fodder w heat cultivars w ere dam aged by frost (Longbow , Im ba, N orm an) and triticale cultivars.
T he overw intering o f rye was satisfactory in m ost places - less than 0.5% o f the a rea had to b e resow n. Especially in B ornholm the rye w as damaged, b u t it w as caused by snow m ould ( G erlachia n ivalis). In January and February, the crops in B ornholm w ere covered by an isolating snow-cover.
In seed prass fields the overw intering of rye grass was unsatisfactory, especially in the case of Italian rye grass. T he advisers estim ated th a t on a national scale approxim ately 60% o f the area had suffered frost dam age. U nsatisfactory overw intering of clover grass fields was seen especially in fields w ith tw o successive crops o f clover, with red-clover and rye grass suffering the severest dam age. T he advisers estim ated that an average o f approxim ately 7% and 11% o f fields with grass crops following o ther crops and fields w ith grass following grass, respectively, had suffered frost dam age.
L ater in the growing season a weak developm ent of ro o ts an d physiogenic spots w ere observed in som e w inter crops, probably caused by bad w intering.
C om pensatory rooting in w inter w heat was also observed. Furtherm ore, b a rre n spikelets, which m ay be caused by cold w eather and w ater deficiency (poorly
developed roots).
Storm dam age. S to rm and hail on the 6th and 7th S eptem ber caused g reat losses of seed and g rain in several areas. H ail caused only a small part o f the loss. O n a national scale th e yield loss was estim ated to am ount to 3 - 4% for cereal crops.
Grey speck (m anganese deficiency) was observed in w inter crops and spring barley in several fields, b u t only weak to m edium severe attacks w ere seen. T he sym ptom s are usually observed in dry and loose soils.
Yellow tip d isease (copper deficiency). Only few cases w ere seen and the attacks were weak.
Barley yellow m o saic v iru s has not b een observed in w inter barley fields i 1985.
However, the fungus Polym yxa graminis which transm its the virus has proved to be widespread in D an ish soils.
Eyespot (P seu docercosporella herpotrichoides). T he possibilities o f infection w ere generally b e tte r in 1984/85 than in 1983/84, especially in Jutland. A t the beginning of Decem ber w eak attacks on rye and w heat w ere observed.
T he forecast o f attacks of eyespot in rye was sent out on the 30th o f A pril.
T here seem ed to b e a need for control in 60% of the rye fields, which was a little m ore than th e year before.
The forecast o f attacks in w heat was sent out on the 14th o f May. T h ere seem ed to be a need for co n tro l in 50% of the fields.
The advisers re p o rte d of attacks in som e rye and w heat fields, b u t with w eak attacks and few m edium severe attacks. In many localities the plants showed poorly developed ro o ts after the winter. G enerally, the attack was w eaker than the year before.
Take-all (G a eu m a n n o m yces gram inis). T h e attacks m ust be described as w eak in 1985.
Mildew (E rysiphe gram in is). C oncerning the severity o f attacks in the rest o f the winter barley and w inter w heat fields the advisers rep o rted on mainly w eak attacks and attacks in few fields in May. T he w heat cultivars ’K anzler’ and ’D isponent’
suffered m o re severe attacks than ’K raka’, ’A nja’ and ’V uka’. T h ere w ere also weak attacks in spring barley in May. A ttacks w ere observed in less than 10% of the fields. M any spring barley fields w ere sown rath er late due to extensive resowing.
In Ju n e attacks in w inter barley and w inter w heat w ere still weak, but with m o re severe attacks in som e w heat fields. A bout 1 /3 of th e advisers reported of m edium severe attacks in spring barley and very little o r no m ildew in resistant cultivars, such as ’Jenny* and ’T a a rn ’. C om pared to the year b efo re the attacks o f m ildew in cereals developed slower this year.
In July th e attacks in w inter w heat and spring barley w ere still described as mostly weak, but w idespread. In 1985, attacks w ere w eak with considerable differences betw een the cultivars, especially in spring barley.
Yellow r u s t (Puccinia striiform is) was observed only sporadically, and with w eak attacks. In a few exceptional cases it was necessary to control the disease. F ro m L olland-Falster th ere w ere rep o rts o f few m ore severe attacks.
Brown r u s t o f w heat (Puccinia recondita) was not very w idespread and o ccurred only with weak attacks.
Brown r u s t of barley (Puccinia hordei) was generally observed with only w eak, sporadic attacks.
Net blotch (D rechslera teres). T h e attacks in spring and w inter barley w ere n o t very w idespread and very weak.
L eaf blotch o f barley (Rhynchosporium secalis). T he attack in spring barley w as very weak and occurred in few fields. 84% o f the advisers rep o rted of 0% attacks in spring barley fields. In w inter barley the attacks w ere a little m o re severe.
Loose s mu t (Ustilago n uda f. sp. hordei) occurred in som e fields, especially in spring barley, b u t only with few sm utted ears. In a few cultivars attacks w ere m ore severe, e.g. in the cultivar ’Jenny’. H ow ever, th e attacks were of no econom ical im portance. In June, 23% of the advisers characterized the attack in spring barley as m edium severe.
S tinking s mu t (Tilletia caries). T h ere w ere no rep o rts o f attacks in wheat.
Speckled leaf sp o t (Septoria tritici) was rath er w idespread, as it is usually the case in th e early spring, b u t with weak attacks, w hich disappeared w hen tem p eratu res rose, and the m icro clim ate becam e less wet.
G lum e blotch o f w heat (Septoria n odoru m ) generally o ccurred with weak attacks and m ostly on the low er leaves. In 98% of the cases th e re were no or w eak attacks.
Brown foot r o t a n d e a r blight (Fusarium spp.) was seen together with grey m ould ( Botrytis cinerea) in som e fields ra th e r late in the growing season, often in cultivars with sh o rt straws. The grains w ere undeveloped and an orange mycelium was often seen.
Fungal diseases in seed grasses. M ildew and to a sm aller extent leaf spot and rust were seen in som e cultivars. T h e attacks w ere generally weak. F rom M øn there were re p o rts of a severe case of rust and powdery mildew in m eadow grass.
Legumes
Grey m ould (B otrytis cinerea) was the prom inent fungal disease in peas in 1985.
In June, w hen th e w eather was rather cold, th e re w ere reports of grey m ould in a small part of the pea fields, but with weak attacks only. In July, which was very wet, th e re w ere reports of several m edium severe attacks, w hereas nearly half the advisers re p o rte d of severe attacks o f grey m ould in August. In several areas rainfall in A ugust and to som e extent in July was far above average.
Especially cultivars w ith a large foliage w ere attacked by fungi. D ue to excessive rainfall the tim e o f harvest was much delayed.
A t one tim e th e re was doubt as to the use o f the peas for forage due to the fungal attack. In m ost cases the fear proved unfounded.
Chocolate sp o t (Botrytis cinerea) was found in som e broad bean fields, b u t mostly with weak to m edium attacks. In A ugust there w ere reports of severe attacks in Midwest Sealand and E a stern Jutland - probably the agressive phase. In S eptem ber there were re p o rts o f severe attacks in W estern Jutland.
Leaf, stem a n d pod sp o t (Ascochyta spp.) generally occurred with very weak attacks. In Ju n e 83% of the advisers rep o rted that leaf, stem and pod spot did not exist in th e fields. In A ugust the attacks w ere still considered generally weak to medium severe (83% of the cases). However, 2 advisers from Funen and Jutland reported of severe attacks in their areas caused by excessive rainfall. T h e attacks occurred very late in 1985 unlike 1982 with early attacks. T he late attack was probably caused by the very low average tem p e ratu re in June and July.
Leaf and pod sp o t (A scochyta fa b a e ) was not w idespread and only weak attacks were seen. F rom W estern Jutland, however, an adviser rep o rted o f severe attacks.
Downy mildew (Peronospora p isi) was far less w idespread and occurred w ith less severity than grey m ould. U nlike grey m ould, downy mildew occurred m ainly in limited areas and w ith m o re severe attacks, f.inst. in the area o f Sailing.
F u sa riu m wilt (Fusarium oxysporum f. sp. p is i) o ccurred only sporadically and with weak attacks.
C lover ro t (Sclerotinia trifoliorum ) occurred with weak attacks only.
O ilseed Rape
O verw intering of oilseed ra p e. Fields with too sm all plants suffered most dam age.
A ccording to an average o f the estim ates sent in by th e advisers, on a n a tio n wide scale approxim ately 12% o f th e w inter rape area show ed frost damage caused by black frost.
B oron deficiency. In July ra p e plants with black wilted tops w ere received. Soil sam ples revealed low occurrence o f b o ro n in the fields.
S clerotinia disease (Sclerotinia sclerotiorum ). O n the 29th of M ay a w arning w as sent out against attacks by the fungus in som e w inter ra p e fields in Funen an d in the N orthern and E a ste rn parts o f Jutland. T he fungus attacked fields, w h ere rap e had been grown before. How ever, control was not necessary in all fields, as, after all, the form ation of the apothecia had taken place at a late stage com pared to the flowering of w inter rape. In spring ra p e warnings of co n tro l w ere send out on the 25th o f Ju n e in the areas of H o rsen s, H aderslev and R in g sted. D ue to extensive frost dam age in the w inter crops m any spring rape fields w ere established ra th e r late (late flowering). This gave rise to the second w arning on the 3rd of July for control in spring rape, this tim e in th e areas of H o rsen s, H aderslev, R ingsted, and som e rap e fields in the areas o f H o lb æ k an d Næstved.
In June, July and A ugust only very w eak attacks o f stem ro t in winter and spring rap e w ere seen. H ow ever, in the areas of M idw estern Sealand, Funen and N o rth e rn Ju tlan d severe attacks in spring rap e were seen in A ugust. In a few cases it w as necessary to expedite the tim e for laying in swaths in the spring rape.
T h ere w ere no rep o rts of attacks by sclerotinia disease in peas. An exam ination carried out by the the R esearch C entre for P lant P ro tectio n in 1985 show ed a high frequency of sclerotia o f the fungus in pea samples.
C lu b ro o t (P lasm odioph ora brassicae). In spring rape, "no attack ” was stated in 67% of the reports. 6 advisers, however, reported o f severe attacks of clubroot in spring rap e in the areas o f M idw estern Sealand (3), N o rth e rn Jutland (2), F u n en (1).
D ark leaf a n d pod sp o t (A ltem aria brassicae, A . brassicicola). Generally w eak attacks which becam e m ore w idespread in the last p art of the growth season,
when tem p era tu res rose.
Grey m ould (B otrytis cinerea) was found in a sm all p a rt o f the fields and with weak attacks. T h e fungus also appeared with prim ary attacks and was m istaken for sclerotinia disease.
Dry ro t a n d c a n k e r (P h o m a lingam ) occurred sporadically with weak attacks. T he fungus was found in w inter rape only - obviously, its cycle does not m atch the development o f spring rape.
Root crops a) Beet
O verwintering o f seed beet. T he frost caused dam age to crops. T h ere w ere rep o rts of w idespread and severe attacks from 42% of the advisers.
Damage in p its. A pproxim ately 10% of the group described with w idespread/severe damage w ere caused by frost which gave rise to putrefaction o r too m uch heat caused by a thick snowcover.
Speckled yellows (m anganese deficiency). T he attack in b eet was described as weak.
M agnesium deficiency. T he attack was observed as no o r a weak attack. T he summer of 1986 was relatively rainy, and m agnesium and boron deficiency problem s are most pro n o u n ced u n d er dry conditions.
H eart ro t a n d d ry ro t (boron deficiency). T h ere w ere reports o f few weak cases only.
Violet ro o t ro t (R h izocton ia crocorum ) was not w idespread and occurred with very weak attacks.
Virus yellows (B e ta virus 4). Exam inations of late pits (15th M ay and 1st June) and pits w ith peach p o ta to aphids show ed that east of the G reat B elt th ere w ere no peach p o ta to aphids in the pits exam ined. Also, th ere w ere few late pits. In Jutland, especially in the areas 7-8 (see illustration) the picture was different.
There w ere a large n u m b er o f pits on 15th M ay and 1st June. G enerally, the occurrence o f peach po tato aphids was w idespread in the pits. H ow ever, rep o rts from the advisers in Ju n e showed that virus yellows appeared only sporadicallly and with w eak attacks. In July all o f the 63 advisers rep o rted that 0% of the
b eet fields w ere attacked by virus yellows in their areas. In A ugust, 84% of the advisers described attacks of virus yellows as none o r w eak. Only 3 advisers rep o rted o f severe attacks (W estern Jutland, E astern Jutland and N o rth ern Jutland).
T he attacks of virus yellows occurred late in 1985. In S eptem ber, however, th ere w ere rep o rts o f several totally yellow beet fields, especially in th e areas of Jutland with m any late and infected pits. In Septem ber, th ere w ere rep o rts of weak attacks from Sealand, L olland-Falster, B ornholm and p art o f Funen.
Black leg (P h om a betae, Pythium spp., A ph an om yces coch lio id es and others) was generally w idespread. T h e re w ere w eak to m edium severe attacks and only few cases o f severe attacks.
Powdery mildew (Erysiphe betae) was seen only in few places with insignificant attacks because o f w et w eather. A lso the attacks occurred very late.
R am u laria leaf sp o t (R am ularia beticola), C ercospora leaf sp o t (Cercospora beticola) and r u s t (U rom yces b eta e) w ere found only sporadically with w eak attacks.
b) P otatoes
P o tato p its - overw intering. A pproxim ately 9% o f the rep o rts described the dam age as w idespread/severe.
P otato leaf roll (S olan u m virus 14) and stre a k (Solan um virus 2) were less w idespread and occurred with weak attacks.
R attle v iru s was not very w idespread and occurred with no or little severity.
1. N orth Sealand
2. C entral and W est Sealand 3. South Sealand, Lolland, Faster 4. B ornholm
5. Funen 6. South Ju tlan d 7. W est Jutland 8. E ast Jutland 9. H im m erland 10. N orth Jutland Regions
Black leg (E rw inia carotovora var. atroseptica) was seen in several fields with weak attacks in 76% o f the cases.
W et ro t (B acteriosis) of tubers was not very w idespread and occurred with weak attacks.
W art disease (Synchytrium en dobioticu m ). 2 new attacks in gardens w ere detected in the autum n 1985. T he G overnm ent P lant P rotection Service has lifted som e of the inhibitive zones, so th at only 7 rem ain.
Common scab (S treptom yces scabies). T h e attack on tubers was w idespread, but was seen m ostly w ith weak to m edium severity.
Black sc u rf a n d stem can k er (R h izocton ia solan i) occurred in weak to m edium severity in m any fields.
Late blight (P hytophthora infestans). T he first warning was sent out on the 1st July, and th e first attacks w ere found the week after. T he 2nd w arning of epidemic o ccurrence o f late blight was sent out on the 19th July. In A ugust the severity of th e attacks was described as weak to m edium in 83% o f the cases. In August the attack spread especially into varieties grown for industrial use. This attack was very w idespread and m ore w idespread than in previous years, due to the excessive rainfall in A ugust - S eptem ber which m ade control o f the disease difficult, and th e spores had been w ashed down to the tubers. T he fungus spores can live in hum id soil for up to 1 m onth.
2. P ests in a g ric u ltu ra l p la n ts 1985 G hita C ordsen N ielsen
C ereals a n d grasses
C ereal cyst nem atodes (H eterodera avenae). In June, 18% of th e advisers re p o rte d o f m edium severe to severe attacks, whereas, in July, th e attacks were described as weak to m edium severe. A t the R esearch C entre for P lant Protection an exam ination of about 250 spring barley fields was carried o u t which showed th a t th ere w ere an unacceptable large num ber of nem atodes in approximately 40% o f the fields.
B ird-cherry ap h id s (R h opalosiph u m p a d i) and g rain a p h id s (Sitobion avenae). T h e first aphids w ere seen in spring barley late in May, especially in the so u th ern p art of the country. In June, the attacks in spring barley w ere described as m oderate, b u t generally w idespread. O ut o f 72 reports, however, 12 cases w ere described as m edium severe to severe attacks. In July, the aphid attacks w ere generally described as no o r weak attacks. However, th e re w ere a few severe attacks in w inter w heat and spring barley, especially in the southern parts of the country. In experim ents carried out with a large n u m b er of aphids yield increases of up to 16 h k g /h a w ere obtained. Especially at high N-levels the aphids w ere persevering. In 1985, the parazitation of the aphids occurred rather late.
T he grain aphid, as so often before, was the dom inant species.
G rain th rip s (L im othrips cerealium and L . den tico m is). Several cases of g rain thrips attacks w ere found in 1985. T he characteristic w hite sheaths were seen especially in rye. In June, 13% of the advisers rep o rted o f m edium severe to severe attacks, w hereas the general rep o rts w ere o f no or weak attacks. In an experim ent with rye infested by m any thrips a yield increase o f 4.0 h k g /h a was o b tain ed after control.
W irew orm s (A griotes spp.). B oth the extension and the severity of the attacks w ere lim ited. 85% rep o rt of no attack.
L eatherjackets (Tipula p a lu d o sa ). T he attacks w ere w idespread in Jutland - especially in S outhern Jutland, N o rth ern Schleswig and C entral Jutland. O n Sealand th e re w ere lim ited attacks. L eatherjackets often occur in connection with spring b arle y and b eet following ploughed grass.
Italian rye grass in pu re culture was also severely attacked, and it was necessary to resow in several cases.
T h e reports described th e severity of the attacks as "no" (18% ), "weak" (16% ),
"medium strong" (37% ), and "severe" (29% ). A ccording to the w eather conditions in the autum n an d soil sam ples taken, weak attacks are expected in 1986.
F rit flies (O scin ella frit). T he first generation m igrated in the w eek 20th to 27th May, which w as later th an usual. This was caused by the very cold spring. D ue to the hard w inter th e population was expected to drop.
T he m igration of the first generation differed significantly from one locality to the other, b u t w as generally weak. O n the 10th of July w arnings against the second generation w ere sent out. This generation, however, took a long tim e because excessive rainfall ham pered the m igration, and the rath er low tem p eratu res delayed the hatching.
T he 3rd as well as th e 2nd generation w ere sm aller than usual.
T he attacks o f b o th the 1st, 2nd and 3rd generation w ere weak in 1985, and they were sm aller in num ber than in 1984.
Saddle gall m idges (H aplodiplosis equestris). T h ere w ere rep o rts of w eak attacks only. So far th e re is nothing indicating a fresh outbreak o f this pest.
Leaf beetles ( O u lem a m elan opu s) occurred with weak to m edium severe attacks.
(Ochsenheimeria vaculella) was found in spring barley in N orth-w estern Sealand.
Experiences w ith this pest which causes blasted spikelets are still limited.
W heat gall m idges ( Contarinia tritici and Sitodiplosis m osellan a). A ttacks in w heat were insignificant.
Bibionid flies (B ib io hortulanus). Extension and attacks w ere very limited.
Potato stem b o re rs (H ydraecia m icacea). O ne attack in m aize was rep o rted . T he attack was confined to the edge o f the field.
Slugs (A griolim ax spp.). In Septem ber - O ctober th ere w ere m any rep o rts o f severe attacks in w inter cereal crops and w inter rape. Resow ing was necessary in several cases. E specially w here w inter cereal crops and w inter rap e followed rape, peas, clover and grass th e re w ere reports o f attacks. Heavy, lumpy types of soil sown by means o f the ro to r harrow system had severe attacks. T he large slug population was ascribed to the favourable conditions for reproduction u nder ra th e r w et and cold w eather conditions during late sum m er and autum n.
Legumes
Cabbage th rip s (Thrips angusticeps). A ttacks w ere w idespread in C entral and S outhern Sealand and in N o rth ern Jutland. T he severity o f th e attack was generally w eak (78% o f the reports). O nly in one locality severe attacks w ere found.
Pea th rip s (K akothrips p isivo ru s). In July the attacks w ere described as n o n e o r weak.
Pea a n d bean weevils (S iton a lineatus). The occurrence was widespread, especially in C entral and S outhern Sealand, on Funen and in C en tral Jutland. In these a re a s the attacks w ere described as weak (61% ), medium strong (29% ) and severe (5% ).
Severe attacks by adults w ere seen on leaves, w hereas the dam age to root nodules by larvae could not be detected immediately. Severe larval attacks may resu lt in yellow wilted leaves, which may look like N-deficiency, because the larvae e a t th e N -containing ro o t nodules.
In A ugust th ere w ere rep o rts of weak to m edium severe attacks by pea and b e a n weevils in clover. 3 advisers rep o rted of severe attacks. In S eptem ber 61% o f th e advisers rep o rte d of m edium severe attacks. Severe attacks w ere seen in W estern Ju tlan d (3 rep o rts), Funen (2), L olland-F alster/S outheast Sealand (2), C entral and W estern Sealand (1).
C ontrol of pea and b e an weevils in weak white-clover was necessary in several cases. W ith low tem p eratu res in O ctober the pea and bean weevils hibernated.
1985 was the 2nd year in a row with severe attacks of p e a and bean weevils in the late sum m er in clover, probably due to a considerable increase in the areas grow n w ith peas, in which th e p ea and bean weevils can b e reproduced and attack the clover after the peas have been harvested.
T o rtrix m oth c a te rp illa rs (C nephasia spp.) w ere generally w idespread in peas in som e areas, but th ere w ere only 3 reports o f m edium severe attacks. In b ro a d beans th e re w ere only few and w eak attacks by tortrix m oth caterpillars.
Pea ap h id s (A cyrthosiphon p isu m ). In June pea aphids had only spread very little, and attacks w ere weak. In July 27% reported of m edium severe attacks, and p ea aphids w ere generally w idespread. In A ugust the attack and the spread h ad decreased, b u t th e re w ere few ra th e r late, severe attacks.
B lack bean a p h id s (A ph is fa b a e ) in field beans w ere generally widespread and o ccurred in July w ith m edium severe attacks i 9 out of 21 reports.
Pea moths (C ydia nigricana). M igration was so low this year, that control o f pea m oths was not necessary. 4 plant protection bulletins on the pea m oth w ere sent out. During th e first week of Ju n e th ere w ere p ea m oths in 2 out of 180 traps distributed all over the country. Beginning and M id July p ea m oths w ere on the wings in approxim ately 15% of the localities. It was not possible to detect any difference in m igration from one region to another by looking at the figures.
O nly the m igration activity was higher on Sealand in Ju n e and July (50% o f the localities with initial m igration), and partly in Ju tlan d (W est, E ast, N orthern Jutland).
R eports from th e advisers also showed weak attacks in June, July and August.
Flower weevils (A p io n spp.) in clover occurred in few fields and generally with w eak attacks. O nly from N orthern Jutland th ere w ere reports o f severe attacks.
Oilseed rape
Blossom beetles (M eligethes aeneus) were w idespread in w inter rap e fields in May. The cold w eath er at the beginning of M ay ham pered the m igration of blossom beetles so m uch th a t attacks in w inter rape w ere m oderate. L ater in the m onth the tem perature rose, and in June w hen the spring rap e is flowering the attacks were described by 70% o f the advisers as w idespread and with m edium severe to severe attacks.
Seed weevils (Ceutorrhynchus assim ilis). By the end o f M ay the m ain part o f the winter rape fields had been infested by the seed weevils with varying severity.
A lm ost half o f th e advisers estim ated the attacks as m edium severe.
T he ocurrence of seed weevils, as was the case for brassica pod midges, was also very w idespread in Ju n e and m ore than half of the advisers estim ated the attacks as medium severe. In July, apart from few severe attacks, only weak to m edium severe attacks w ere seen in w inter rape and no or weak attacks in spring rape.
Brassica p o d m idges (Dasyneura brassicae). T he brassica pod m idge m igrated by the end of M ay. O n the 28th of M ay warning against the 1st generation of the brassica pod m idge was sent out and control was necessary approxim ately 5 days later.
The overw intering conditions for the brassica pod m idge w ere good in 1984/85.
Therefore th e re was a risk of m oderate to severe attacks in areas which the year before h ad had a large population o f brassica pod midges (N orth Schleswig, Northern F u n e n and S outhern Sealand). In Ju n e th ere w ere rep o rts of very widespread attacks by brassica pod midges in w inter rape with m edium severe
attacks in m ore than half o f the reports. In July the attacks were generally w eak to m edium with few severe attacks, however. In spring ra p e there were generally no or weak attacks.
T h ere w ere rep o rts of insufficient control o f brassica p o d midges in sp ite of several sprayings w ith pyrethroids, probably because th e control was ap p lied too late or due to a vigorous vegetation (com bined with a large density o f brassica pod m idges) resulting in quicker dilution of pyrethroids in the rape p lan ts than usual.
W arning against the second generation of brassica pod m idges was sent o u t on the 27th of June. In m ost places evidence of the occurrence o f the first g en eratio n of brassica pod m idges was found in w inter rape. In fields w ith insufficient co n tro l the attacks w ere severe (30 - 40% of the pods w ere destroyed.
Flea beetles (P hyllotreta spp.). Spread and attacks w ere very lim ited.
C abbage stem flea beetles (Psylliodes chrysocephala) did n o t cause problem s, one adviser in S outhern Sealand, however, decribed the attack as m edium strong.
Cabbage th rip s (Thrips angusticeps) did not cause problem s in winter ra p e . In spring rap e the occurrence was m oderate all over th e country. In a few places in S outhern Sealand th e re w ere cabbage thrips in m ost o f th e fields. In M ay, the attacks w ere estim ated as w eak (68% ) or m edium severe (21% ), whereas o n e ad
viser reports on severe attacks. T he spread and the attacks seem ed to b e m o re severe than in 1984.
C abbage stem weevils (Ceutorrhynchus quadridens). T h ere w ere generally n o o r weak attacks. H ow ever, th ere w ere several cases o f severe attacks. The cabbage stem weevil attracted m ore attention in 1985 than in previous years. T h e light, wilted stem s that the cabbage stem weevil leaves behind, w ere in a few cases m istaken for sym ptom s o f sclerotinia disease.
C abbage ro o t flies and tu rn ip ro o t flies (D elia radicum , D . floralis) o ccurred in w inter and spring rap e with only few attacks of no or weak strength.
D iam ond-back m oths (Plutella xylostella) occurred very sporadically and w as of no im portance.
Swede gall m idges (C ontarinia nasturtii). 34 advisers observed no attacks, w hile 10 advisers saw weak attacks and only one reported on m edium severe attacks.
C abbage bu tterflies (Pieris brassicae, P. rapae). T h e re w ere few w eak attacks.
Cabbage a p h id s (Brevicoryne brassicae) was less w idespread and with weak attacks.
Root crops.
a~> Beet
Beet nem atodes (H eterodera schachtii). Only 5 rep o rted o f occurrences - there were both w eak and severe attacks.
Cabbage th rip s (Thrips angusticeps). A s in 1984 th ere w ere w idespread attacks in beet in 1985. H ow ever, the attacks w ere much weaker, and resow ing was unnecessary.
In May, approxim ately 40 advisers estim ated the extent and dam aging effects of the following pests (percentage):
PESTS ATTA CK S
no weak m edium severe
Wireworms 22 64 11 3
Pygmy beetles 58 39 3 0
Collembola 71 21 8 0
Millipedes 76 24 0 0
Beet leaf m iners 71 11 14 4
Pygmy beetles (A tom aria linearis) occurred as in 1984 in a few fields, w here the individual cases gave rise to dam age.
Beet leaf m in ers (P egom yia hyoscyam i). Spread and severity was in M ay as in previous years, an d it was found in approxim ately 20% of the fields, o f which a few had severe attacks. In A ugust 4 advisers had seen severe attacks.
Beet carrio n beetles (B litophaga opaca) was m ore w idespread than in 1984, but only 8 advisers out of 69 rep o rted of medium strong attacks.
T ortrix m oth larv ae (Cnephasia spp.) w ere w idespread, b u t only 3 advisers saw medium strong attacks.
N ut meg m oth (D icestra trifolii) and cabbage m oth (M am estra brassicae) occurred in several fields, b u t with weak attacks. Even though the nut m eg m oths prefer dry conditions they occurred with severe attacks in N orthern Jutland. 1985 is the third year in a row with severe attacks by larvae o f the nut m eg m oth in beet in Northern Ju tlan d .
C utw orm s (Agrotis segetu m ). D u e to the wet w eather conditions, attacks w ere less w idespread and generally weak.
Peach p o ta to a p h id s (M yzus persica e) and black bean a p h id s {Aphis f a b a e ) . In 1985, 7 plant protection bulletins concerning aphids in b e e t were sent o u t in Ju n e - July.
T he bulletins w ere based on rep o rts from the advisers on th e num ber of p each p otato aphids and black b ean aphids registered in beet fields all over the country.
A t th e beginning of July a w arning was sent out for control of peach p o ta to aphids on M øn, S outhern Sealand and Lolland-Falster. O n e week later co n tro l was necessary on Funen. F rom several areas too little inform ation had b een sen t in during this period as to the num ber of peach p o tato aphids in the fields exam ined, and therefore it was not possible to estim ate th e need for control, if any. Especially from areas with m any late and infested b eet pits reports w ere few.
O ut o f 40 spindle tree localities exam ined in the spring, black b ean aphids o ccu rred in 3 localities. In 1984, no overw intered eggs were found on spindle trees.
A t the beginning o f June, black bean aphids w ere w idespread in the so u th ern parts of the country and from the end of June until the beginning of July th e re w ere w idespread, but weak attacks in most parts. By the end o f June and as late as by the end of July th ere w ere severe attacks on the islands and in the so u th ern parts of the country, at th at tim e th ere were no signs o f parasiting yet. C o n tro l caused som e problem s in the southern parts. A lso in th e experim ents th e b a d effect o f several o f the system ic phosphorous agents was observed, perhaps du e to resistance developing.
T h e black b ean aphids occurred late in 1985, b u t with ra th e r severe, late attacks on the islands and in the sou th ern parts o f the country.
b) Potatoes
P o tato cyst nem atodes (H eterodera rostochiensis). Two advisers rep o rte d of attacks.
C utw orm s (Agrotis segetu m ). T he turnip m oths m igrated later this year than usual- not until 10th July did the phero m o n e traps catch many anim als.
C onsidering the rainfall and tem perature conditions, severe attacks by cutw orm s w ere not expected. A plant protection bulletin was sent o u t o n the 25th o f Ju n e . O n the 16th o f July the second plant protection bulletin was sent out. T he catch of turnip m oths decreased in Sealand and Funen. O n Sam sø a decrease late in
June was follow ed by a considerable increase in catches. In Jutland catches w ere generally large except in Southern Jutland.
C olorado beetles (L eptinotarsa decem lin eata) w ere observed in 1985 with severe attacks in a new locality, a private garden in Lolland-Falster. They had probably overwintered from 1984. A lso from T ø n d er th ere w ere rep o rts o f the occurrence o f 19 sum m er beetles in a private garden. In 1985 th ere w ere a total o f 4 rep o rts on the occurrence o f Colorado beetles.
3. D iseases a n d p ests o f h o rtic u ltu ra l p la n ts 1985 (L ars A. H obolth)
V ariations are few in the percentual distribution o f enquiries when com pared to an average o f the five preceding years (table 1). T he enquiries tend, how ever, to b e directed m o re tow ards specific subjects, and so the n u m b er of enquiries on mycology, bacteriology, virology and zoology has increased a little.
T able 1.
P ercentual distribution of registered enquiries
Phy- Myco- B acte Viro- Z o o Unex
sioge- logi riolo logi- logi D i plain
nical cal gical cal cal verse ed
A verage 14.8 41.8 7.5 4.9 24.5 5.8 0.6
of 5 years 1980-84
1985 10.1 44.2 9.2 6.0 27.2 3.7 0.06
(total num ber: 1672) C lim atic dam age
W hen spring was well advanced, m any trees and bushes show ed signs o f injuries caused by the w inter. M any roses, b o th the old plants and th e grafted ones died.
A pparently th e grafted plants th at h ad been ridged up a fter the grafting h ad taken place suffered fewest injuries.
M any tulips w ere dam aged by too m uch ethylen, possibly d ue to the cold sto res having been too carefully locked to keep out the cold.
T he late spring h am p ered the developm ent of Chinese cabbage when it was p lan ted out, so that m any plants form ed flowers before heads. B ecause o f the cold w e ath e r in Ju n e m any outd o o r cultures requiring warm w eather sto p p ed developing. T his w as th e case f.inst. of sw eet corn, large cucum ber and gherkins. In straw berries th e w eather resulted in an insufficient pollination o f the b erries, and this explains th e large num ber o f deform ed straw berries found. L ate r in th e summer several local hailstorm s caused dam age to various crops. In onion th e skin was dam aged so that different fungi gained access to the onion.
Fungal diseases
Clubroot (P la sm o d io p h o ra brassicae) is still found now and then in plantlets. T he symptoms o ften ap p ea r so late that the plants have already been planted in the field, before th e sym ptom s can be seen. C onsidering the vigorous developm ent o f the fungus in th e course o f one to two weeks after the planting had taken place there can b e no doubt that they w ere infected already during the germ ination.
A s seed transm ission o f this disease is not known of, suspicion m ust be directed towards the cultivation m edium . Infected fields have been found, w here the previous crop was not cabbage but o ther cruciferae crops, for instance oilseed rape and m ustard. T hese crops may cause problem s, because attacks m ust be very severe to b e detected, as the roots a re not lifted during the harvest, which would reveal the typical swellings of the roots.
Pythium spp. destroys the roots of m any glasshouse cultures. T h e slightest imperfection o f th e cultivation is often the beginning o f an attack o f the fungi.
This could b e a to o com pact standard soil, causing the roots to suffocate, o r a tem porary im perfection o f the irrigation system, creating a conductivity so high that the roots a re destroyed at the slightest drying up o f the soil.
Phytophthora spp. is just as w idespread as Pythium in pot plant nurseries. This fungus is often detected m ore quickly, because frequently it is developing up into the plants, so th a t the infection can b e seen over the soil surface, and the injuries caused by it a re m o re drastic than those caused by Pythium .
Leathery ro t (P ytophth ora cactorum ) was found several tim es in straw berry cultures. T he typical sym ptom is a num ber o f brownish, coriaceous berries in the clusters.
White Tip of leek (P hytophthora porri) is a com m on disease in m any leek cultures, perhaps because this culture, like m any o th er cultures, is grow n in an insufficient crop rotation.
Downy mildew of onion (P eron ospora destructor) was found som ew hat later in 1985 than w as th e case the preceding year. T he extension of the attack seem s to indicate that the com m on m ethod of cultivating this crop with onions set very near sown onions leads to m ore severe attacks by this fungus.
Downy mildew o f cabbage (Peronospora p arasitica) was fairly w idespread in the autumn. In cauliflower, infection could be found even in the heads, w here thin blackish brow n stripes appeared. O ften the stripes radiate from the ram ifications of the sprigs.
Downy mildew of lettuce (B rem ia lactucae) is often found bo th in outdoor and
