II. A dvisory work in L yngby
1. D iseases in agricultural plants 1985
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