Field of activ ity

T he institute continued its research and testing within the a re a of weed biology and control including herbicide testing and approval. In addition, the institute is responsible for research, testing and approval of grow th regulators for agricultural crops.

D istrib u tio n o f m ain task s

A g ricu ltu ral crops in the area of the institute, root-propagated weeds and spraying techniques (O le Perm in).

T esting and experim ents in ag ricu ltu ral crops (E gon Ju h l Petersen and P e d e r E lbæ k Jensen).

H o rticu ltu re, vegetables, fruit and nursery cultures (G eorg Noyé).

F orestry, w indbreaks and coverts (T hom as Rubow).

Weed biology, distribution and spread (C. H olm -Nielsen).

Aftereffect o f herbicides in soil (Johannes Røyrvik).

E xperim ents in co n tain ers a n d clim ate cham bers (P er N ielsen Kudsk, T o rb en O lesen and Jens L indegaard K ristensen).

Non-chem ical weed control (Jakob V ester).

D am age th resh o ld s fo r weed control (P eter Kryger Jensen).

The advisory service (K aren Ravn).

1. Field experim ents in connection with research, testing a n d advisory w ork as well as sp ray in g techniques

Control of Elym us rep en s (com m on couch) (Ole Perm in)

Experiments w ere carried out with fluazifop-butyl (Fusilade) to establish the length of th e effect on com m on couch at different dosages. T he com m on couch, had been ploughed. T he experim ents will be continued with m ore herbicides.

Herbicides for control of com m on couch and wild oat-grass w ere tested in an experiment w ith 17 different crop species, w here the tolerance of the cultivated plants was assessed. In 1986, the effect o f fluazifop-butyl (Fusilade) and haloxyfop-ethoxyethyl (G allant) was examined in the following crops: Brassica napus var. oliefera, Carum carvi, Linum usitatissim um , Pisum sativum , Vicia faba, Lupinus luteus, Trifolium repens, Trifolium pratense, M edicago sativa, H ordeum vulgare, Triticum aestivum , Lolium m ultiflorum, P o a pratensis, Festuca pratensis,

D uring the first th ree years wild oat plants also sprouted from seeds laid in a depth o f 15 cm, but not from seeds laid in a depth of 30 cm. No wild oat p lan ts have sprouted from the seeds after 5 years.

In the spring of 1986, the wild oat seeds, from varying depths, were dug up an d placed on the ground surface for germ ination. Only in th e case o f direct sow ing w ithout stubble preparation, did wild oat seeds from th e 30-cm-deep layer germ inate with 9 p er m^.

T olerance tests in w inter crops (O. Perm in)

T olerance tests w ere m ade with increasing dosages of chlorotoluron (Dicuran) in 6 varieties of w inter wheat. T he tests showed a pronounced difference in th e tolerance of the varieties. T he following varieties are listed in order o f decreasing tolerance: K raka, Kanzler, Falke, A nja and Longbow.

T he tolerance of triticale and Triticum aestivum (K raka) to a number o f soil and leaf-applied herbicides at 3 dosages was exam ined by treatm ents in th e autum n on 2 m ^ plots. Triticale (Lasko) seem ed, on th e whole to be m o re sensitive to the herbicides used than w heat (Triticum aestivum ).

T he effect of horm one products of the ester type was exam ined in small plots w ith application in the autum n w hen the w inter w heat h a d 1, 2, 3, 5 an d 5 leaves. D am age which reduced th e overwintering ability, was seen. However, no considerable dam age was seen with horm one com pounds of the ester type.

T olerance tests in peas (O. Perm in)

T he tolerance o f peas to com binations of soil and leaf-applied herbicides w as investigated. Supplem entary application of leaf-applied herbicides may b e necessary in case the soil herbicides do not have a satisfactory effect. A c e rtain yield decrease was seen after an application o f leaf herbicides having previously b een tre ate d with cyanazin (Bladex). W hen leaf-applied herbicides were applied after a previous treatm en t with napcopam id (stom p), th e re was a significant decrease in the yield.

T reatm en ts for the control of com m on couch (E lym us repen s) and pests o ften coincide, and, in practice, a m ixture of the com pounds will often be used.

Prelim inary experim ents in small plots showed th at the insecticides Cym bush, Sum icidin and Pirim or did not increase the dam age to peas when applied in com bination with bentazon + M C PA (Basagran M C PA ). H ow ever, the damage w as increased when mixed w ith bentazon + M C PA (B asagran M C PA ) and fluazifop- butyl (Fusilade).

Tolerance te sts in o th e r crops (O. Perm in) effect on weeds. H erbicides for desiccation o f broad beans w ere tested.

A number o f new herbicides which may b e used as alternatives to D inoseb control of dicotyledonous weeds in peas w ere exam ined in tolerance tests with 17 different cro p species, including lupin, b road beans, oilseed flax, caraway, spring rape, clover an d grasses. T he purpose of the experim ents is to see how other crops tolerate th e com pounds, so that their suitability as an undersow n crop and the possibilities o f controlling the crops may be estim ated.

Herbicide sp ray in g technique (O. Perm in)

Experiments w ere carried out using 4 different sizes o f flat spray nozzles 4410- 10, -14, -16, an d -14 (m ade by H ardi) at 3 different pressures: 1.5, 3.0 and 6.0 bar, with th e quantity of liquid varying from 57 to 497 1/ha. W hen bromophenoxim (F aneron) was applied against dicotyledonous w eeds in spring barley, the effect on the weeds was significantly sm aller with nozzle 4410-10 at between the various types o f special sprayers or nozzles.

Spraying technique in connection with fungicides (O. Perm in)

The effect o f a fungicide m ay depend on how m uch and w here it is deposited

th e deposit was significantly larger on the top leaf w hen Girojet or C D A sprayers w ere used instead of hydraulic sprayers. T h e Danfoil deposited significantly less.

G irojet and C D A deposited m ore on the top part of the stem s than the hydraulic sprayer, and less on the two lower parts.

R egistrations o f deposit by area show a considerably sm aller deposit with D anfoil and C D A than with hydraulic sprayers. T he registrations w ere m ade by m eans o f 40 cm pieces o f filter paper. However, the registration m eth o d must be im proved, since air currents m ay carry small droplets, for instance from Danfoil, away from the filter paper.

T he deposit in ng p e r cm ^ corresponds to g per ha.

This shows th at especially D anfoil deposits a considerably larg er amount on th e leaves and stem s, both at the top and a little further down in the plants. G iro jet and C D A leave a relatively larger deposit on the u pper p a rt o f the plants th a n the hydraulic sprayer.

T he registration of the biological effect of fungicides applied with special sprayers will continue.

Experim ents with a crop tilter in winter w heat showed increased effect against m ildew and Septoria w hen a crop tilter was used. It w as seen that m o re fungicide was deposited on the stems, both in w inter w heat and spring barley, w hen using a crop tilter.

T he influence of distribution from the CDA on the effect o f growth regulators in spring barley, was investigated in experim ents using m ixtures of eth ep h o n (C erone), sp read er (Sandowitt) and propiconazol (Tilt 250 E C ). When com pared with the effect o f application from an ordinary field sprayer with flat spray nozzles and 200 1/h a , th ere was a tendency to a g reater reduction in straw length when the chem icals w ere applied by the C D A sprayer with a M icrom ox distributor head and 101 w ater/h a.

T he drift was registered by m eans of the tracer N a fluoreceine. The D anfoil 45 1/ha, G irojet 41 1/ha, C D A 30 1/ha and ordinary field sprayers were used in spring barley at stage 10-10.1. T he drift was registered at distances of 1, 3, 6, 9, 12, 24, 36, 48, 60 and 72 m from the area sprayed. A t a distance of 1 m the drift from D anfoil was less than from ordinary field sprayers. At a distance of 12 m and m ore, the drift was larger from the special sprayers than the ordinary field sprayers.

2. Testing of com pounds

Testing of h erb icid es, desiccatants a n d growth reg u lato rs in a g ric u ltu ra l crops (E.

Juhl P etersen a n d P. E lbæ k Jensen)

A great n u m b er of herbicides for use in w inter crops was also registered for evaluation in 1986, and from the autum n of 1985 a num ber o f trials w ere carried out in the 3 w inter crops: wheat, barley and rye.

Very heavy frosts occurred during the w inter 1985-86, and half of the w inter barley trials w ere lost. T he surviving w inter seed corn trials, however, w ere not so badly dam aged by the frost as the year before, and the yield was fairly good.

The capacity for carrying out field trials was increased in 1986 by the employment o f an agricultural research assistant and the purchase of another car. The existing team split up, and two work team s were form ed, each having one car and respectively 2 and 3 research technicians and 1 assistant.

The purpose o f increasing the capacity was to carry out m ore experim ents with a view to developing strategies for weed control. F urtherm ore, a g reater num ber of herbicide tests could be carried out at m ore sites and under m ore varied conditions, and m oreover, they could be tested on a larger num ber of species. In 1986 the developm ent o f strategies concentrated on maize, grass seed and Am sinckia sp. (which is a new and difficult w eed species).

Am sinckia is a new w eed in D enm ark. It does not cause any serious problem in cereals as it can b e controlled by two types o f herbicides. In dicotyledonous crops the problem s have been considerable, as A m sin ck ia is a very competitive plant and m ay replace the crop if it is not controlled. Prom ising results were obtained with m ost o f the herbicides tested in fodder beet and peas.

In maize production, the m ain problem was atrazine-resistant groundsel plants as well as black nightshade and green foxtail. E xperim ents to control other weeds were also carried out.

In grass seed production weeds will repeatedly occur as a problem as the crop is perennial and th e tolerance to herbicides is lower than in cereal crops. A t the same time, th e seed m ust not be contam inated by o ther species which consequently have to b e rem oved. Special efforts w ere m ade to find suitable methods for control o f m ono- and dicotyledonous weeds.

In cereal crops, th e testing of various derivatives o f chlorsulfuron continued. The Du Pont p ro d u ct L 5300 was of interest as it has considerably shorter

persistence than G lean 20D F and is consequently less dangerous to subsequent crops. D P X L 5300 seem s to have the sam e effect on the w eed species which can be controlled by G lean 20 D F and possibly a b etter effect on field pansies.

Charlock germ inating in the spring in w inter barley show ed that the effect o f som e of the active ingredients, diflufenican and isoxaben, is retained in the soil, from the tim e o f application just after sowing o f the w inter crop, until th e spring.

T herefore, the further testing of these two agents will include observations for phytotoxic persistence.

Experim ents w ere carried out to examine spring w eed control - in winter and spring cereals - using horm one mixtures containing m echlorprop or dichlorprop from which the inactive isom er o f the propionates had b een removed. It tu rn e d out that the new propionates at a dose o f 55% of the old proprionates, had th e sam e w eed control effect.

A lthough the use o f the new propionates does not involve any actual reduction of the active ingredients, plants and soil are nevertheless exposed to sm aller quantities of alien chem ical agents.

T he trials included desiccatants and growth regulators.

T he two new grow th regulators paclobutrazol and triapentenol had a good straw - shortening effect on several crops. T here was not m uch lodging in 1986, an d therefore an estim ation of the preventive effect against lodging was difficult.

Experim ents with desiccation in peas showed that am ong th e compounds teste d R eglone (diquat) had the quickest effect, but the use of R eglone for this purpose is not yet allowed.

By the end o f the year, 25 herbicides and one desiccant w ere approved. O nly 9 of these are on the m arket.

R eevaluation o f previously registered pro d u cts a n d biological efficacy d a ta in connection with re g istratio n of new pesticides (E. Ju h l P etersen, G. Noyé a n d T.

Rubow)

In 1986 the N ational Agency of Environm ental Protection did not ask for reevaluation o f any previously registered products.

However, th ere was an increasing num ber o f requests fo r efficacy data in connection with applications to the Agency for registration o f new herbicides. 41

products w ere considered, and in m ost cases the docum entation was sufficiently good for recom m ending registration. T he 41 products all contain known active ingredients, and in a num ber of cases, it was a m atter o f extending the field of application of products which had already en tered the m arket.

G eorg Noyé

In 1986 the horticultural dep artm en t chiefly concentrated on three main subjects:

T h e official testing af herbicides, herbicides to rep lace diquat-dibrom id preem ergence and herbicides to control resistant weed species, especially S en ecio vulgaris in different row crops.

T esting o f herbicides

In 1986, 25 herbicides and 2 desiccatants were subm itted for testing.

T h e distribution am ong the crops was as follows: 3 in chives, 2 in onions, 1 in leeks, 1 in carrots, 2 in cabbage, 1 in caraway, 7 in green peas, 1 in b e e tro o t, 1

in celeriac, 1 in straw berries, and 5 i 9 different vegetables, 1 in asparagus, 1 in lawns, 12 in nursery crops, 3 in orchards, and 4 in fruit bushes.

T h e below m entioned chem icals all obtained approval - o r extended approval- for use, by the D anish R esearch Service for Plant and Soil Science.

1. H oltox (22.5% atrazine + 22.5% cyanazine) was approved for control o f seed w eeds in som e varieties of transplanted nursery crops and in shrubberies.

2. Fusilade (25% fluazifop-butyl). - T he approval was extended to include Elym us repens in straw berries.

3. PP005 (12.5% fluazifop-butyl). - The approval was extended to include caraway, asparagus, carrots, leeks, beetroot and celeriac.

4. G allant 125EE (125 g haloxyfop ethoxyethyl). - T he approval was extended to include straw berries as well as Abies nordm anniana, Picea abies, Sorbus and Spiraea in bo th nurseries and shrubberies.

5. A falon (50% linuron). - T he approval was extended to include peas.

6. G oal 25 W P (25% oxyfluorfen). - The approval was extended to include certain nursery crops in transplant beds.

7. Stom p (33.5% pendim ethalin). - The approval was extended to include several woody plants.

A s yet, only A falon, H oltox F, Fusilade and Stom p have b een approved fo r use by the N ational Agency o f E nvironm ental Protection.

Substitutes fo r d iq u at-d ib ro m id (Reglone)

A series o f trials to com pare Reglone with other herbicides for w eed control, pre crop em ergence, started in 1984. T he trials were also carried out in 8-9 crops in 1985-86.

The use of a foliage-applied herbicide, p re crop em ergence, is m ost frequent in horticultural crops w here it is often difficult to control w eeds after crop emergence. In agricultural crops, the m ethod is usually used in connection with direct drilling, b u t in certain years it m ay be necessary to spray overw intered weeds, such as Stellaria m ed ia and P o a annua p re sow ing/em ergence of b eet and oilseed rape.

The trials show the contact effect and to som e extent the systemic effect of the chemicals. F u rth erm o re, the soil effect is examined.

In drilled onions, the results from 1985 w ere confirm ed (Noyé, 1986a). T otril and Buctril had a m ilder effect than R eglone when controlling dicotyledonous weeds.

Monocotyledons m ay be controlled by R oundup pre crop em ergence.

The pea trial shows that all the herbicides may be used prior to em ergence.

Roundup, applied post crop em ergence, caused sprout dam age in germ ination tests carried out on th e harvested peas.

In chrysanthem um , both R oundup and T otril may substitute Reglone. W hen using Basta, the tim e o f em ergence m ust be taken into account.

In radish, th e last chance for treatm ent is at the point of em ergence. B asta and low dosages o f R o u n d u p and T otril may replace Reglone.

Spinach to lera tes T otril ju st as well as Reglone, but R oundup and B asta may also be used as long as the tim e of em ergence is respected.

In curly kale, all the chemicals m ay replace Reglone, pre crop em ergence.

Roundup and B asta have given particularly good results.

Caraway seem s to to lerate all the herbicides, although large dosages o f Totril cause m ore dam age than Reglone.

Oilseed ra p e has to lerated Basta well, and especially R oundup, post crop emergence. A pplied pre em ergence, all the herbicides may be used.

In fodder beet, the tim e o f em ergence is critical for tolerance of all th e herbicides.

R esistan t weeds

A num ber o f experim ents w ere carried out in nurseries to exam ine the resistance o f Sen ecio vulgaris to herbicides of the triazine type, an d to fmd o th e r herbicides suitable for this purpose.

T he experim ents did not show any m arked tendency that S en ecio had developed a strong resistance to triazine, b u t the population density w as so considerable that the traditional simazine treatm en t did not have any satisfactory effect o n the weeds.

A num ber of herbicides w ere tested, and particularly diuron and oxyfluorfen h ad a b e tte r effect on Senecio than simazin.

IV. CO NTROLLED ENVIRO NM ENT EX PERIM EN TS P. Kudsk and T. O lesen

Herbicide sensitivity to ra in a fte r spraying

A num ber o f experim ents concerning the rainfastness o f herbicides w ere carried out in 1986 by m eans o f the rain sim ulator constructed in 1985.

Since rainfall after spraying does not influence the m ode of action, b u t only the proportion o f active agents reaching the site o f action, it was possible to use a parallel line assay when calculating the results. This m akes it possible to estimate the loss o f active agent during a shower.

Glyphosat (R oundup) and fluazifop-butyl (Fusilade) were examined, and the results show ed th at a longer dry spell was required after an application of glyphosate ( > 6 hours) than after treatm en t with fluazifop-butyl (about 2 hours).

It was also found th at m ore than 0.5 m m rainfall would wash off glyphosate whereas less th an 2 m m did not wash off any considerable proportion of fluazifop-butyl.

The addition o f 0.5% Frigate (Tallow A m ine Ethoxylate 800 g/1) to glyphosate led to a significant increase in the effect on barley, both with and w ithout rainfall.

A container experim ent sprayed with chlorsulfuron (G lean) showed that 4 hours’

dry w eather betw een application and rainfall was not sufficient to ensure a satisfactory effect. R ain 30 m inutes after the spraying resulted in an effect corresponding to a loss of 60-80% of active ingredient, depending on the length and quantity o f th e rainfall.

Difenzoquat (A venge), however, requires a dry period o f over 6 hours in o rd er to obtain a satisfactory effect on A ven a fatua.

The influence o f additives a n d adm ixtures on the herbicide effect

These exam inations w ere started to find the best com binations o f herbicide and additive m ixtures. O ne o f the aims is to reduce the present herbicide dosage.

In a container experim ent, barley tre ated with glyphosate (R oundup) showed that the dosage o f glyphosate could be reduced by 75% when adding 0.5% Frigate.

However, subsequent experim ents with E lym u s repens showed th at Frigate does not increase th e effect of R oundup to the sam e degree as in barley.

The herbicides and herbicide mixtures used in sugar b eet w ere tested in mixtures with am m onium sulphate, as experim ents with o ther herbicides have shown that

am m onium sulphate m ay increase the effect of herbicides. T his experiment did n ot show any significantly increased effect by adding am m onium sulphate.

A container experim ent was carried out to find out partly whether it w as effect was biggest when the plants w ere under drought stress.

The influence of fungicides containing m aneb on th e effect o f hormone p ro d u c ts

seem to indicate th at it is the form ulation rath er than the m aneb itself which reduces the effect of th e herbicides.

Consequently, grow ers are advised not to use m aneb in connection with weed control, especially if reduced herbicide dosages are used.

Consequently, grow ers are advised not to use m aneb in connection with weed control, especially if reduced herbicide dosages are used.

In document Plant diseases, pests and weeds in Denmark 1986 (Sider 82-104)