The Institute continued its research and experim ental work within th e areas of weed biology and w eed control, in the widest sense o f these w ords including herbicide testing and giving approval for use. In addition, the Institute is responsible fo r research, testing and giving approval for use of grow th regulators for agricultural crops.
Distribution of main tasks
Field trials concerning developm ent, testing and advisory work in agricultural crops (O le P erm in)
Testing of herbicides, desiccants and grow th regulators in agricultural crops. (Egon Juhl P etersen and P e d e r elbæ k Jensen).
Re-evaluation and evaluation of efficacy (E . Juhl P etersen, G. Noyé and T. R ubow ).
H orticulture (G eo rg Noyé).
Forestry, w indbreaks and coverts (T. Rubow).
Weed biology (C. H olm -N ielsen assisted by S. T horup).
Experim ents in containers and clim ate cham bers.
Herbicide persistence and the rain-fastness o f herbicide mixtures (P er Nielsen Kudsk and K nud E rich Thonke og Jens L indegaard K ristensen).
After effect o f herbicides in soil (Johannes Røyevik).
The advisory service (K aren Ravn).
II. AGRICULTURE
1. Field trials concerning development, testing and advisory work in agricultural crops.
Control of common couch (Elvmus repens) (O. Permin)
The long-term effect o f chemical products applied to control Elym us repens has been investigated. T he basis for the experim ent are 15 cm long rhizom e pieces planted in each plot in O ctober, 1984. In 1985 b eet w ere sown on the experim ental area and tre a te d twice with 1, 1 /2 and 1 /4 o f the norm al dose o f fluazifop-butyl (Fusilade). W hen 1 /2 and 1 /4 o f the norm al dose was applied a few Elym us repens plants w ere capable o f continuing growth, though this was reduced by the com petition from the beet. A fter the beet w ere harvested, the dug up shoots of Elymus rep en s which had been treated with a norm al dose w ere unable to form
new shoots w hen left to germ inate under laboratory conditions. The long-term effect o f the tre a tm e n t will b e investigated in spring barley in 1986. T he te st was o rd ere d by ICI.
Control of wild oat-grass (Avena fatua) (O. Permin)
E xperim ents w ere continued to exam ine how quickly cultivated land is em ptied o f viable A vena fatua seeds w hen a ploughfree cultivation m ethod is used. G rains o f A vena fatua w ere sown in depths of 5 ,1 5 and 30 cm in the autum n o f 1980.
D irect drilling w ithout an initial preparation of the stubble field in the autum n gave the least num ber of germ inated wild oat plants, and th e n only from a d ep th o f 5 cm. T he m ore intensive the preparation of the soil th e g reater the num ber o f wild oat plants which germ inated, and the greatest n u m b er was found w here ploughing had been carried out. F o r the first th ree years wild oat seeds which h ad b e e n sown in a d ep th of 15 cm also germ inated, b u t n o germ ination w as registered from seeds sown at a depth of 30 cm. A fter 5 years no wild oat plants germ inated from the seeds sown. In the years to com e germ ination ability of th e rem aining seeds will be exam ined.
Tolerance trials in winter crops (O. Permin)
In tolerance trials with 7 varieties of winter wheat, chlortoluron (Dicuran 500 FW ), applied in increasing doses and at two different tim es have been tested.
N o dam age was found in the cultivars K raka and D isponent when sprayed im m ediately after sowing and after germ ination in N ovem ber. Im ba, Kosak and C alif to le rate d trea tm e n t bo th with norm al and double doses applied just after sowing. Sleipner and C itadel tolerated norm al doses b u t n o t double doses im m ediately after the sowing. D ouble doses applied after germ ination caused severe dam age on the varieties Kosak, Sleipner, Calif and C itadel. T he experim ental work has been carried out for C iba Geigy. T he tolerance test with chlortoluron included 5 varieties of w inter barley, Igri, G erbel, Hasso, M am m ut and Freya. None of them survived the winter. T h e experim ental plot was resow n in the spring with barley, spring oilseed rape, peas and beet w ithout previous ploughing. The yield of all the varieties sown tended to be reduced w here a double dose o f chlortoluron had been applied in the autum n. In the course o f the grow ing season in June severe visible dam age was found in all the varieties. U ndersow n crops of grass and clover in barley w ere com pletely destroyed.
O rien tatin g experim ents on th e effect of horm onal com pounds in w inter w heat applied in the autum n show ed dam age in the w heat which red u ced its ability to overw inter. T he horm onal com pounds o f the ester type w ere n o t found to cause any severe dam age.
Tolerance trials in peas (O. Permin)
Experim ents w ere carried out in peas to test th eir tolerance to com binations of soil and leaf-applied herbicides. If the control o f the w eed turns out to be unsatisfactory, it may, in practice be necessary to use leaf-applied herbicides also.
T he residual com pounds trifluralin (Treflan), cyanazin (Bladex) and pendim ethalin (Stomp) did n o t dam age the yield of peas when applied in a com bination w ith the leaf-applied herbicides bentazon (Basagran) and bentazon + cyanazin (B asagran + Bladex). Also, no yield decrease was registered w hen bentazon (B asagran) was field beans, b u t lenacil show ed poor weed control.
Tolerance trials in flax (O. Permin)
T he object o f th e trial is to find alternatives to D N O C , which was previously used on flax. O rien tatin g trials using 3 doses showed th at possibilities are good for using b e n ta z o n (B asagran), with or w ithout M C PA , brom oxynil (B rom inal), chlorsulfuron (G lean ) and dichlorpicolin acid (M atrigon).
T he application of a nu m b er o f soil herbicides im m ediately after sowing was tested.
Time of spraying and additives for herbicides in beet (O. Permin)
R educed doses m ake it necessary to carry out treatm en t at the correct stage of Protection. T he work is interdisciplinary and com prises interdisciplinary projects in which T he C rop H usbandry D epartm ent and D anish A gricultural Engineering Institute participate. T h e object is to optimize spraying techniques which is an essential elem ent in the efforts to reduce doses and to avoid an unnecessary strain on the environm ent. T he trials which have been carried out in agricultural
crops for the In stitu te of W eed Control will b e m entioned below.
Technical Sprav experiments with herbicides (O. Permin)
Experim ents w ere carried out with 4 different sizes o f nozzles 4110-10, 4110-14, 4110-16 and 4110-24 at 3 different pressures 1.5, 3.0 and 6.0 b ar, so th a t the liquid quantity varied from 53 up to 497 1 liquid p er ha. A systemic herbicide was applied against dicotyledonous weeds in spring barley. T he prelim inary result showed that by applying bo th at an early and a late developm ent stage th e effect tended to b e less w ith the smallest nozzle 4110-10 com pared with the nozzles 4110-14, -16 and -24.
A n experim ent o rd e re d by NAB to test the influence o f quantity o f liquid on the effect of difenzoquat in double, norm al, 1 /2 and 1 /4 o f norm al doses show ed a significantly b e tte r effect against wild oats w hen 1 /2 and 1 /4 o f no rm al doses were diluted in 75 1 of liquid com pared to 300 1 of liquid per ha.
Technical snrav experiments with fungicides (O. Permin)
Experiments w ere carried out in spring barley on the biological effect of propiconazol (T ilt 250 E C ) propiconazol + tridem orph (Tilt tu rb o 475 E C ) using different spraying systems. 1 /2 and 1 /4 of norm al doses tended to im prove the effect against m ildew w hen a crop opener was used and a pneum atic nozzle. A crop opener is a boom which is lowered to say half the height of the crop making an opening into which th e spray is applied. In a pneum atic nozzle a stream of air is added in th e nozzle. T here was no definite im provem ent in the effect of the other spraying system s com pared to the standard, which was nozzle 4110-14, 3 bar and 150 1 o f liquid per ha at a forw ard speed o f 7 k m /h .
Examinations o f th e spray deposit on the plants showed a significantly increased deposition on th e m iddle and lowest pa rts o f the leaves and stem s, w hen a crop opener was used.
Experim ental w ork was done for Ciba Geigy.
Application w ith specialized sprayers, such as D anfoil at 45 and 60 1 o f liquid per ha and the C D A sprayer at 10 1 per ha, and 1 /2 o f norm al dose gave satisfactory effect against mildew. T he effect obtained using the specialized sprayers was n o t b e tte r than that obtained with the hydraulic field sprayer with nozzle 4110-10, 3 b a r and 75 1 of liquid per ha.
Technical spray experiments with growth regulators (O. Permin)
The effect of eth ep h o n (C erone) on spring barley in liquid volum es of 250, 125
and 62 1 o f liquid p er h a has been examined. F lat fan nozzles 4110-24, -16 and-10 at 3 b a r and at a forw ard speed o f 7 k m /h w ere used. T h e effect has b e e n assessed by m easuring the straw length. The results from 3 years’ trials show that spraying with C erone in 2 /3 of norm al dose w ithout w etter in 62 1 liquid p e r h a gave a reduction in straw lenght similar to that obtained with a norm al dose and 250 1 o f liquid p er ha. A dding w etter (0.1% Sandovit) gave an increase in the straw length reduction effect, so that 2 /3 o f the dose + w etter corresponded to norm al dose w ithout w etter. W hen w etter was added, a reduction of the liquid volum e did not increase the effect significantly, but 125 1 ten d ed to give a b e tte r straw length reduction effect than 250 1 of liquid p er ha. 67 1 of liquid p er ha was n o t quite as stable as 125 1 o f liquid p er ha.
In a orientating experim ent it was examined as to w hether th e quantity of liquid used to distribute ethephon (C erone) could, advantagously, be reduced, when th e plants w ere covered with dew. T he result showed a b e tte r straw reduction effect with 100 1 than with 200 1 of liquid per ha when application took place in the m orning with a high atm ospheric humidity, both w ith and w ithout dew on th e plants. T he effect was p o o rer when spraying took place later in the day in a lower atm ospheric humidity.
2. Experiments with herbicides, desiccation compounds and growth regulators in agricultural crops (E. Juhl Petersen and P. Elbæk Jensen
T h e testing carried out in 1985 was still very m uch influenced by the interest in th e use o f herbicides in w inter crops. Many of these com pounds were sent in for testing for use in the autum n, and in the autum n of 1984 a n u m b er of experim ents w ere m ade in the 3 w inter crops, wheat, barley and rye.
T h e hard w inter of 1984-85 caused crop failure in th e w inter barley experim ents and the experim ents with Longbow and Falke wheat, which accounted for 50% of the experim ents m ade. A registration o f the weed was carried out before the r e sowing of these fields. C onsequently it was possible even at this early stage to obtain an im pression of the effect o f the com pounds. T h e frost damage was so encom passing that it was im possible to estim ate w hether th e herbicides applied had added to the failure of the crop.
T h e overw intered experim ents w ere dam aged to a g re a te r o r lesser degree by w ater during the thaw, and this resulted in some uncertain yield assessm ents.
Several analogues o f chlorsulfuron w ere sent in for testing in cereals, each of them having slightly different weed control properties. A couple of com pletely new active chemicals, diflufenican and isoxaben, had a b ro ad and good effect against w eeds when used in w inter cereals in the autum n. In beet different
phenm edipham com pounds w ere tested and also a new w ater-based form ulation, a so-called flow able form ulation. The effect of this com pound on the w eeds was very much p o o re r than the usual em ulsion concentrates, which em phasises the great im portance of the form ulation on the effect of phenm edipham .
In peas, bo th residual herbicides and leaf-applied herbicides in the form of tank mixtures o f cyanazin and M CPB o r bentazan w ere tested. T he tested residual compounds h ad a m o re unreliable effect than the tank mixtures.
Desiccation experim ents w ere carried out in peas, rape and potatoes. N one o f the tested com pounds took effect as quickly as diquat (R eglone), but in an experim ent in spring ra p e th e quick desiccation was a disadvantage, as a few days before the havesting th e early autum n gale in S eptem ber blew off about 80% o f the seeds in the experim ent.
Experiments w ith grow th regulators w ere carried out in grass seed, rap e and cereals. Two new types of chemicals, paclobutrazol and triapentenol w ere mainly tested. T hese com pounds are chiefly taken up by the roots. T herefore it is essential that th e soil is moist when sprayed. In experim ents in cocksfoot, red fescue and ryegrass, these com pounds had a good straw reducing effect, im peded or delayed lodging and gave good yield increases. T he future o f these com pounds is, despite th e good result in 1985, perhaps som ew hat uncertain, as paclobutrazol is very persistent in the soil and may have an adversely effect on the succeeding crop. T riap en ten o l is perhaps, because of the chemical similarity to certain fungicides, contributing to a developm ent of fungicide resistence, which will strongly limit th e areas of application of the com pound.
By the end o f th e year 28 com pounds w ere approved o f which 12 as yet had not been au thorized by the N ational Agency o f E nvironm ental Protection.
3. Re-evaluation and evaluation of efficacy (E. Juhl Petersen. G. Nové and T.
Rubow).
In connection w ith the re-evaluation of the older chemicals o rd ered by the National A gency o f E nvironm ental Protection, an evaluation of application and of the consequences o f lim iting or withdrawing approvals for dichlobenil, petroleum oil and alachlor was carried out in 1985.
Supplem entary statem ents w ere given concerning a re-evaluation o f atrazine, and negotiations w ere conducted with the Agency’s B ureau of Chem icals and Pesticides concerning alternatives to the phenol com pounds.
A s the N ational Agency of Environm ental P rotection has not been able to re evaluate all th e com pounds approved by the Toxicological B oard before 1st January,
1986, it has been stipulated th at all applications for approval o f compounds sen t in after 1st January, 1986 m ust b e treated as new com pounds with re g a rd to docum entation and evaluation, this also include known active ingredients.
This resulted in a stream o f applications for approval late in the year, follow ed by inquiries from the N ational Agency o f Environm ental P ro tectio n to the R e search C entre for P lant P rotection for evaluations of efficacy o f these com pounds.
In 1985, 15 evaluations of efficacy were carried out in connection w ith th e application to th e N ational Agency of Environm ental P ro tectio n for approval of herbicides and grow th regulators. D uring the last m onth o f the year, 10 m o re applications w ere received, which could not b e exam ined until the beginning o f 1986, because they arrived as the year’s evaluation was being finalized.
All the evaluated products contained known active ingredients.
III. H O R TIC U LTU R E (G eorg Noyé)
1985 was very m uch influenced by the distribution o f rainfall which caused th e soil to b e m ore o r less m oist in the surface throughout all the growing season.
Consequently, all the soil herbicides were extrem ely effective from the beginning of the year - in all crops with a "short growing season" m ost o f the weed p roblem s w ere solved by applying residual herbicides only, w hereas th e crops of longer d uration w ere well established before further treatm en t becam e necessary.
In the long term crops such as fruit and berry and nurseries th e "wet" soil cau sed the degradation of otherw ise persistent herbicides to tak e place so quickly th a t the soil herbicides did not have the intended long-term effect. The lack o f a long-term effect, together with herbicide tolerant (resistent) weeds provoked a large increase in the test w ork with alternative residual herbicides an d supplem entary leaf-applied herbicides in horticultural crops.
IV. FORESTRY. WINDBREAKS