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Summary: Resume: Zusammenfassung The application of a proprietary herbicide mixture containing dicamba, 2,3,6-TBA, MCPA and mecoprop to winter wheat, at twice the normal dose and when nodes were detectable, severely depressed grain yield. Grain number was reduced but the greatest effect was a diminution of grain size suggesting that the herbicide had interfered with grain swelling. This contrasts with previously published descriptions of floret sterility as the main symptom induced by late sprays of dicamba. The value of different methods of cereal yield assessment are discussed. To ascertain the effects of herbicide treatments on the number and size of grains, they should be removed from car samples by hand. Effets d'un melange herbicide contenant du dicamba sur les composantes du rendement en grain du ble d'hiver. L'application d'une specialite herbicide constituee par un melange de dicamba, de 2,3,6-TBA, de MCPA et de mecoprop, sur un ble d'hiver au double de la dose normale et lorsque les noeuds ont ete decelables. a provoque une diminution importante du rendement en grain. Le nombre de grains a ete reduit, mais l'effet le plus important a ete une diminution de la taille des grains, ce qui amene a penser que l'herbicide a interfere avec le gonftement des grains Ceci ne Concorde pas avec les publications anterieures qui ont decrit la sterilite des epillets comme le symptome principal induit par des traitements tardifs avec du dicamba. La valeur de differentes methodes d'evaluation du rendement des cereales est discutee. Pour s'assurer des eftets des traitements herbicides sur le nombre et la taille des grains, ceux-ci doivent etre extraits a la main des epis echantillonnes. Die Wirkung von Dicamba-Mischungen auf die Ertragskom-ponenten von Winterweizen Die Behandlung von Winterweizen mit der doppelten Aufwandmenge einer amtlich zugelassenen Mischung von Dicamba, 2,3,6-TBA. MOW und Mecoprop zur Zeit als die Halmknoten gerade sichtbar waren, fuhrte zu einer erheblichen Kornertragsreduktion. Die Behandlung bewirkte eine geringere Kornzahl und vor allem kleinere Korner, was den Schluss zulasst, dass das Herbizid den Prozess der Kornschwellung beeintraachtigte. Dieser Befund steht im Gegensatz zu fruheren publizierten Beobachtungen, in denen die Blutensterilitat als das wichtigste Symptom spater Dicamba-Spritzungen betrachtet wird. Es wird die Bedeutung verschiedener Methoden zur Ertrags-schatzung bei Getreide diskutiert. Um die Wirkung von Herbizidbehandlungen auf die Zahl und Grosse dcr Korner sicher zu erfassen, wird empfohlen, die Korner aus Ahrenproben von Hand zu entfernen.

SUMMARY The decimal code for the growth stages of cereals, devised by Zadoks, Chang & Konzak (1974), is reproduced with stylised drawings of selected stages of wheat, barley and oat plants. Expanded definitions of some of the descriptive phrases are designed to assist the application of the code to agrochemical research, development and use in the UK.

SUMMARY Screening tests exposed varietal differences in the tolerance of winter wheat to high doses of the wild oat herbicides difenzoquat and diclofop-methyl. Subsequent yield trials at recommended and higher doses confirmed the sensitivity of Score and Sportsman to difenzoquat and showed Atou, Bouquet and Hobbit to be less tolerant than some other varieties. In most varieties, earlier spraying proved safer than treatment at or beyond the beginning of jointing. Varietal differences with diclofop-methyl were smaller and inconsistent. Crops damage from these two herbicides was more severe in another experiment the following season, in which isoproturon at double the recommended dose also caused severe damage but flamprop-methyl was fairly well tolerated by all varieties.

SUMMARY Winter wheat varieties were treated with the wild-oat herbicides difenzoquat and diclofop-methyl at several growth stages in a series of four field experiments. High rates of difenzoquat damaged the winter wheat varieties Bouquet, Sportsman, Hobbit and Maris Huntsman but not Hustler. Treatment of the sensitive varieties during tillering stimulated excessive tiller production, resulting in more ears with fewer and smaller grains than on the unsprayed controls; later applications reduced the number of grains and severely depressed yield. In contrast, the early applications of diclofop-methyl, during tillering, were more damaging than the later ones. Bouquet was more tolerant of diclofop-methyl than were the other varieties tested.

Summary: The tolerance by winter wheat of two types of herbicide was examined in field experiments over 3 years. When overdosed or sprayed late, an ioxynil + mecoprop mixture had a greater margin of safety to the crop than mixtures containing dicamba or 2,3,6-TBA. Herbicide mixtures containing MCPA, applied before the leaf sheaths of the crop began to extend in the spring caused ear deformities. Spraying dicamba mixtures when the crop was jointing resulted in narrowed ears and shrivelled grain, In one experiment the latter effect was produced by a dicamba mixture, at twice the recommended dose, when sprayed on any of ten dates, covering crop development stages from 6-leaves through to jointing. Varieties differed in their tolerance of the dicamba mixtures; Maris Ranger was most sensitive but part of this difference could have been due to differences in the stage of development of the varieties at the time of spraying. Resume: Comparaison de la resistance du ble d'hiver a des melanges d'herbicides contenant du dicamha, du 2,3,6-TBA ou de rioxynil La reesistance du bie d'hiver a deux types d'herbicides a ete examinee dans des essais au champ poursuivis pendant trois ans. Lorsqu'il y a eu surdosage ou traitement tardif, un melange ioxynil + mecoprop a fait preuve d'une marge de securite plus grande vis-a-vis de la culture que les melanges contenant du dicamba ou du 2,3,6-TBA. Le melange d'herbicides contenant du MCPA, applique avant que le degainement des feuilles de la cereale ne commence a se produire au printemps, a provoque des deformations de l'epi. l'application de melanges contenant du dicamba lorsque la cereale etait en cours de montaison a provoque une reduction de la largeur des epis et l'apparition de grains rides. Dans une experience, l'effet le plus tardif a ete provoque par un melange contenant du dicamba, au double de la dose recommandee, lorsque le traitement a ete effectueaňimporte laquelle des dix dates comprises entre les stades de developpement 6 feuilles et la montaison. Les varietes ont manifeste des resistances differentes aux melanges contenant du dicamba, la variete‘Maris Ranger’s’ est revelee plus sensible, mais une partie de cette difference pourrait etre due a l'ecart entre les stades de developpement atteints par les diverses varietes au moment du traitement. Zusammenfassung Ein Vergleich der Vertraglichkeit von Winterweizen gegenuber Herbizidmischungen die Dicamba, 2,i,6-TBA oder Ioxynil enthalten In dreijahrigen Feldversuchen wurde die Vertraglichkeit von Winterweizen gegenuber Herbiziden untersucht. Bei uberdosierungen oder spater Anwendung hatte eine Mischung von Ioxynil + Mecoprop eine grossere Sicherheitsspanne gegenuber der Kultur als Mischunger die Dieamba oder 2,3,6-TBA enthielten. Herbizidmischungen mit MCPA verursachten Ahrendeformationen, wenn sie vor der Bestockung angewendet wurden. Spritzungen von Dicambamischungen zum Zcitpunkt des Erscheinens der Halmknoten fuhrten zu schmalen Ahren und Schrumpfkorn. In einem Versuch kam es zur Bildung von Schrumpfkorn, wenn Dicambamischungen mit doppelter Aufwandmenge zu irgenundeinem von zehn Anwendungszeitpunkten zwischen dem 6-Blattstadium und dem Erscheinen der Halmknoten eingesetzt wurden. Es bestanden Sortenunterschiede in der Empfindlichkeit gegenuber Dicambamischungen, wobei die Sorte Maris Ranger am empfindlichsten war. Diese Unterschiede konnten aber auch darauf zuruckzufuhren sein, dass die Sorten zum Behandlungstermin verschieden weit entwickelt waren.

SUMMARY Three commercial herbicides, at the rates normally recommended for selective weed control in cereal crops, deformed the roots of spring wheat plants grown in sand culture. Affected roots produced large numbers of short swollen lateral branches which later grew on to form tassel-like bundles of side roots. Only the mecoprop and MCPA components of the mixtures were responsible for the deformities; ioxynil and dicamba had no effect. Mecoprop applied to the rooting medium severely deformed the roots but foliar application also resulted in some abnormalities. The effects of the herbicides on root and shoot dry weights were not correlated with their deformative effects.

SUMMARY The development of several varieties of winter wheat {Triticum aestivum) in early spring was studied in order to relate the progress of apical differentiation to easily measured external characters and so provide a guide to the correct timing of herbicide applications. Leaf sheath lengths were more closely related to apical development than were tiller or leaf numbers. Spikelet differentiation occurred when the longest sheaths were c. 5 cm tall. Application of a growth regulator herbicide before this stage of development caused ear deformities in the crop at harvest. A measure of leaf sheath length might, therefore, replace the ambiguous criteria presently used to judge the stages of winter wheat most tolerant of herbicides.

SUMMARY The decimal code for the growth stages of cereals devised by Zadoks, Chang & Konzak (1974) is reproduced here with expanded definitions of some of the descriptive phrases and stylised drawings of selected stages of wheat, barley and oat plants.