Compound models describing the relationship between dosage of (Z)- or (E)-isomers of 1,3-dichloropropene and hatching behaviour of Globodera rostochiensis

Abstract

Abstract Batches of increasing numbers of Globodera rostochiensis cysts were exposed to a range of concentrations of the (E)- and (Z)-isomers of 1,3-dichloropropene. The cysts were of identical origin. Temperature during treatment was 10 degrees C, humidity 100%, and time of exposure 8 days. The integrals of concentration time products (CT) created were 0, 3, 7, 14, 31, 60, 125, 242, and 437 mug/ml day for the (E)-isomer and 0, 3, 16, 59, 240, and 419 mug/ml day for the (Z)-isomer. Survival was estimated by hatching tests 1.5, 3, and 7 months after treatment. The relationship between dosage of (E)-isomer and numbers of hatchable nematodes followed a log-logistic equation at all hatching dates. Hatchability, and therefore lethal dosages, increased at the later dates of the hatching tests: 7 months after treatment, practically all treated nematodes had recovered and hatchability of treated and untreated nematodes was the same. A log-logistic relationship was also found for dosage (Z)-isomer and numbers of hatchable nematodes 1.5 months after treatment. When hatching tests of nematodes treated with the (Z)-isomer were made 3 and 7 months after treatment, the results were better explained by a compound model assuming two independent log-logistic effects, one stimulating hatch at low dosages and one reducing hatch at all dosages. Only the (Z)-isomer of 1,3-dichloropropene was effective as a nematicide. Modeles composites decrivant la relation entre dose des isomeres (Z) ou (E) du 1,3-dichloropropene et le comportement d'eclosion de Globodera rostochiensis - Des lots comprenant un nombre croissant de kystes de Globodera rostochiensis ont ete exposes a une serie de concentrations des isomeres (Z) ou (E) du 1,3-dichloropropene. Ces kystes avaient la meme origine. Le traitement, d'une duree de 8 jours, etait effectue a 10 degrees C et a une humidite relative de 100%. Les integrales des produits concentration / temps (CT) ainsi creees etaient de 0, 3, 7, 14, 31, 60, 125, 242 et 437 mug/ml jours pour l'isomere (E) et de 0, 3, 16, 59, 240 et 419 pour l'isomere (Z). La survie a ete estimee par des tests d'eclosion apres 1, 5, 3 et 7 mois. La relation entre dose de l'isomere (E) et le nombre de nematodes eclos suit une equation log-logistique pour toutes les durees. La capacite d'eclosion, et donc les doses letales, augmentent si les tests d'eclosion sont differes. Sept mois apres le traitement, pratiquement tous les nematodes ont recupere et l'eclosion est identique chez les nematodes traites et non traites. Une relation log-logistique a egalement ete mise en evidence entre les doses de l'isomere (Z) et le nombre de nematodes eclos apres 1,5 mois. Lorsque les tests d'eclosion sur les nematodes traites avec l'isomere (Z) etaient differes jusqu'a 3 et 7 mois apres le traitement, les resultats s'expliquaient mieux a l'aide d'un modele composite prenant en compte deux effets log-logistiques independants, l'un stimulant l'eclosion aux faibles doses, l'autre reduisant celle-ci pour toutes les doses. Seul l'isomere (Z) du 1,3-dichloropropene est efficace en tant que nematicide.