Azadirachtin, a triterpenoid substance from the neem tree, Azadirachta indica A. Juss., Meliaceae, was evaluated for its antifeedant and insecticidal properties to the European corn borer Ostrinia nubilalis Hübner. The 50% protective concentration for larval feeding on treated corn disks (PC50) was 3.5 ppm for neonate larvae and 24 ppm for third instar larvae. Azadirachtin severely reduced larval growth at 1 and 10 ppm in a meridic diet and eventually caused 100% mortality at 10 ppm and 90% at 1 ppm. At 0.1 ppm azadirachtin showed no significant effect on larvae but altered the sex ratio in favor of male moths during adult emergence and arrested oviposition of female moths. Nutritional indices for naive and habituated third instar larvae suggested that reduction of growth was due to toxicity as shown by a lowered efficiency of conversion in the azadirachtin treated groups, rather than changes in digestibility. No clear evidence of tolerance was observed in the habituated group. The data suggest that at 10 ppm azadirachtin is an effective botanical insecticide for control of O. nubilalis. RÉSUMÉ Propriétés anti‐appètantes et insecticides de l'azadirachtine envers la pyrale du maïs, Ostrinia nubilalis On a examiné les propriétés anti‐appétantes et insecticides de l'azadirachtine, une substance triterpénoïde provenant d'Azadirachta indica envers la pyrale du maïs Ostrinia nubilalis. La concentration effective pour causer 50% d'inhibition de l'alimentation larvaire (PC50) sur des disques foliaires a été de 3.5 ppm pour les larves de premier stade et de 24 μg/8 pour celle de troisième stade. L'azadirachtine a sévèrement réduit la croissance larvaire à des concentrations de 1 et 10 ppm dans une diète méridique et, éventuellement, a causé 100% de mortalité à 10 ppm et 90% à 1 ppm. A 0.1 ppm l'azadirachtine n'a pas eu d'effet significatif sur les larves maïs a modifié l'indice de masculinité en faveur des mâles au moment de l'émergence et a empêché l'oviposition chez les femelles. Les indices nutritionnels pour les larves naïves de troisième âge et celles ayant subi une accoutumance suggèrent que la réduction de croissance est le résultat d'une intoxication comme le démontre une efficacité réduite de transformation chez les groupes traités à l'azadirachtine, plutôt que des changements de digestibilité. Il n'y a pas d'évidence claire de tolérance dans le groupe ayant subi l'accoutumance. Les résultats suggèrent qu'à 10 ppm l'azadirachtine est un insecticide botanique efficace envers O. nubilalis.

No abstract

In 1955 and 1956, while sampling corn stalks for larvae of the European corn borer in experimental plots at St. Jean, the author noted 23 adults of Coleomegilla maculata lengi Timb. and two adults of Coccinella novemnotata Hbst. that were parasitized and attached to the upper surfaces of corn leaves. Each beetle was astride a freshly formed cocoon and was held by a network of silk; many were alive when found. The parasite cocoons and the hosts were placed in closed petri dishesfor observation. The parasites that emerged were identified by Dr. W. R. M. Mason, Entomology Division, Ottawa,as Perilitus coccinellae (Schrank) (= Dinocampus terminatus (Nees).

This is a report on a program to sample the European corn borer, Ostrinia nubilalis (Hbn.), with the object of obtaining reliable statistics for life tables (see e.g. Morris, 1955; LeRoux and Reimer, 1959).Basic studies on factors determining abundance of the European corn borer are few, some of the most notable having been carried out by Barber (1926), Huber et al. (1928), Thompson and Parker (1928), Stirrett (1938), Vance (1943), Baker et al. (1949), Bigger and Petty (1953), Everett et al. (1958) and Chiang and Hodson (1959). None of these studies was a thorough study of mortality factors in development of the European corn borer from endemic to epidemic levels. A number of specific factors known to be important in the epidemiology of this species have been investigated by Arbuthnot (1949), Neiswander (1952), Goleman (1954), Chiang and Holdaway (1955), and Chiang (1959), and the application of biometric techniques to the sampling of corn borer populations has been studied by Beard (1943), McGuire (1954), and Bankcroft and Brindley (1956). None of the latter authors have, however, investigated sampling techniques relating to the development of life tables for this species.

Des études génétiques portant sur la résistance du maïs-grain (Zea mays) aux attaques de la kabatiellose causée par le Kabatiella zeae ont consisté en des essais de croisements diallèles 8x8. Chez les huit lignées utilisées, l'action additive des gènes semble avoir été déterminante quant à la résistance aux attaques du feuillage. Il y a eu un certain degré de dominance chez quatre groupes de gènes. L'hérédité au sens strict a été évaluée à 75%. La lignée V312 a été la plus résistante à la maladie tandis que les lignées F522, WF9 et L2039 sont apparues sensibles.Genetic studies of resistance to Kabatiella zeae causing eyespot in grain maize (Zea mays) were conducted using an 8 x 8 complete diallel cross. In the eight inbreds used, the additive component appeared to be the most important in determining resistance to eyespot. There appeared to be at least four genes showing some degree of dominance. Narrow-sense heritability was estimated at 75%. Inbred V312 was the most resistant line among the eight lines in this diallel set, whereas F522, WF9 and L2039 appeared to be susceptible