Neem Seed for the Management of the Banana Weevil,cosmopolites sordidus germar (coleoptera: curculionidae) and Banana Parasitic Nematode Complex

Abstract

The study was conducted in western Kenya, a prime banana growing area during the period of May 1996 to February 1999. The objectives were to control the banana weevil and parasitic nematodes with neem materials, thereby reducing yield losses and contributing to sustainable banana production.The repellent, antifeedant, ovipositional deterrent, and growth inhibitory effects of powdered neem seed (NSP), kernel (NKP), cake (NC) and neem oil (NO) on Cosmopolites sordidus and its population build-up were studied in the laboratory and outdoors tests at ICIPE's Mbita Point field station (MPFS).In choice tests, 48 h after release, less than 30% of weevils settled under neemtreated banana corms while more than 75% settled under untreated corms. In a feeding test, weevil larvae did not feed or fed little on neern-treated corms. Larvae caused little damage to neem-treated corms, but untreated corms were heavily damaged, indicating a strong repellent and antifeedant effect of neem seed derivatives on C. sordidus.Compared with the untreated control, 3-10 times fewer eggs were laid by female in neem-treated corms. Egg hatchability was less than 25% in neem-treated corms and more than 50% in the control.Neem treatments also inhibited larval growth and development. Forty to 60% of 2nd-instar larvae died in 14 days when confined to neem-treated banana pseudostems; the survivors were small in body size and weighed 4 to 6 times less than those in the control where less than 20% larvae died and adults were recovered.The higher the concentration of neem materials, the higher was the severity of effects.Efficacy of neem materials against the banana weevil and parasitic nematodes was evaluated under controlled pest infestation levels at MPFS. Effective rates,methods and frequency of application of the selected neem materials were determined at MPFS and in farmers' fields, under different levels of soil fertility and pests infestation.In a pot experiment, four weeks after planting, NSP, NKP, or NC was applied at 5g per plant to plants inoculated with 500 nematodes and 5 pairs (females and males)of the banana weevil. Compared with control, 1.5 months after the treatment, neem materials application significantly reduced the nematode population and weevil damage on a par with Furadan applied at 5 g/plant. Similar results _were obtained with the application of neem materials to pared or unpared banana suckers planted in I 00 or 200/ drum's capacity and inoculated with 2000 nematodes and 5 pairs (females and males) of the banana weevil per drum.NSP- or NC-treated unpared suckers supported much fewer nematodes than the pared treated suckers with the same neem products, obviating the need for paring of suckers. NKP and NO applications were toxic to the banana plant and were excluded from further testing.Soil application of powdered NSP or NC against the banana pests was more effective than their application in aqueous forms. Application of NSP or NC at planting time and then at 1, 2, 3, or 4- month intervals to plants grown under controlled pest infestations in drums significantly reduced nematode density and the weevil damage