Effect of planting dates on the Yield and Control of major Insect Pests of Soybean (Glycine max (L) Merril) in Southeastern Nigeria

Abstract

The effect of planting dates on the yield and control of major insect pests of soybean were studied in the 1995 and 1996 planting seasons at Umudike, Southeastern Nigeria. The incidence of the defoliators, Monolepta duplicata Sahl and Ootheca mutabilis Linnaeus in all the planting dates were earlier (2 weeks after planting, 2WAP) up to 8WAP. However, the stink bugs, Nezara viridula Linnaeus and Aspavia armigera Fabricius were found infesting soybean pods from 8WAP to 14 WAP. The peak populations of the defoliators and stinkbugs were recorded at 4WAP and 10WAP, respectively. The crop planted on August 20 had a significantly (P<0.05) higher incidence of the defoliators and stinkbugs than in other planting dates, with soybean planted on July 21 being the least infested. Seed yield was significantly (P<0.05) higher on soybean planted on July 21 than in other planting dates. Hence, seed yield reductions of 30.3% and 28.8% were obtained from crops planted on August 20, when compared with the crop planted on July 21, in 1995 and 1996, respectively. This indicates that soybean could be planted in July, especially within the second and third week to reduce the level of yield loss mainly caused by stinkbugs and defoliators.


[IJARD Vol.3 2002: 121-126]