Influence of Planting Date and Spacing on the Infestation and Damage to Two Soybean Varieties by
Insect Pests at Samaru, Zaria
ADAMU, R.S., DIKE, M.C., ONU, I. and OGUNLANA, M.O.
ABSTRACT: The influence of planting date and spacing on the level of infestation and damage to soybean by the major insect pests was investigated at Samaru during the 1994 and 1995 wet seasons. The major insect pests of soybean were Ootheca mutabilis Salh, pygomorpha vignaudi Guer, Nezara viridula L., Agonoscelis versicolor Fab and Halydicoris ventralis Dall. Planting date and spacing had no significant effect on percentage defoliation by the insects. The highest percentage defoliations recorded were 13.8 and 15% for 1994 and 1995 respectively, These were below the economic threshold level of 30%. The number of sucking bugs per plot, percentage pod damage per plant, 100 seed weight and seed damage index were not significantly affected by planting date and spacing. There were no significant differences (P < 0.05) between the varieties in terms of insect infestation and damage in both years. However, planting date significantly affects seed yield per hectare. The first plantings had significantly (P < 0.05) higher seed yield than the other subsequent plantings .