The study was carried out in the 1991 and 1992 growing seasons, in Cruz Alta, Rio Grande do Sul State. The objective was to evaluate the infestation levels of Diloboderus abderus Sturm, 1826 (Coleoptera: Melolonthidae) on black oats (Avena strigosa L.), flax (Linum usitatissimum L.), corn (Zea mays L.) and sunflower (Helianthus annuus L.) under no-tillage. Increasing number of larvae/m² decreased plant population, plant biomass and yield. Control levels were different among the four crops species. Results of the insect damage suggested the control level of 12 larvae/m² in flax, 10 larvae/m² in black oats, 0.5 larva/m² in corn and 0.4 larva/m² in sunflower as indicator for these crops seed treatment with insecticides.
Insecta; white grubs; control; damaged plants; no-tillage
