Monitoring and efficacy of selected insecticides for European corn borer (Ostrinia nubilalis Hubn., Lepidoptera: Crambidae) control

Abstract

The European corn borer (ECB), Ostrinia nubilalis (Hΰbner) (Lepidoptera: Crambidae), is the major arthropod pest of corn in Croatia. However, chemical control is carried out only in maize for seed production, and in sweet corn. A 3-year investigation was carried out in corn fields in northwest Croatia to establish the most attractive pheromone lure for ECB monitoring, the optimal timing of insecticide applications, and the efficacy of selected insecticides against ECB. During each of the 3 years, the pheromone lures E, Z and E/Z («Isagro») were evaluated in the field from May to July. Insecticides were sprayed 14–20 days after the maximal capture in 2002 and 2003. In 2004, three different trials were set up: one trial with one early treatment (when corn was in the R49 development stage according to the extended BBCH scale); one with one late treatment (when corn was in the R65 development stage according to the BBCH scale); and one with two treatments in both stages. In the trials studying Bacillus thuringiensis var. kurstaki (B.t.k.), insect growth regulators (IGR), spinosad and classical chemical insecticides were applied. Pheromone lure E was the most attractive for monitoring ECB flights throughout 2 years of investigation. Insecticide efficacy depended on application timing. The insecticides most suitable for integrated pest management (IPM) programs, including spinosad, B.t.k. and IGR, resulted in high (spinosad) to moderate (B.t.k.) efficacy. The efficacy of IGRs indicates the need for earlier application. The efficacy of chemical insecticides depended on the year and the insecticide. The organophosphate (OP) insecticides and pyrethroids gave moderate to good results; imidacloprid did not provide significant efficacy. One application of all insecticides based on proper (early) timing resulted in the same efficacy as two applications of the same insecticides.