engleski

Optimal Timing and Efficacy of Ecologically Acceptable Insecticides in the European Corn Borer (Ostrinia Nibilalis Hubn., Lepidoptera : Pyralidae) Control

Ostrinia nubilalis Hübn., European Corn Borer (ECB) is one of the most important pest in Croatia. In spite of its importance, chemical control is often carried out only in maize for seed production or in sweet corn. When pesticides are applied following problems could appear: how to detect optimal application time ; how to choose the most acceptable and most effective insecticide and how to apply it. The use of pheromone traps is the most common and most practical method for establishing proper application time. There are 2 strains of ECB pheromone traps, E and Z with different attractiveness on various ECB populations. Ecologically acceptable insecticides suitable for ECB control (especially in sweet corn production) belong to the three main groups: microbiological insecticides (Bacillus thuringiensis var. kurstaki- B.t.k.), insect growth regulators (IGR) and naturalytes (spinosad). In order to establish the most attractive pheromone product and optimal time for applying insecticides and to establish the efficacy of different insecticides against ECB, a three year investigation was carried out in period 2002-2004 in corn fields in central part of Croatia. Three types of pheromones produced by « ; ; Isagro» ; ; E, Z and E/Z were set up in the field at the begining of the moth eclosion. The insecticides were sprayed 14-20 days after the maximal daily catch in 2002 and 2003. In 2004, three different trials were set up, one trial with one early treatment, one with one late treatment and one with 2 treatments. In the trails B.t.k., IGR, spinosad and classical chemical insecticides were applyed. The percent of infested plants was established by visual method before and after the spraying. Ten days after the insecticides application 10-20 plants per plot were dissected and the % of infested plants, number of tunnels per plant and number of larvae in the sample was established. Intensity of attack was calculated. Based on the collected data efficacy was calculated either by using Henderson- Tilton or Abbot formula. The significant difference in the number of moths on different types of pheromone trap was recorded in 2002 and 2003 while in 2004 the total number of caught moths was too low for accurate conclusions. Pheromone trap, type E was the most attractive in two years of investigation. Efficacy of insecticides depended on the proper application timing. Very high efficacy (between 80 and 96%) was obtained with spinosad applied in the doses of 0.2 and 0.3 l/ha. Spinosad is very suitable for IPM programs, especially for sweet corn production because of very short safe period. Efficacy between 70 and 80% was reached with application of B.t.k. in the doses of 0.75 and 1.0 kg/ha. Efficacy of classical chemical insecticides depended on the year and insecticide. OP insecticides and pyrethroids gave moderate to good results and imidacloprid didn't reach significant efficacy. IGR insecticides resulted with moderate efficacy what implicates the need for earlier application timing. The results shows that one treatment on proper (earlier) time resulted with the same efficacy as two treatments. One treatment conducted too late resulted in very poor efficacy.

pheromones; european corn borer; control

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