Careful choice of insecticides in integrated pest management strategies against Ostrinia nubilalis (Hübner) in maize conserves Orius spp. in the field

A long-term field experiment was set up in April 2011 at Legnaro, Italy, within the European Project PURE, to evaluate two Integrated Pest Management (IPM) tools against conventional pest management in maize-based cropping systems (MBCS) that involved different crops every year. Three foliar insecticide treatments were applied against Ostrinia nubilalis (Hübner) in 2011 and 2014 when maize was present in the rotation. Lambda-cyhalothrin was applied as the conventional management (CON), while chlorantraniliprole and a biological insecticide containing Bacillus thuringiensis var. kurstaki were tested for IPM1 and IPM2, respectively. The minute pirate bug (Orius spp.) was the most abundant among the beneficial organisms and was considered as the indicator species to evaluate the impact of the insecticide treatments tested. Statistical analysis showed no significant difference in Orius nymphs (N), adults (A) and total population (N + A) before treatments, whereas after treatments Orius was significantly lower in the CON than in IPM in all cases. No differences in Orius population were determined between IPM1 and IPM2. The percentage reduction calculated in total Orius (N + A) after the three insecticide treatments ranged from 91% for CON, 18% for IPM1 to 4% for IPM2. The latter had a significantly higher number of plants broken below the ear, total number of broken plants and damaged ears by O. nubilalis compared to CON and IPM1, but no significant difference was determined between treatments in percentage ear surface damaged, being below 1% in all cases. Treatment with chlorantraniliprole did not affect Orius population confirming its selectivity towards this species, conserved Orius at the same level as B. thuringiensis var. kurstaki and had similar efficacy to the CON against O. nubilalis.