Abstract
Alternative ways to control caterpillar pests and reduce the use of pesticides in apple orchards are in the interest of the environment, farmers and the public. Great tits have already been shown to reduce damage under high caterpillar density when breeding in nest boxes in an experimental apple orchard. We tested whether this reduction also occurs under practical conditions of Integrated Pest Management (IPM), as well as Organic Farming (OF), by setting up an area with nest boxes while leaving a comparable area as a control within 12 commercial orchards. We showed that in IPM orchards, but not in OF orchards, in the areas with breeding great tits, apples had 50% of the caterpillar damage of the control areas. Offering nest boxes to attract insectivorous passerines in orchards can thus lead to more limited pesticide use, thereby adding to the natural biological diversity in an agricultural landscape, while also being economically profitable to the fruit growers.
Highlights
Biological control of pests is becoming increasingly important as an answer to the resistance of harmful insects to pesticides, the adverse public attitudes to pesticides and the increasing restriction of their use due to legislation [1]
In this study we investigated whether great tits can reduce caterpillar damage in commercially managed apple orchards, with either Integrated Pest Management (IPM) or Organic Farming (OF), by measuring damage levels of the apples in areas with and without breeding great tits
There was a significant effect of the presence versus absence of great tits: a significantly lower percentage of apples was damaged in the area with nest boxes compared to the control area in the same orchard (Table S1; repeated measures ANOVA with binominal errors: treatment: x2(1) = 4.71, P = 0.03, orchard type x treatment x2(1) = 3.88, P = 0.049; test without interaction: treatment: x2(1) = 4.03, P = 0.045)
Summary
Biological control of pests is becoming increasingly important as an answer to the resistance of harmful insects to pesticides, the adverse public attitudes to pesticides and the increasing restriction of their use due to legislation [1]. Most of the studies on birds as biological pest control agents do show a reduction in the population size of harmful insect species [review see 3,4,5]. Within the breeding season great tits mainly forage for caterpillars, which is the preferred food for their nestlings [7,8,9,10] Caterpillars in orchards, such as winter moths Operophtera brumata L. and tortricid moths, are key pests [1,2]. These features together suggest that great tits can serve as biological control agents for caterpillars in orchards. The question remains, whether great tits can be effective in reducing damage under commercial management with lower caterpillar densities
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