SIDE-EFFECTS ON SPIDERS OF PLANT PROTECTION PRODUCTS COMMONLY USED DURING SPRING AND AUTUMN IN BELGIAN PEAR PRODUCTION

Pear sucker (Cacopsylla pyri L.) is the most important economic pest in Belgian pear production. Biological control by naturally present predatory bugs Anthocoris sp. can be very successful, although in most cases the numbers of predatory bugs are insufficient in spring and autumn. In this context, the potential of other beneficial arthropods was investigated. Spiders (Araneae) have the potential to buffer pest populations and are abundantly present in spring and autumn in pear orchards. For that reason, two experiments were carried out to examine how spiders can be integrated into pest management. In laboratory and field experiments, plant protection products commonly used in pear growing in spring and autumn were tested on spiders. The laboratory trial showed that deltamethrin (Patriot^®) and spinosad (Tracer^®) have considerable lethal side-effects on late instars of Araniella cucurbitina. Abamectin (Vertimec^®) and emamectin benzoate (Affirm^®) had more limited effects. In the field experiment, deltamethrin, abamectin in combination with an adjuvant, and spinosad turned out to be the most harmful tested products for spiders. There were indications that thiamethoxam is harmless for spiders, whereas it suppresses the pear sucker population.