Importance of naturally occurring predators for pear sucker control


Abstract: The pear psyllids Cacopsylla pyri, (L.) and C. pyricola (Foerster) are the most important pests in pear orchards throughout Europe because they have developed resistance to many insecticides and cannot be reliably managed in modern intensive orchards. Communities of insect predators can naturally regulate populations of these psyllids, but populations are often inadequate for effective biocontrol. Anthocorid predatory bugs, earwigs, ladybirds and spiders are considered to be among the key contributors. Anthocorids largely migrate out of pear orchards in autumn and return after flowering in spring. Spiders predate adult psyllids in their webs or actively hunt on the trees at night and ladybirds react by migrating into orchards when psyllid numbers rise and other food sources are scarce later in the season. Earwigs (Forficula auricularia L.) are less mobile, and overwinter in the soil within the orchard, but populations may decline to very low levels in pear orchards for a variety of reasons including the direct and indirect adverse effects of pesticides and/or lack of food. This paper focuses on 1) the remediation of predators in a pear orchard, 2) the comparison of pear sucker numbers to insecticide spray programmes in 8 orchards and 3) the findings of the first year of a project aimed at identifiying insecticides that are harmful to earwigs in laboratory tests. We conclude that one of the key aspects of pear sucker management in orchards is to avoid the use of pesticides that harm key predators at key stages of the predators’ lifecycle. This research has led to recommendations for pear sucker management with a new emphasis on using only the pesticides safest to important pear sucker predators.

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