Stability of Cacopsylla pyricola (Hemiptera: Psyllidae) Populations in Pacific Northwest Pear Orchards Managed with Long-Term Mating Disruption for Cydia pomonella (Lepidoptera: Tortricidae).

Kaushalya Amarasekare,Peter Shearer

doi:10.3390/insects8040105

Kaushalya Amarasekare, Peter Shearer

Open Access

https://doi.org/10.3390/insects8040105

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Abstract

This study focused on conservation biological control of pear psylla, Cacopsylla pyricola, in the Pacific Northwest, USA. We hypothesized that insecticides applied against the primary insect pest, codling moth Cydia pomonella, negatively impact natural enemies of pear psylla, thus causing outbreaks of this secondary pest. Hence, the objective of this study was to understand how codling moth management influences the abundance of pear psylla and its natural enemy complex in pear orchards managed under long-term codling moth mating disruption programs. We conducted this study within a pear orchard that had previously been under seasonal mating disruption for codling moth for eight years. We replicated two treatments, “natural enemy disrupt” (application of two combination sprays of spinetoram plus chlorantraniliprole timed against first-generation codling moth) and “natural enemy non-disrupt” four times in the orchard. Field sampling of psylla and natural enemies (i.e., lacewings, coccinellids, spiders, Campylomma verbasci, syrphid flies, earwigs) revealed that pear psylla populations remained well below treatment thresholds all season despite the reduced abundance of key pear psylla natural enemies in the natural enemy disrupt plots compared with the non-disrupt treatment. We speculate that pear psylla are difficult to disrupt when pear orchards are under long-term codling moth disruption.

Highlights

Pear psylla, Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae), is one of the most important insect pests of pears (Pyrus sp. (Rosaceae)) in Washington, Oregon and other pear-growing states in the USA
We were unable to induce outbreaks of pear psylla following insecticide applications that were designed to interfere with conservation biological control of pear psylla [5]
In part, that previous reductions in insecticide applications applied for codling moth management in an area-wide codling moth mating disruption program caused these orchards to have several years of low levels of pear psylla, which carried over during the two years we conducted that study

Summary

Introduction

Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae), is one of the most important insect pests of pears (Pyrus sp. (Rosaceae)) in Washington, Oregon and other pear-growing states in the USA. Cacopsylla pyricola (Foerster) (Hemiptera: Psyllidae), is one of the most important insect pests of pears (Rosaceae)) in Washington, Oregon and other pear-growing states in the USA. Pear psylla can rapidly build up and damage both fruits and trees [1]. Outbreak levels of pear psylla often result in downgraded fruit and/or increased harvest and postharvest costs of pears. Pear psylla is considered as a current and chronic issue in pear crop production and its management is a high priority in these orchard systems [2]. Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) is another key insect pest of pears. Most pear pest management programs in the USA rely heavily on multiple, targeted insecticide applications for codling moth [3].

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