Chrysoperla Carnea For Control Of Scirtothrips Perseae In California Avocado Orchards

Biological Control 31 (2004) 268–275 www.elsevier.com/locate/ybcon

Evaluation of factors influencing augmentative releases of Chrysoperla carnea for control of Scirtothrips perseae in California avocado orchards
Mark S. Hoddle*, Lindsay Robinson
Department of Entomology, University of California, Riverside, CA 92521, USA Received 30 October 2003; accepted 15 June 2004 Available online 10August 2004

Abstract Weekly releases of Chrysoperla carnea for control of Scirtothrips perseae were evaluated in replicated field plots in two commercial avocado orchards in southern California, USA. Two release techniques and rates commonly employed by commercial pest control advisors who routinely use this generalist predator for S. perseae control were assessed. Release technique one utilized C.carnea eggs glued to paper squares that were stapled to leaves of experimental trees at a rate of 41,000 eggs per ha. Release technique two used a motorized backpack sprayer to apply a dry mixture of lacewing eggs and larvae to trees at a rate of 514,501 per ha. Pest populations were monitored by making bi-weekly population counts of S. perseae larvae and adults on leaves, and adult densities weresimultaneously monitored in each experimental plot with yellow sticky cards. In the laboratory, degree-day accumulation until death of immature C. carnea was determined at temperatures representative of field conditions when predators were provisioned with varying amounts of food or different food types. Preference for S. perseae instars by first, second, and third instar C. carnea was assessed inthe laboratory, and intraguild predation towards larvae and adult females of a co-occurring generalist predatory thrips, Franklinothrips orizabensis, was investigated along with intraspecific predation rates. Both release strategies failed to significantly reduce S. perseae populations in comparison to non-treated control plots. Approximately 35–96% of C. carnea eggs and larvae applied with themotorized sprayer landed on the ground. C. carnea larvae lived for approximately 1–2 days when provisioned with either no food, an avocado leaf or avocado pollen. Longevity was extended to 14–15 days when prey was provided. C. carnea larvae showed no preference for first or second instar S. perseae, all predator instars attacked first instar F. orizabensis, but only second and third instar C. carneamanaged attacks on second instar F. orizabensis larvae. No adult female F. orizabensis were attacked and no attacks by F. orizabensis on C. carnea were recorded. Second instar C. carnea engaged in the highest levels of intraspecific predation. Ó 2004 Published by Elsevier Inc.
Keywords: Degree-days; Franklinothrips orizabensis; Intraspecific predation; Prey preference; Quality control

1.Introduction Avocado thrips, Scirtothrips perseae Nakahara (Thysanoptera: Thripidae), is native to Mexico and Guatemala and is an exotic pest that has been present

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Corresponding author. Fax: 951-827-3086. E-mail address: mark.hoddle@ucr.edu (M.S. Hoddle).

in California (USA) avocado (Persea americana Miller) orchards since 1996 (Hoddle et al., 2002a). Economic analyses have indicated that S.perseae costs the California avocado industry millions of dollars annually due to reduced market value of fruit that results from feeding damage caused by larvae and adult thrips, and associated management expenses to reduce damage to the harvestable commodity (Hoddle et al., 2003). Consequently, research sponsored by the California Avocado

1049-9644/$ - see front matter Ó 2004 Published byElsevier Inc. doi:10.1016/j.biocontrol.2004.06.007

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Commission has focused on identifying control options for S. perseae and evaluating the efficacy and impact optimization of either new or currently employed pest suppression tactics. Three management strategies have been subjected to extensive research and include: (1)...