Crysoperla carnea

Plant volatiles mediate orientation and plant preference by
the predator Chrysoperla carnea Stephens (Neuroptera: Chrysopidae)

Abstract

Control of the red spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae), using the predator Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) is common in integrated pest management programs of vegetable crops such as eggplant (Solanummelongena), okra (Abelmoschus esculents), and peppers (Capsicum annum), but not on tomato (Lycopersicum esculentum). A study was conducted to test whether plant volatiles mediate the adult orientation behavior of C. carnea on these four crops. The olfactory response of C. carnea to volatiles from several vegetable host plants of its prey, T. ludeni, was investigated in a Y-tube olfactometer.

Volatilesemitted by eggplant, okra, and peppers elicited a positive behavioral response from both C. carnea males and females in an olfactometer. Volatiles emitted by mite-infested plants elicited stronger behavioral responses in C. carnea males and females than uninfested healthy plants. Odors from mechanically damaged plants and plants with mite damage only attracted the predators.
However, odorsemanating from mites alone did not evoke any response from C. carnea. In contrast, C. carnea did not respond to volatiles from uninfested healthy tomato plants or mites with or without damaged plants or mechanically damaged tomato plants.

Therefore, the results suggest that odors from eggplant, okra, and peppers are attractive to C. carnea, while odors from tomato are not. _ 2002 Elsevier Science(USA). All rights reserved.
Keywords: Chrysoperla carnea; Neuroptera; Chrysopidae; Eggplant; Okra; Pepper; Tomato; Tetranychus ludeni; Orientation; Host finding; Y-tube
olfactometer; Plant volatiles

1. Introduction

The red spider mite, Tetranychus ludeni Zacher (Acari: Tetranychidae), is one of the most destructive pests of vegetable crops in the sub-tropics (ChannaBasavanna, 1971). Thismite feeds on black bean, Phaseolus vulgaris L. (Morros and Aponte, 1994), cowpea, Vigna unguiculata Savi. (Singh, 1995), mulberry, Morus alba L. (Narayanaswamy et al., 1996), sponge gourd, Luffa acutangula Roxb. (Koel et al., 1997), Crotalaria anagyroides HBK (Sannigrahi and Talukdar, 1998), and can cause substantial losses. Eggplant and okra are often damaged by high densities of mites (Reddy andBaskaran, 1991). Nymphs feed on leaves from inside the web initially, moving out onto the leaf surface as they develop. Foliar feeding causes white stippling and bronzing of the leaves and veins which results in leaf dessification and leaf loss. Sometimes, leaves become coppery and then brittle as a result of feeding by T. ludeni (Ansari and Pawar, 1992). Adults often spin silken threads overleaves, forming profuse webbing, which provides a suitable microhabitat for the replenishment of the colony (Sumangala and Haq, 1994). Their rapid developmental rate and high reproductive potential enable them to reach damaging population levels very rapidly under growing conditions. T. ludeni populations which occur throughout the year in the sub-tropics become higher during April and reach peaknumbers from May to July (Puttaswamy and ChannaBasavanna, 1980). However, population increases are associated with periods of low rainfall and relative humidity and high temperatures.
Green lacewings are considered to be one of the most effective generalist predators (New, 1975). They feed on Lepidoptera eggs and young larvae, aphids, spider mites, scales, psylla, mealybugs, whiteflies, thrips,leafhoppers, and other soft-bodied prey (Canard et al., 1984; New, 1988). Lacewings are highly predacious and cannibalistic as larvae (Nordlund, 1993). Larvae insert their mandibles into their prey, inject digestive enzymes, and suck out body fluids (Olkowski et al., 1991) while adults mostly feed on nectar, pollen, and honeydew and some are predatory (Coppel and Mertins, 1977). Past research has...