Affiliation:
1. Research scholar, Division of Acarology, Dept. of Zoology, University of Calicut, Kerala, Pin: 673635, India
2. Professor, Division of Acarology, Dept. of Zoology, University of Calicut, India
Abstract
Tetranychus neocaledonicus, the commonly called vegetable spider mite is a highly polyphagous pest, infesting over 500 species of economic plants. The species has been categorized as a major pest, inducing considerable feeding damage on vegetables, fruit crops, medicinal plants, ornamentals, plantation crops etc. The present study was concentrated to assess the predatory potential of a phytoseiid predator, Neoseiulus longispinosus on the different life stages (egg, larva, nymphs and adults) of T. neocaledonicus under laboratory conditions. Separate experimental set ups were prepared with leaf arena of mulberry plants and known numbers of different life stages of the pest mite were maintained on individual leaf arena. For evaluating the predatory potential, adult females of N. longispinosus were introduced on to the individual leaf discs in the arenas and observations were made under a stereomicroscope to record the response of the predator to the individual life stage of the pest mite. The number of prey stages consumed by the predator on individual leaf arena was recorded for a time interval of 24 hrs and the rate of consumption on individual prey instar was calculated. Except at the time of oviposition, the adult predator was found to make active prey searching movement randomly, in and around the prey patches. By sensing the prey through successive contacts with the first pair of legs and pedipalps, the predator initiated feeding actively, and sucked out the entire fluid content with its mouth parts. The adult predator showed a specific preference to feed on the egg stage of the prey mite while the predator nymph exhibited preference to the nymphal stages of the prey. A decreasing sequence in the order egg > larva > nymphs> adult was recorded in the feeding preference of the adult predator towards life stages of the prey mite and the per cent consumption on egg, larva, nymphs and adult female stages was 48.4, 29.9, 26.6 and 9.3 %, respectively. However, the feeding preference of the nymphal stage of the predator showed a slight deviation in the order nymph > larva > adult > egg and the mean rates of consumption were 31.3, 22, 11.2 and 10.3 %, respectively. Data gathered on consumption rates of the predator upon statistical analysis revealed a significant variation towards different stages of T. neocaledonicus, thereby establishing a specific preference to prey eggs by the predator.