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Effects of Temperature and Host Stage on the Rate of Encapsulation of Eggs and Larvae of Anagyrus Pseudococci (girault) by Its Mealybug Host

Khandakar Shariful Islam
Present Address: Department of Entomology, BAU, Mymensingh, Bangladesh.

Mahbuba Jahan
Present Address: Department of Entomology, BAU, Mymensingh, Bangladesh.

Abstract/ Executive Summary:

Encapsulation or eggs and larvae or the encyrtid parasitoid Anagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae) was investigated in the laboratory by dissecting third instar nymph and adult female mealybug. Pseudococcus affinis (Mask.) (Homoptera: Pseudococcidae). The encapsulation frequency was influenced with the temperature. The percentage or eggs and larvae or the parasitoid . A psdeudococci encapsulated by third instar nymph increased from 81.23% at 18°C to 91.98% at 30°C. With adult mealybugs. the percentage or encapsulation was slightly higher than with third instar and ranged from 84.64% to 95.25% at 18°C and 27°C respectively. At extreme high temperature (33°C) percent encapsulation declined in the adult stage. Size (length) of the capsule increased with higher temperature in both the host stages. Implications or the results arc discussed in relation to the use of A pseudococci in controlling P. affinis.

Keywords: Larvae, Eggs, Mealybug host

Location: The laboratory of Wye College, University of London

Start Date:

End Date:

Program Area: Pest Management

Commodity: Insects

Objectives:

To assesses the ability of P. affinis at different life stage and rearing temperature for successfully encapsulate the eggs and larvae of A. pseudococci.

Methodology:

The experiments were conducted in the laboratory of Wye College, University of London. The culture of the mealybug, P. affinis was established on potato sprouts. The parasitoid A. pseudococci was reared on another mealybug species, Planococcus citri (Risso). The culture of parasitoids .and hosts were maintained at 26 ± 1°C, 50-60% R.H. and 12L: 12D photoperiod. Size of the third instar nymph and adult female was determined. One hundred and fifty mealybugs from each physiological age were separated from the original culture and transferred into the experimental arena, a ventilated plastic sandwich box (17 x 11 x 5 cm) containing a potato tuber with small sprouts. Both the third instar and adult hosts were parasitized separately by releasing 150 female parasitoids of 3-4 days old into the experimental arena for one hour at 27°C. The parasitized hosts were then kept in the incubators at 18, 21, 24, 27, 30 and 33°C with a variation of 0.5°C with 50-60% R.H. and 12L: 12D photoperiods for 6 days after which all the parasitized mealybugs were preserved in 80% ethanol and dissected out in insect saline solution under a microscope and assessed the percentage of completely encapsulated eggs and larvae. Length of capsules at different temperatures in two stages of P. affinis were measured.

Source of Information: Bangladesh J. Agri. 1997,Vol-22: 27-33

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Observation in this study also revealed that some of the eggs of the parasitized mealybugs turned black that might be an effect of parasitism. This is comparable with cassava mealybugs parasitized by Epidillocorsis lopezi (DeSantis). Although the parasitized mealybugs survive by their defence reactions, this change in their own eggs would result in a reduction in progeny production of the host, indirectly contributing to the success of biological control.

Knowledge Management: Journal