Search

Corcyra cephalonica (S.) commonly called rice meal moth or rice moth is an important stored-product pest all over the world. The larvae feed on broken grains of cereal, pulses, oilseeds, dried fruits, nuts, and spices by constructing the silken webs. The excessive use of pesticides and chemical compounds used for the management of this pest led to the development of resistance and also harms the environment. To overcome these problems in the recent years, green nanotechnology has emerged as a promising tool for pest control. The present study of the experiment was conducted at the Centre for Nanotechnology Laboratory, UAS, Raichur. The green nanoparticles of zinc, copper, and silica were biosynthesized from Spinach leaves; tulasi leaves and paddy husk respectively, and these nanoparticles were characterized by Zetasizer, UV–Vis spectroscopy, X-ray diffraction (XRD), and Scanning electron microscope (SEM). The biophysical characterization revealed that the zinc, copper, and silica nanoparticle has Spindle, spherical, and agglomerated spindle-shaped with a mean particle size of 87.94, 84.15 and 23.65 d. nm respectively. The pesticidal effects of these green nanoparticles were used as stored product insect protectants compared to malathion as a standard reference. Data obtained from different concentrations (250, 500, 750, 1000, 1250, and 1500 ppm) of zinc, copper, and silica green nanoparticles indicated that the increase in concentration and exposure period resulted in increase in larval mortality, pupal mortality and adult deformity. Among the different concentrations, 1500 ppm of zinc, copper, and silica nanoparticles proved to be superior. Similarly, of the different nanoparticles, silica nanoparticles excelled followed by zinc and copper nanoparticles.

The biological hypothesis that female parasitoids can adjust their fecundity schedule according to host availability, and tradeoff longevity with fecundity was tested in a thelytokous oophagous parasitoid, Trichogramma brasiliensis Ashmead (Trichogrammatidae: Hymenoptera) parasitising the rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae). The tradeoff between early and late reproduction revealed that this wasp was able to exploit practically all available hosts during the first day or first few days of adult life. During spells of host unavailability, it was able to adjust its fecundity schedule accordingly. There was a negative relationship between survival and reproduction. Adult females survived shorter (10 days) when an unlimited supply of hosts was present, but longer (16 days) when no hosts were provided. These observations suggest the potential suitability of T. brasiliensis for inundative releases even in conditions of fluctuating host availability.

Incorporated in this paper were the results of a study made on the quantitative variation of total carbohydrate, protein and lipid in whole body, fat body and integument of the larval and pupal developmental stages in rice moth, Corcyra cephalonica (St.) a storage grain pest. All three macromolecules referred to in case of whole body, exhibited a progressively decreasing trend from larva to pupa. In fat body total carbohydrate and protein contents were more in pupa than larva, while in integument the said nutrients were less in pupa than larva, showing the reverse results. The lowering down of the nutrients’ level under stress caused by pyrethrum (a botanical insecticide) was also observed. The physiological and statistical significance of these findings was discussed.

Eggs (1,2 and 3-day-old), larvae (early and late) and 4-day-old pupae of the rice moth, Corcyra cephalonica (Stainton), were treated with 60Co gamma-radiation at doses from 0 to 100 krads. Evaluation of moth radiosensitivity by the survival of treated eggs, larvae and pupae led to the following sequence of stages in order of increasing radioresistance: for the eggs, 1, 2 and 3-day-old; for larvae and pupae, early larvae (5 days after hatching), late larvae (5 days before pupation) and 4-day-old pupae. Twenty five kiloradians was found to be the most likely unit for disinfestation by radiation of C. cephalonica.

Implantation of additional corpora allata (CA) into the last instar larvae of Corcyra cephalonica resulted in the production of extra larval instars, larval-pupal intermediates and adultoid larvae. Moths metamorphosed from the extra larval instars were externally normal. The juvenoid, hydroprene, when given to last instar larvae, prolonged the larval life span, induced extra larval moult and the moths metamorphosed from such larvae were larvoid adults. Extra pupal instars were produced when this juvenoid was applied to early pupae. Moths obtained after pupal treatment were adultoids. Another juvenoid, methoprene, prolonged larval life and produced giant larvae without extra moult. Incompletely moulted extra larval instars, larval-pupal intermediates and adultoid larvae were formed. Moths obtained after both larval and pupal treatments were externally normal. The percentage of moths obtained after the application of both the juvenoids was small. The antiallatotropin, precocene II, had no creditable effect on the duration of larval or pupal life. Application to both larvae and pupae, pretreated with hydroprene, largely minimized the hydroprene-induced effects. Pupal treatment, however, produced pupal-imaginal intermediates. The moths obtained from precocene-treated larvae or pupae, with or without juvenoid pretreatment, were externally normal.

The sensitivity of 1-day-old eggs of Corcyra cephalonica Staint., to ionizing radiation has been investigated in view of a possible future application of sterile-insect technique to the control of this species. Further, the irradiation effects on subsequent developmental stages were evaluated. A dose of 5 krad prevented hatching of eggs, while a dose of 4 krad was the highest dose that allowed an adequate percentage of the irradiated eggs (28.23) to complete development to the adult stage. While the mating percentage and mating frequency of resultant adults appeared to be unaffected, the percentage of multiple mating was variable and no clear pattern emerged. Egg production and fertility of P, adults was decreased significantly and all effects of the treatment were more severe for pairings of both sexes resulting from irradiated eggs than pairings of either sex with unirradiated partners. However, the results show that a dose of irradiation low enough to permit adequate numbers of adults to develop from irradiated eggs (4 krad) is insufficient to induce high levels of sterility. Therefore, irradiation of eggs for mass production of either sterile or partially sterile adults was found not to be feasible.