SOME ASPECTS OF THE NUTRITIONAL AND CHEMICAL CONTROL OF TRIBOLIUM CASTANEUM (HERBST) (COLEOPTERA : TENEBRIONIDAE)
The present investigation deals with the effects of cereal flours (wheat, barley and rice) on the red flour beetle, Tribolium castaneum (Herbst). It was found that cereal flours had significant effects on the growth of T. castaneum producing lighter 10-day old larvae and the heaviest male mature larvae on rice flour. Cereal flour produced heavier pupae and rice flour produced the heaviest male adults and barley flour produced the heaviest female adults in comparison to controls grown on the wheat – yeast medium.
The cereal flour did not significantly lengthened the larval and pupal periods, except for barley flour. Barley flour produced the most deleterious effects on the growth and development of the insect.
The lowest percentage of adults was obtained on control flour and the highest on the cereal feed. Thus cereal flours significantly increased the number of active feeding stages and thereby increased the rate of infestation of food materials.
The cereal flours also significantly reduced the fecundity of T. castaneum. The fecundity of the female was observed in the order: rice < barley < wheat. The highest fertility was observed for eggs resulting from females reared on the control and the lowest fertility was observed for the eggs resulting from females reared on barley. This would obviously have a significantly check on the population of this pest.
This seems to be promising for controlling the pest through nutritional regulation.
The effect of the pyrethreoid, lambda-cyhalothrin on larvae and pupae of the red flour beetle, Tribolium castaneum (Herbst) was investigated. The investigation was designed into two phases : the first of which was to evaluate the effect of lambda-cyhalothrin on the pupal periods and the second was to assess the mortality potential of the pyrethroid on the 5-day and 10-day old larvae from different foods. The results are summarized in the following paragraphs:
In the present investigation it was found that lambda-cyhalotrhin produced no significant effect on pupal periods of T. castaneum.
The contact toxicity effects of lambda-cyhalothrin investigated with 24h exposure to larvae of T. castaneum. Showed should that contact toxicity of the insecticide was significantly influenced by both the insecticidal concentration and varieties of cereals.
The LC50 of Lambda cyhalothrin was recorded as 0.12 µg/ cm2 , 0.67 µg/ cm2 and 1.14 µg/ cm2 respectively for wheat, barley and rice for 5 day old larvae at 24h post exposure.
On the other hand the LC50 of lambda-cyhalothrin was recorded as 0.85 µg/ cm2, 0.66 µg/ cm2 and 0.65 µg/ cm2 respectively for wheat, barley and rice for 10 day old larvae after 24h post treatment.
Lambda-cyhalothrin was more effective on 5-day old larvae than on 10-day old larvae of T. castaneum
Various types of deformities were observed in insects surviving insecticidal treatments, and no adults emerged from the concentrations used in the present work. Lambda-cyhalothrin seems to be effective in controlling T. castaneum.