Factors influencing the combined efficacy of microbial insecticides and inert dusts for the control of Trogoderma granarium

Combined action of various inert dusts (diatomaceous earth DE and zeolite) and microbial insecticides (abamectin and spinetoram) was evaluated against Trogoderma granarium Everts at Grain Research Training and Storage Management Cell, department of Entomology, University of Agriculture, Faisalabad, Pakistan during the year 2018-19. Doses were 750 ppm in case of inert dusts and 1 ppm in case of insecticides. Efficacy was checked on wheat, rice and maize at three different temperatures (15, 25 and 35 degrees C) and two relative humidity levels (55 and 75%). Mortality data was taken 1, 3, 5 and 7 days after treatments. Factorial under Completely Randomized Design was used for analysis. In all combinations tested, complete mortality (100%) of the insects was achieved at 35 degrees C + 55% R.H. after 14 days of exposure. But in general, mortality was higher at increased temperature and decreased R.H. With an increase in exposure period, mortality was also increased. Wheat was most susceptible as compared to rice and maize regarding the mortality of insects except in cases of 100% mortality. Results suggested that both DEs and zeolites can be combined with insecticides in order to achieve complete control of this specie but certain factors like dose, temperature, R.H., commodity and exposure time are important in affecting their efficacies which should be kept in mind for the integrated control of this insect. This is first report in which zeolite is used in combination with insecticides against Trogoderma granarium.

Automated summary

The study evaluated the combined action of diatomaceous earth and zeolite with abamectin and spinetoram against Trogoderma granarium. Complete mortality (100%) of insects was achieved at 35 degrees C and 55% R.H. after 14 days of exposure. Results indicated that higher temperature and reduced R.H. led to increased mortality rates.