Abstract
An assay was designed to evaluate the efficacy of each entomopathogenic fungus, Beauveria bassiana, and diatomaceous (DE) and their combinations at concentrations of 1 × 106 and 1 × 108 conidia kg−1 of wheat and 200 and 400 ppm, respectively, on the red flour beetle, Tribolium castaneum (Herbst) (Tenebrionidae: Coleoptera), infesting wheat. Percent mortality of T. castaneum was recorded after 7, 14, and 21 days. Percent mycosis on dead cadavers was assessed after 21 days. Alive adults were removed from plastic jars after 21 days and kept for the next 60 days to assess the progeny production. The results indicated that the highest concentrations of B. bassiana and DE in their combinations were more effective for the virulence and progeny suppression of T. castaneum. Maximum mean percent mortality (88.13%) was recorded by B. bassiana (1 × 108 conidia kg−1 of wheat) and DE (400 ppm) in their combination after a 21-day exposure interval, while a minimum percent mean mortality (10.00%) was recorded by B. bassiana (1 × 106 conidia kg−1 of wheat) alone. The maximum percent mycosis (78.89%) on dead cadavers was recorded at a low concentration rate (1 × 106 conidia/kg) of B. bassiana. Mean progeny adult emergence was the highest (62.67 adults) at the low concentration of B. bassiana alone. Present studies showed that B. bassiana and DE are more effective in combination against T. castaneum on wheat as both substances are advantageous.
Highlights
The red flour beetle, Tribolium castaneum (Herbst) (Tenebrionidae: Coleoptera), is among the most destructive insect pests of stored products all around the world (Mahroof and Hagstrum 2012)
Insect culture Adults of T. castaneum were obtained from the culture that reared in the laboratory on wheat flour at 28 ± 2 °C and 65–75% R.H
The mycosis data were recorded from the dead cadavers of T. castaneum that were collected from each treatment upon mortality assay termination
Summary
The red flour beetle, Tribolium castaneum (Herbst) (Tenebrionidae: Coleoptera), is among the most destructive insect pests of stored products all around the world (Mahroof and Hagstrum 2012). The efficacy of DE often varies with the formulations, treatment methodology, treated commodity, and other factors (Athanassiou et al 2007 and 2008) Both DE and EPF as grain protectants have different mechanisms of action and affect the insect cuticle, so their use in combination has been proposed by scientists as means of minimizing the applied doses (Akbar et al 2004). Akbar et al (2004) testified that the blend of Beauveria bassiana with the diatomaceous earth had a synergistic effect and better results against the larvae of T. castaneum Since both substances EPF and DE persist on the grains, it appears that such a mixture may have a certain gain as a durable and long-term protectant. In addition to parental adult mortality, the rate of mycosis and progeny production of T. castaneum on the treated kernels was evaluated
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