Effect of Fungal Colonization of Wheat Grains with Fusarium spp. on Food Choice, Weight Gain and Mortality of Meal Beetle Larvae (Tenebrio molitor)

Abstract

Species of Fusarium have significant agro-economical and human health-related impact by infecting diverse crop plants and synthesizing diverse mycotoxins. Here, we investigated interactions of grain-feeding Tenebrio molitor larvae with four grain-colonizing Fusarium species on wheat kernels. Since numerous metabolites produced by Fusarium spp. are toxic to insects, we tested the hypothesis that the insect senses and avoids Fusarium-colonized grains. We found that only kernels colonized with F. avenaceum or Beauveria bassiana (an insect-pathogenic fungal control) were avoided by the larvae as expected. Kernels colonized with F. proliferatum, F. poae or F. culmorum attracted T. molitor larvae significantly more than control kernels. The avoidance/preference correlated with larval feeding behaviors and weight gain. Interestingly, larvae that had consumed F. proliferatum- or F. poae-colonized kernels had similar survival rates as control. Larvae fed on F. culmorum-, F. avenaceum- or B. bassiana-colonized kernels had elevated mortality rates. HPLC analyses confirmed the following mycotoxins produced by the fungal strains on the kernels: fumonisins, enniatins and beauvericin by F. proliferatum, enniatins and beauvericin by F. poae, enniatins by F. avenaceum, and deoxynivalenol and zearalenone by F. culmorum. Our results indicate that T. molitor larvae have the ability to sense potential survival threats of kernels colonized with F. avenaceum or B. bassiana, but not with F. culmorum. Volatiles potentially along with gustatory cues produced by these fungi may represent survival threat signals for the larvae resulting in their avoidance. Although F. proliferatum or F. poae produced fumonisins, enniatins and beauvericin during kernel colonization, the larvae were able to use those kernels as diet without exhibiting increased mortality. Consumption of F. avenaceum-colonized kernels, however, increased larval mortality; these kernels had higher enniatin levels than F. proliferatum or F. poae-colonized ones suggesting that T. molitor can tolerate or metabolize those toxins.

Food Safety Issues Related to Uses of Insects for Feeds and Foods

“…In the study by Guo et al. (), larvae of the mealworm T. molitor were reared on wheat kernels infected with four Fusarium species. Several mycotoxins were measured in the kernels and larvae, however, the concentrations in the larvae were generally much lower than in the kernels.…”

Volatile-organic compound changes in rose twigs consequent to infection with rose powdery mildew

“…The olfactory system of an insect allows the insect to detect and identify VOCs and to behave in certain ways in response (De Moraes et al, 1998;Liu et al, 2017). Microorganisms such as fungi can produce VOCs or indirectly induce a plant to produce VOCs, and both types of VOCs can attract or repel insects (Guo et al, 2014). It is important to understand PMIs between fungi and insects to improve integrated pest management programs and to allow new genetic varieties of plants to be developed (Franco et al, 2017).…”

Efficacy of alpha-cypermethrin and thiamethoxam against Trogoderma granarium Everts (Coleoptera: Dermestidae) and Tenebrio molitor L. (Coleoptera: Tenebrionidae) on concrete

“…Another species of major importance is the yellow mealworm beetle Tenebrio molitor L. (Coleoptera: Tenebrionidae) (Aitken, 1975;Guo et al, 2014). Despite the fact that this species is very common in warehouses and food processing facilities, the data for the efficacy of insecticides against T. molitor are disproportionally few.…”