Deterioration in Stored Wheat Infested with Tribolium audax or Tribolium confusum (Coleoptera: Tenebrionidae)

Abstract

Adults of Tribolium audax Halstead or Tribolium confusum Jacquelin du Val were placed in bottles of wheat plus ground wheat (23:1, wt:wt) to determine effects of the insects on grain deterioration over 20 wk at 30°C and 70% RH. T. audax increased in numbers to =125 insects per 130 g wheat compared with 500 insects per 130 g wheat for T. confusum by 20 wk. Seed germination decreased to 5% in the T. confusum treatment, 15% in the T. audax treatment, and 25% in the whole wheat controls by 20 wk. T. confusum damaged up to 39% of the wheat germs and 18% of the endosperm during the study, whereas T. audax damaged =15 and 7% of the germs and endosperm, respectively. Seed moisture content remained between 13.8 and 14.8% in all treatments. Fat acidity values of the wheat in all treatments at 30°C increased with time, but there were no significant differences between treatments. The field fungus Alternaria sp. decreased in all treatments and virtually disappeared by 5 wk. The storage fungi Penicillium spp. and Aspergillus glaucus group generally infected fewer seeds in insect treatments than in wheat controls; the lower infection rate probably resulted from insect consumption of molds and the release of quinones by the Tribolium. T. audax is unlikely to cause severe damage to wheat in granaries because of its slow rate of development and low rate of increase compared with that of T. confusum .