Effect of non-ionizing radiation (UVC) on the development of Trogoderma granarium Everts

Abstract

Various instars of khapra beetle Trogoderma granarium were exposed to ultra-violet rays (UVC) to assess their effect on each instar and their potential in breaking the developmental cycle of the khapra beetle. Eggs aged zero (recently laid), 24 and 48 h were exposed to UVC at a radiation intensity of 31.4±0.02 W m −2. Doses equivalent to 3 min (56.52 J cm −2), 8 min (150.72 J cm −2), and 12 min (226.08 J cm −2) resulted in death of all eggs, with a hatch of 96.6% in the control. Mortality of UVC-irradiated larvae increased proportionally with increase in UVC dose, while, for each dose, mortality was inversely related to age of larvae at irradiation. Thus, at a UVC dose of 56.52 J cm −2, larval mortality was 98.3%, 93.3% and 83.3% and adult emergence was 1.7%, 6.7% and 11.7% for 1–9, 10–18 and 19–27 day-old larvae, respectively. Similar effects were observed for UVC doses 150.72 and 226.08 J cm −2 with an increase in the overall mortality of larvae and a decrease in adult emergence. Effect of irradiation of 0, 24 and 48 h-old pupae with doses of UVC, was inversely related to age of pupae at irradiation. Thus, at 56.52 J cm −2, mortality as pupae was 91.7%, 71.7% and 73.3% and adult emergence was 0%, 3.3% and 1.7% for 0, 24 and 48 h-old pupae, respectively. Premature emergence of deformed adultoids was 25% when 24 and 48 h-old pupae were irradiated with the above dose. At a dose of 225.08 52 J cm −2 there was no adult emergence. Death as pupae was 98.3%, 96.7% and 78.3% and premature emergence was 1.7%, 3.3%, and 21.7% for pupae irradiated at 0, 24 and 48 h-old, respectively.