Individual and combined effects of contact insecticides and high temperatures on Mediterranean flour moth,Ephestia kuehniellaZeller (Lepidoptera: Pyralidae)

Abstract

BACKGROUND Mediterranean flour moth or mill moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) is a common pest of cereals and flour throughout the world. In this study, eggs, third instar larvae, pupae and adults of E. kuehniella were exposed to five elevated temperatures at a range of 45 to 65 °C for 5, 8, 10, 14, 18, 23 and 30 min. The effect of cypermethrin and dichlorvos was assessed on third instar larvae. The larvae were exposed to the insecticides on glass and concrete arenas and their mortality was recorded 24 h after treatment. To determine combination effects, the third instar larvae were transferred into the Petri dishes treated with LC25 (lethal concentration that kills 25%) of each insecticide and exposed to high temperatures for the period of time equal to LTi25 values (time needed for killing 25% of tested insects). RESULTS Exposing the eggs, third instar larvae and adults of E. kuehniella to 55 °C for 30, 18 and 30 min respectively, resulted in 100% mortality. In the pupa, exposure to 65 °C caused 100% mortality after 23 min. Based on the LTe50 values (temperature needed to cause 50% mortality in the tested population), pupa was the most tolerant life stage to the temperatures tested. The LC50 values of cypermethrin and dichlorvos were 423.1 and 2608.5 mg active ingredient (a.i.) L−l on glass, and 2525.0 and 13502.8 mg a.i. L−l on concrete, respectively. The effect of cypermethrin was synergized by high temperatures. CONCLUSION High temperatures, cypermethrin and dichlorvos were effective against E. kuehniella. Exposure to combination of lower doses of cypermethrin and high temperatures at short time intervals may have potential in managing this pest. © 2021 Society of Chemical Industry.

Efficacy of Extreme Temperatures on All Life Stages of the Mediterranean Flour Moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

“…Not surprisingly, we found that exposure to 30 • C did not result in a considerable mortality of the different E. kuehniella life stages, which can be considered expectable given that this temperature is suitable for the development of this species [11,32]. However, the "jump" from 30 to 40 • C resulted in a high mortality, which was close to 100% for eggs and larvae, and 100% for pupae and adults, provided that the exposure is 24 h. Given that the usual target temperature and exposure level for commercial heat treatments is 50 • C [13,22,23], our data show that E. kuehniella is likely to be more susceptible to heat than the other stored product insects, which can be considered in commercial heat treatments.…”

“…The available data for heat under laboratory conditions for E. kuehniella are relatively few and definitely less than those for cold. Sadeghi et al [10] tested the effect of microwave heating on larvae of E. kuehniella and found complete mortality at 900 W for 50 s. In a recent study, Javanshir et al [11] tested different life stages of E. kuehniella at elevated temperatures in combination with two different insecticides (cypermethrin and dichlorvos) and found that susceptibility to high temperatures can be influenced by life stage. In that study, the authors reported that pupa may be the most heat-tolerant life stage [32].…”

“…this species, several measures have been taken in different facilities and commodities such as contact insecticides [3], impregnated nets [4], mating disruption [5], trapping [2,6], cold treatment [7,8] and heat treatment [9,10]. For instance, Javanshir et al [11] tested the effect of cypermethrin and dichlorvos with high temperatures that range from 45 to 65 • C and found that the combination of a low concentration of both insecticides with high temperatures can be effective for the control of eggs, third instar larvae and adults of E. kuehniella. Moreover, Sieminska et al [5] tested mating disruption for a long duration of monitoring E. kuehniella and found that the reduction was lower in the first year than in the second.…”