Effects of hypoxia on acoustic activity of two stored-product pests, adult emergence and grain quality

Authors: NJOROGE, A. - Purdue University; Mankin, Richard; SMITH, B - Purdue University; BARIBUTSA, D - Purdue University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2019
Publication Date: 5/14/2019
Citation: Njoroge, A.W., Mankin, R.W., Smith, B., Baributsa, D. 2019. Effects of hypoxia on acoustic activity of two stored-product pests, adult emergence and grain quality. Journal of Economic Entomology. 112(4):1989-1996. https://doi.org/10.1093/jee/toz110.
DOI: https://doi.org/10.1093/jee/toz110

Interpretive Summary: Hermetic storage and other anoxia treatments are becoming useful as low-cost methods for protecting stored products from insect pests, particularly in sub-Saharan Africa. Scientists at Purdue University in collaboration with a scientist at USDA-ARS, Center for Medical, Agricultural and Veterinary Entomology in Gainesville, Florida, conducted studies of the timing of mortality of rice weevil and cowpea weevil after exposure to low levels of oxygen utilizing acoustic detection as evidence of mortality. Under modified atmospheres containing less than 1% oxygen, the pest insects were not able to survive longer than 4 days. This information is useful for to inform farmers and warehouse managers how long it takes to cause mortality after low-oxygen treatments and considers the potential effects of ending treatments early.

Technical Abstract: Modified atmospheres such as hermetic storage are widely used for the control of stored grain insect pests. To improve their effectiveness, there is need to better understand insect responses to low-oxygen environments. Adult Callosobruchus maculatus on cowpea and Sitophilus oryzae on wheat were exposed to hypoxia treatments consisting of 1, 3 and 5% oxygen levels for 14 d. Acoustic activity was monitored during the experiment, and insect mortality and grain quality were examined immediately after the hypoxia treatments. Adult emergence was assessed 45 d post-treatment. All three hypoxia treatments eliminated acoustic activity of both species within 4 d. There was neither insect survival for both species nor significant grain damage immediately after 14 d exposure to hypoxia treatments. No adult insects emerged 45 d post-exposure on grains maintained at 1% oxygen level for 14 d. However, at 3% and 5% oxygen levels, there were eggs on cowpea, holes in wheat, and emerging adults for both insect species 45 d post-exposure. Although insect activity ceased within 4 d when hypoxia was maintained below 5%, there is need to explore exposure beyond 14 d for 3 and 5% oxygen levels, to ensure to avoid potential adult emergence from eggs and other insect life stages post-treatments. Maintaining 3 to 5% hypoxia conditions for a longer duration would ensure no sufficient oxygen is available for progeny development.