Mortality of stored-food beetle larvae exposed to a controlled atmosphere enriched with nitrogen and containing above-minimum levels of oxygen

Insect pests of stored foodstuffs can cause different types of damage. The larval stage is often the chief culprit, causing serious damage to food commodities while being the most resistant to hypoxic treatments. Knowledge of the response to treatment during each development stage is necessary for pest management programs. This research aimed to evaluate the possibility of using a nitrogen controlled atmosphere as an alternative to biocide treatments against larvae of five important species of stored-food beetles (Coleoptera), and to improve the effects of hypoxia at above-minimum oxygen levels (O2 > 1%), with changing temperatures and relative humidity levels, given that several studies have shown that lowering the relative humidity and increasing the temperature improves the effectiveness of controlled atmosphere treatments. The species tested were Sitophilus granarius (Linnaeus), Oryzaephilus surinamensis (Linnaeus), Stegobium paniceum (Linnaeus), Trogoderma inclusum LeConte and Tribolium confusum Jacquelin du Val. Larvae were exposed to atmospheres containing low percentages of oxygen (3%, 5%), at four different relative humidities (15%, 35%, 55%, 75%) and two different temperatures (23°C, 30°C) for 7 days. Total mortality was achieved in very few cases, and only under the most unfavorable conditions of the lowest levels of relative humidity and oxygen content. Results varied from species to species, so it is evident that the efficacy of treatment by controlled atmosphere is species-dependent.