Biological activity of two new pyrrole derivatives against stored-product species: influence of temperature and relative humidity

Abstract

Members of the pyrrole group are likely to have interesting properties that merit additional investigation as insecticides at the post-harvest stages of agricultural commodities. In the present work, the insecticidal effect of two new pyrrole derivatives, ethyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3i) and isopropyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3k) were studied as stored-wheat protectants against two major stored-product insect species, the confused flour beetle, Tribolium confusum Jaquelin du Val adults and larvae and the Mediterranean flour moth, Ephestia kuehniella Zeller larvae at different doses (0.1, 1 and 10 ppm), exposure intervals (7, 14 and 21 days), temperatures (20, 25 and 30°C) and relative humidity (55 and 75%) levels. For T. confusum adults, in the case of the pyrrole derivative 3i, mortality was low and it did not exceed 32.2% in wheat treated with 10 ppm 3i at 30°C and 55% relative humidity. Progeny production was very low (<1 individual/vial) in all combinations of 55% relative humidity, including control. In the case of the pyrrole derivative 3k, mortality reached 67.8% at 30°C and 55% relative humidity in wheat treated with 10 ppm after 21 days of exposure. Progeny production was low in all tested combinations (≤0.7 individuals/vial) of 55% relative humidity, including control. For T. confusum larvae, in the case of the pyrrole derivative 3i, at the highest dose, mortality was 82.2% at 25°C and 55% relative humidity whereas in the case of 3k it reached 77.8% at the same combination. In contrast, mortality at 75% relative humidity remained very low and did not exceed 13.3%. For E. kuehniella larvae, the highest mortalities, 44.4 and 63.3%, were observed in 10 ppm at 25°C and 55% relative humidity for both pyrrole derivatives. The compounds tested here have a certain insecticidal effect, but this effect is moderated by the exposure, the target species, the temperature and the relative humidity.

Developing a Hazomalania voyronii Essential Oil Nanoemulsion for the Eco-Friendly Management of Tribolium confusum, Tribolium castaneum and Tenebrio molitor Larvae and Adults on Stored Wheat

“…Spinetoram and spinosad [45] had high larval mortality reaching 98.9% in a mixture of the two insecticides after 14 days on treated wheat kernels, while the adult mortality reached 67.8% for the same mixture after 14 days on treated wheat kernels. Similarly, studying the effectiveness of eight pyrrole derivatives, a better larvicide than adulticide action has been detected [46][47][48].…”

Etofenprox as grain protectant for the management of five key stored-product insect pests

“…To obtain first instar larvae, T. confusum or E. kuehniella eggs were collected from flour by using a sieve of 60 mesh (250 micron, W.S. Tyler, Mentor, OH, USA), then placed in chambers at 25 °C and 65% RH and the newly hatched larvae (24 h old) were collected (Boukouvala et al 2016).…”

“…One other important abiotic factor that influences the efficacy of insecticidal formulations is RH. For instance, a storage environment with elevated RH levels may increase the degradation of the insecticide or may reduce the contact between the insects and the toxic agent (Boukouvala et al 2016). For diatomaceous earths (DEs), noted that increase of RH from 55 to 75% reduced the effectiveness of the Brazilian DE Keepdry ® against R. dominica and S. oryzae adults.…”

Sensitivity of polyphagous (Plodia interpunctella) and stenophagous (Ephestia kuehniella) storage moths to residual insecticides: effect of formulation and larval age

“…In this regard, very abundant studies are available for Coleoptera (Athanassiou et al ., 2008; Kavallieratos et al ., 2011), Psocoptera (Guedes et al ., 2008; Athanassiou et al ., 2014), and Acarids (Hubert et al ., 2005; Stara et al ., 2011, 2014). There are also several studies demonstrating residual activity of insecticides as grain protectants against Pyralid moths; E. kuehniella (Pozidi‐Metaxa & Athanassiou, 2013; Boukouvala et al ., 2016); P. interpunctella (Arthur, 1989, 1994, 1995, 1996; Fang et al ., 2002). Yue et al .…”