گیاه پزشکی (تربیت مدرس)
سال:1400 | دوره:10 | شماره:1 |تعداد مقالات:15

The Greenbug Schizaphis graminum (Rondani), one of the major pests of cereals, overwinter as adults and nymphs in temperate regions. The aphid population increases in early spring as the weather conditions become favorable, but it gradually decreases in mid-June as air temperature rises. Adult aphid colonies were acclimated to measure cold tolerance at 20, 15, 10, 5, and 0 ° C for one week. In contrast, other colonies were acclimated to measure heat tolerance at 20, 25, and 30 ° C for one week and 35 ° C for two days. Then, the lowest temperature resulting in 50% mortality (LLT50) and the highest temperature resulting in 50% mortality (ULT50) of tested populations were defined. Moreover, changes of sugars and polyols were studied at the end of each thermal regime. The lowest LLT50 was-13. 2 ° C at 0 ° C and the highest ULT50 was 40. 1 ° C at 35 ° C. In the cold acclimation condition, glucose was the highest at 0 ° C and reached to 80. 9 μ mol/g f. w. However, in the heat acclimation condition, the mannitol was the highest at 35 ° C and reached to 43. 7 μ mol/g f. w. Findings indicate that high temperatures due to climate change could be a threat to aphid population size and distribution.

The present research was performed to evaluate the bioactivity of Citrullus colocynthis (L. ) and Melia azedarach L. extracts against three major stored grain insect pests including Tribolium castaneum (Herbst), Trogoderma granarium Everts, and Sitophilus granaries (L. ). Toxicity and enzyme inhibition activity of acetylcholinesterase (AChE), α-carboxylesterase (α-CE), β-carboxylesterase (β-CE), acid phosphatases (ACP) and alkaline phosphatases (ALP) in three insect species induced by both plant extracts were evaluated at four different dose rates viz., 5, 10, 15 and 20%. Results showed maximum mortality (34. 29%) in S. granarius with M. azedarach at maximum interaction of time and dilution level. In T. castaneum and T. granarium maximum recorded values for mortality were 30. 87% and 18. 95%, respectively, with extract of M. azedarach. Plant extract of C. colocynthis reported a maximum mortality of 21. 92%, 19. 18% and 16. 89% in T. castaneum, S. granarius and T. granarium, respectively. Findings proved that both plant extracts had decent lethal impacts on tested insect species. Exposure of studied insects to plants extracts also resulted in significant inhibition of AChE, α-CE, β-CE, ACP and ALP. All tested enzymes in three insects were maximally inhibited by plant extract of M. azedarach except α-CE which was slightly more inhibited in S. granarius and ACP which was highly inhibited in T. granarium and S. granarius, by plant extract of C. colocynthis. Outcomes exhibit that plant based extract of M. azedarach is more pronounced in stored grain insect pests and propose the capability of using these plant extracts for safety of stored commodities as a safe substitute for insecticides.