Limitations of allometry, morphometry, and fluctuating asymmetry in detecting environmental stress caused by lead soil contamination in aphids under field conditions

ABSTRACT One of the tools used to investigate the influence of environmental contaminants and other stresses on the development of organisms is the analysis of morphometric traits used to detect changes in growth and size patterns. To evaluate the effects of the heavy metal lead (Pb) present in experimentally contaminated soil on the morphometric traits of the aphid Brevicoryne brassicae (L.) reared on cultivated Brassica oleracea L. (var. acephala), we analyzed three different metrics: morphometry, allometry, and fluctuating asymmetry (FA). Additionally, we aimed to assess the effectiveness of these analyses in detecting environmental stress. We cultivated kale plants in soil contaminated with the maximum allowable limit of Pb for local soils in Brazil, and the colonization of plants by aphids occurred naturally under field conditions. After collection, we photographed and measured the antennae, tibiae, and total body length of aphids from the control and contaminated treatments. We observed no significant differences in the allometry and morphometric analysis, and the presence of the contaminant did not result in any observed FA. The study demonstrated that the morphometric trait analyses employed were not effective in detecting environmental stress resulting from field exposure of aphids to Pb in soil, since these insects suffered a reduction in their population density in the presence of Pb, as indicated in our previous findings. This result diverges from those found in studies conducted under laboratory conditions. We discussed mechanisms of metal accumulation, detoxification in aphids, and population aspects in natural conditions.

Comparison of Insecticidal Efficacy of Commonly Used TCM Pesticides and Preliminary Research on Compatibility / 中国中医药信息杂志

Objective To lay the foundation of new botanical pesticides by screening the insecticidal efficacy of 10 commonly used TCM pesticides.Methods Slide immersion method, trace intravenous drip method and insect body dipping method were respectively used to measure contact action of water extract and ethanol extract of the 10 commonly used TCM pesticides toTeranychus cinnbarinus,Brevicoryne brassicaeandMythimna separate, with herbal extracts to three kinds of insect pests of corrected mortality as observation indexes,Results Alcohol extracts for three kinds of insect pests were found to have contact action, and water extracts had no obvious effect. The Stemonae Radix alcohol extract had obvious contact action on three kinds of insect pests, and corrected mortality rates were 78.7%, 85.9%, and 96.7%, respectively; ethanol extracts of Angled Bittersweet, Sophorae Flavescentis Radix, Xanthii Fructus and Kansui Radix showed good contact action to Teranychus cinnbarinus,. The volume ratio of compatibility among Angled Bittersweet, Sophorae Flavescentis Radix, Xanthii Fructus and Kansui Radix was 2:1:1.5:1.5:1.5:1.5. The insecticidal activity to Teranychus cinnbarinus, was stronger than extracts of single herbs, and corrected mortality was 96.5%. Alcohol extracts of Stellera, hellebore, white mustard seed, and Xanthii Fructus showed good contact action toBrevicoryne brassicae. When the volume ratio of compatibility among Xanthii Fructus, Stemonae Radix, Stellera, and hellebore was 1:1.5:2:2, the activity toBrevicoryne brassicae increased. and corrected mortality was 93.1%.Conclusion The insecticidal activity will be enhanced after TCM extracts are under compatibility.

Host quality of different aphid species for rearing Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae)

This study aimed to evaluate the quality of the aphid Myzus persicae (Sulzer), Lipaphis erysimi (Kaltenbach) and Brevicoryne brassicae (L.) as hosts for the parasitoid Diaeretiella rapae (McIntosh). Parasitization by D. rapae was higher on M. persicae than on L. erysimi and B. brassicae. The time of development of D. rapae from egg to mummy or egg to adult male or female were shorter on M. persicae than on L. erysimi and B. brassicae. Moreover, D. rapae showed no significant differences in the emergence rate, sex ratio and longevity when reared on the three aphid species. Myzus persicae was the largest aphid host, with B. brassicae and L. erysimi being of intermediate and of small size, respectively. Diaeretiella rapae reared on M. persicae was larger than when reared on L. erysimi and B. brassicae, and females of D. rapae were significantly larger than males on M. persicae, but males of D. rapae were larger than females when reared on L. erysimi. No difference in size was detected between males and females in parasitoids reared on B. brassicae. Among the aphid species studied, M. persicae was found to be the most suitable to D. rapae.