Agrochemicals

Field-evolved resistance of Helicoverpa zea to crops expressing Cry insecticidal proteins from Bacillus thuringiensis (Bt) is widespread across the United States. To comparatively evaluate physiological factors associated with Bt susceptibility, we analyzed two laboratory strains (Benzon and SIMRU) and one field colony obtained from a commercial corn field near Pickens, Arkansas. Biochemical assays of larval midgut extracts showed that Pickens exhibited significantly altered activities of chymotrypsin-like proteases, aminopeptidase N (APN), and alkaline phosphatase (ALP) compared with the SIMRU or Benzon colonies, with differences varying by larval instar. In contrast, trypsin-like protease activities did not differ significantly among the three colonies. Gene expression analyses of ten serine protease genes and seven candidate Cry receptor genes (including cadherin, ATP-binding cassette family C2, ALP, and four APN genes) revealed significant transcriptional differences in the Pickens relative to the lab colonies. Collectively, these results suggest that chymotrypsin-like proteases may play an important role in the activation of Cry toxins in H. zea. Altered chymotrypsin and APN activities, together with differential gene expressions in the Pickens population, likely contribute to reduced Bt susceptibility. The biochemical and molecular differences provide insight into potential physiological factors underlying reduced Bt susceptibility and may inform future Bt resistance monitoring and management strategies.

Drosophila suzukii (Diptera) is a polyphagous fly responsible for a huge loss in production of thin-skinned berries, usually controlled with low-selective synthetic pesticides, which can be toxic for biodiversity and human health. Biorational control of D. suzukii is challenging, despite many known lethal compounds, since most experiments happen in laboratory conditions, and agroecosystems include complex biotic and abiotic variables. Nanoencapsulation rises as an efficient alternative for optimizing pesticide development by protecting active ingredients and increasing selectivity. This review aimed to gather recent (over the last 5 years) research about plant-derived insecticides with the potential to control D. suzukii, examining their toxicity mechanisms and exposure methods, and to identify research gaps and perspectives, especially for nanoproducts. These efforts resulted in the selection of 31 articles, evaluating lethality and behavioral modulation caused by plant-based compounds, which exerted mainly attraction, repellency, and oviposition deterrence. Most studies were carried out under laboratory conditions, mostly testing plants from the Lamiaceae and Asteraceae botanical families, indicating essential oils as potential short-life pesticides against every life stage of D. suzukii, although their physicochemical instability limits field application. There are few studies addressing nano-pesticides for controlling D. suzukii, and these data contribute to botanical prospection for pesticide compounds and point to the development of plant-based nano-pesticides for controlling D. suzukii as a research gap with potential to enable field trials.

The fungicide Imazalil (IMZ) is widely used to maintain the freshness of fruits and vegetables after harvest. Despite its widespread use, the neurotoxic effects of IMZ remain poorly studied. Thus, in this work, we aimed to investigate the effects of subacute IMZ exposure on memory and learning, as well as on cholinesterase (ChE) activity, in orally exposed rats. To do so, Wistar rats were exposed to doses corresponding to 1/8, 1/4, and 1/2 of the LD50 of IMZ. Each dose was divided into four equal parts and administered once daily for four consecutive days, while behavioral performance was assessed using the Barnes Maze. On day 5, we measured ChE activity in the hippocampus and serum. The enzymatic activity assays demonstrated a dose-dependent decrease in both cholinesterase activities at 1/4 LD50 of IMZ. In addition, rats in the control group exhibited a typical learning curve in the Barnes maze, characterized by reduced latency and fewer attempts to locate the escape box from the first session (S1) to the final session (S4). The typical learning curve was prevented by a 1/4 LD50 treatment. Additionally, this dose prevented an increase in spatial navigation strategy use, observed in the control group (S1 vs. S4). To our knowledge, these results proved that IMZ inhibits in vivo the activity of both brain and serum ChEs, and exhibits evidence of learning and memory impairments, suggesting that IMZ has neurotoxic effects in rats, probably mediated by alterations in the cholinergic system.