Comparative biological activity of abamectin formulations on root-knot nematodes (Meloidogyne spp.) infecting cucumber plants: in vivo and in vitro.

The root-knot nematodes (Meloidogyne spp.) are considered one of the most destructive diseases in the world. In Egypt, farmers primarily rely on chemical nematicides, which have become costly to control. Currently, abamectin is a bio-based pesticide used as an alternative tool against Meloidogyne spp. on cucumber plants (Cucumis sativus L.). During the current research, four tested abamectin formulations were DIVA (1.8% EW), RIOMECTIN (5% ME), AGRIMEC GOLD (8.4% SC) and ZORO (3.6% EC) compared with two reference nematicides namely, CROP NEMA (5% CS) and TERVIGO (2% SC). The main results showed that, in vitro study elucidated that the most effective formulations of abamectin as a larvicidal were EW with LC50 value of 21.66 µg ml-1. However, in the egg hatching test, the formulations of abamectin SC (2%) and EW were the most effective in reducing egg hatching, with LC50 values of 12.83 and 13.57 µg ml-1. The calculated relative potency values showed diversity depending on the two referenced nematicides. On the other hand, in vivo study, the results indicated that, all tested formulations of abamectin recorded general mean reductions in root galls (23.05-75.23%), egg masses (14.46-65.63%). Moreover, the total population density declined by 39.24-87.08%. Furthermore, the influence of abamectin formulations, in the presence of root-knot nematodes, on the growth of cucumber plants parameters, such as root dry weight, root length, root radius, root surface area, shoot dry weight and shoot height, as well as the content of macro-elements (N, P and K) exhibited varying levels of response.

Contact toxicity and biochemical impact of metaldehyde against the white garden snail Theba pisana (Müller, 1774).

BACKGROUND: Terrestrial snails are one of the most damaging threats to sustainable agriculture. Chemical control using molluscicides is the main approach used to combat these agricultural pests. Metaldehyde is the active ingredient in most snail control products in use. However, its toxicity indices and mode of action have scarcely been investigated. For the first time, we characterized the metaldehyde contact toxicity indices against the white garden snail Theba pisana. The biochemical impact of metaldehyde on acetylcholinesterase (AChE), aspartate aminotransferase (AST) and alanine aminotransferase (ALT), alkaline phosphatase (ALP) and glutathione S-transferase (GST) activities and the lipid peroxidation (LPO) level was investigated. RESULTS: The median lethal dose (LD50 ) values at 24, 48 and 72 h of treatment were 11.33, 8.53, and 6.87 µg g-1 body weight (BW), respectively; while, the median lethal time (LT50 ) values were 88.16, 55.85, and 25.67 h when doses of 6, 8, and 12 µg g-1 BW were applied, respectively. In the snails treated with 2.83 and 5.67 µg g-1 BW (» and ½ LD50 at 24 h of treatment) and 2.13 and 4.27 µg g-1 BW (» and ½ LD50 at 48 h of treatment), higher AChE, GST, AST, ALT, and ALP activities as well as higher levels of LPO were observed compared with that of untreated snails. CONCLUSION: Metaldehyde displayed dose- and time-dependent contact toxicity. The biochemical results suggest that metaldehyde may have neurotoxic and cytotoxic actions in terrestrial snails. Application of metaldehyde in ways that could control pest snails and slugs and reduce its negative impact on the environment are discussed. © 2021 Society of Chemical Industry.