Impact of neonicotinoid seed treatment of cotton on the cotton leafhopper,Amrasca devastans(Hemiptera: Cicadellidae), and its natural enemies

Abstract

BACKGROUND Neonicotinoid seed treatments suppress populations of pest insects efficiently and can enhance crop growth, but they may have negative effects on beneficial arthropods. We evaluated the effects of either imidacloprid or thiamethoxam on the abundances of a sucking pest, the cotton leafhopper (Amrasca devastans), and its arthropod predators under field conditions. We also evaluated the impact of seed treatment on transgenic cotton plant growth, with pests and natural enemies present or absent. RESULTS Imidacloprid and thiamethoxam reduced pest abundance, with greater effects when dosages were higher. Treatment at recommended doses delayed the pest in reaching the economic damage threshold by around 10–15 days (thiamethoxam) and 20 days (imidacloprid). Recommended doses also enhanced plant growth under all tested conditions; growth is affected directly as well as via pest suppression. Neonicotinoid applications reduced abundance of beneficial arthropods, with lower populations after higher doses, but negative effects of imidacloprid were not apparent unless the manufacturer‐recommended dose was exceeded. CONCLUSION Imidacloprid applied at the recommended dose of 5 g kg−1 seed is effective against A. devastans and appears to be safer than thiamethoxam for natural enemies, and also enhances plant growth directly. We caution, however, that possible sublethal negative effects on individual beneficial arthropods were not evaluated. © 2015 Society of Chemical Industry

Variation in susceptibility and selection for resistance to imidacloprid and thiamethoxam in Mediterranean populations of Orius laevigatus

“…Similarly, in a field trail using seed treatment of cotton, thiamethoxam had a greater suppressive effect than imidacloprid on Orius sp. populations (Saeed et al, 2015). The effects of these neonicotinoids on other Orius spp.…”

Effects of clothianidin‐treated seed on the arthropod community in a mid‐Atlantic no‐till corn agroecosystem

“…Contrary to the sticky card data, visual counts of leafhoppers on plants were significantly higher in the insecticide treated plots. Since these sucking insects are susceptible to neonicotinoids, it is possible that they were sub‐lethally intoxicated, which could have reduced their mobility and increased the chances of being counted during visual plant inspections . Like thrips, leafhoppers rarely reach damaging levels on corn in the mid‐Atlantic US.…”

“…Since these sucking insects are susceptible to neonicotinoids, 58,60 it is possible that they were sub-lethally intoxicated, which could have reduced their mobility and increased the chances of being counted during visual plant inspections. 61 Like thrips, leafhoppers rarely reach damaging levels on corn in the mid-Atlantic US. Other herbivores, including corn leaf aphids, corn blotch leafminers, corn flea beetles, and several species of plant bugs, were significantly reduced by 28 to 55% in the clothianidin-seed treated plots.…”

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 2: impacts on organisms and ecosystems

“…Thus, cotton plants grown from seeds treated with thiamethoxam at the recommended doses (3 g/kg) reduced the populations of natural enemies of the cotton leafhopper by about 35%, in particular those of Chrysoperla sp., Orius sp., and spiders, whereas cotton plants grown from seeds treated with imidacloprid (5 g/kg) did not lead to significant reductions (i.e., < 10%) of the same species (Saeed et al 2016). Trials in South Dakota demonstrated the effectiveness of seed treatments of thiamethoxam and imidacloprid, whether alone or in combination with foliar sprays of beta-cyflutrin, for controlling aphids.…”

“…However, it is important to note that sublethal effects were not evaluated in the study (Saeed et al 2016). Uhl et al (2015) studied trophic interactions in a threelevel food chain mesocosm: wild strawberry Fragaria vesca, wood cricket Nemobius sylvestris, and nursery web spider Pisaura mirabilis.…”