Translocation and translaminar bioavailability of two neonicotinoid insecticides after foliar application to cabbage and cotton

Abstract

A laboratory study was undertaken to investigate the leaf systemic properties and the translaminar aphicidal activity of two commercialised neonicotinoid (chloronicotinyl) insecticides. For that purpose [14C]imidacloprid was subjected to uptake and translocation studies in cabbage and cotton after foliar application. Foliar penetration and short-term translocation patterns of imidacloprid were similar in both plant species. Nevertheless imidacloprid penetrated twice as much into cabbage leaves as it did into cotton leaves. It showed a comparable translaminar behaviour and was entirely translocated acropetally, indicating its well-known xylem mobility. The translaminar and acropetal movement of imidacloprid and acetamiprid were quantified by simple laboratory bioassays using the green peach aphid, Myzus persicae (Sulzer), and the cotton aphid, Aphis gossypii (Glover), as typical homopteran pests for cabbage and cotton, respectively. A single dose (7.5 micrograms AI per leaf) applied to the upper leaf surface of cabbage and cotton was tested against aphids feeding on the lower leaf surface both close to and distant from the site of application 1, 5 and 12 days after treatment. The translaminar residual activity of imidacloprid on cabbage leaves was superior to that of acetamiprid, whereas its translaminar efficacy against A gossypii on cotton was inferior to that of acetamiprid. However, oral ingestion bioassays using an artificial double membrane feeding system revealed no significant differences in intrinsic activity between the two neonicotinoids tested.

Uptake and persistence of pesticides in plants: Measurements and model estimates for imidacloprid after foliar and soil application

“…The low octanol/water partition coefficient furthermore indicates low adsorption behaviour of the active ingredient into organic matter. Nauen et al [17] and Buchholz and Nauen [33] reported that imidacloprid can be penetrated through plant cuticles via diffusion, but in contrary to our experiments, the active ingredient was applied using surfactants or emulsifiers (leaf wetting agents) favouring penetration. However, the main portion of imidacloprid applied to the plants resided on the surface or in the epicuticular waxes of the cuticle.…”

“…It would minimize worker and consumer exposure to the pesticide, result in a uniform application, and prevent runoff of pesticide by spray drift into the environment. A comparative field study of the systemic efficacy of imidacloprid against whiteflies conducted by Buchholz and Nauen [33] revealed that the active ingredient was more effective after soil application as compared with foliar application. van Iersel et al [36] reported that the control of whiteflies was better after subirrigation than on hand-watered plants that received a drench application of imidacloprid.…”

Assessing Insecticide Hazard to Bumble Bees Foraging on Flowering Weeds in Treated Lawns

“…Neonicotinoids are mainly acropetally transported in the xylem [15], [16], [33]. Given clothianidin's prolonged (>9 month) half-life from field dissipation in soil [34], it is unlikely that, in just three weeks, degradation of residues in the root zone can explain the lack of acute effects on bees foraging on clover that bloomed after mowing.…”

“…Clothianidin is the least water-soluble neonicotinoid used on turf [34]. Sorption of neonicotinoids to soil organic components reduces the amount that is translocated [33], [35]. Translocation is driven by transpiration and plant growth, processes likely to be greater for foliage than for floral tissues and nectar.…”

N-demethylation of neonicotinoid insecticide acetamiprid by bacterium Stenotrophomonas maltophilia CGMCC 1.1788

“…However, S. maltophilia mainly degrades AAP and only transforms a part of AAP to low toxic metabolite IM 2-1 at a low molar ratio. It had been reported that AAP was superior after foliar application, whereas IMI soil application demonstrated a much greater systemic activity (Palumbo et al 1999;Buchholz and Nauen 2001) although the metabolic mechanism in soil was not clear. Based on our results, the low efficacy of AAP in soil application can be attributed to the fact that AAP could be easily degraded and the partial degraded intermetabolitedemethylated IM 2-1 remained less bioactivity.…”