Carbofuran residues in grasshoppers and vegetation from aerially sprayed prairie pastures: Potential effects on wildlife

Abstract

Deposition and persistence of carbofuran in vegetation and grasshoppers of two prairie pastures were measured after single aerial applications at 134 g a.i per hectare in 1987 and 1988. Mean depositions on horizontal filter paper samplers were 43 1 and 64 9% of the nominal rate in the two applications Variability of deposits, measured as C V.s, were 76 4% and 86 9% Carbofuran residues in vegetation and grasshoppers were less variable than those in deposit samplers, with C V s of 40 6 and 70 6% in vegetation and 58 6 and 32 5% in grasshoppers for 1987 and 1988, respectively. Residues declined by 50% in 24 h both years from initial concentrations (3 h postspray) in vegetation of 13 3 and 10 8 μg/g Initial residues in grasshoppers averaged 2 2 μg/g in 1987 and 3.9 μg/g in 1988; the mean for both years was 2.5 μg/g Grasshoppers contained the same concentration of carbofuran 3 h after spraying, whether collected live or dead Maximum residues of 5 7 μg/g were found in grasshoppers from two of the 40 sites sampled in both years A model fitted to the data indicated that there may have been about a 24 to 44% loss of residues from vegetation, probably due to volatilization and other processes, before samples were collected at 3 h There was a decline in residues per grasshopper of 30% in 24 h both years, which was not evident when expressed as micrograms per gram because of desiccation of the dead insects The concentrations of carbofuran in the vegetation and grasshoppers were typical of aerial spraying, hence, they may be used as baseline values for estimating exposure of herbivores and msectivores to insecticide deposits from similar spray events by adjusting for rate of application Deposits measured on filter papers were positively related to concentrations in vegetation and grasshoppers Calculations of the potential effects on wildlife of ingesting sprayed grasshoppers, combined with other routes of exposure, indicated a relatively low hazard for herbivorous rodents but a relatively high hazard for insectivorous adult passerines and their young Monitoring passerines in a related field study did, however, not reveal any effects on survival within 3 d of spraying carbofuran.

Effects of Two Grasshopper Control Insecticides on Food Resources and Reproductive Success of Two Species of Grassland Songbirds

“…0.8 g of grasshoppers in a bout of feeding to satiety. At the concentration of carbofuran found on grasshoppers in a pasture sprayed at the same rate as in the present study, 2.5 g/g, Forsyth and Wescott [32] calculated that nestling clay-colored sparrows would consume 0.2 mg of carbofuran/kg body weight in a day, approx. 14% of the LD50 of adults (1.4 mg/kg [5]).…”

“…Residue analysis of silica gel spray deposit plates in the three experimental plots for each compound showed that 82, 57, and 73% of the target rate of 6.25 g a.i./ha of Decis and 76, 118, and 96% of the target rate of 132 g a.i./ha of Furadan reached the vegetation. These deposition rates were typical or slightly higher than other published values [31,32].…”

“…Because the depression of AChE by carbofuran is short-lived (approx. 4 h to return to normal in 3-d-old mallard ducklings [43]) and it breaks down rapidly in grassland vegetation (2 d to less than 50% [32]), the risk of nestlings receiving a lethal dose after the first day seems to be slight. Adult birds feeding on contaminated insects also risked poisoning, which, even if sublethal, could be of consequence to the survival of their young.…”

Insecticide residues in Australian plague locusts (Chortoicetes terminifera walker) after ultra-low volume aerial application of the organophosphorus insecticide fenitrothion

“…There are surprisingly few published data with which to compare these values. Average residue-perunit dose values of 2.3 mg/g and 23.5 mg/g for live and of 15.9 mg/g and 29.5 mg/g for dead grasshoppers in 2 yr of aerial spraying with carbofuran have been reported previously [19]; and similarly, in a study using acephate [20], the average calculated residue-per-unit dose values in live and debilitated ground-sprayed locusts were 17.6 mg/g and 22.8 mg/g, respectively. Our values may therefore be low compared with other values for orthoptera.…”

Effects of grasshopper‐control insecticides on survival and brain acetylcholinesterase of pheasant (Phasianus colchicus) chicks

“…Grasshopper concentrations were consistent between the two spraying events used in their preparation. In a previous study, grasshoppers collected following aerial applications of Furadan at 134 g a.i./ha to two pastures contained mean carbofuran concentrations of 2.2 and 3.1 g/g wet weight for live grasshoppers and 3.9 g/g for dead grasshoppers [25]. Grasshoppers in the gullets of California gulls that died on agricultural land recently sprayed with Furadan contained 4.2 to 7.2 g/g carbofuran [5].…”