Effects of some foliar fungicides on the chrysomelid beetle Gastrophysa polygoni (L.)

Abstract

The effects of the fungicides benomyl, thiophanate‐methyl and triadimefon on the chrysomelid beetle Gastrophysa polygoni were investigated in the laboratory. Contact with a suspension of benomyl (1.5 g a. i. litre−1 did not affect the hatchability of the eggs. Larvae were reared on shoots of knotgrass (Polygonum aviculare) that had been sprayed with suspensions of benomyl, ranging in concentration from 0.1 to 5.0 g a. i. litre−1. The mortality to the adult stage, of larvae reared on shoots treated with concentrations of benomyl of 0.5 g a. i. litre−1 and above, was significantly higher than that of control larvae. At concentrations of 2.0 g a. i. litre−1 and above, no larvae survived to the adult stage. The LD50 was 0.78 g a. i. benomyl litre−1. The LT50 values at concentrations of 1.0, 2.0 and 5.0 g a. i. benomyl litre−1 were 22.6, 12.6 and 5.3 days, respectively. The mean weights of adults bred from larvae that had been reared on shoots treated with benomyl (0.5 and 1.0 g a. i. litre−1) were significantly less than those of adults bred from control larvae. The mortality of larvae, reared on shoots of P. aviculare treated with triadimefon (0.5 g a. i. litre−1) or thiophanate‐methyl (1.0 g a. i. litre−1), was also significantly higher than that of control larvae. Females kept on plants of P. aviculare treated with benomyl (1.5 g a. i. litre−1) laid similar numbers of eggs to those kept on untreated plants, and the hatchability of the eggs was not affected.

The sub‐lethal effects of foliar fungicides on the mustard beetle, Phaedon cochleariae (F.) (Col., Chrysomelidae)

“…Previous work with oral ingestion and topical applications of benzimidazole and triazole fungicides to chrysomelid beetle larvae (G. polygoni) were shown to cause significant mortalities (VICKERMAN and SOTHERTON 1983). However, the present work with similar fungicide groups (although different compounds) with P. cochleuriue larvae did not produce such effects.…”

“…During the 1970's a range of compounds were introduced to control diseases such as leaf blotch, rusts, powdery mildew and the many stem-base lesions attacking cereal crops. In a 62 km2 study area in west Sussex, the percentage of cereal fields treated with foliar fungicides increased from 0 O/ O in 1970 to 76 O/o in 1980 (VICKERMAN andSOTHERTON 1983) and has now reached approximately 100 Yo. Over the same period disease indices for both mildew and rust incidences have decreased (AEBISCHER and P o n s 1990).…”

“…Several studies have investigated the effects of foliar fungicides on the beneficial arthropod fauna of cereal fields, either on the insects preferred by gamebird chicks or on natural enemies of cereal aphids. VICKERMAN and SOTHERTON (1983) showed that larvae of Gmtrophysu polygon2 (L.) (Col., Chrysomelidae) reared on plants treated with benomyl and thiophanate-methyl (benzimidazoles) and triademefon (a triazole) at a range of dose rates had significantly higher mortalities than did control larvae at rates approximating those used in the field, and that surviving larvae had a slower rate of development.…”

The effects of the foliar fungicide pyrazophos on beneficial arthropods in barley fields

“…If these arthropods are to be incorporated into integrated pest management programmes in Britain, greater care must be taken in the choice of pesticides used in the crop. This obviously includes insecticides (Vickerman & Sunderland, 1977;Powell et al, 1985 ;Brown, Shires & Lawton, in press) but also herbicides (Vickerman, 1974;Speight & Lawton, 1976;Powell, Dean, Dewar & Wilding, 1981;Sotherton, 1982) and fungicides (Vickerman & Sotherton, 1983;Powell et al, 1985).…”

The survival of gamebird (Galliformes) chicks in relation to pesticide use on cereals

“…Pesticide use on cereals can reduce arthropod abundance both by killing them directly as do insecticides and some fungicides (Vickerman & Sunderland 1977, Vickerman & Sotherton 1983, Sotherton 8t Moreby 1984 and by removing their host plants by herbicides (Southwood & Cross 1969, Vickerman 1974, Sotherton 1982. Thus cereal pesticides may be responsible for the widespread decline of gamebirds on farmland in the UK and such an effect may have profound consequences for other farmland wildlife (Rands et al 1985, Rands & Sotherton in press).…”