Interactions between the chrysomelid beetle Gastrophysa viridula, the weed Rumex obtusifolius and the herbicide Asulam
Published source details
Speight R.I. & Whittaker J.B. (1987) Interactions between the chrysomelid beetle Gastrophysa viridula, the weed Rumex obtusifolius and the herbicide Asulam. Journal of Applied Ecology, 24, 119-129.
Published source details Speight R.I. & Whittaker J.B. (1987) Interactions between the chrysomelid beetle Gastrophysa viridula, the weed Rumex obtusifolius and the herbicide Asulam. Journal of Applied Ecology, 24, 119-129.
This study is summarised as evidence for the following.
Control weeds without damaging other plants in conservation areasAction Link
Control weeds without damaging other plants in conservation areas
A replicated, controlled laboratory study (Speight & Whittaker 1987) found that the systemic herbicide asulam had little influence on the survival or rate of development of the green dock beetle Gastrophysa viridula when used as a contact agent on eggs, first-instar larvae or adults. However, the ingestion of asulam-contaminated broad-leaved dock Rumex obtusifolius leaves reduced female fertility by 64% (a reduction in number of egg batches rather than in numbers of eggs per batch) and extended the time to reach the adult stage by 3-4 days. There was no effect on female longevity. Presence of asulam in dock leaves had no significant influence on egg-laying or feeding site selection. Fifteen replicates of each of the following treatments were sprayed on batches of 30 eggs, 20 first-instar larvae or one adult: high (5 ml/l) or low (1.25 ml/l) asulam concentration and a water control. In addition, 45 first-instar larvae were fed dock sprayed with one of the three treatment solutions. Female beetles that were carrying eggs were also put in 20 ‘choice chambers’ with leaves sprayed with each treatment; location, area of leaf consumed, position and numbers of egg batches were recorded after 6 hours.
The same authors (Speight & Whittaker 1987) also undertook a replicated, controlled study of asulam use in unmanaged grassland in the UK and found that broad-leaved dock Rumex obtusifolius survival was unaffected by beetle grazing or spraying with a low concentration of asulam (1.25 ml/l) and at high asulam concentrations (5 ml/l) only 40% of plants were killed. Numbers of first generation green dock beetle Gastrophysa viridula were similar on treated and untreated plants, but numbers of the second generation were significantly higher on untreated than treated plants. Shoot and root dry weights of asulam-treated plants were significantly lower than untreated ones. Beetle-grazing did not further reduce the dry weight of asulam-treated plants, but did those treated with water. Second generation beetles laid four times as many eggs on untreated plots and survival from eggs to larvae was 25% compared to just 4-12% on treated plots. Four blocks of six plots (4 m²) received the three treatments, each in the presence or absence of beetle-grazing. One-month-old docks were planted (16/plot) in April 1981. In May, 144 adult beetles were released in randomly allocated ‘grazing plots’ (12/plot); herbicide treatments were applied in June. Numbers of beetle eggs, larvae and adults were counted on four plants on each grazed plot from May-October. Dock plant material was harvested in August and October 1981 and February and April 1982 and dry weights and leaf areas (untreated plots) obtained.