Studies on the ecology of Aphis craccivora Koch (Hem., Aphididae), the vector of rosette disease of groundnuts, in Uganda

Abstract

Observations on Aphis craccivora Koch at Serere, Uganda, in 1964–68 showed that dry season carry-over of aphids could occur on the common weeds Euphorbia hirta and E. prostrata; at other times aphids were seen on Gliricidia sepium, Cassia tora, Centrosema pubescens and Macroptilium atropurpureum, the last two being increasingly used as pasture legumes. In pot tests, attempts to transfer the virus through G. sepium, Cassia tora, Stylosanthes guianensis and Centrosema pubescens were unsuccessful. Volunteer groundnuts growing in open situations were an important source of virus and vector. Field studies on menazon-sprayed and unsprayed plants closely or widely spaced showed that aphid numbers increased rapidly on the groundnut crop 31–45 days from emergence but declined rapidly as the plants matured. Superficially the plants appeared to be free of aphids but large populations were often found on hypanthia, flowers and gynophores. Coccinellids, especially Cheilomenes sulphurea (Ol), were important predators. Aphid numbers were far higher on groundnuts with low plant densities, possibly because the number of favoured feeding sites is increased, but the number of plants infested was not significantly different at high and low densities. Yellow panels had little effect on aphid numbers. Spraying with menazon (294 g active ingredient/ha, 5 times) prevented breeding by incoming alates.

Aphids and their natural enemies in vegetable agroecosystems in Benin

“…Cheilomenes propinqua was listed by Catling (1970) as a coccinellid feeding on the brown citrus aphid in South Africa. The predator C. sulphurea was identified as one of the key natural enemies of A. craccivora in Uganda (Davies, 1972). The species was imported from Angola to France to test for its efficacy on Aphis fabae Scopoli (Hodek et al, 1984).…”

Etiology, Ecology, Epidemiology and Control of Groundnut Rosette Disease in Africa

“…It is very likely that in some countries in Africa viruliferous aphids invading groundnut fields originate from rosette-infected volunteers (Storey and Bottomley, 1928;Evans, 1954;Adams, 1967;Davies, 1972;Yayock et al, 1976). Yayock et al (1976) speculated the cause and source of the 1975 rosette epidemic in Nigeria by comparing the conditions that existed during the 1974 normal year and those of the 1975 when there was an epidemic.…”

Groundnut Rossette: A Virus Disease Affecting Groundnut Production in Sub-Saharan Africa

“…Since the viral agents of the disease are not seed-borne, the primary infection must be introduced into the crop by viruliferous aphids. Secondary spread from the initial foci of disease within a field occurs by way of apterae and nymphs (12,16,(27)(28)(29). The nature and pattern of disease spread can be influenced by plant age, crop density, timing and efficiency of transmission by viruliferous aphid vectors that reach the crop, proximity to the source of primary inoculum, climatic factors, and predators and parasitoids of vector populations within the crop.…”