PestWeb | Lupin Aphids

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Crop Insects

NEW SEARCH	Lupin Aphids
	Aphis craccivora, Myzus persicae, Acyrthosiphon kondoi, Macrosiphum euphorbiae, Brachycaudus helichrysi
Lupin aphids ? Agriculture Western Australia		Description Three species of aphids are important lupin pests, with two others occurring sometimes. Cowpea aphids are black, or dark grey-green, sometimes with a white "dust" over them. Dense colonies can develop on individual plants, or in well defined patches. Infestations start in the growing tip, and spread down the stem, causing leaf bunching and stem twisting. Cowpea aphids tolerate warm dry weather, and can be severe on water stressed plants. Water stress and warm weather before flowering can result in heavy, extensive infestations. Greenpeach aphids are waxy green (except the winged adults, which are almost black). Occasionally, colours of individual wingless greenpeach aphids can range from a pale yellow-green to an orange-red. They usually feed in buds and flowers, and do not often form large dense colonies. Generally they are widespread, in low numbers, rather than well defined patches. They tolerate cool/moist and warm/dry conditions. Bluegreen aphids are large matt bluish green aphids, found in buds and flowers, usually without developing large dense colonies, and may be widespread through a crop. In lupins, they are more gregarious than greenpeach aphid, but less so than cowpea aphid. They prefer cool or warm/moist conditions. Potato aphids are large, bright green aphids, often with a darker green stripe down the middle of the back. They do not usually develop large colonies, and are of minor significance. Leafcurl plum aphids have attacked new varieties of low alkaloid lupins (cv. Yorrel) in some seasons. While not common or widespread, infested crops have been seriously affected. The aphids are pale yellow-green, with very short cornicles on the back. They heavily infest plants in patches, and cause a twisting bunching of leaves, and finally a wilting of the stems.
Four main winged and wingless lupin aphids ? Agriculture Western Australia		Life cycle Winged aphids fly into lupin crops from surrounding vegetation and pastures. Spring population size depends on autumn and winter conditions. Long autumn growing periods allow early buildup and spread of aphids. Mild (not cold) winters allow further development and spread of winged aphids, which can establish many small colonies of wingless aphids throughout a crop. Reproduction is rapid if plant growth and spring weather is favourable, until the colonies are large, and winged aphids redevelop. All aphids are female and give birth to live young, without mating. Healthy plant on the right and plant with seed borne CMV infection on the left. Viruses carried by flying aphids are transmitted to plants as they feed and establish colonies. Wingless aphids feeding on infected plants can also crawl to healthy plants (through the canopy or after falling to the ground) and spread disease. Viruses can be brought into crops from outside paddocks, or spread within a crop from infected plants.
Cowpea aphid infestation ? Agriculture Western Australia		Damage Aphids feeding on lupins can cause yield loss before plant symptoms become obvious. Large colonies, with more than 40 aphids per stem, cause distortion of leaves, stems and flowers. By the time such symptoms are evident, there will have been yield loss that cannot be recovered by spraying to control the aphids. The crop should be treated before aphid numbers increase markedly. The economic loss over a paddock depends on the area infested, and on the numbers of aphids in each growing tip or bud. Yield losses are greater if virus transmission also occurs. Virus infection causes additional plant symptoms. Aphid feeding slows growth, distorts flowers, and reduces pod set and fill. Viruses transmitted by the aphids cause a range of symptoms, including "shepherds crook", stunting, and leaf yellowing. Low numbers of aphids can spread viruses, whereas larger widespread populations are needed to cause direct feeding loss. Virus diseases can cause significant yield loss in lupins. Aphids can carry and spread these diseases, at population levels that cause little damage from direct feeding.
Healthy versus CMV infected plant ? Agriculture Western Australia		Control Aphid numbers can rise and fall rapidly, mainly in response to weather conditions, so they are virtually impossible to predict beyond a few days. The potential for grain yield loss is high if five or more aphids are found in 30 per cent of buds on the main stem or first branches of a plant, and 15 per cent or more of the crop is affected at this level. Waiting until colonies are large, and plant damage symptoms are obvious, is too late; yield loss has occurred and cannot be recovered. The type of aphid does not matter. Greenpeach aphid is more difficult to kill than the other aphids, and higher rates of aphicide should be used. An aphicide that does not kill beneficial insects (wasps, ladybeetles, lacewings, hoverflies) is preferred. It may be necessary to apply aphicide twice in a season, as each set of buds and flowers develop. Spot spraying may be effective. Cucumber Mosaic Virus (CMV) is carried over in seed from infected plants, and can also be transmitted by aphids. Within a crop, aphids spread CMV from plants growing from infected seed. Usually the disease is localised and patchy, but yield losses due to the virus can exceed 50 per cent if the infection spreads throughout a paddock early on. Recommended management strategies include early seeding, high seeding rates to generate dense stands, use of uninfected seed, and strategic application of aphicides to kill aphids in late winter/early spring. Bean Yellow Mosaic Virus (BYMV) spreads into paddocks from neighbouring pastures. It is usually restricted to paddock edges, but occasionally widespread infections occur, resulting in severe yield loss. Sparse crops (low seeding rate, seedling loss) are especially vulnerable. Management strategies include high seeding rates to generate dense stands, cereal barriers around the crop, heavy grazing of adjoining pasture paddocks to reduce aphid numbers, and strategic aphicide sprays.