Colour - Shiny black.
Abdomen - Sometimes is covered with a white dust.
Length - 1.9 mm long.
Legs - 6.
Winged and wingless forms.
All aphids are females and give birth to live young without mating. Winged aphids fly into host crops from surrounding vegetation they persist on in very low numbers over summer. The severity of the cowpea aphid damage is determined mainly by seasonal conditions. A long mild autumn enables an early build up and spread of winged aphids that can establish many small colonies. A mild winter further encourages development and aphid spread, setting up populations for severe crop damage if left unchecked.
Habitats:Origin and History:
The cowpea aphid infests a wide range of leguminous species including lupins, peas, faba beans, clovers, medics, potatoes and canola. Infestations are initially dense colonies on individual plants or in well defined patches. These may spread throughout the crop if weather remains fine and warm. The infestation starts in the growing tip or flowering spike and spreads down the stem. Hosts under heavy aphid attack can suffer distorted leaves and stunted growth with lower leaves wilting. If infestations occur during flowering, pod set and fill can be greatly reduced or prevented. Apart from damage through direct feeding the cowpea aphid is also capable of transmitting viruses such as the cucumber mosaic virus and bean yellow mosaic virus.
Management and Control:Leaving insecticide application until colonies are large, and plant symptoms become obvious is too late. A number of insecticides are available for the control of cowpea aphids. It is important to use aphicides that do not harm beneficial where possible.
Thresholds:Yellow lupins are more sensitive than Narrow-leaved Lupins which are more sensitive than White Lupins to aphid damage.
On lupins, if 30% of the growing tips have more than 30 aphids then
a) on varieties with moderate or greater aphid tolerance. apply a single spray, one to two weeks after reaching this threshold or
b) on varieties with less than moderate tolerance, apply a spray immediately and a follow up spray in two weeks time if necessary.
See Pest Susceptibility of Lupin Varieties for rankings of varieties.
On Faba Beans and Lentils, aphid infestations probably have to be very heavy or
early before it is worth spraying.
Related Species:Similar Species:
WADA, Bulletin 4185 "Insects and Allied Pests of Extensive Farming".
WADA, Bulletin 4179 "Producing Lupins in W.A.".
Francoise Berlandier, Agriculture WA (pers. comm.)
David Pfeiffer, Agriculture WA (pers. comm.)
Acknowledgments:Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.