With spring just around the corner and temperatures rising, the chance of increased aphid numbers and damage is likely. Now is the time to keep a close eye on your crops and watch for increased aphid activity in your paddocks.

Aphids are small, soft-bodied insects with long, slender mouthparts that they use to pierce stem, leaf and other tender plant parts and suck out plant fluids.

When the weather is warm, many species of aphids can develop from newborn nymph to reproducing adult in 7 to 8 days. Because each adult aphid can produce up to 80 offspring in a matter of a week, aphid populations can increase with great speed.

If your crops are infected with high numbers of aphids there are a few obvious signs to help you with your diagnosis. Aphids will generally colonise on the growing points of your plants, so getting down onto your knees and investigating will be essential. Heavy infestations can deform leaves and growing points, and can stunt plants. Other symptoms could be leaf curling, yellowing and even leaf drop in severely infested crops.

Yield loss from aphids can vary between different crop types, growth stages and plant health. Cereal crops can endure relatively high numbers of aphids without a reduction in yield unless they are under stress. Before taking to your crop with chemicals, monitor the activity of beneficial insects (lady birds, parasitic wasps, hoverflies, lacewings) by checking for dead aphid bodies. Also if some good rain is coming, this could reduce aphid numbers and damage, which could save you an extra pass over your paddock. However if 20% of your plants (cereals, canola, pulses) are infected in your paddock, consider using a chemical treatment to ensure yield loss is limited.

Several chemical measures can be implemented to control aphids but you must choose carefully. It is common for synthetic pyrethroids (SPs) to be the first choice as these will also control other pests. These chemicals, in crops with high levels of infestation, may not be as effective in controlling aphids. It is also believed that the overuse of the SPs is leading to resistance in target and non-target species and for these reasons should not be your first choice for aphid control.

Primicarb is a control specific for aphids and will not harm the beneficial insects in your paddock. Be sure to check your PIRSA spray charts and always read labels before heading out to spray. For further information contact your nearest Rural Solutions SA office.

Author:  Kieran Wauchope, Sustainable Ag Systems Consultant, Rural Solutions SA

Contact: Kieran Wauchope, Rural Solutions Pt Lincoln, Telephone (08)8688 3409 Email wauchope.kieran@saugov.sa.gov.au