Vetch - Insect and Disease Management

Insect management

During emergence, monitor crop for red legged earth mite, pasture looper, cutworm and lucerne flea. Common vetch is very susceptible to attack by red legged earth mite at emergence.

Monitor for aphids from early growth until flowering. Monitor for native budworm from flowering to the end of pod development.

Redlegged earth mite, pasture looper, cutworm and lucerne flea

As a precaution against redlegged earth mite, pasture looper or cutworm, avoid sowing common vetch into old pasture paddocks that have had a high proportion of cape weed. Alternatively a prophylactic application of insecticide (synthetic pyrethroid) mixed with the first application of a knockdown herbicide may be used. If lucerne flea has been a problem in the paddock previously, than apply a prophylactic organophosphate insecticide together with the synthetic pyrethroid.

These insects cause sporadic damage that is usually seen soon after the crop emerges. Threshold levels for their control have not been determined for vetches in Western Australia. Heavy infestations of these insects will severely retard plant growth. Usually one prophylactic spray of a pesticide is sufficient to manage these insects, but the emerging crop must still be monitored to ensure the production and expansion of the new leaves occurring at a faster rate than the damage is occurring by the remaining insects.

Aphids

Inspect the crop at more than 10 locations and count the number of aphids present on 30 plants. Spray insecticide if aphids are present on more than 30 percent of plants inspected at these locations. Use dimethoate, primicarb or maldison. Look closely at the growing points of the shoot where aphids develop infestations. Some aphid species colonise clumps of plants or attack weaker plants and thin patches in the crop. The crop may require multiple sprays in these patches.

Damage form aphids tends to be greater in drier regions and seasons. Aphids can also cause damage by spreading viruses and make plants more susceptible to fungal diseases.

The black cowpea aphid is the most common aphid found on vetch. Infestations start when small numbers of winged adults fly into the crop from elsewhere. These lay nymphs which, in turn, mature and start reproducing. The population continues to grow and feed on the crop. If left unchecked, large

numbers of aphids will cause direct feeding damage that cause wilting, loss of flowers and pods.

Native Budworm

Monitor the crop for native budworm and spray insecticide (synthetic pyrethroid) during pod set if the number of caterpillar averages more than four grubs per 10 sweeps of a sweep net. Monitoring should begin at flowering and continue at regular intervals throughout pod development. Usually one well-timed spray is sufficient to control native budworm, but it is important to maintain a monitoring schedule even after spraying.

Disease management

Fungal Disease

Botrytis Grey Mould, (Botrytis cinerea) Chocolate Spot (Botrytis fabae), Ascochyta Blight and Rust are important diseases of common vetch in Western Australia. Effective and profitable management of these diseases is possible using a combination of rotation, paddock selection, time of sowing and ensuring good plant health. Fungicide use alone are unlikely to provide an economic return.

The following strategies should be used:

• Isolate the crop from potential inoculum sources
  Avoid paddocks that have either been sown to either vetch in the past three years, or faba bean or narbon bean in the two previous years. Also avoid paddocks that are within 500 m of last year’ faba bean, common vetch or narbon bean, chickpea or lentil stubble.
• Ensuring volunteer common vetch have been well controlled in the previous crop
• Use the variety Morava in high rainfall areas to reduce the incidence and severity of rust infection
• Use clean seed
• Sow within the recommended window. Sowing too early will encourage disease.
• Monitor the crop for disease symptoms and spray fungicide if necessary

Suggested foliar fungicide treatments for common vetch. Note: use higher rates in thicker crops. (adapted from: Grain Legume Handbook, 1987)