Plant health monitor

Press, 9 December 1983, Page 23

Plant health monitor

With harvest only a few weeks away growers should be thinking about cleaning out grain storage facilities to prevent possible later infestation by stored product pests.

Make sure all residues from cleaning are dumped well away from the storage facilities or are burnt. For details obtain copies of AgLinks FPP 200 and FPP36B.

Grain yields could be high this year so growers should also check that storage capacity will be adequate. With dryer conditions now prevailing, aphid populations will now be building up rapidly. Remember that plants under some moisture stress are more prone to damage by pest and diseases.

Three aphids are present now in cereals — cereal aphid, rose-grain aphid and grain aphid. Make sure you can distinguish between them. Different crops are damaged to varying degrees by these aphids.

Cereal Aphid This dark green aphid found mainly at the base of plants is especially prevalent in spring-sown barley. They carry barley yellow dwarf virus (8.Y.D.V.) and can often be missed if plants are not pulled from the ground. It is too late to spray in many cases, but if a herbicide has yet to be applied, then incorporate an insecticide. Think about monitoring and prevention next year by applying insecticides at sowing or incorporating with herbicides if aphids are present.

Rose-grain Aphid This light green aphid on leaves is now building up. Oats are most susceptible, but most crops are in full head and should not require spraying. If the crop is less advanced, then spray if two aphids occur on average on the top leaf. Earlier infestations will have spread B.Y.D.V. into crops. Wheat crops should not require attention for this aphid now. Barley crops are more critical. If aphids are abundant and the crop can be driven over — then spray. Tank mix with herbicides if possible to reduce costs. If crops are more advanced, it is doubtful if any economic return can be achieved, especially if insecticide has to be applied from the air. Experience has shown that irrigation reduces populations through wash-

ing-off aphids and encouraging fungal pathogens of aphids.

Grain Aphid Numbers are starting to increase in wheat. This bottle green aphid with dark patches on the legs can be seen on the leaves and stems but will later climb into the heads (unlike the rose-grain aphid which has not been observed in the head). Delay spraying until an average of five aphids per head are seen. Refer AgLink FPP 509.

Clover seed crops • Clover case bearer moth numbers are building up. Sample crops very regularly from now on and see AgLink FPP 620. Not all springtails cause damage. Don’t spray to kill the small, black elongated springtail as it feeds entirely on plant litter. The small orange globular springtails may damage clover, but only at very high densities. The larger bottle green globular “lucerne flea” springtail can cause damage and growers should watch out for this pest in particular. Sample flower heads for aphid populations. If an average of five aphids per flower is seen a spray could be worth while. The use of bromophos or dichlorvos will controL.both. this pest and clover case bearer. Be very careful how you use such insecticides; they will kill bees if not applied properly. _______