Damage from field insects is not generally a major factor for oat crops, however there is a zero tolerance to insects in export hay. Significant damage can occur if insect populations build up.
Planning rotations to minimise pest carryover, timely sowing, adequate crop nutrition and good control of weed and root diseases will all assist in reducing the likelihood of crop attack by insect pests.
Check crops regularly throughout their growth for field insects. Control redlegged earth mite and lucerne flea during the seedling stage if necessary. Aphids should be checked for and controlled from flag leaf stage and later in crops considered to be high yielding. Aphids can also transmit barley yellow dwarf virus (BYDV). If growing susceptible varieties in areas with moderate to high BYDV risk then spraying the crop with a synthetic pyrethoid at 4-5 weeks after sowing is advisable.
Correctly identifying the insect is critical for their successful management.
There are several important pest species and adults range in size from 5-20mm. Adults are usually brown or blackish beetles. The beetles fly readily and are attracted to lights. Cockchafer larvae are characteristically 'C' shaped creamy white grubs ranging from 2-25mm long.
The complete life cycle may take one or two years. Some species have a long larval stage which extends over 12-18 months. In most species the larva is active during late autumn and winter. In these species pupation occurs in spring and adults emerge in early summer. Feeding, mating and egglaying may occur throughout summer.
Cockchafer larvae feed underground and some species are serious pests which may cause patches and poor growth in pasture and may slow growth or kill large areas of cereals and lupins. Young plants without extensive root systems are worst affected. The adult beetles are also very destruction as they feed on tree foliage.
Control of cockchafer larvae is rarely warranted. The pest species in this state cannot be controlled with chemicals after planting as the larvae remain underground. Cultivation, shallow planting and a high seeding rate may help to overcome the problem. The problem is most serious when early growth is slow. Large populations may be present under young crops and in pasture without causing significant damage.