During the latter part of the wheat growth season the Brown Ear Aphid and Oat Aphid are often found feeding in the ear. Although some of the other aphids (see Insect pests of leaves and stems) may also migrate into the ear, these two species are the most commonly encountered.
Bollworm larva on wheat ear Feeding damage caused on kernels
Bollworm (moth) Feeding damage on leaves
DistributionBollworm is primarily a problem in the small grain production areas of the Western Cape and on wheat produced under irrigation throughout the country. It occurs sporadically under dryland production in the Free State.
DescriptionYoung larvae are usually a dark colour while older larvae vary in colour from green, yellow, pink to red-brown, brown and black. All larvae have characteristic pale longitudinal stripes on either side of the body. Mature larvae vary from 30 to 40 mm in length and have a small number of single hairs on the body. Moths vary in colour from brown to yellow brown, the hind wings being lighter in colour with a characteristic broad, dark apical band. The wingspan is approximately 40 mm and the body is 18 to 20 mm long. Eggs are yellow-white and turn brown just before they hatch. The pupae occur in cells 25 to 75 mm below the soil surface.
Feeding position and damage symptomsInitially, small larvae feed on the chlorophyll of leaves resulting in white blotches and streaks appearing. As the insects and crop matures, the larvae migrate into the ear where they feed on the developing kernels. This results in direct yield loss as well as quality degrading.
ControlChemical control can be considered when 10% of the ears are infested with one or more larvae per ear. Early scouting to monitor (young) larval activity on the leaves should be performed in areas where bollworm is known to be an annual problem. Chemical interventions can be considered when larvae are sighted on 30-40% of plants.
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