Steve Ellis
Field thrips can damage both peas and beans. Attacks are most severe when growth is slow or on stony soils. As peas or beans begin to emerge in the spring, thrips feed inside the tightly rolled leaves of the growing point. Young leaflets appear pale and slightly distorted and, if held to the light, small translucent markings are obvious. On beans, leaves may appear shiny and speckled with sooty black markings. A rusty brown discolouration may develop on the undersides of bean leaves. It may be possible to see the thrips if the leaflets of affected seedlings are carefully unfolded.
Often peas and beans can outgrow the pest with no long-term effects on the crop. However, occasionally when the attack is severe, peas may develop multiple secondary shoots and develop as small bushy plants. Bean leaves may die off completely and crop growth can be severely slowed for a week or two. In areas where damage is seen in most years an insecticide treatment can be justified. Trials undertaken by PGRO have shown that Hallmark with Zeon technology has given a useful and consistent reduction of leaf damage. The product is approved for use on peas and beans for weevil control. Early treatment is essential and where thrips damage is confirmed as the peas are just emerging, and before the leaves have
expanded. PGRO advise that a single spray should be applied as soon as possible. In beans, the thrips feed on the leaf surface and often more exposed. In this case, a contact insecticide will provide adequate control. Winter beans seldom require insecticide treatment.
