Western flower thrip: a major seasonal threat to brassicas

This important pest damages brassicas by sucking sap from the leaves. Its population can grow rapidly, so scouting is essential, says Bill Kerr.

- Bill Kerr

The western flower thrip (Frankliniella occidentalis) arrived in South Africa on imported chrysanthemum cuttings in the 1980s. An invasive pest, it targets a variety of vegetables (including brassicas), fruit, and cut flowers.

It is also a vector of tomato spotted wilt orthotospovirus, and causes damage to tomato, lettuce and pepper crops. (Fortunately, thrips do not spread any brassica diseases.) Initially unaware of the thrip's arrival in South Africa, I started to notice that the cabbage leaves were becoming slightly distorted, puckered and dull. When I turned them over, I was amazed to see thrips feeding. I had never seen this before.

The experts I contacted could not help me. In fact, they could not believe I was having thrip damage in my region!