Dealing With Spotted Wilt Virus

Growing Swiss Chard

- Bill Kerr

Tomato spotted wilt virus (TSWV) became a major problem for growers in South Africa with the accidental introduction of the western flower thrip via chrysanthemums.

The virus does great damage: new shoots bend over, spotted lesions appear on the leaves, and the plant pales to a lighter green. The plant’s growth and productivity both suffer.

As its name suggests, this thrip targets flowers. The pollen-bearing anthers of a tomato flower are fused into a cone with the base covering the ovary. This is the first stage of what will eventually become the tomato.

This cone hides and protects the thrips, which feed on the ovary and surrounding area by scraping it with rasp-like left jaws. This causes zipper-like and ‘cat face’ markings on the fruit. At the same time, they transmit TSWV.