|For the past couple of years my cabbage heads have been badly damaged (unusable) by something which causes a black spotting all over the leaves throughout the head. It reminds one of mildew, but it has been suggested that it is damage from an insect called thrips. Is this true, and what can I do to prevent total loss of my cabbages?|
|I can't say for sure, but it could be thrips. These tiny insects cause silvery brown streaks and spots on the leaves. You can deter thrips by spreading diatomaceous earth under the plants and on the undersides of the leaves. You might also try planting thrip-resistant varieties such as 'Super Red 77', 'Multikeeper', 'Albion', and 'Hilton'. These are available from Stokes Seeds, 800-396-9238, web site www.stokeseeds.com
There are other possible causes, including various diseases. Look closely at the damage. If there are water-soaked or sunken areas, it's more like a disease problem.