Tuesday, July 19, 2011
My Poor Brassicas and Cabbage Worms
I start many of my vegetables indoors even during the summer. But it seemed wasteful to keep the recent planting under lights in the cellar and so I put them outside in the shade during the day and on the open back porch each night. I began to notice that there was some leaf damage and a few days ago they were looking pretty chewed up as shown in the photo to the right. When I looked at them there was brown "dust" on some of them. Each day the damage was worse. Finally I looked more carefully and noticed the following:
This close the villain becomes clear. See the two parallel cabbage worms on the right most leaf. I found two more worms later that day. The next day I found another four worms.
The source of the cabbage worms is the little cabbage white butterflies that are so common in my garden. I suppose damage to the other brassicas in my garden is from the same source but plants in the garden grow so quickly that the damage is insignificant. And perhaps there are predators (toads and birds) that pick some of them off. The ones on my little seedlings were able to chew away unmolested.
Undeterred I planted all of these miserable looking seedlings in the garden during yesterday's rain. What was in the tray were collards, zen (an Asian green), komatsuna (another Asian green) and dinosaur kale. The komatsuna was the least damaged and the zen the most damaged. I don't know whether that had to do with the chemistry of the plants or simply their proximity to where the eggs were laid.
Next year I will be more observant. The brown "dust" that I observed was the frass (droppings) of the caterpillars (worms). The way I located most of them was by seeing where the frass was and looking carefully in that area.