Tuesday, July 26, 2011

Dry, Hot Weather

We had a wet April but recently we have been in an extended dry spell, and, more recently, very hot weather. In the past seven days we had four days in a row over 90 degrees, one of which reached 101 degrees. With that heat and no rain (and little moisture in the soil) plants suffer. In my garden the cucumbers and summer squash most dramatically show the effect. By early afternoon on those very hot, dry days they looked like they were dying. Their leaves - both cucumbers and squash have lots of leaves and only root in one place - get seriously wilted. Once the sun goes down they perk up again if I have watered in the past day or two. But fruit growth appears to stop. We recently picked large amounts of squash (nearly 10 pounds one day) and cucumbers (more than 10 pounds one day). But now there are no squash or cucumbers to pick. I assume one plant mechanism when it is hot and there is little moisture available is to stop making the fruit that uses so much water.

If I am correct, when we get rain (if we get rain) and cooler weather the little cucumbers and squash will again form and grow.

I had thought that one of the summer squash plants that had really wilted and tipped over had succumbed to the squash vine borer. But I can't find any evidence of damage to the stem of the plant. No frass. No holes that I can find. So maybe the cheese cloth I wrapped around their young stems did work. Time will tell. I hope that the time for the insects that lay the vine borer has passed because I just planted some more squash and cucumber seeds.

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.