Up to now the garden has been free of pests. Last weekend I noticed the white cabbage moths fluttering around the garden, so I knew I had to get protection in place soon for the brassicas. So I spent Sunday putting up the hoops and row cover to protect the row of broccoli and kale in my in-ground plot. On Monday I took a look at my turnips and radishes in the raised beds and was amazed at the flea beetle damage done in just a few days. Just a few days ago there was not a hole to be seen, now the plants are crawling with the tiny black beetles.
The Broccoli raab and Soloist Napa cabbages were doing really well and are now just pin cushions. It doesn’t pay to be a pioneer, you just wind up with arrows in your back. There are no brassicas elsewhere in the garden and no wild mustard anywhere near. When you get a hatch of hungry crucifer flea beetles and your garden has the only meal around, expect to be attacked.
Likewise, the radishes and turnips are damaged, while the kohlrabi are untouched The trouble I have is they are small plants that get put here and there in the garden and it is difficult to come up with a system to protect them. These were sprayed heavily with Spinosad on Monday to hopefully knock down the population. Spinosad is effective against flea beetles but is not yet licensed for them. I will alternate the Spinosad with a pyrethrin spray. Both are approved for organic gardens.
For the in-ground plot, I am organizing it by row. The row in the back is the large-rooted brassicas, specifically broccoli, kale and Brussels sprouts. I used black plastic mulch to minimize watering and inhibit weeds. Since these plants do not have to flower (in fact, we do not want them to flower), they can remain covered. The hoops you see are 10-foot (3 m) sections of inexpensive 1/2-inch (1.3 cm) plastic electrical conduit, pressed into the soil and bent over. The material is PVC, which is not ideal, but at least it is marked to be UV-resistant. You could use PEX water tubing, but it is not UV-resistant and rapidly breaks down when exposed to sunlight.
The key to this system is the availability of 10-foot wide (3 m.) fabric. I used Agribon 19 which I sourced from Johnnny’s Seed. I bought the 250 foot roll so it should last me a while. The trick was to get the fabric over the hoops. Of course, as soon as I was ready to raise it over the hoops, a breeze started blowing. I had to have another gardener help me and I had to use large binder clips to hold it in place. So far it has held up to the usual windy conditions we get in the spring and the brassicas underneath are bug free (although they got sprayed with the Spinosad just in case). It’s necessary to seal the edges because the flea beetles are fully capable of getting underneath. Hopefully this will keep the plants beetle and caterpillar free this summer.