Thursday, March 31, 2011
Time Plantings to Avoid Insect Pests
I attended the insect biocontrol session at the Georgia Organics Conference a few weeks ago. Dr. John Ruberson was one of the presenters. He brought up the topic of timing of plantings to avoid insects but had little to say about it. At the farm tour that afternoon i asked if he had published any research on the subject. His answer was that he is very interested in doing that research but has not been able to get any funding for it. We agreed that it would be a very worthwhile subject to investigate. One of my former students who attended the same session asked me if i had anything to contribute to the topic. Why yes i do. This is for Linda.
What i am about to present is based on my own observations of my garden over the years. My advice to you is to make your own observations in your gardens, keep records of when you first see pests on your plants and how long into the season you see them. From those observations you can develop a plan specific to your garden that can help you avoid some pest damage.
Zucchini and squash
Squash vine borers are a common problem here in the south. Just when the plants get big and start to flower in mid-June the borers attack. Just when you think you will be able harvest some fruit the following week the whole plant collapses. That is the result of the vine borer larvae eating the stems of the plants from the inside out.
Notice i said mid-June. That is when i usually start to see the damn things. What i do is start my seeds in pots indoors in mid-March for planting out after all danger of frost has passed, around April 15th here. That way i get 6 weeks head start in comparison to planting seeds in the ground after the soil has warmed up at the end of April. By the time the borers arrive i am already harvesting zucchini. I have been planting 2 heirloom zucchini varieties, Costata Romanesco and dark grey, that show some resistance to borer damage. Starting in early June i check the base of the plants every morning to look for signs of borers. You will see a tiny hole with "sawdust" around it at the base of the stem. At that point you can take a knife, slit the stem and kill the larvae. The borer seems to prefer yellow squash over zucchini so i do not plant it any more. It might work as a trap crop.
Eggplant likes really warm soil. Plant it early and it just sits there not growing until the soil gets really warm. Last year i planted mine about the end of April and between the flea beetles and the colorado potato beetle larvae they got eaten up and many of them died. The year before i planted in late May and had good success.
Last year is saw potato beetles in the middle of April, the earliest i have ever seen them. Flea beetles emerge from the soil at this time of year. I saw some yesterday. They complete their first generation around the end of May so i time my eggplant planting to try to get in between the generations. The soil has warmed up by then so the plants will grow faster able to resist an early onslaught of flea beetles. Again, i plant a large plant so it has a better chance of survival. Once the plants get a foot or so tall and are growing vigorously the flea beetles don't cause much damage. My friend and master gardener, Jennifer, has observed that flea beetles can only jump 2' high. ( they get their name because they jump like fleas). She plants her eggplant in pots that sit on stumps to keep them well out of reach of the jumping beetles.
A strong healthy plant is less susceptible to the potato beetle larvae but they can do a lot of damage quickly. It is important to be vigilant and pick those suckers off and kill them before their numbers multiply.
Have you experienced the tiny holes in the sides of cucumbers (squash and melons too) in the middle to late summer? That is the result of the larvae of the pickleworm moth boring into the fruit to feed. Dr. Ruberson said that they overwinter in Florida and migrate up here each year. This year i am starting my cucumbers indoors now to get a head start so i can harvest before the pickleworms arrive. I read a report recently about North Carolina farmers have good success with a late cucumber crop. This year i plant to start a new crop in August to see if i can grow a fall crop here. It would be nice to have cucumbers in October and to extend the pickling season too!
Learning the rhythms and patterns in the garden through patient observation will make you a better gardener and a better person.