Question: Every year we have problems with squash vine borers on our zucchini and pumpkins in our Pennsylvania garden. Do you have any organic solutions?
Answer: Squash vine borers can be a destructive pest of summer squash, winter squash, and pumpkins, but there are some strategies you can use to limit the damage. The adult moth lays brown eggs in spring on the stem of squash plants near the base of the plant. The eggs hatch into white larvae that tunnel into the stems to feed for four to six weeks. Eventually their feeding causes the plant to wilt and die.
You can plant types of squash that are more resistant to borer attacks, such as butternut and green striped cushaw. For all other squash, one of the best controls is to prevent the adult from laying eggs on the plants. Cover newly emerged or planted squash plants with a floating row cover secured well to the ground. This material lets air, light, and water in but blocks the adult borer from laying eggs. Once the squash begin to flower remove the row cover to allow bees to pollinate the crop. In your area, there is only one generation of vine borers a year, so by planting a little later than normal and covering plants, you may be able to avoid damage. To be sure, check weekly for holes in the stem and, if found, inject the microbial insecticide Bacillus thuriengensis (Bt) into the stems to kill the borers.
For zucchini, try growing some newer parthenocarpic varieties (self-fruitful), such as 'Perfect Pick' and 'Partenon', under row covers their entire life. Since these varieties don't need pollination for fruit production, they can be covered right through fruiting.
Question: I mixed a layer of dried leaves into my raised beds this spring in my Minnesota garden. Is this going to cause problems with my vegetable plants?
Answer: Dried leaves are rich in carbon-containing organic matter. As microbes are decomposing the dried leaves, they are taking nitrogen from the soil. Once the leaves are all broken down, the microbes die off, releasing this nitrogen back into the soil. This temporary "stealing" of nitrogen can pose a problem if young seedlings are growing in the bed before the leaves have decomposed.
To counteract the effects of this nitrogen deficiency, amend the soil when planting this spring with a high nitrogen, organic fertilizer such as alfalfa meal, composted chicken manure, or fish meal. This fertilizer will help feed young seedlings until the high carbon dried leaves are broken down. Your plants shouldn't skip a beat and will continue to grow fine.