While reading The No-spray Way to Protect Your Plants, I remembered my experience with last year’s cabbage crop. I started seeing cabbage moths coming around, so I bought a row cover big enough to cover one row. After a few weeks, I noticed the row with the cover was getting chewed up worse than the uncovered row. Puzzled, I removed the row cover and picked off as many little green worms as I could find.
Obviously the moths had gotten to my cabbages before I covered them. But why was the uncovered row less chewed up? In searching for green worms on the uncovered row and finding very few, I discovered small yellow wasps were doing the job for me. For the rest of the summer, I left the wasps alone and let them build their nests under the eaves of my shed. Of the 30 cabbages I picked, I found not a single cabbage worm. I do believe in row covers, but I now believe in little yellow wasps, too.
Many birds and insects, including wasps, feed on caterpillars. Paul’s report is a perfect example of how natural enemies can keep pest damage to a minimum. Some gardeners even install bottomless birdhouses in their gardens to provide nesting boxes for beneficial paper wasps. — Mother