Root maggots which infest the roots of beet, turnip, radish and sometimes onion can be controlled by placing insecticide in the soil when planting seeds. Several pesticides are effective, but the most commonly available in sevin dust. Organic gardeners can use diatomaceous earth instead. It is also helpful to sprinkle a little on top of the soil just as seedlings emerge from the soil.
Root maggots sometimes also attack cabbage family vegetables. They can stunt or kill the plants. Sprinkle sevin or diatomaceous earth around seedlings when you transplant them.
Leaf miners can make tiny little tunnels in the leaves of lettuce, spinach, Swiss chard, and other leaf vegetables while they are quite small. Neem Oil and Spinosad are two organic controls.
Vegetables can be protected from many insects including root maggots, leaf miners and cabbage worms with fabric row covers. Fabric row covers are lightweight blankets made of spunbonded polypropylene which is sunlight, rain and air-permeable. They offer 4 benefits: 1) Capturing warmth, resulting in healthier plant growth and earlier yields. 2) Protecting plants from damaging winds. 3) Effective control of maggots, leaf miners and many other insects. 4) Protecting your plants from light frost, thus extending the growing season. Row covers can be placed over plants and secured with soil on the edges. They rest lightly on the plants and are pushed up as plants grow. On line sources include johnnyseeds.com and territorialseed.com
Allen Wilson is a Vancouver gardening specialist who blogs at http://blogs.columbian.com/gardening-with-allen/. Email Allen Wilson at allenw98663@yahoo.com.