Covers for individual plants
Individual cone-shaped screen covers, made from standard
window screen fixed to a wooden frame, can be useful in
the home garden. They are easily constructed and can be used
year after year. Covers can be removed when plants grow
big enough to tolerate damage.
A barrier that can be used
to protect transplants, but is not as effective as the screen
cone, is a
3-inch-diameter disk of tarred paper, foam rubber, or other
sturdy material placed flat around the base of each plant
as it is transplanted. Each disk has a hole in the center
for the stem to go through. The disk will prevent flies
from laying eggs near the plant stems and may provide places
for the aggregation of predatory ground beetles that eat
the maggot's eggs and larvae.
Be sure transplants are maggot-free before planting them.
Once maggots are infesting a crop, there is no reliable way
to control them.