Root maggots
Root maggots [Image]
are the larvae of various small flies including cabbage, onion, and
carrot rust flies. They are serious threat to
Cabbage, carrots, beet, beans, peas, mustard,
radish, cauliflower, broccoli, brussel sprouts and turnip
in the early part of
their growing cycle, especially after a series of cool, wet springs.
The
adults emerge in early spring and lay eggs on the seedling base. Upon
hatching, the larvae burrow into the roots.
Dusting the plants with
diatomaceous earth
will help deter this pest. Applying
beneficial nematodes
to soil before planting will help to reduce any potential
outbreak before it begins.
Cabbage Maggot
A very destructive early season pest is the
cabbage maggot . This pest not affects you guessed it ... cabbage,
and can also wreak havoc on other members of the Brassica family
...cauliflower, broccoli, brussel sprout, as well as radish, turnip,
and beets.
The adult resembles the common house fly ,only a bit smaller, being
about a quarter of an inch in length. The fly is a darkish ash gray
and has black stripes on the thorax as well as black bristles over
the body [Image]. The female will lay eggs which will hatch into white,
legless maggots. These maggots feed on the roots of the previously
mentioned vegetables. The maggots will develop into brown egg shaped puparia which are to be found from one to four inches down in the
soil [Image]. During the winter period the maggot lives in the soil,
The presence of beneficial nematodes
and diatomaceous earth
in the soil at this point will severely retard the advance of this pest.
As
Spring comes around and the soil warms up, the adult will emerge
from the ground and begin to mate. Eggs will then be laid on the
soil close to the host plant. After about a week the eggs will hatch
and the tiny maggots will begin feeding on the roots . They tunnel
through the roots destroying them. Within a month the maggots will
turn into a pupae and two to three weeks later the adult will come
forth and the cycle begins again.
If natural controls prove ineffective
Malathion
is recommended
University of California - IPM Cabbage Maggot
The Cabbage Root Maggot in Newfoundland and Labrador
Seed Corn Maggot
The pale yellowish-white seed corn maggot
burrows into seeds already in the soil. Sprouts of several
vegetable crops are attacked by this seed infesting maggot. The
Adult Fly looks pretty much like a common house fly...
slight size difference.
Although it is called seed
corn
maggot it is much more likely to damage beans, peas, cabbage,
turnip , onion, radish and spinach. It is a close relative of
the onion maggot and the cabbage maggot.
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The seed corn maggot passes the winter in the soil in the maggot
stage inside a dark brown, cocoon-like puparia, 1 1/2 to 2 inch
long.
The first-generation flies emerge about planting time. These
flies are grayish-brown to slightly greenish in color and about
1/5 inch long. The flies deposit their eggs in the soil where
there is an abundance of decaying organic matter , or on the
seed or young, developing plant. The second and third generation
appear in mid- and late summer.
The hatching maggots make their way to the sprouting seeds where
they bore into, feed on, and often destroy the cotyledons and
growing point of the seed of young plants.
Seed corn maggot populations vary greatly depending on
environmental conditions , take precautions prior to planting to
keep damage from this insect to a minimum. Otherwise, this
critter will probably not be detected until seeds and seedlings
are lost.
Plant in a seedbed only deep enough for adequate soil moisture.
Plant after the ground is warm enough for rapid germination and
growth.
Reduce use of organic fertilizer in the seeded row, whenever
possible, if and only if there has been a problem in the past
with these pests.
One
control option is to plant seeds pretreated with a product
containing diazinon,
if unavailable, granules may be worked into the soil before
planting.
Penn State Dept. of Entomology Fact Sheet
Perdue University- Field Crops
References
- Sittig's Handbook of Pesticides and Agricultural Chemicals
- Growing Vegetables West of the Cascades: The Complete Guide to Natural Gardening