Armyworms |
Armyworms are
green-striped caterpillar larvae of the adult armyworm moth. Armyworms got
their names because they travel in small armies, eating everything in their
paths. A common pest of grass, armyworms will also eat corn, beets, beans,
clover, flax, millet and other grains. There are specific steps you can take to
remove armyworm infestations from your grass or fields. Additionally, there are
some natural methods for keeping armyworms at bay.
MANAGING
ARMYWORM IN GRASSES
Look for early signs. Because they feed at night, you may not see the
caterpillars right away. Brown spots on your lawn are often the first sign that
you have an armyworm problem. An increase of the number of birds in your yard
may be an indication of armyworms. The earlier you treat the problem, the
easier it is to control and less damage a lawn will sustain
Mow the
lawn. Trimming your
grass short is perhaps the best way to discourage the presence of armyworms.
Consider mowing your lawn a bit shorter than you normally would, and keep it
groomed.
Water the
grass. Watering your
grass, especially when done right after mowing, also causes caterpillars to
move on to other lawns. Develop a regular watering routine, and remember to
also water your grass right after mowing.
Use
insecticide.
Spraying the grass with a liquid insecticide is a very effective way to
eradicate armyworms. Granular insecticides are generally less effective against
armyworms. Choose a liquid insecticide, and follow all manufacturers’
instructions (as these can vary from product to product).
Leave the
lawn alone for three days. After you apply liquid insecticide to your lawn, it is important to
avoid mowing and watering for at least three days. This gives the insecticide
time to work.
CONTROLLING
ARMY WORM IN THE FIELD
Look for
armyworms and/or droppings. Look under your plants for armyworms and/or signs of their frass
(droppings). You may also find larvae hiding under plant debris. If you are
growing barley or wheat, you may find worms inside of the heads.
- Newly hatched armyworms may have no distinguishing marks, but older armyworms will be either brown with yellow stripes or green with light stripes.
- Armyworm droppings resemble black pepper.
Mow your
hay fields. If
armyworms have infested your hay field, mowing the field is the first course of
action. As the hay dries, the armyworms lose interest in it as a food source
and move on.
Use
insecticide. You can
apply insecticides to the field using either ground or aerial equipment. The
following insecticides have been proven effective on controlling armyworms:
- Asana XL should be used only on corn crops and should not be applied within 21 days of harvest.
- Permethrin is also only for use on corn and should not be used within 30 days of harvest.
- Carbaryl (Sevin) may be applied either to corn or wheat. Do not do more than two applications and do not it apply within 21 days of harvest.
- Ethyl is useful for corn, sorghum and all small grains but can only be applied with an aerial application. Do not apply ethyl within 12 days of harvesting corn or sorghum, and within 15 days of harvesting small grains. After you apply the ethyl, post notices that the field is being treated, and stay out of it for three days.
- Lorsban can be applied to corn and sorghum. Do not allow livestock to graze in the field for at least 15 days after you apply lorsban. Do not feed meat or dairy animals grains treated with Lorsban until at least 35 days have passed.
- Lannate or Malathion can be used on all crops. Do not spray these insecticides within seven days of harvest and stay out of the field for two days after treatment.
- Methyl is used for aerial application on corn and small grains only. Do not apply it within 12 days of a corn harvest, or 15 days of a small grain harvest. Post notices in the fields, and stay out of them for two days.
- Warrior can be used in corn, sorghum or wheat fields. Do not apply it within 20 days of corn harvest or 30 days of sorghum or wheat harvest.
Getting
rid of armyworms without pesticides
Watch for
moths. In order for
your natural approach to be effective, you must catch the infestation early. In
early spring, begin monitoring for the presence of moths, and/or damage to your
plants.
- Armyworm moths are grey with distinctive white dot on their forewings.
- You may choose to set pheromone traps to catch moths. This will allow you to get a better look at their markings.
Release
trichogrammer wasps.
If you've caught the problem early in the season (late spring or early summer),
you can release trichogramma wasps. These wasps will parasitize and ultimately
kill armyworm eggs.
- You can purchase these wasps from some garden supple stores, or online.
Attract beneficial
insects and birds. Unfortunately, the
use of pesticides and insecticides can kill beneficial insects, along with
armyworms. Instead, by encouraging the presence of these insects, as well as
birds, you can naturally keep your armyworm population at bay. You can do this
by avoiding the use of insecticides/pesticides, and by planting wildflowers.
Apply
neem oil. If the
introduction of other pests has not done enough to quell your armyworm problem,
try using neem oil spray. Apply neem oil spray to your crops, making sure to
cover stems and the undersides of leaves, as well. Avoid watering for at least
1-2 days after application.
- Neem oil can be destructive to armyworms at various stages of their development.
- Additionally, neem oil is anti-fungal.
In Malawi, some farmers used
a filtrate of Tephrosia vogelii in a soap solution. Crush the leaves of T.
vogelii and soak in water for about 48 hours, then filter. Mix the filtrate
with some powder soap and apply the liquid onto the funnel of corn which has
signs of the army worm. You may repeat the application if you still observe
that the worm is alive.
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