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Scouting this Growing Season: Insects
By Justin Petrosino, ANR Extension Educator
OSU Extension, Darke County
If you’ve been as busy as I
have, you might not have noticed but spring is only a month away. It’s
even closer if you believe the varmint out in PA. Over the next few
weeks we’ll discuss what you’ll need to be keeping an eye out for in
the fields this season. This week we’ll focus on those pesky bugs.
We’ll continue on with diseases and then my favorite topic, weeds.
This year we have a few
developments in bugs. Actually they are called insects. The true bugs
are the Hemipterans, an Order of the Class Insecta. Nomenclature aside,
bugs are bugs and we aren’t happy until they are squished! When wheat
breaks dormancy this spring we need to be on the lookout for two
insects. The cereal leaf beetle used to be controlled by a parasitic
wasp, but for some reason in some areas the wasp isn’t doing as good of
a job as it used to. Starting in May you should be scouting your fields
looking for the larvae covered in a slimy substance. After sampling 30
plants in the field if you have 2 or more larvae per stem you have
reached the economic threshold. I’ll monitor reports from Kentucky on
armyworm flights and come June will let you know if they will be a
problem.
In corn we have good news
and bad news. The bad news is western bean cutworm numbers are on the
rise. The moths have been flying in from the west over the past few
years. Last year we found the first fields with eggs deposited in Ohio.
However, none of the fields reached the economic threshold of eggs or
larvae on 8% of the plants. This year I’ll have traps throughout the
county to monitor the flight and I’ll put out information starting in
July. If eggs or larvae are present on 8 corn plants out of the 100
plants you check in the field, treatment is warranted. If you do not
see eggs or the larvae have made it into the ears insecticide
applications will be a waste of money. There are Bt hybrids available
with the Cry1F gene for control, but they can be pricey. Proper
scouting and monitoring can save you a lot of money on seed if you use
a Non-GMO.
Possibly, a good consequence
of folks using Bt hybrids is the decrease in European Corn Borer and
Corn Rootworm populations. Are we ready to say, ‘stop using Bt hybrids
because populations are that low’? Not yet, unless you plan to scout
and monitor populations throughout the season. Corn rootworm typically
was a problem in rotations with corn following corn because of its
lifecycle. Simply rotating to another crop is enough to control the
Western and Northern Corn Rootworm. However, the first year variant of
the western corn rootworm does lay eggs in soybean fields which infest
next year’s corn. There are several solutions to this problem. One is
to rotate to wheat, simple and effective. You can use a Bt hybrid with
root worm control. Another option costs you only a couple of dollars
and gets you some exercise. Monitor 6 yellow sticky traps in your bean
field starting mid July for 6 weeks. If you get more than 5 beetles per
day, use a full rate of a seed treatment or Bt hybrid next year.
Too much work to save a few bucks? If you’ve got a son/daughter or
grandson or granddaughter old enough to hike out in the bean field and
ID beetles they could always use one more chore to teach them
responsibility.
Aphids have been on a two
year high/low cycle since the 90s when we realized the pattern. 2011 is
shaping up to be a high year somewhere in the state. We should monitor
fields for 250 aphids per plant in soybeans. If that population is on
the rise it’s time to treat. Populations of insects fluctuate
throughout the season. When we apply insecticides willy nilly with an
‘insurance’ program we risk two things. The first is resistance. Over
use of pesticides causes us to find resistant pests. We’ve been through
this with ALS herbicides, glyphosate, insecticides, and now strobilurin
fungicides. If we abuse it we have the potential to lose it and the
product to replace it, if we have one, is always more expensive. We
also risk killing beneficial organisms. If your aphid population, or
other insect for that matter, is declining and you treat, you can kill
the ladybugs and lacewings that are causing that decline. Save the
insecticides for when they are actually needed. An application that is
not warranted or poorly timed is a bad investment. For more information
on these pests, our state specialists Dr. Ron Hammond and Dr. Andy
Michael have a great website at http://entomology.osu.edu/ag. If you are
interested in monitoring for western bean cutworm or first year corn
rootworm contact Justin Petrosino at OSU Extension, Darke County (937)
548-5215 or petrosino.3@osu.edu.
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