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8.
Vegetable Scouting Report for week of July 10-15-from
Sweet
Corn
Looking at many corn fields we are
finding something that goes against what we usually find in the field.
European corn borer (ECB) adults normally fly between the end of May and the
middle of June. After the flight, because the adults find the most mature
corn most attractive, larvae populations are usually highest in the most mature
corn. The percentage of ECB worms in later plantings decreases until the
second flight begins in late July. This summer, we are finding more ECB
worms in the second and third plantings than the first plantings. I think
this is because of all the rain we had in May and June. We had an up and down
flight where normally the flight peaks and then numbers go down after
that. This is a guess but in any case, we are seeing higher percentages
of ECB in later corn plantings as we go along.
It is quick and easy to find out how much ECB you have in your fields.
Walk through the field and stop randomly at 5 locations. Inspect 5 plants
at each location for ECB feeding damage - holes, saw dust and windows in the
leaves around the tassel. Scouting is quick because you are only looking
for the presence or absence of feeding damage. If you see damage on a
plant, keep a running count of that number. When you've inspected 25
plants, multiply the number of plants with holes times four and this gives you
a percentage of field infestation. If you are over 15% than a control is
called for.
Scout your fields for tassel emergence. With the warmer weather, the
tassels are opening quickly and since the ECB larvae do not like the heat, they
do not stick around very long. After tassel, the larvae either drop down
to the ear or they bore into the stem making them more difficult to
eliminate. When you see around 30-40% of the field with the tassel just
starting to stick out, make your first application. Since the field will
be coming quickly, the time before your second application will be shorter,
maybe 2-3 days. Keep an eye on your fields that are about to come into
tassel as sprays at tassel are the most effective at controlling the
worms. For organic growers, Entrust, the organic formulation of Spintor,
works very well.
Potatoes
As stated earlier, late blight has been
found on
Leaf hopper is being found in very high numbers in most fields. Go out
and flop a plant into the row and shake it, than flop the plant to the other
side of the row. Inspect the ground for leaf hoppers that have fallen off the
plant onto the ground. This is an easy way to see what is happening in
the field. We've already started to see some burning on susceptible
varieties. The edges of the leaves will turn dark brown. Eventually
the whole plant will turn brown and die. It's important to pay attention
to leaf hopper because they can seriously decrease yield without being very
evident. For conventional growers, Phaser and Thionex are the insecticides
least toxic to ladybird beetles This is important for aphid
suppression. For organic growers, the options are limited. Pyganic
is the only product that is organic certified that will do the job.
The only other thing being found in potato fields is bacterial black leg.
This is when water gets into a damaged stem and causes the stem to turn black
and rot usually producing a strong smell. You often see this problem
worst in spray rows where the plants are damaged by tractor wheels. Later
in the season, if the heavy rains continue, you will see black leg as a result
of European corn borer damage.
Vine crops
We found the first powdery mildew (PM) on
summer squash this week. It will always be the first vine crop to develop
this disease so it is a good idea to try to isolate it from your other vine
crops especially cucumbers. Otherwise the PM will jump from one crop and
planting to another. Be on the lookout for Phytophthora crown rot because of
all the rain. Plants will wilt and the stems will decay at the soil
line. Phytophthora is a common problem in many grower's fields. We
usually see it later in the season when the fruit collapses. This early,
with all the rain, we can see the problem on young plants. Not much to do
but hope we get drier conditions.
Cornell Recommends
The online version of the 2006 Integrated Crop and Pest Management
Guidelines for Vegetables is now available at http://www.nysaes.cornell.edu/recommends/
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9. Take
a look at this issue of New Ag Network-a newsletter for and by In this
issue –July 12,
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10.
On August 23, 2006
For information on the agenda, registration and directions please
visit the web site www.mottgroup.msu.edu
or call Vicki
Vicki Morrone
Organic Vegetable and Crop Outreach Specialist
C.S. Mott Sustainable Food Systems
303 Natural Resources Bldg.
517-353-3542
517-282-3557 (cell)
517-353-3834 (fax)
