FIELDAND
FORAGE
CROPS
FIELD
The information and recommendations in this newsletter are applicable to
North Carolina
and may not apply in other areas.
The major bollworm moth flight can be considered in progress
throughout North Carolina, except for portions of our northern tier
of counties. As of the morning of July 26, in a few cases the
flight seems to have bisected the county. In Bertie County, for
example, July 26 2-day light trap count was 143, while in two other
traps in the county were 4 and 13 moths. Two Northampton County
light trap counts were less than 10, while the Scotland Neck and
the Halifax light traps in Halifax County contained 91 and 64
moths, respectively. Although the above reports are not exactly
staggering numbers, the increases in trap counts, along with the
egg numbers received from consultants and agents, indicate the
flight should be underway all the way into Virginia by early next
week. Some trap counts in the area where the flight has been
underway are on the high side, as was the case in the Sampson
County trap (1,352 moths on July 24). Egg levels at the Cherry
Hospital Farm near Goldsboro on July 26 were in the 50 to 150 range
in our various test plots, with small bollworms and budworms in the
1 to 2 percent range. Additionally, about 1/3 of the bollworm
complex adults observed were the harder-to-kill budworm species.
Although we expect some rather dramatic differences in field
attractiveness and susceptibility to bollworms
, budworms and
European corn borers at the beginning of the moth flight. Because
much of our crop is on the lush side, most cotton fields will be
vulnerable and attractive to egg-laying moths in the next two
weeks.
As is so often the case, careful, frequent scouting and close
adherence to established thresholds will provide cotton producers
the best opportunity of quickly responding to potentially damaging
levels of bollworms and taking advantage of situations which favor
low bollworm damage (high levels of beneficial insects, light egg
lay, early crop maturity, etc.) over the next 2 to 3 critical weeks
of the growing season. Our heavy boll loads will steer many of our
now-susceptible fields towards rapid cutoff and lessen the odds of
late season damage from European corn borers,
fall armyworms and
stink bugs. For the several weeks, the present susceptibility of
cotton crops and high yield potential argue for a quick and
protective response to threshold levels of either eggs or larvae.
A high proportion of North Carolina cotton fields contain small
aphid colonies in the terminals and upper leaves
, with honeydew
beginning to occur in fairly low levels. A number of cotton fields
have also been reported to have moderate to high aphid levels. In
the case where very small colonies seem to exist as immature aphids
for long periods of time, the size and shape of these small aphids
can be very confusing for scouts attempting to inspect terminals
and fruit for bollworm eggs. Although the scouting is still more
time consuming due to the presence of these aphids, a hand lens
will allow the scout to quickly separate these aphids from bollworm
eggs similar in size. As a general rule, where these aphid
populations have increased in size, I have noted the beginnings of
aphid parasitism (presence of mummies). Attempts at control are
generally discouraged due the effectiveness of natural control and
the presence of aphid populations resistant to most of the common
aphid pesticides. Aphids are not likely to be resistant to one
pesticide, Admire, which is also generally sparing of beneficial
insects. However, the broadcast rate will likely be in the $12 per
acre range, and the standard recommendation of no treatment also
works in virtually all cases, and the price is hard to beat.
Although budworms do not typically make up much of our bollworm
flights, they comprised enough of last year's flight to make
control more difficult in a number of fields, particularly in the
south central to southeastern part of the cotton production areas.
If scouts notice budworm moths (with the 3 stripes on the front
wings) in cotton fields, it may indicate the potential for a
caterpillar population which will be more difficult to control.
European corn borers are always a potential threat in late-
maturing, rank fields in areas of significant corn acreage.
European corn borer flights often do not peak until 1 to 2 weeks
until after the bollworm moth peaks, and thus might not have
provided any indication of size yet. However, European corn borer
adults seem to be present at higher levels than at this time last
year. Recognizing consistent levels of the
sawdust-like frass
that the European corn borer larvae leave adjacent to stem
penetration holes, or flushing the moths from around or within
cotton fields will provide a clue as to potential upcoming trouble
from the boll-damaging larvae. Fall armyworm
adults and larvae are
showing up in a few of our fields, but so far at low levels. This
may be a pest to watch for in the southern part of North Carolina,
as fall armyworms are building in states to the south.
Sclerotinia blight is becoming a very serious problem in the northern-most counties in North Carolina. This is a good time to use DMI fungicides for leafspot control as they do not aggravate the sclerotinia blight problem. Rovral is our only fungicide for sclerotinia. Growers can expect about 50 percent control from this fungicide. Favorable weather conditions started about 12 days ago and it appears that these conditions will continue for a while.
I anticipate southern stem rot (white mold), rhizoctonia limb rot and leafspot will be significant problems in peanuts soon. Growers should be warned to take action to manage these diseases.
Weather-based advisories have done an excellent job of anticipating
disease problems. This is a good season for peanut growers to
observe the advantages of anticipating disease problems prior to
their occurrence using the disease advisories.
Web page last updated on 29 July 1996 by Stephen J. Toth, Jr..
