Telephone (912) 754-8040
Effingham County
284 Hwy 119 S – POB 308
Fax (912) 754-8409
August 10, 2012
Effingham County AG News
What a difference the recent rains have made to the 2012 crop. Corn harvest has begun in the
county, but has been slowed down due to the afternoon thundershowers. The crops are looking
the best they have all season at this present time thanks to the moisture and break in high
temperatures. Hopefully, the rains will continue to be timely and corn harvest resume. Please
look at the information below as stink bugs, kudzu bugs, armyworms, white mold and several
other issues are of upmost importance at this time of the growing season.
Cotton
Stink Bugs: Stink bug damage reports are all over the board, ranging from low to high and there
does not appear to be any pattern to the variability. Some fields which have been blooming for
several weeks have yet to exceed threshold whereas others may have been treated two times.
Scout and treat accordingly based on internal boll damage. Also be observant for stink bug
species makeup, the ratio of browns to southern green also varies by location.
Corn Earworm and Fall Armyworm: Corn earworm numbers have generally been low but
again populations are variable. We have not received any reports of fall armyworm in cotton to
date, but this is the time of year we would expect to see falls. Dr. Stormy Sparks, Extension
Vegetable Entomologists) reported high numbers of fall armyworms in a late planted sweet corn
trial. Both Bollgard II and WideStrike provide good control of corn earworm and fall
armyworm, but supplemental foliar sprays may be needed. In general WideStrike is more likely
to have corn earworm escapes when compared with Bollgard II. On the flip side, Bollgard II is
more likely to have fall armyworm escapes when compared with WideStrike. Scout and react in
a timely basis when necessary. Most corn earworm escapes occur near the uppermost bloom in
blooms and under bloom tags. Most fall armyworm escapes occur on bolls in the mid to lower
canopy and in blooms; be sure to examine plants closely for fall armyworm if you notice a boll
which appears to have feeding or etching on the inner surface of boll bracts. Small fall
armyworm will often feed on the inner surface of boll bracts before penetrating the boll. The
threshold for fall armyworm is about 2X that of corn earworm. (Phillip Roberts)
Soybeans
Yield Impact: Yield data has been collected from 19 replicated trials in Georgia and South
Carolina. Yield was numerically reduced in unprotected plots in 16 of 19 trials with an average
yield loss of 18 percent and a range from 0-47 percent. Kudzu bugs feed on plant sap and can be
considered a stress inducing pest. Excessive kudzu bug feeding negatively impacts soybean
yield by reducing pods per plant, reducing beans per pod, and/or reducing seed size. The
mechanism of yield loss is likely due to the physiological timing that stress occurs on the
soybean plant. These yield loss components are very similar to what we observe on soybeans
which are drought stressed.
Scouting and When to Treat (Threshold): Kudzu bugs can be scouted using a 15-inch
diameter sweep net. Kudzu bug populations can be extremely high, especially on field edges.
We are suggesting a threshold of one immature kudzu bug per sweep. This suggested
threshold is based on 2011 field trials where a single properly timed insecticide application
preserved soybean yield. In the majority of trials we have conducted, nymphs usually appear at
about the R-2 to R-3 growth stage. If adult numbers are extremely high (multiple adults per
sweep) and soybeans are stressed, treatment should be considered; this is a judgment call but the
idea is to avoid bug induced stress on soybeans that are also stressed for some other reason.
Growers should consider using Dimilin as a preventive treatment for velvetbean caterpillar since
kudzu bug insecticide applications will be disrupting natural controls. (Phillip Roberts)
I continue to take soybean leaf samples weekly and the lab has not confirmed it in the soybean
rust sentinel plot in Effingham County as of yet. The closest find of soybean rust to our location
was found on kudzu in Appling County. Good yield potential + bloom to early pod development
= advised use of a fungicide. Especially where dimilin, boron, or kudzu bug sprays are going
out. You can track the movement of soybean rust at the following website: www.sbrusa.net
Peanuts
Diseases currently reported as troublesome: Early leaf spot and white mold (“exploding now”
according to Dr. Tim Brenneman.
To effectively manage diseases in a peanut field in August, producers must have implemented an
effective management program much earlier in the season. Beyond choice of peanut varieties
with improved resistance to important diseases and decisions about crop rotation, fungicide
programs typically begin 30-45 days after planting. If the start of a fungicide program is delayed
too long, for whatever reason, much of August and September will be spent playing “catch-up”
with disease management, and this battle is not easy and rarely results in a satisfactory
conclusion.
However, August is a CRITICAL month for disease management, even if the start of a fungicide
program occurred months ago. Here are the reasons I place particular importance on disease
control in August.
1. Warm/hot temperatures prevail in August, increasing risk to white mold.
2. The risk to tropical storms increases in August; while a tropical storm may bring muchneeded rain, it will also bring moisture needed for disease to develop, rain-splash and
wind to move fungal spores, and saturated fields that may result in a significant delay in
fungicide application.
3. By August, the canopy of foliage will be well-developed in many fields. A dense canopy
will not only increase the risk to disease because of trapped humidity/extended length of
leaf wetness, but it will also shield the important “crown” of the plant from fungicide
applications.
4. By August, the amount of inoculum (i.e., spores from leaf spot pathogens) and nematodes
will have been steadily increasing and this will increase the “pressure” on the crop. With
regards to leaf spot, more spores, a denser canopy, and increased chances for delays in
fungicide applications all can lead to problems with disease management.
5. Finally, by August, the pods should be developing below the soil surface; the
development of pods and pegs increases the amount of plant tissue that must be
protected. Unfortunately the pods and pegs are the MOST difficult part of the plant to
protect. (Bob Kemerait)
Forages
Be on the lookout for Armyworms. Take a moment to scout your hay fields and pastures for
worms. Many locations have been sprayed recently or are currently being sprayed to control
worm infestations.
A number of insecticides are labeled for use on caterpillars in pastures. Familiar stand-bys are
Lannate and Sevin. Lannate requires a 3-day harvest or 7-day grazing interval. For Sevin, the
interval is 14 days. More recent additions to the list include a number of pyrethroid insecticides,
Tracer and the insect growth regulators Dimilin and Intrepid. The newest product registered on
pastures for caterpillars is Coragen (chlorantraniliprole).
Labeled pyrethroids include cyfluthrin (Baythroid), cyhalothrin (Karate and others) and
cypermethrin (Mustang and others). These are contact insecticides that have relatively short
residual activity in the pasture system in the hot weather usually associated with caterpillar
infestations, but they have no grazing restrictions and do a good job of controlling small to
medium size worms. Tracer is labeled at 1-2 oz. per acre, and the only grazing restriction is the
cows should not graze until sprays have dried. Pre-harvest interval for hay is three days.
Dimilin and Intrepid work by disrupting the molting process, and will not kill the worms as
quickly. These products are very effective on small (<½” or so) worms, but less effective as the
worms get larger. They are not a rescue treatment for heavy infestations of large armyworms.
There is no grazing restriction for Dimilin or Intrepid. Coragen gives longer residual control and
is labeled at 3.5-5 oz. with no grazing or harvest restrictions. (Will Hudson)
For those of you who are planning on overseeding pastures or planting small grains for grazing
this fall, be sure to scout for armyworms. If armyworms invade the small grain seedling in the
early stages, they can potentially destroy it. Do not let armyworms destroy the investment of
your winter grazing forage and delay the date the cattle will be allowed to graze.
Upcoming Dates of Interest
August 15 – Peanut Shade Tree Meeting – Effingham County
August 16 – Southeast Georgia Research and Education Center Field Day – Midville
September 12 – Georgia Cotton & Peanut Field Day – Tifton
September 18-19 – Grazing School – Tifton
If you have any questions or I can be of assistance to you, please do not hesitate to give me a call
at 754-8040 (office) or 429-8004 (mobile).
Bill Tyson
Effingham County Extension Coordinator/Ag Agent