2-Plants: Good news for GE-companies - Future lies with GE-cotton plus insecticides

[GENETNL <genetnl@xs4all.be>]

----------------------------- GENET-news -----------------------------

TITLE:  Stink bugs emerging as major pest in Southeast cotton
SOURCE: Farm Press, USA, by Paul Hollis
        http://www.farmsource.com/News_Trends/newsarticles.asp?
        ID=16099
DATE:   April 27, 2000

-------------------- archive: http://www.gene.ch/ --------------------


Stink bugs emerging as major pest in Southeast cotton

STINK BUGS have emerged as a major pest in Southeastern cotton 
production primarily because of the reduced use of broad-spectrum 
insecticides for managing the boll weevil and the budworm/bollworm 
complex. "The success of the Boll Weevil Eradication Program and the 
widespread adoption of Bt cotton have played a significant role in 
reducing insecticide inputs for these prominent pest groups," says 
Jeremy Greene, University of Georgia Extension entomologist. "When 
insecticides routinely are applied for weevils and worms, populations 
of stink bugs are suppressed incidentally."


Rapid increase

In Georgia alone, Bt cotton acreage has risen from 30 percent of the 
total crop in 1996 to about 60 percent in 1999, he says. In addition, 
insecticide resistance is driving the development of more selective 
insecticides that target worms, and most of these have little or no 
activity on stink bugs, notes the entomologist. Stink bugs, says 
Greene, are active during most months of the year, feeding on 
numerous wild and cultivated host plants. "Damaging populations 
usually are observed in cotton during the months of July, August and 
September. During the spring and early summer, stink bugs develop on 
wild hosts such as clover and on cultivated crops such as corn, wheat 
and vegetables," he says.


Good control

Organophosphorus insecticides such as dicrotophos (Bidrin), methyl 
parathion, Penncap-M and acephate (Orthene 90S) provide good control 
of stink bugs in cotton, according to Greene. Pyrethroid insecticides 
also will offer some control and are useful when populations of 
bollworms and stink bugs are present at the same time, he says. 
Growers can determine when to treat for stink bugs by monitoring bug 
density with either a drop cloth or a sweep net, and by examining 
bolls for feeding symptoms.

There are several advantages, he says, to examining bolls as opposed 
to looking for bugs. "Bolls are easy to find, and looking for bugs 
can be difficult and time consuming. Also, cotton may be too high or 
too short to sample with a cloth or net. Examining bolls also allows 
growers to evaluate the effectiveness of different treatments. And, 
it can mean less time spent in the field," says Greene. Another 
reason for examining bolls, he adds, is that fire ants in 
conservation-tillage fields can become a problem for slow-moving drop-
cloth operators. As stink bugs age, says Greene, they can cause 
increasing damage to bolls in terms of visible symptoms of feeding 
and yield loss. Late instars - fourth and fifth - can cause damage 
comparable to that caused by adults. Bolls younger than three weeks 
from white bloom remain susceptible to damage from stink bugs, he 
says, but susceptibility decreases with age.


Treatment thresholds

All states in the Southeast have adopted the same treatment threshold 
for stink bugs in cotton with minor variations, he says. Thresholds 
are as follows:
- Georgia, South Carolina, North Carolina, Florida and Alabama
  - all use one stink bug per six feet of row (shake cloth).
- North Carolina and Florida - four bugs per 100 sweeps.
- South Carolina and North Carolina - one bug equals one adult or 
  large nymph.
- Georgia and South Carolina - Twenty percent damage to small bolls.
- North Carolina and Alabama - Ten percent damage to thumb-sized 
  bolls.

"Generally, an insecticide application is recommended at one bug per 
six feet of row. Because bugs occasionally are difficult to detect, 
most states now recommend a threshold for treatment based on a 
percentage - 10 or 20 percent - of bolls damaged by stink bugs." At 
season's end, there still is too much stink bug damage being found in 
cotton fields in the Wiregrass region of south Alabama, says Ron 
Smith, Auburn University Extension entomologist.

"A stink bug is going to do most of its damage to the bolls, from the 
time boll blooms have just dropped off up until bolls are about 18 to 
20 days old. After the bolls are 18 to 20 days old, they're hard 
enough so that stink bugs won't damage them," says Smith. Smith 
advises growers to look for stink bugs in the top of the plant or 
wherever the youngest bolls are found.

Stink bugs, he says, probably are not a factor in Alabama cotton 
fields until mid or late July. "August basically is our stink bug 
month. The stink bug damage will be big, sunken indentions in the 
cotton boll. You can slice into that and see staining of the lint 
where the stink bugs attempted to feed on the seed. Where the snout 
goes through the boll wall will leave either a brown area or one or 
more locks. In some cases, the entire boll is knotty at the top," 
says Smith.

When using the drop-cloth method of monitoring for stink bugs, he 
advises growers to carefully slide the cloth under the plant and then 
shake the plant or shake off the plant onto clear ground. "Shake the 
plant really good and look for the number of adult and immature stink 
bugs that fall. If you're using a drop cloth, look around it, because 
all of the stink bugs won't hit the cloth," he says. The most 
economical treatment for stink bugs probably is Bidrin, says Smith. 
Methyl parathion also does a good job, but it doesn't have much of a 
residual effect, he adds. "Pyrethroids also give us pretty good 
suppression, but that won't be good enough if the stink bugs are over-
running you," he says.


Ron Smith, Auburn University Extension entomologist.

"A stink bug is going to do most of its damage to the bolls, from the 
time boll blooms have just dropped off up until bolls are about 18 to 
20 days old. After the bolls are 18 to 20 days old, they're hard 
enough so that stink bugs won't damage them," says Smith. Smith 
advises growers to look for stink bugs in the top of the plant or 
wherever the youngest bolls are found.

Stink bugs, he says, probably are not a factor in Alabama cotton 
fields until mid or late July. "August basically is our stink bug 
month. The stink bug damage will be big, sunken indentions in the 
cotton boll. You can slice into that and see staining of the lint 
where the stink bugs attempted to feed on the seed. Where the snout 
goes through the boll wall will leave either a brown area or one or 
more locks. In some cases, the entire boll is knotty at the top," 
says Smith. When using the drop-cloth method of monitoring for stink 
bugs, he advises growers to carefully slide the cloth under the plant 
and then shake the plant or shake off the plant onto clear ground.

"Shake the plant really good and look for the number of adult and 
immature stink bugs that fall. If you're using a drop cloth, look 
around it, because all of the stink bugs won't hit the cloth," he 
says. The most economical treatment for stink bugs probably is 
Bidrin, says Smith. Methyl parathion also does a good job, but it 
doesn't have much of a residual effect, he adds. "Pyrethroids also 
give us pretty good suppression, but that won't be good enough if the 
stink bugs are over-running you," he says. 




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