1. Thrips- The heaviest pressure encountered this season was
from about May 1-20. From monitoring 5 thrips trials, it appeared to me that
thrips were later than normal moving from wild hosts and wheat to cotton. In
addition, thrips pressure was not uniformly heavy. In some fields it seemed
only low to moderate pressure was encountered. Cotton is growing very rapidly
now and once it reaches the fourth leaf stage should be safe from economic
thrips injury. Cotton planted on or about May 15th, with seed treatments,
should not need a foliar overspray. Remember that seed treatments give adequate
protection under most conditions until about 21 days after plant.
2. Grasshoppers- We lost another 45 ac. field in Talladega
County to grasshoppers last week. The cotton was in the “crook” stage of
emergence when attacked by grasshoppers. The strange thing about grasshopper
feeding is that you can never predict when they will turn to cotton to feed.
Grasshopper numbers do not mean much as far as thresholds. Sometimes a low
number will cause a lot of damage and other times high numbers will result in
no feeding. The usual damage from grasshoppers to cotton is in the form of stem
feeding. They will feed on and cut the stem of the plant anytime from the crook
stage up to about the 2-3 true leaf stage. Most grasshoppers in the system now
are adults and are rather difficult to control. A max labeled rate of a
pyrethroid or .75-1.0 lb. acephate is the usual grower choice in May. Back in
March and April, a low rate of most any cotton insecticide will do a good job
when the grasshoppers are still immatures.
3. Slugs- We have had two more locations last week where
slugs were damaging stands of cotton or soybeans. This brings a total of five
or more locations with loss of stands to slugs this season. These fields are
always in no-till, high crop residue situations. Usually the grower/consultant
looks in day time and sees pillbugs or snails and not slugs- only when
observing at night do we find the real culprit, slugs. They bury deep in the
residue during the day and only feed at night. Snails and pillbugs normally do
not feed on cotton or soybeans. There is not much a grower can do about slugs.
Metaldehyde at 10-40#/ac. is the only recommended chemical. At $2.25/lb. this
would cost $25-85/ac. and controls, even then, may not be 100%. Seems to me
that replanting would be the best alternative to slug damaged stands. Slug
damage seems to usually be when cotton or soybeans are following corn.
