Cotton Insects (Phillip Roberts)
The question has been asked if we should manage insects differently in late planted cotton.
The answer is no, however we cannot afford to make any mistakes as mistakes will be costly.
A late planted crop will have limited time to effectively bloom and set harvestable bolls.
Cotton with a more extended effective bloom period may compensate and recover from
some management mistakes (i.e. delays in maturity and/or lost fruiting positions). Scout
closely, use thresholds, and make good decisions with insecticide selection and timeliness of
application. It is likely that we will need to scout and manage June planted cotton until the
end of September. A few specific points to consider for insect pest you will likely encounter:
1. Thrips are the most consistent and predictable insect pest of cotton. We are all familiar with the
stunted growth and crinkled leaves associated with thrips feeding. Excessive thrips damage will
delay maturity up to 7-10 days which is unacceptable on late planted cotton. Historically thrips
infestations are low on June planted cotton. Cotton planted in June also has rapid seedling growth
which allows the plant to better tolerate feeding. Don’t assume thrips injury will be low in your
fields as delays in maturity could have significant impact on yield potential.
2. Aphids will infest most cotton fields during June each year. Populations vary from year to year
and even field to field. We normally see aphid populations crash in July due to a naturally
occurring fungus. On late planted cotton aphids may infest cotton in the seedling stage. Stress
from aphid feeding on seedlings will slow development (delay maturity) which may limit yield
potential of late planted cotton.
3. Tarnished Plant Bug is a sporadic pest of cotton in Georgia. Plant bugs feed on small squares
with needle-like mouthparts; damaged squares will be shed by the plant. Plant bugs can be
sampled with sweep nets or drop cloths. Square retention should also be monitored. Our goal is
to retain at least 80 percent of first position squares when entering bloom. Poor square retention
will delay maturity and again have significant impact on yield potential of late planted cotton.
4. Corn Earworm typically first infest cotton in mid-July. Corn earworm completes a generation in
about four weeks. In recent years there has been much discussion about corn earworm and
erosion of efficacy with Bt cottons (this is especially true in the Mid-South and North Carolina.
Three gene Bt cottons are commercially available and will provide additional protection
compared with two gene Bt cottons. Bottom line is to scout and use thresholds and be timely
with insecticides if needed regardless of technology used.
5. Stink bug infestations are typically higher in June planted cotton compared with April and early
May planted cotton. Scout and use thresholds. Remember that the threshold is lower during the
3rd-5th week of bloom.