What is in this article?:
- Thrips waiting to pounce on North Carolina cotton?
- Treatment threshold
• Thrips could very well become a problem during the third week in May for many North Carolina cotton producers when the residual effectiveness of the seed treatments begins to play out.
GOOD EARLY seed treatment activity (note expanded cotyledons), followed by subsequent loss of residual at 2.5 weeks (note ‘possum-eared’ next 4 true leaves). Seedlings approaching 5 true leaves are out of danger from additional damage.
With cotton planting seriously getting under way during the first couple of days in May, thrips have not yet played their hand.
This will probably change during the third week in May for many North Carolina cotton producers when the residual effectiveness of the seed treatments begins to play out.
So far, our temperature and moisture conditions over much of the state, though a little cold recently, have been favorable for both seedling emergence and insecticide uptake. This was certainly the case at Upper Coastal Plain Research Station near Rocky Mount where good stands emerged within 6-7 days at all six our early May 1-2 planted thrips tests.
Thrips levels following one of the seed treatments there averaged only 1/10 of one adult and no immatures, while the untreated check in the same test averaged 1.2 adults and 1/10 of an immature thrips in one of our tests on Wednesday May 9. With these low thrips levels, we could see no difference between any of the treatments at 8 days after planting.
Hopefully, that’s the case over most of the state for cotton planted last week. Remember, however, that next week’s report could be much different as thrips levels build and the residual of seed treatments begins to run out.
Easy to talk about on paper, thrips counting and seedling damage assessments can be less than straightforward in the field.
Following emergence, seedlings can appear “beat up” for a number of reasons, in addition to thrips damage.
For cotton that is scouted following a seed treatment, granular insecticide or and in-furrow spray, always be sure to focus attention to the developing bud area and confirm the presence of live thrips with either a hand lens or by beating several seedlings onto a flat surface to look primarily for the small yellowish immatures.
The presence of immatures often indicates that the seed treatment or other insecticide has begun to run out.
The very tiny 1stand 2ndinstar immature thrips can be difficult to see with the naked eye due to their small size and their presence in the hidden folds of bud tissue.