Now that we are mostly past the thrips window, people are beginning to ask about managing plant bugs in cotton. For better or worse, my recommendations have not changed substantially in the last 10 years. Thiamethoxam (Centric) or imidacloprid are my likely first choice of insecticides prior to bloom. Transform WG (1.5 oz/acre) is also an option but I prefer to hold that chemistry until near or early bloom, when nymphs or more likely to be present. Fitting Diamond (4 – 6 oz/acre) in just prior to or during early bloom is also an option, but remember you need to tank mix this will something that will also kill adults.
Recommended treatment thresholds:
- First 2 weeks of squaring = 8 tarnished plant bugs per 100 sweeps
- Third week of squaring until bloom = 15 tarnished plant bugs per 100 sweeps
- Remember our goal is to maintain 80% square retention through the pre-bloom window, so be more aggressive in situations where retention had dropped to or below 80%.
Typical use rates:
- Centric = 1.75 – 2.0 oz/acre, with the rate often increasing with the size of cotton or the size of the infestation. Use the higher rate when pressure is high.
- Imidacloprid = maximum labeled rate which varies based on formulation (read the label)
- It’s become pretty common to mix a reduced rate of Centric (1 – 1.25 oz) with a full rate of imidacloprid. Imidacloprid products are cheap, but adding Centric improves “knockdown” while keeping costs down. You are getting more active ingredient for the same price you might pay for a full rate of Centric.
Note: The use of pyrethroid insecticide or acephate is strongly discouraged prior to bloom. Pyrethroids are not effective and potentially flare infestations of spider mites and aphids. Acephate may also flare secondary pests, but we also need to reserve this product’s efficacy for later in the season (and future years). Bidrin is NOT labeled for use between first square and first bloom.
Don’t forget about the new Cotton Insect Guide at http://guide.utcrops.com/cotton/cotton-insect-guide/.