Labor Day: Another Day in the Field for Farmers, Pests Alike

 It’s safe to say farmers rarely take a holiday on Labor Day. To them, Labor Day is a busy time of the season and there is little time to relax. You can say the same thing with pests, too.

Indeed, I am seeing cotton growers working daily to manage growing aphid populations in their maturing fields. Because more bolls are opening, growers are treating their fields to prevent a major outbreak down the road. They are worrying about developing sticky cotton down the road.

Thanks to the nagging heat wave that enveloped the Valley last month, I’m spotting more aphids than usual for this time of year. These pests love the heat and they tend to reproduce faster in hot weather. We certainly had our share of heat last month – it was the hottest August in more than a century.

Aphids are on the increase in the Valley cotton fields.
- UC IPM photos by Jack Kelly Clark

Right now, acala planted early in the season (April 15-25) are at 20 to 30 percent boll opening. Pima, which is harvested very late in the season, is at 5 to 10 percent opening.

I’ve heard a few growers have gone all out and using stronger treatments for aphids that essentially wipe out beneficial insects. That can open a Pandora’s Box. By following this route, growers bet the harsher treatment will get through the time to defoliate the plants and eliminate the pest problems.

I call that rolling the dice and betting you don’t get bit with snake eyes. The reason: If there is cooler weather down the road then the boll ripening process will slow down. That means aphids could resurface and force growers to apply another treatment. The defoliation target date is around September 20 with harvest coming around October 15 to 25. It can be particularly tricky with later ripening pima varieties.

For the most part, growers are turning to softer chemicals that will control aphids while protecting beneficial insects. That is the preferred practice for the growers who participate in our project. You preserve biological controls and let natural predators gobble up the aphids. This protects the environment and public health while saving time, labor and money in the long run.

Cotton growers need to monitor their fields for whiteflies.

Another worrisome pest I am spotting in the field is the whitefly. The pest is starting to show up in cotton as nearby tomato fields start to dry. I’m spotting mostly greenhouse whiteflies (here is a picture gallery to distinguish between whiteflies - http://ucanr.org/sites/CottonIPM/Useful_Reources/ with some silverleaf showing up in the plants. Again, the heat has sped up the population buildup and  harvest in other crops is accelerating the migration of whiteflies into lush cotton fields.

To assess whiteflies, you want to examine the fifth leaf down from the terminal. Check the a quarter-sized area between the central and left side main veins and for presence or absence of nympths (3^rd or 4^th instar). Learn more about aphid and whitefly monitoring and management guidelines from UC IPM.

Meanwhile, mites are popping up on some places. They’re most likely coming from nearby almond orchards. These pests can defoliate the leaves and leave you with bare cotton, which increases exposure to pests. For now, mites are a major threat, but they warrant monitoring. Growers also need to keep an eye for worms, which can move into cotton from drying alfalfa and tomato fields nearly.

Some orchards have almonds drying on the ground.

On the almond front, field scout Horine has taken nuts samples from all the orchards and found everything pretty clean. Overall, mites don’t pose a serious problem at the moment. For those growers dealing with mite pressure, they go ahead and spray for the pests if the nuts are still on the trees, says retired University of California entomologist Walt Bentley. In the meantime, hullsplit continues to vary – even within the same orchard.  So far, things are going pretty smoothly.

Save the Date: Spread the word about our annual Cotton Farm Tour on Friday, October 19. Once again, the price is right: Free. We meet at 8:30 a.m. at the Best Western Apricot Inn, 46290 West Panoche Road, Firebaugh. Check the Sustainable Cotton Project website for details and to RSVP.