Monday, June 25, 2012

Let's Draw a Roadmap for a Successful 2012 Cotton Crop

Remember drawing a treasure map as a kid. You drew elaborate lines and plotted landmarks leading the treasure awaiting the end of the hunt.

I relived those days many times in the past week. In this case, the treasure is a sea of fluffy white cotton fiber awaiting growers during the fall harvest. I spent hours mapping the fast-growing cotton plants across the Valley.

- Graphic by Texas AgriLife Extension Service 
Plant mapping can be rather simple. You don’t need to be a Van Gogh or make it complicated.  In fact, by making it easy, you are likely to continue mapping the development of your cotton plants. The work will help you make future management decisions and give you a good indication of the yield in the fall.

I’m seeing plants with 80 to 100 percent fruit retention – a very good rate. For Acala upland cotton,  growers normally can expect a 60 to 70 percent retention rate. Pima cotton is a little less precise to predict.

Lygus, however, is in full force in the cotton fields. It’s not surprising to see numbers rise following the third cutting of alfalfa in nearby fields. On the positive side, the lygus population could be even higher in cotton if growers didn’t follow best management practices and leave strips of uncut alfalfa to keep the pest from migrating into cotton.

Growers need to keep an eye on lygus in the coming weeks.
Still, cotton growers need to continue monitoring their fields and follow the trends carefully.  You can download a pdf of UC Integrated Pest Management’s guidelines about fruit retention and lygus monitoring.  It includes a handy chart to record your monitoring information.

I want to caution growers about jumping the gun on pest treatments. For example, I checked a field last Monday and found eight to nine adult lygus in my sweep net, which would put you at the threshold of treating your field. But a few days later, I re-checked the field and found the numbers had dropped to three to four lygus per 50 sweeps of my net.  The likely reason for the drop is the lygus “took a drink” in the cotton field and then returned to the nearby alfalfa field. Lygus actually prefer the conditions found in alfalfa.

So far, I haven’t heard or seen growers treating their cotton fields for spider mites and lygus. That’s good. Usually you will see growers on their first or second treatment this time of year. My guess is the strip alfalfa and the increase in hay acreage is dampening the pest pressure in cotton this year.

We’ve finished collecting petiole, or leaf stem, samples and sent them off to the lab. The results should be back in about a week. That will give us an idea whether plants need more nitrogen or have been fertilized too much.

Before the season heads into July, I want a take a look back at the spring. With the recent heat wave, plants are developing ahead of schedule. I wouldn’t be surprised to see cotton planted early in the season to starting blooming by the end of this week. Normally, you see bloom around the Fourth of July. An early bloom extends the growing season. It also gives growers a little insurance against early fall rains.

Beet armyworms are on the rise in Valley alfalfa fields.
- UC IPM photo
Looking at alfalfa, I’m finding a slight increase in beet armyworms. It’s important for alfalfa growers to conduct weekly pest monitoring and scout their fields before cutting. That way, you can determine if treatment is needed to prevent pests from migrating to nearby fields such as tomatoes and cotton. The good news is I haven’t heard of any growers treating for worms. Good management practices do pay off.

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