Monday, August 6, 2012

It’s All About Timing When It Comes Time to Stop Worrying About Lygus in Cotton

 As we approach the start of August, I am beginning to see evidence of cut-out in cotton fields around the Valley. The timing couldn’t be better.

I’m finding during my field sweeps a general increase in lygus counts – anywhere from a 25 to 50 percent pick up from the week before. Dr. Pete Goodell of UC IPM provided these charts about lygus counts and fruiting branches from information gathered from fields in our San Joaquin Sustainable Farming Project

There is a large upswing lygus nymphs in these fields.
Retention is still good, but these numbers should give
some pause, especially the number of immobile nymphs.
 Cut-out is the final stage of cotton plant growth before the boll opens. This means you see mostly mature fruit on the plant with an absence of squares and blooms. Generally the plant has set more than 95 percent of its yield. UC IPM says you can stop monitoring for lygus about 10 days after cut-out. Check the UC site for more about how to time the count date.

Fruiting branches from all fields. Have we reached cut-out?
For now, growers need to continue with their plant mapping and monitoring for lygus in the field. Mapping helps you determine when to stop watching out for lygus. For the most part, I’m seeing four nodes above white flower. I’m reminding growers that lygus still can cause damage to small bolls. Remember, every boll counts. It’s money in your pocket at harvest time.
In the meantime, aphids are showing up here and there. But I’m spotting an increase of ladybugs and green lacewings, which at the moment can keep aphids in check. Growers are wrapping up their last irrigation. Before you know it, we’ll be on the backstretch of the harvest time finish line.

Everything is moving along with alfalfa. Growers have wrapped up their fourth cutting and are preparing for the fifth harvest. I’m noticing a little more aphids and worms in the fields. But I haven’t seen any growers treating their fields.

For almond growers, Merced County UC Cooperative Extension farm advisor David Doll, author of the popular Almond Doctor blog, spoke at our recent field day and offered some tips about pre- and post-harvest task:

As we approach harvest we want to cut that water back. But we don’t necessarily want to eliminate the application of water. We want to dry trees down so they can be shaken without much damage. But we want to make sure we are applying some water. We don’t want to go two weeks with no water. The other thing to keep in mind is as we approach the post-harvest period it’s a good time to make the consideration for foliar sprays. That includes boron.

 If you are battling with rust disease, knock the leaves off tree to reduce overburdening inoculation. In late October, apply 25 to 35 pounds of zinc sulfate to trees to knock off leaves. When applied in the fall, this nutrient can help break the rust and shot hole disease cycle. It’s important to remember when you knock the leaves off with that zinc spray you’re not going to get any uptake of any that zinc. So if you have a zinc deficit, you need to make that application earlier in the post-harvest period, probably with the boron.

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