Covering The San Joaquin Valley Since 1991
Lygus remain in play up and down the valley. We’re not hearing about runaway problems, but the pest is present. This continues to be a relatively light mite year, based on our most recent round of calls.
No DD60 table this week. Due to technical problems, this week’s DD60 data was unavailable.
COTTON FIELD CHECK: LYGUS/RETENTION
Pete Goodell, Extension IPM Advisor, issued a Cotton Field Check on Saturday, July 4, that reviews lygus and fruit retention evaluation methods. It includes tips and directions for lygus monitoring and retention evaluations, plus a sample scouting sheet, threshold formulas and tables.
Vern Crawford, PCA, Wilbur-Ellis Co., Shafter: "Lygus have been kind of weird. Some growers already have sprayed twice. We can’t figure out where they’re coming from unless it’s related to growers mowing orchards or from other crops being harvested. Pete Goodell (Extension IPM Specialist) has theorized that this generation originated from lygus that came out of safflower last year after those horrible problems, then disseminated into permanent crops. I’m hearing other people up and down the valley talking about lygus treatments. Most people say mites are light, and I have to agree. We sprayed some cotton the other day where we were laying by and had a trace of mite, so we included a miticide.
"The hay looks pretty good, low prices aside. I’m hearing about some worms around. I’ve found beet armyworms in some of our corn, but it’s been fertilized and watered and growing so fast that worms can’t keep up with it. We won’t worry about them until the next cycle in 2 to 3 weeks."
Mark W.F. Carter, PCA, Agri-Consultants, Los Banos: "About 75% of our fields are in bloom, with the rest not quite there yet. We’ve just finished the Temik, and growers were going to knock down the ditches and cultivate everything and put on foliar fertilizer and Pix. But with this heat they figured they would get too far behind on water if they did that now. We put on Zephyr 3 weeks ago at a 4 oz/acre rate, and mites aren’t too bad right now. We’ve treated about 25% of our crop for lygus. Most of them came out of the grower’s own hay field where strips weren’t left.
"Tomatoes are progressing, and we’re making another worm and fungicide spray. The first harvest day is around August 15, so we’ll be thinking about shutting off water on the first fields in a couple of weeks. We’re spraying all of our alfalfa for yellow stripe armyworms, the first time we’ve treated worms in alfalfa this year. Between treatments needed in tomatoes and alfalfa, I think the applicators are starting to fall a little behind."
Bob Hutmacher, Extension Cotton Specialist: "Even with the recent heat, a lot of cotton still looked pretty good this past week in fields checked in Kern, Kings and Fresno Counties. High temperatures of about a week ago probably didn’t damage cotton much, other than in fields that were also very water stressed. We had temperatures up to 107 and higher-than-normal nighttime lows, but that did not coincide with a big fruit load. The same level of heat and high night temperatures would typically do more damage if they occurred later in boll development due to the effect on photosynthetic rates and carbohydrate partitioning.
"We’ve been following a fair number of Pima and some Acala fields that had missing first and second position fruit in the first 2 to 3 fruiting branches over the past few weeks. But in our more recent retention analysis, the numbers in that cotton have started looking quite a bit better. In the next 5 to 6 fruiting branches after those earlier losses, many fields have 80%-plus retention in first and even second position squares and blooms.
"Given the timing of many fields at early bloom, it’s prudent to try and identify developing problems, like severe water stress, lygus pressure or other insect issues. If one of your key goals in a water-short year is to limit the need for late irrigations and the dependency on a top crop, then you’ll need most of the current batch of developing blooms and small bolls to keep plants on track for decent yield potential.
"We decided to go ahead with applications of materials like Carbine and/or Provado this week for mild to moderate lygus populations in some of our research fields. To date, lygus populations have not been dramatically high in any of these fields at any of our research or variety trial sites. But we did have counts of 3 to some as high as 8 per 50 sweeps, with some indications of building nymph populations."
Pete Goodell, Extension IPM Entomologist, Kearney Ag Center, Parlier: "I was called to an Acala field this week because of a sustained lygus movement out of alfalfa and possibly wheat. The field had 7-plus counts per 50 sweep over a 2-week period, and that resulted in 2 insecticide applications. There was no evaluation by the PCA or consultant regarding fruit retention. After collecting the information, it was obvious the field had not sustained much damage for the population present, and crop development was not delayed. While insecticide intervention was justified by the population density, knowing fruiting pattern could have provided additional information.
"I want to remind everyone that combining the fruiting pattern with lygus numbers is a powerful tool that has been available since the early 1990s. The results from a fruit retention analysis provide important information about growth and development of the crop. While the initial measurement is somewhat labor intensive, after the bottom fruit set is established for the field, data gathering is not very intrusive during the standard field scout check. Fruit evaluation does not need to be conducted weekly but only during critical periods when lygus have moved into a field or to evaluate the result of an application for lygus.
"For more information, see the Cotton Field Check for July 4, 2009. Feel free to contact me – firstname.lastname@example.org – if you have questions or would like to request a field review of the process."
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