"There is a little bit of everything this year. There is a tremendous range of conditions," University of California Extension Cotton Specialist Bob Hutmacher said at a recent mid-season Madera/Merced county grower/pest control adviser meeting in Dos Palos, Calif.
Early planted fields suffered seedling disease problem from a wet, cold spring planting season, and the setback remained evident into the middle of July with stress from weakened root systems. However, many later planted fields looked "quite good" as warm weather arrived, albeit late. The first 100-degree day was not recorded until around July 1.
Monitor, monitor, monitor for fruit set, pest levels and irrigation scheduling were the three biggest recommendations for growers and pest control advisers from Hutmacher, UC IPM specialist Pete Goodell and Fresno County farm advisor Dan Munk.
Hutmacher said the wide range of variability precludes this from being a blanket Pix year. Monitor fields to determine if Pix is a good choice this season. It may cost yield unless the right plant growth regulator decision is made.
And, avoid water stress, said Hutmacher. There were water stressed fields headed to cutout in mid July, and there was no turning them around. One caveat on avoiding water stress came from Munk who suggested if plant mapping is showing high vigor and low fruit set, it may be wise to wait a couple of extra bars of the leaf water potential measurement chart to irrigate. This may force more fruit set.
The set is late with the lateness of the crop. The crop was hit with an oppressive heat wave about the middle of July with about 20 days of 100-plus temperatures. That could cause fruit shed and if coupled with high nighttime temperatures, result in pollen sterility. Others say that the lateness of the crop could be good, precluding the cotton from setting some of its crop during high heat periods. It all depends on when the cotton was planted as to the impact of the heat.
With the lateness of the season, Hutmacher re-emphasized past research that indicated a flower on Aug. 1 does not become a harvestable boll until Sept. 26. An Aug. 23 flower does not become a harvestable boll until Nov. 3.
Lygus migrating from tarweed along Interstate 5 along the West Side of the valley have caused problems as Goodell predicted earlier. Some growers had treated 4 times for lygus by mid-July. Goodell said growers had no choice but to protect squares, but the consequences of wiping out predators/beneficials with the lygus treatments could be costly later in the season.
"Many growers already have a lot of pest control cost in this crop and they are still facing possible worm, aphid, mite and whitefly control costs of $100 or more per acre," said Goodell.
Just like the plant variability Hutmacher noted, Goodell has seen the same thing in the pest arena. While some fields had been treated four times for lygus by mid July, others had not been treated at all. Pockets of aphids protected by ants have been found in fields. Worm pests have been a problem in some areas. Goodell has seen pest problem pockets within fields.
On the weed front, Ron Vargas, UC Extension farm advisor for Merced and Madera counties said he has been getting many calls about a big proliferation of star thistle this season from all the rain.
The issue of weed resistance to glyphosate and other herbicides continues to grow. Anil Shrestha, UC IPM weed ecologist at the UC Kearney Ag Center, said California has officially become the 11th state in the nation to declare marestail/horseweed resistant to glyphosate.
However, marestail can be controlled mechanically, and Vargas said the newly registered tree and vine herbicide Rely also will control it. In row crops Ignite is basically the same compound as Rely.
Ignite will be the herbicide for use on herbicide-resistant Liberty Link cotton when it is introduced into California in a few years. It is registered now for post-directed weed control in non-Liberty Link cotton.
Vargas has been evaluating Ignite on some of the tougher weeds in California: nightshade, pigweed and field bindweed. It was not expected to do well on nightshade, but that use may be it brightest future.
In trials Vargas conducted this season, Ignite provided 84 percent to 90 percent control of field bindweed 32 days after treatment.
It also gave good control of black nightshade and pigweed.
However, it is the field bindweed control that has Vargas excited. Bindweed is a major problem since left uncontrolled it can climb up cotton plants and create many problems.
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