Cotton Plants Thrive in Warm Weather; However Very Hot Weather Is Another Story

It’s a good thing we had a tremendous rainy season. And our cotton growers aren’t dry land farmers like those in the Southwest.

Cotton plants thrive in warm climates. But hot, hot prolonged heat is another story.

That’s why field scout Damien Jelen reports seeing growers turning on the irrigation spigots and giving their cotton plants a healthy dose of H2O.  “They’re pushing water because of the heat,” he says.

Growers giving cotton a hefty dose of irrigation due to heat.

You might ask “if cotton likes warm climates, why are farmers rushing to irrigate their fields? 

First, let’s go through a brief science lesson. Cotton plants are about 10 degrees cooler than the air temperature. The reason is the plant features a natural air conditioner: Almost all the water taken in by the plant evaporates to provide cooling. During July, the amount of evaporative cooling from one acre of cotton equates to the same cooling produced by 50 to 100 home air conditioners.

A study in Arizona found the canopy temperature in well-watered cotton fields averaged 88 degrees on a day when the air temperature surged to a scorching 121 degrees. In contrast, poorly watered fields recorded a canopy temperature of 104. 

OK. So what does this mean?

Cotton is blooming.

Simply put, high temperatures combined with water stress can lead to smaller bolls, the loss of bolls and leaf damage. Leaf damage can cause cutout to take place too early or impact crop set. That’s not good.

As we close out the month, the National Weather Service says the average high temperature for July was 101.7 degrees for the Fresno region. The forecast for the start of a new month: More triple-digit weather for the foreseeable future. Yikes.

Good thing we’re no longer in a drought – or don’t dry land farm our cotton.

For now, the heat hasn’t triggered a serious pest infestation. “Pest pressure is down right now,” Damien says. It’s good that alfalfa growers, who have wrapped up another cutting for the season, are following best management practices and leaving strips of uncut alfalfa in their fields that neighbor cotton fields. That can keep pesky lygus bugs from migrating into cotton.

Almonds hulls continue to split as harvest season nears.

Meanwhile, field scout Jenna Mayfield says webspinning spider mites are becoming an issue for almonds. “A lot of growers have been treating for mites.” While mites won’t cause problems this year, the pests will cause the loss of leaves and hurt next season’s crop.

“They affect the set of the trees the following year,” Jenna says.

Right now, many orchards are around 50 percent hull split. In another couple weeks growers should start shaking off their nuts, signaling the start of harvest.

Jenna also notes a mysterious ailment is cropping in a few orchards. For some reason, the leaves are turning yellow and the trees are dying – on newly planted and established trees.“Something is going on and no one knows why. They can’t figure out why their trees are dying.”

  

Certainly, growers don’t want to replant trees if you’re not sure if the problem will show up again.

Stay tuned.