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.

There’s Smoke and Fire in the Hot Air Across the Valley

Where there’s smoke, there’s fire.

Well, in this hot, dry post rainy season, this trite phrase is more than cliché around these parts.  In recent days, thick, brown choking smoke has enveloped the Valley.

Coupled with the summertime triple-digit temperatures, the smoky conditions make it tough for growers, farm-hands and others who earn a living working outdoors. It’s also rough for folks with respiratory conditions.

The fire: A massive, out of control blaze in Mariposa County, east of Merced, and other locales around the Golden Brown State.

“The smoke is really bad,” says almond field scout Jenna Mayfield. “It also has been really hot.”

The Fresno region, for instance, recorded triple-digit temperatures for 16-straight days this month, before dropping to 98 “cool” degrees last Wednesday. Ah, 100-degree weather returned over the weekend.

In almonds, there could be a different kind of fire smoldering in orchards: namely pests.

Peach twig borer numbers on the rise.

“Peach twig borer was getting a lot higher last week, more than previous weeks,” Jenna said. The spate of very hot weather triggered the uptick.  We’ll see how the numbers shape up this week.

Peach twig borer, or PTB, produce four generations each year. The larvae, or small caterpillars, damage the nuts as well as growing shoots. They cause shallow channels and surface groves. Sometimes, PTB damage can be masked by navel orangeworm damage. The reason: NOW will feed on earlier damage caused by PTB.

In some instances, growers have no other choice but to treat their orchards for the pests. Here are some monitoring tips from UC IPM:

Natural enemies can keep PTB larvae in check in the orchards.

• Use past history, including results from harvest samples from the previous year, to determine if your orchard will require treatment.
• Preferred treatment timing is during the dormant period (combined with oil sprays if there is concern for San Jose scale, European red mite, or brown almond mites) or at full bloom and petal fall (may be combined with bloomtime fungicide sprays, but check restrictions on compatibility).

Of course, exploring biological controls before determining whether to treat the orchard is a good management practice. PTB doesn’t have lots of friends – the pest boasts some 30 natural enemies.

Almond kernels damaged by PTB.

“In some years and orchards, these natural enemies destroy a significant portion of larvae, but they may not reduce twig borer populations below economically damaging levels. Ants also can be found preying on peach twig borer larvae.”

Right now, PTB isn’t a major threat as almond hulls begin to split. But, Jenna warns, “it’s something to look out for.”

Hull Split Timing Crucial for Harvesting Almonds Successfully

After months of watching their orchards go from bud to bloom to nut, the big moment has arrived for almond growers.

It’s hull split time. That means growers will start shaking the nuts off the trees soon.

Field scout Jenna Mayfield reports about 15 percent of hulls are split open in trees. Harvest starts when 95 to 100 of the hulls have split.

Unsplit almond stage. (UC IPM photos)

As we all know, of course, fruit – whether it’s a peach or an almond – doesn’t ripen uniformly. Oh, that would be too easy.

For almonds, hull split usually starts in the upper and outer sections of a tree in the southwest area – where it gets the most sun during the day. The nuts on the top of the tree are the least mature.

Initial separation of hull.

As a result, it’s important for growers to continue monitoring the progress of hull split to protect against pests. Jenna notes growers have been applying hull split sprays to combat bugs such as navel orangeworm (NOW). University of California Integrated Pest Management says NOW applications should be done during the start of hull split and the beginning of egg laying.

Hull at the deep "V" stage.

Peach twig borer and hull rot fungi are other concerns at hull split. Remember, the hulls provide a protective shell and after they split open the nuts are exposed to these bugs. It’s important to harvest the crop as soon as possible to limit pest exposure.

Split of ess than 3/8-inch.

Initial drying stage.

The first thing growers need to do is find out if hull split has started. Sometimes, it’s tricky to see through the foliage and branches. A handy trick is using a pole pruner to cut small branches from the top southwest section of five or six trees to see if hulls are starting to split.

Here are some other tips from UC IPM:

• Continue monitoring trees until 95 to 100 percent of the fruit at eye level are visibly split.

        To determine when to start harvest, growers can hit a tree limb to see how easily the nuts come  off. Then test shake a few more trees. When 99 percent of the nuts are shaken from the test trees then the time is right to start shaking the entire orchard.

Complete drying stage of almond.

• Harvest blocks with poorest sanitation first.

·  

Historically, shaking starts in early to mid-August. But Jenna has seen in the past growers starting tree shaking as soon as July 25 in the Northern San Joaquin Valley.

Nothing Beats Low-Tech When It Comes to Mapping Cotton Plants Developing in the Fields

Remember those days when book stores sold street maps and county map books.

  

Baby boomers can still visit AAA and pick up the old-fashioned folding maps. Millennials will snicker and pull out their smart phones tap into their Google Maps, Apple Maps or QuickMap apps.

So far, we haven’t found one for cotton plant mapping. Growers still have to do their mapping the old fashioned way as they keep track of developments in the field to help reap a successful yield at harvest time.

Plant mapping, or monitoring, comes in handy because it allows growers to identify potential problems and better manage their cotton. For example, mapping can aid in the timing of pest management decisions.

Field scout Damien Jelen has been mapping to monitor plant development. He reports fields are showing about 70 percent retention in squares. 

As a rule, there usually is only 25 to 60 percent retention of first position squares on fruiting branches 10 through 12. You start to worry when the first position  square retention on the upper five fruiting branches come in under 80 percent. This could be caused by insect damage or the lack of moisture.

In past, the routine was very labor intensive because it mirrored the detailed plant maps used by researchers, who recorded every fruiting part of the plant. But subsequent studies found gathering numbers for a few sites will produce useful information.

Rather than comb the field, you can go to four areas of a field and measure five plants in each area. The cotton season can be divided into four management periods:

·         From plant emergence to square: This is when you count plant stand and height and the number of nodes. Walk around the field and check for drainage issues, missing rows and pest damage. This information will help with replanting and pest management decisions.

·         From firstsquare to first bloom: In this stage, sample at least five plants in four different sections of the field. Then collect information about plant height, the number of nodes, fruiting branches and square retention. Also record fruit set and growth. This information is important for crunching numbers and guiding decisions on pest control and the possible use of growth regulators. For example, square retention calculations can assist in developing pest management strategies.

·         From first bloom to cut-out: This is the time when the plant becomes larger. You record plant height, number of nodes, nodes above first position white flower and first position squares above the white flower and first position bolls below white flower in the first or second position. This information indicates how the crop is developing and provides insights about vegetative growth and boll development as you approach cut-out – the final stage of plant growth before the bolls open.

·         From Cut-out to defoliation:Measure the plants for boll retention, boll re-growth and boll opening. Noting nodes above cracked boll will help with the decision about the timing of defoliation.

UC IPM offers a wealth of information and tools for cotton growers monitoring cotton plant growth. Perhaps one day some app developer will come up with a cotton plant mapping app.on their website

Meanwhile, on the almond front, field scout Jenna Mayfield reports hulls are starting split in trees on the outside margins of orchards. Mites are starting to show up and a number of growers are starting to apply miticides.

FIELD DAY: Learn about the latest developments in cotton during a 10 a.m. field day  Tuesday at Pik-A-Lok Farms on Bass Avenue in Mendota. Featured speakers  at the free even are:

·         Dr. Pete Goodell, UC Cooperative Extension and UC Statewide Integrated Pest Management emeritus, who will cover pests and pesticides and how to manage the crop for lint yield and quality.

·         Dan Munk, UCCE Fresno County farm advisor and cotton specialist, who will discuss monitoring cotton for improved yield performance.

·         Bob Hutmacher, UCCE extension specialist  of the Westside Research and Extension Center, who will provide an update on Race 4 fusarium in the region, cotton diseases and plant development issues.

Continuing education credits of 1.5 hours have been approved. The field day is sponsored by the San Joaquin Sustainable Farm Project. For more information, contact Project Director Marcia Gibbs at (530) 370-5325.

When Will Almonds Hulls Split? Here’s a Hint: Look Back to Winter, Early Spring Weather

 It may be the Fourth of July holiday tomorrow, but growers will still be out during the morning hours to double check the progress of their orchards.

Field scout Jenna Mayfield says growers have little time to rest and fully enjoy the holiday. They are quickly preparing for the start of the harvest season.

Hull split will be starting in the Valley.

Indeed, this is the time hull splitoften takes place – the first week of July.  There are many factors that influence the splitting of the green hull enveloping the shell: weather, the amount of stress on the trees and almond variety.

You might think the late spring and early summer weather greatly influences the start of hull split. But University of California, Davis researcher Ted DeJong found in a study that weather during the first 90 days after bloom is the best forecaster. Simply put: cooler weather during this period will translate into a later hull split while warmer conditions lead to an earlier split. You can learn more online about DeJong’s model on hull split predictions.

Late winter and early spring conditions influence hull split.

Now on to tree stress. Merced County’s UC Cooperative Extension farm advisor David Doll says there are indications the amount of stress and nutrients in trees influences hull split duration. For example, let’s say the trees are stressed in June. This will decrease the amount of water in the hulls, which means drying time is faster as they start to split.

Normally, the Valley experiences heavy heat in June – think the prolonged triple-digit heat wave we just went through. This extreme heat leads to stress because of the inability to manage irrigation properly.

Almond trees showing major signs of stress.

The nitrogen level in trees also influences the rate of split. Trees with a higher amount of nitrogen will have a longer period of hull split, Doll says.

Of course, you have to consider the overall health of the orchard. Orchards with trees that are growing vigorously experience less stress and have higher nitrogen levels. This can lead to an uneven ripening of the nuts on the trees. The result can be the nuts in the top part of the tree will split two to three weeks before the almonds on the bottom half. Uneven ripening isn’t good. This condition will delay harvest, which increases the risk of pest and disease infestations.

The lesson here, according to Doll, is the value of embracing best management practices such as proper irrigation techniques and nitrogen management. The payoff is an easier time during shaking and harvest.

Meanwhile, field scout Damien Jelen says growers are wrapping up another alfalfa cutting – which is good because worms counts had been on the upswing.

The story is different in cotton. As expected, lygus bugs continue to be worrisome. Damien reports seeing some damage to squares.

Lygus damage found in cotton squares.

“The southeast part of the Valley is getting hit pretty hard,” he said.  In one field, for example, Damien recorded 36 lygus bugs per 50 sweeps of his net. UC Integrated Pest Management guidelines put the treatment threshold at 2 bugs per 50 sweeps in late June. The threshold at the beginning of July bumps up to 7 to 10 lygus per 50 sweeps.

Damien says one grower already has treated for lygus. His advice to cotton growers: stay vigilant because it’s already shaping up to be a big year for lygus.