Controlling Aphids Can Be a Sticky Issue for Growers

This time of year cotton fields start turning the corner from a sea of pink, yellow and white flowers to an ocean of lush green bolls. 

Here is a close-up photo of aphids. -- UC IPM Photo

Lurking in the background, though, are pests that can damage the crop and inflict economic pain. Field scout Carlos Silva reports cotton aphids are taking center stage on the pest front right now in a number of fields, particularly in the Firebaugh region of Fresno County.

About of third of the cotton plant leaves he has inspected are infested with aphids. “Growers are starting to think about how they may need to get rid of the pest,” Carlos says.

Aphids can be found throughout the season and cause different kinds of problems during the growth stage of the cotton plant. During the spring, heavy aphid populations can cause leaves to crinkle and stunt seedling growth.

 

Aphids are found on the back of a cotton plant leaf.

Carlos says growers need to be vigilant with their monitoring programs. UC IPM says it’s important for growers to be aware of both the number of aphids and the color of the pests. Small yellow aphids develop slowly from nymphs to adults and don’t produce many offspring. As a result, their populations don’t increase quickly. On the other hand, darker green and black aphids reproduce rapidly and their populations can explode.

Natural enemies such as parasitic wasps, minute pirate bugs, bigeyed bugs and green lacewings can help control aphids. “There are a lot of green lacewings in the fields,” Carlos says.

Honeydew residue creates a sheen on a cotton plant leaf.

However natural enemies won’t be enough to tackle a heavy aphid infestation. But chemical treatment isn’t a simple solution. Here’s what UC IPM says:

 

“Chemical management of cotton aphid can be extremely erratic and unpredictable. Part of the problem is that cotton aphid has developed resistance to many chemical classes, including organochlorine, organophosphate, carbamate, and pyrethroid insecticides. In addition, these broad-spectrum pesticides kill the natural enemies of the cotton aphid. Another resistance concern is with the neo-nicotinoid insecticides. Repeated applications of any neonicotinoids can result in resistance to all neo-nicotinoids.”

Parasitic wasps can help control aphids.  -- UC IPM photo

“To manage resistance, follow the basic principles of IPM: (1) spray only when pests reach economic thresholds; (2) start with the most selective pesticides and avoid pyrethroids early in the season in order to preserve natural enemies; (3) save the broad-spectrum pesticides for mid- to late-season aphid outbreaks; and (4) rotate insecticides that have a different mode of action group number if you have to spray more than once.” Go online to UC IPM’s cotton aphid management site to see a table that summaries insecticide resistance guidelines.

Overall, cotton development is progressing well. Growers are irrigating their fields for the third time this season. The plants are at about 12 to 13 fruiting branches.

In alfalfa, growers are preparing for another harvest. So far, it appears many growers have enough water available for another cutting.
 
Carlos reminds growers to continue leaving strips of uncut alfalfa to create a habitat for lygus bugs and keep them migrating to nearby cotton fields. “There still is a lot of lygus in the alfalfa fields,” he notes.

There’s Something Shaky about the Almond Harvest

It is shake and bake time.

That’s right. Field scout Jenna Horine is reporting the first sightings of almond growers shaking nuts off the trees. The fresh almonds will be baking on the ground a few days before being swept up and collected.

It’s not our imagination. The start of the almond harvest has been getting a little earlier and earlier in recent years, thanks to the dry winters we have been experiencing across the Golden “Brown” State the past four years. The almond season has been getting a jumpstart during the drought.

Almond tree shaking is starting to  occur on the  westside.

Jenna says her records indicate the first shaking in the northern San Joaquin Valley took place around July 25 last year. She expects more growers to start knocking nuts off the trees this week.

The early shaking occurred on the westside, which is normally warmer and drier end of the Valley. The soft shell nonpareil variety is the first to develop and be harvested. Commercially, they are the most versatile and widely used almonds because the skins can be easily removed and the smooth kernels “allow for easy, blemish-free processing,” according to the Almond Board of California.

 

Later in the season, growers will go back into the orchard and shake trees with the hard shell varieties such as the butte and mission. Jenna says the hullsplit is still a ways off for these varieties.

Ending irrigation two weeks before shaking protects trees.

David Doll, the almond expert and pomologist with UC Cooperative Extension in Merced County, reminds growers to stop irrigating about two weeks before harvest to prevent tree damage due to shaking. Damage to the bark is the most common problem from mechanical shaking.

 

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.

Fallen nuts aren't left too long on the orchard floor.

Mechanical shaking should be started when the interior of the orchard is at about 95 to 99 percent hullsplit. Another factor to determine harvest timing is the need to avoid navel orangeworm damage to the nuts on the tree and ant damage on the ground. The longer the nuts are in the orchard the more likely there will be pest damage.

Usually, the nuts on the ground are hullable within two weeks. Jenna says growers often will remove the nuts from the orchard floor rapidly for pest and disease management purposes.

Meanwhile, Jenna says she has spotted stink bugs in some orchards. Areas near heavily traveled dirt roads are grappling with mites. Overall, though, pest pressures appear under control for growers.

In other crops, field scout Carlos Silva says alfalfa growers should be harvesting again over the next couple weeks. Weevil counts are up in some fields, but still under the threshold to consider treatment. But growers need to keep a close eye on weevils to keep them in check.

Fruit retention has been good in cotton fields.

Cotton plants are developing nicely, averaging about 11 fruiting branches. Fruit retention ranges from 65 to 70 percent. That’s a good rate. Anything below a 55 percent retention rate could be troublesome. Check out UC IPM’s online publication about fruit retention and lygus monitoring.

Carlos points out he is snagging two to four lygus bugs per 50 sweeps of his sweep net, which about half the rate for growers to start considering treatment. Again, a regular monitoring program is important.

Dusty Roads Might Stir Up Mite Trouble for Almond Trees

Every year, we talk about dusty roads and spider mites, especially during the hot summer months.

Kicking up dust will stir up mite populations.

 

These pests will reproduce quickly in hot weather and are most populous from June to September. Dusty conditions can trigger outbreaks.

To help control mites, growers should “apply water to pathways and other dusty areas at regular intervals,” UC IPM says. “Water- stressed trees and plants are less tolerant of spider mite damage. Be sure to provide adequate irrigation.”

Mites feed tree leaves and can lead to defoliation in the most severe situations. Major mite damage can cause a loss in yield.

Example of a web spinning mite issue.

Of course, keeping dust down on roads and providing trees and plants with enough water becomes a little problematic – and costly – for farmers during a severe drought. But growers have little choice because watering down roads and watering crops is matter of economic survival.

Field scout Jenna Horine sees out water trucks out regularly sprinkling H2O agua on dirt roads around melon fields bordering almond orchards. The melon harvest is in full swing, which means lots of trucks running in and out of the fields.

“It’s important to keep the dust down,” Jenna says. The recent heat wave was driving up mite numbers in the almond orchards. However, Jenna notes that most growers have applied miticides in their hullsplit treatments. That has kept mites under control for now.

Check beneficial populations before treatment.

Of  course, non-chemical, biological ways are effective in controlling mites too. UC IPM advisors point out growers could hold back on second miticide applications to give beneficial insects a chance to build their population to knock down mites. Under this approach, growers have to be comfortable enough to tolerate some amount of leaf damage to give beneficials enough time to gobble up the mite population. Yes, it’s a good practice to check on the beneficial insect population in the orchard before deciding to spray.

Cotton plants, too, can suffer mite damage – in which leaves turn yellow or red and then drop. This condition could hamper development of cotton squares and bolls, causing them to fall to the ground. Whole plants can become defoliated. Early plant and fruit development are when mites become the biggest threat.

Cotton fields are receiving the second irrigation of the season.

Field scout Carlos At the moment, Silva says lygus bugs have been in check in most fields. Plant development – around 10 to 11 fruiting branches – and fruit retention is good.

“Everything is growing quickly,” Carlos says, pointing out cotton plants are getting their second helping of irrigation water this season.

Field Day Alert: Don't forget the summer Alfalfa Field Day on Wednesday from 10 a.m. to 12:30 p.m. at Bowles Farming at the intersection of Hereford Road and Bisignani Road in Los Banos. The speakers are UC IPM advisor Dr. Pete Goodell on insect management; UCCE Davis alfalfa extension specialist Dr. Dan Putman on current issues, including weeds, water quality and availability and summer retirement of alfalfa fields; Merced County Deputy Agricultural Commissioner Sean Runyon on an update of chlorpyrifos regulations; and Cannon Michael of Bowles Farming. Continuing education credits for farmers and PCAs, including 30 minutes of regulations, will be available. For more information contact Marcia Gibbs at (530) 370-5325 or marcia@sustainablecotton.org

Little Time to Rest as Almond Growers Prepare for Hullsplit

Despite the sunrise-to-sundown work schedule, the Fourth of July holiday brought a welcome, but brief respite for growers – a time for barbecues, fireworks and get-togethers with friends and family. But there’s no rest for the weary.

Almonds are heading into hullsplit around the valley.

Almond growers, for instance, are keeping an anxious eye on their crop as it heads toward the backstretch to harvest time. Field scout Jenna Horrine reports growers are figuring out the timing for hullsplit sprays to protect against crop-damaging pests. 

UC IPM and extension advisors recommend growers follow an IPM and resistance-management approach to managing navel orangeworm (NOW) and spider mites. Most growers will spray for NOW at hullsplit and many make another application two or three weeks later.

Often, there are enough natural enemies in the orchard to control mites during the late season. If treatment is necessary, combining miticides with the hullsplit spray for NOW can save money by avoiding a separation application.

Monitor for pests before treatment.

Here’s what UC IPM says about hullsplit treatment: time the spray to the beginning of hullsplit “if eggs are being laid on egg traps; otherwise time it to an increase in egg-laying on traps or the predicted initiation of egg-laying following hullsplit. Hullsplit is determined to begin when sound fruit in the tops of the trees begin to split. At this time, the nuts at eye level will be less mature than those at the top and have only a deep furrow in the hulls. Nuts in the top southwest quadrant of the tree split first. Blank nuts (usually 3 to 5 percent) will split one to two weeks ahead of sound nuts. Use a long-extension pole pruner to cut small branches from the top portion of five or six trees in the orchard to check whether hullsplit nuts are blank or sound.”

Check traps for pest eggs.

“Check for eggs on egg traps. If hullsplit has begun, but eggs are not being laid, wait until egg-laying starts. After hullsplit begins, egg-laying on traps may decrease due to competition of the traps with the new crop nuts. Therefore, if you do not see eggs on traps, use degree-days and apply a treatment at 1,200 degree-days from spring biofix,” UC IPM says

Weekly monitoring of spider mites and predators should determine if miticide applications are needed.“When monitoring for spider mites, PCAs should also be looking for six-spotted thrips, predatory mites, spider mite destroyers and minute pirate bugs,” says David Haviland, an entomologist and almond expert with UC Cooperative Extension in Kern County.

UC guidelines call for treating for mites if half of the leaves sampled have mites. If there are no predators, then treatment should be made if 25 percent of the leaves are infested.

Jenna again stresses this is the time to closely monitor their orchards to keep on top of the pests and avoid a sudden population explosion just before harvest. Jenna says one orchard is already seeing the first signs of the hulls splitting. Other growers are expecting the almond hulls to start splitting soon.

Cotton plants are starting to experience bloom in the field.

Before we know, harvest time will be here. Jenna notes the earliest tree shaking last year came on July 25.Shaking time is around the corner.Meanwhile, field scout Carlos Silva says cotton growers are wrapping up the second irrigation of the growing season. The plants are at the colorfully flowering stage, lighting up fields with various shades of pink, white and yellow. So far, there aren’t any major issues with pests.
In alfalfa, growers are pretty much finished with another cutting and leaving strips of uncut alfalfa to keep lygus from migrating to nearby cotton fields. “There are a lot of beneficial insects in the alfalfa fields,” Carlos says.
  

Field Day Alert: Growers are invited to attend a Summer Alfalfa Field Day on Wednesday, July 15 from 10 a.m. to 12:30 p.m. at Bowles Farming at the intersection of Hereford Road and Bisignani Road in Los Banos. The speakers are UC IPM advisor Dr. Pete Goodell on insect management; UCCE Davis alfalfa extension specialist Dr. Dan Putman on current issues, including weeds, water quality and availability and summer retirement of alfalfa fields; Merced County Deputy Agricultural Commissioner Sean Runyon on an update of chlorpyrifos regulations; and Cannon Michael of Bowles Farming. Continuing education credits should be available. For more information contact Marcia Gibbs at (530) 370-5325 or marcia@sustainablecotton.org