Monday, July 16, 2018

Hot, Humid Weather Worrisome for Almond Growers

Bing… A short text message arrived on field scout Jenna Mayfield’s cell phone, reading “Hulls stopped splitting!”

The almond grower’s text was rather tongue-and-check, yet insightful at the same time. It appeared a build-up of hot, humid weather over the several days last week seem to slow hull split in his orchard.

Adding to grower anxiety, a few summer showers fell in parts of the Valley last Thursday night, cranking up humility levels as the daily high temperature reached the 100s. “We usually get this kind of humidity in September. To have it in July is definitely not normal.”

Humid weather and sprinkles worried growers.
Weather experts blamed monsoon moisture coming from the Arizona area for bringing the Hawaii-like humidity to the Valley and Northern California.  Yes, it was unusual to see lots of clouds in the sky on Friday and a higher-than-normal humidity during the mid-afternoon.

“Almonds grow best when we have super dry climate,” Jenna points out. “If the humidity continues it could be a problem. It may slow hull split.” But forecasters say continued triple-digit temperatures and drier afternoons are on tap this week, easing the minds of many almond growers.

Still, Jenna says some growers are hedging their bets and adding fungicides to their hull split sprays for navel orangeworm.  Growers already were adding miticides to their hull split sprays.

Yes humidity in orchards can lead to foliar diseases such as alternaria leaf spot. The symptoms are large brown leaf spots that turn black as the fungus spreads on the leaf surface. The leaf spots develop quickly in July and potentially can cause defoliation. 

Orchard humidity also can trigger rust and scab, which is a relative of alertnaria. These two diseases also can cause defoliation and weaken trees, impacting future almond production.

Humidity can trigger alternaria leaf spot. (UC IPM photo)
Meanwhile, field scout Damien Jelen says bug pressure has dropped in cotton, which is good news after a recent uptick in crop-threatening lygus bugs. During his field visits, Damien snared an average of one to two lygus for every 50 passes of his sweep net. The results about normal for lygus this time of year.

Growers are leaving uncut strips of alfalfa near cotton fields.
Damien says alfalfa growers with fields near cotton have been doing a good job leaving uncut strips of alfalfa during recent cuttings. These strips create habitats for lygus to stay in alfalfa during harvest rather than migrate to cotton.
The worm counts are high in alfalfa. But growers appear to be holding off treatment, reasoning the worms issue dissipates after each cutting.  Damien advises growers to remain vigilant about pest issues in alfalfa.

Monday, July 9, 2018

Splitting Hulls Can Create Opening for Pests to Threaten Almonds Before the Harvest

You might say almonds are in the backstretch before harvest.

Field scout Jenna Mayfield reports almond hulls are starting to pull apart, signaling the first shaking of nuts off the trees is about a month or so away.

As the hull starts to split open, the shell is the only protection from pests trying to eat the almonds.
 “A lot growers are getting ready to do their hull split sprays,” Jenna says. That means some anxious days are ahead as growers do their calculations to determine the timing of their sprays to protect their crops from a second generation of navel orangeworm (NOW) egg laying.

Initial separation stage of the hull. (UC IPM photos)
Another top concern is spider mites. “They can flare up anytime,” Jenna says. While mites haven’t been a major issue right now, many growers are likely to hedge their bets and add miticides to their hull split spray so they can save money by avoiding a separate application.

Protecting the nut crop from NOW is critical at hull split, and the first spray should be made at or before 1 percent hull split.

The hull is split less than three-eighths of an inch wide.
Here’s what UC IPM says about hull split treatment: Time the spray to the beginning of hull split “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 hull split. Hull split is determined to begin when sound fruit in the tops of the trees begin to split.”

Initial drying of the hull.
“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 hull split nuts are blank or sound.”

In this photo, the hull is completed dried out.
“Check for eggs on egg traps. If hull split has begun, but eggs are not being laid, wait until egg-laying starts. After hull split 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.

Jenna says one grower is planning to do his hull split spraying this week. Others should follow suit this month. The first shaking will come a couple weeks after hull split application.

“We should see the first harvesting at the end of July or early August,” Jenna says.  

While growers are figuring out their hull split spraying schedule, they also are making sure the orchard floors are clear of leaves and debris ahead of shaking. They are a making sure ants are taken care of before harvest.

Monday, July 2, 2018

Patience, Second Look Pays Off for the Pocketbook and Environment in the Valley

The pest numbers were up. The grower was worried.

His dilemma at this crucial stage in the development of his cotton plants:
Should he move ahead and treat his field with pesticides to control the potentially crop-damaging bugs? Or should he wait a bit longer, hope the pests go away and avoid treating the field – a move that could risk a population explosion that ultimately could damage his yield at harvest.

Growers weigh decisions on treating their field for pests.
This is real life drama in the Valley – no mocked up reality TV show. 

 What should he do?
First, let’s set up the situation. Earlier pest monitoring reports indicated a higher than desired count for lygus bugs populating his field. Lygus, as many cotton growers know, can cause big-time damage to developing cotton bolls.

“He wanted to spray for the pests,” field scout Damien Jelen says.
But before making that final decision, the grower and Damien rendezvoused at the field. Damien pulled out his trusty sweep net and canvassed the field.

Sweep. Sweep. Sweep….

“I found one count,” Damien recalled. Translated: Out of 50 passes of his sweep net, Damien snared only one lygus bug – way below the numbers from previous field visits and well below the threshold UC Integrated Pest Management recommends for treating for lygus in cotton.

The decision: Hold off spraying.

Yes, patience does pay off. And having Damien provide another set of eyes to supplement monitoring by the grower’s pest control adviser can certainly yield dividends. As in this case, it can avoid an expensive pesticide treatment while keeping chemicals out of the environment.
Sweep nets will catch pests populating a field.

For field scouts like Damien, the key tool of his field scouting practice is no fancy high-tech gadget. It’s a sweep net – akin to a heavy-duty, oversized butterfly net.

Using it in the field to collect pest samples takes practice to ensure results from different practitioners produce comparable results.

In cotton, for example, sampling for lygus starts when the cotton plant develops its first square. Samples should be taken twice a week. UC IPM recommends sampling each quarter of a field and taking even more samples in fields larger than 8 acres. Do 50 sweeps across one row of cotton to sample for lygus, making sure the sweeps don’t overlap. Lygus monitoring can end when acala plants have 5 nodes above white flower and Pima has 3.5.

It’s common for people to sweep from right to left and then step forward and sweep again left to right. After 5 sweeps, you pull the net through the air to push the bugs into the bottom of the net bag. UC IPM recommends taking a sample in four different spots in a field.

If it’s hard to count the bugs while in the field, place the insects in a bag and cool the contents to slow done pest movement.  UC IPM provides information about treatment thresholds for various pests.

While lygus counts jumped up as the early summer heat took hold, Damien says the numbers leveled out in the past week. So far, Damien hasn’t seen many signs of a large number of damaged cotton squares on the ground.

 Of course, there are still some four months – and a long summer – left until the harvest. You can be sure Damien and growers will remain vigilant until then.

Monday, June 25, 2018

Lygus Sweeping into Cotton while Mites Hitting Almonds

The uber-hot weather greeting the start of summer in the Valley is triggering a big uptick in lygus bugs populating cotton fields.

Field scout Damien Jelen is snaring four to five lygus for every 50 passes of his is sweep net. In one field, he recorded eight pests per 50 sweeps. In comparison, the count was one to two lygus bugs the previous week, which is about normal for this time of year.

“The lygus numbers are up. Growers are monitoring it. They do not want it to go on too long,” Damien says.“The hot weather is contributing to the increase.”The triple-digit temperatures along with harvesting of nearby alfalfa fields have combined to boost the lygus numbers in cotton.

Sweep nets snaring lygus bugs in cotton.
Here is the lygus threshold from UC Integrated Pest Management:

·  June 15-June 30:  more than two lygus bugs per 50 sweeps
·  Mid-Squaring (1st flower - 1st mature boll, beginning of July):  seven-10 lygus bugs (at least one nymph) per 50 sweeps and expected or better fruit retention. If retention is higher than expected you may be able to wait and monitor again that week before making a treatment decision. If retention is lower than expected and lygus bugs are present, consider treating.
·  Late Squaring (after 1st mature boll): 10 lygus bugs/50 sweeps, including the presence of nymphs
“The above thresholds are guidelines to be used with square monitoring, depending on the particular weather patterns. For example, during warm springs they are very reasonable, because cotton is setting fruit early and has high retention potential.

Moreover, UC IPM adds: “In contrast, late plantings, vigorous cotton, and high plant populations promote lower fruit retention and therefore thresholds will be lower. Additionally, duration of fruit retention may vary according to the cotton cultivar present in the field. The longer the fruit is retained, the longer it will be attractive to lygus bug populations. Finally, success in retaining early squares will greatly determine the final yield; therefore protecting cotton during the early square formation period (June) is critical. Protection during the early season is very complex. Factors such as low lygus bug numbers, high susceptibility of cotton, and variability in sampling require the grower to be extremely vigilant and ready to act at an instant.”

Lygus numbers have increased in cotton fields.
Damien is passing along his findings to growers, who will compare those numbers to the counts from their pest control advisers. It’s good to have a second pair of eyes monitoring the fields.

“If there is a spike by the end of the week, growers may order spraying,” Damien says. Growers should look at using reduced-risk materials.

There are two options for spray timing - during early fruiting  when monitoring indicates lygus densities are low and square retention is only slightly off (5 percent), re-inspect the field again in three days if square retention continues to be slightly off normal. Use product that preserves natural enemies. When population densities of lygus are high and potential for repeated and sustained invasion, may needed quicker acting.

Here are some chemical options: There is some resistance to organophosphate, carbamate and pyrethroid insecticides. Suggested chemicals to use are Carbine, Belay,Steward, Diamond, Brigade, Baythroid or Warrior.

Damien reminds growers with alfalfa fields adjacent to their cotton to leave uncut strips of alfalfa during harvest. This will provide a habitat for lygus – which prefer to live in alfalfa than cotton – when the alfalfa is cut.

Almond growers are concerned about mites in their orchards.
Meanwhile, the heat also is causing a spike in mites in almond orchards. “Growers have been spraying the edges of the orchards to control mites,” field scout Jenna Mayfield says. “Mites are pretty much the pest issue right now.”

UC IPM notes that “mites damage foliage by sucking cell contents from leaves. The damage begins with leaf stippling. Leaves can turn yellow and drop off. High numbers of mites cover tree terminals with webbing. Crop reduction and reduced vegetative tree growth shows up the year after damage occurs.”
Jenna says almond hulls are starting to split in most orchards. “If growers have not done their hull split spray yet, it’s on their agenda.”