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Almond bait traps monitor pre-hullsplit NOW levels

Almond bait traps monitor pre-hullsplit NOW levels
Many growers are still not using one of the best tools to monitor almonds’ most destructive pest —  navel orangeworm (NOW).

California’s 750,000 acres of bearing almond orchards are heavily laden with what is projected to be another record crop.

It was just a decade ago when prophets of doom were saying the industry would collapse economically when the crop topped 1 billion pounds.

Since that ominous prediction, it has exceeded the billion pound mark nine out of the last 10 seasons. It is slowly climbing to the breathtaking pinnacle of 2 billion pounds in a season, a seemingly unimaginable level 10 years ago.

This year’s crop is estimated to be 1.75 billion pounds, and marketers say they’ll need every pound to meet a growing worldwide demand for California almonds.

The rocket ride to this season’s projected crop has also been equaled on the price side. When the naysayers were predicting the billion pound meltdown, the average price to growers averaged less than $1 per pound. Over the past decade, the average has not fallen below $1 per pound. The average over the past seven years has been almost $2 per pound.

It has been a series of crops obviously worth protecting, and overall growers and PCAS have done that well. However, University of California IPM entomologist Walt Bentley said many growers are still not using one of the best tools to monitor almonds’ most destructive pest —  navel orangeworm (NOW). Failure to evaluate whether NOW poses a threat often results in unneeded sprays, he said at an almond management field day sponsored by the San Joaquin Sustainable Farming Project.

Bentley told growers and PCAs in Joe Del Bosque’s almond orchard west of Firebaugh, Calif., that almond meal bait traps will not provide pinpoint number treatment thresholds. However, they can provide a good overview of the presence or absence of NOW population levels and whether to treat to protect almonds before hull split.

The first line of defense against NOW is to destroy overwintered mummy nuts, almonds that were left hanging on the tree after harvest. These are perfect habitat for overwintering NOW. Removing them by shaking dormant trees and destroying the mummies is highly recommended. A lack of a winter sanitation project is an invitation for NOW damage without spring or hullsplit sprays.

NOW survive in these mummies and when the new crop hulls split, it is dinner time.

“Navel orangeworm will not get into your new crop in May,” but growers are protecting that crop when they control overwintered moths laying eggs, he said. That is not necessarily news to growers, who have been reluctant in the past to treat earlier than hullsplit because older pesticides could flare other pests like spider mites.

Bentley said newer, reduced risk insecticides do not spawn secondary pests and good coverage of these could have a significant impact on overwintered NOW before new crop hullsplit.

Bait traps

Bentley said he is “frustrated because more people are not even utilizing NOW egg traps to monitor spring and summer moth activity.” Trece and Suterra make NOW egg traps.

These bait traps are filled with pressed almond meal and oil. “The oil is extremely important to attract the moths to lay eggs and should be 10 percent by weight. Do not put dry almonds in a trap and expect to trap eggs.”

• Black traps work best.

• Place one trap per every 10 acres, for at least four traps per orchard.

• Choose trees that are at least five trees in from the edge of the orchard.

• Hang traps at head height on the north side of non-pareil trees, 1 to 3 feet inside the drip line of the tree. • Avoid areas where traps will be hit with sprinkler irrigation.

For larger orchards, divide sampling blocks into portions that can be sprayed as a unit. Orchards that exceed 1,000 acres can be divided into larger sampling blocks, if conditions within each block are uniform.

• Change baits every 4 weeks or if bait gets wet.

• Look for flat eggs that are laid mostly on the ridges of the trap or on the raised lettering on the top and bottom of the trap. Eggs will be white when first laid, but turn orange-red before hatching. Clean eggs after each monitoring visit.

• Graph numbers of eggs laid at each trap. This will give growers and PCA an idea of when new generations of navel orangeworm are laying eggs.

Bentley said PCAs and growers should look at the history of the traps over a three to five week period in season to determine NOW levels. Past NOW history in individual orchards is also a good element to consider determining the need for a pre-hullsplit spray.

It could be worth the effort. He said a well-timed May spray could preclude a hullsplit spray because populations were knocked down early.

When to spray

When to spray remains a judgment call tempered by harvesting.

“If you have your own harvesting equipment, you can make a judgment call on when to begin harvest to avoid harvest time NOW damage,” said Bentley.

However, if a grower is dependent on a custom harvester to shake his trees and get the nuts into the trailers, it is a different story. Protecting the nuts at hullsplit or before takes on much more urgency.

“If you’re a 50 or 100 acre grower, you are the bottom man on the totem pole,” he said. “I would take a more cautionary approach to treating for navel orangeworm.”

Navel orangeworm did not get its reputation as the No. 1 pest in almonds without causing significant damage. However, “You cannot run scared. I hate to say it, but I have seen some horrendous (treatment) recommendations when spraying was completely off timing and in hard shell varieties,” Bentley said.

“Ask questions of the person making the recommendation. Do not be afraid to question the PCA,” he said.

“You want to take care of the problem you have without making unnecessary treatments.”

Leaffooted plant bug has surfaced as a problem this season in southern San Joaquin Valley almond orchards. However, Bentley has not seen the problem in the central part of the state.

Nevertheless, he urged growers and PCAs to be vigilant for the pest which is hard to monitor for its presence, but not for its damage.

“You should try to detect leaffooted plant bug early in the season. You are not going to find the bug as easily as you will the damage,” he warned.

Leaffooted plant bugs often retreat behind leaves when approached. Bentley said growers can use a large, metal garbage can lid to hold bottom side up under large limbs to catch falling leaffooted bugs or stink bugs when the limb is struck by a small bat or broomstick.

Leaffooted plant bug can damage nuts from the nutlet all the way to harvest. It can knock nuts off at bloom; suck juice out of formed nuts and even puncture mature nuts, leaving black spots on the kernel. Bentley said some packers are now discounting nuts for the spots, even though the leaffooted plant bug does not downgrade nut quality.

Leaffooted plant bug is particularly damaging to thin shell varieties.

They aggregate out of an orchard in places like an old shed or in pomegranates. They also can migrate early from pistachios to almonds.

As this year’s heavy tree loads mature toward harvest, limbs touch the orchard floor and become ladders for ants.

Look for colonies in orchards and use baits, if ants are present. “Baits are effective and relatively cheap,” added Bentley.

“Ants climb the limbs, not the trunks,” Bentley pointed out.

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