California almond growers cannot be faulted for strolling through their orchards gazing up with smiles on their faces at an excellent crop sagging tree branches downward.
Who wouldn't grin with prices likely around $2 per pound and strong demand for the third consecutive 1-billion pound crop predicted from the state's 550,000 acres of bearing almond orchards.
Harvest starts in August in Kern County. However, when almonds are shaken to the ground for later pickup, growers could start losing income in a hurry they were looking at in June to what many are predicting could be a bad ant year.
“We tell growers to look down when they are walking their orchards,” says Blue Diamond fieldman for San Joaquin and Stanislaus counties Mel Machado. “Look down and be aware of ant populations because once those nuts are on the ground, growers can lose a lot of money very quickly to ants.”
Ant damage as low as 2 percent can cost growers $50 or more per acre in lost yields and rejects, said Machado.
Machado has seen ant damage in Butte variety almonds escalate at a rate of 1 percent per day, and Buttes are supposedly less susceptible because they have a tight less susceptible because they have a tight shell and are a late variety.
It is not just damage to the almonds that cost growers money, but ants can eat a lot of almonds in a hurry. “I have growers tell me that they don't have an ant problem because they had few rejects from ant damage,” said Machado. “They may not have high rejects because ants ate the almonds before the harvester could pick them up. Just a 1 percent yield loss on a one-ton crop at $1.80 per pound is loss of $36 per acre.”
Heavy ant year
Machado and Rob Kiss, his counterpart in Southern Stanislaus and Northern Merced counties, said this is shaping up to be a heavy ant year.
“We have been talking up ants because of the dynamics accelerated by high temperatures this spring. Ant populations are heavy,” said Machado. “We have seen growers go with traditional ant control timing, but there are so many ants left that it is apparent a second treatment will be necessary. You may kill half the ant population, but what is left is still enough to economically damage the crop.”
These treatments would likely be with ant baits. However, Lorsban is still registered in almonds and it may be used to knock down damaging populations immediately ahead of harvest.
A second bait treatment may be more critical in young orchards where high ant populations can cause significant damage to a crop that would be smaller than that from a mature orchard.
Kiss, speaking at a Valent USA ant control field day in Madera County recently, said this crop appears to have a thick hull. “For some reason when you have a thick hull, it tends to pull away the shell seal.” This makes the nut meat more susceptible to ant damage.
“We had similar problems last year and were nailed on some of that. We hope it does not happen this year, but we are set up for the same kind of problem.”
The ant problem is growing not only in almonds, but other tree crops as well. Fortunately, there are effective tools to control ants, including a pair of highly selective and environmentally safe ant baits, Esteem from Valent and Clinch from Syngenta, plus the bazooka for ants, Lorsban.
Ironically, it is the change in almond management away from organophosphate pesticides and to lower water use drip and micro irrigation that is exploding the ant problem. Non-cultivation and cover crops also have led to ideal ant habitat.
“We have created a perfect microhabitat for ants,” said Kiss. “Drip lines have become freeways for ants building condos along those freeways.”
And when almonds go on the ground, the very social ant population announces “let's go get ‘em boys,
“It does not take very long to open up a lot of problems,” said Kiss.
While the micro irrigation environment is ideal for ants, flood irrigators should not be lulled into believing they cannot get ant damage.
“I have seen horrendous ant problems in flood irrigated orchards. Ants will move to high ground on berms, mounds and levees above the water level. When the nuts are on the ground the ants attack, attack,” said Machado.
Kiss and San Joaquin County University of California Cooperative Extension Farm Advisor Benny Fouche said ant damage should not surprise growers.
“Sampling is easy: Knock a hole in a jar lid, put some Spam, a hot dog or some almonds in it and count the ants,” said Kiss.
There are as many as 15 ant species found in orchards, but only two cause almond crop damage, said Fouche. They are the Southern Fire Ant and the Pavement Ant. There is a third ant found in California that also damages almonds. It is the Red Imported Fire Ant (RIFA), but the state is actively working to eradicate it and is having success. RIFA represents a major human and environmental health hazard and that is why the state will pay to eradicate RIFA in almonds orchards.
Fouche said growers and pest control advisers need to take time to identify the various ants. Most are beneficial insects. They eat larvae of damaging pests like twig borer and navel orangeworm.
“It takes time to identify these ants. You cannot run out into an orchard and identify various ants in 10 minutes,” he said. “However, once you have identified different species with a hand lens or other magnification, it becomes easier to visually spot problem ants.”
The Pavement Ant is the predominantly damaging ant in almonds in Northern California while the Southern Fire Ant is the most common in Southern California. Growers in the central part of the state can find both in orchards.
There are no clear thresholds for controlling ants. Fouche recommends sampling nuts at harvest for damage and then making an economic decision on whether to treat based on percent nut damage. Growers can also sample for ants prior to harvest.
“If you are losing only $5 per acre to ants is one thing, but if you are losing $40 per acre, it may be worth treating,” he said.
Baits currently available are effective and selective, taking out only the Pavement, Southern Fire Ants and RIFA.
“The only complaint I have about the baits is that they may be too easy to apply,” he said. “You use so little that it is almost invisible and you have to be careful that you are getting the right amount at the right time.”
As for timing, Fouche said growers must listen to their PCA and handler fieldman to put out bait early enough to control ants before harvest. For Esteem that is 8 weeks before harvest.
Clinch works quicker and can be applied closer to harvest, as close as four weeks.
Esteem is an insect growth regulator. It has the same active ingredient as Knack, a widely used silverleaf whitefly control product. Clinch is abamectin, the same active ingredient used in Agri-Mek. Both products are carried back to ant colonies by workers were the products disrupt the reproductive cycle.
Carried to colony
Esteem is one-half percent active ingredient pyriproxyfen dissolved in soybean oil and applied to corn grit particles, according to Mike Ansolabehere, Valent field market development rep.
The bait is picked up by worker ants and carried back to the colony where worker ants ingest it and feed it to the queen and developing larvae. The developing larvae are unable to mature and the queen is sterilized.
“The bait does not affect the worker ants,” said Ansolabehere. “That is why it is important to apply Esteem eight weeks before harvest. That gives enough time for the worker ants to die naturally.”
Esteem is applied at a rate of 1.5 to 2 pounds per acre. It remains viable for five to six days after application if it does not get wet, adequate time to be carried back to the colonies. It is effective only against Southern Fire Ants, Pavement Ants and Red Imported Fire Ants.
Esteem is now labeled on most of the major orchard crops in California.
Ansolabehere added that it is more difficult to control ants with baits when there is a heavy ground cover, especially spotted spurge. “Ants love spotted spurge seed,” he added.
Ansolabehere said Valent is developing a new Esteem formulation with only 17 percent soybean oil. It is now being tested in the lawn and landscape market. It is not as oily as the 20 percent soybean oil formulation now on the market.
“Esteem has a tendency to accumulate around the spreader because of the soybean oil. If we can reduce that oil content a lot of that would be alleviated,” he said.
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