Posts Tagged: biocontrol
Sugar-feeding ants protect pests that infect trees and damage the fruit they bear. Insecticides are often a go-to solution, but may kill beneficial insects in the process, too. Thankfully, Mark Hoddle, University of California Cooperative Extension entomologist and biological control specialist at UC Riverside, together with UCR colleagues in chemical engineering, developed a biodegradable hydrogel baiting system that targets ant populations, which protect sap-sucking pests from their natural enemies. Control of ants allows beneficial parasitoids and predators to greatly reduce pest populations.
Deciding to expand Hoddle's research was a “no-brainer” according to David Haviland, UC Cooperative Extension farm advisor in Kern County.
Haviland is investigating active ingredients that can be effectively used in hydrogel baiting systems. His research builds on Hoddle's use of alginate gels, also known as water beads, soaked in sugar water to control Argentine ants.
“What we're doing in California can benefit places like Florida, Texas, Mexico and beyond,” Haviland said.
The Hoddle lab conducted two years of orchard research showing that when ants are controlled, the amount of citrus flush infested with Asian citrus psyllid (ACP), a mottled brown insect that vectors the pathogen causing citrus greening, decreases by 75%. Citrus flush refers to newly developed leaves.
“But benefits are not restricted to just ACP with Argentine ant control, as natural enemies destroy colonies of other sap-sucking pests too,” said Hoddle. “For example, citrus mealybug infestations on leaves were completely eliminated by natural enemies, 100% control, while densities of fruit infested by mealybugs were reduced by 50%.”
The Hoddle lab's success inspired Haviland to consider how this approach will fare in different regions of the state where there are different crops, different pests and different ant species.
Haviland has worked for many years on solid baits that are effective and affordable for ants that feed primarily on protein, like fire ants in almonds, but successful control measures for sugar-feeding ants that drink their food have been elusive.
“Therefore, we're using hydrogels to essentially turn a liquid bait into a solid, making it effective and commercially adoptable,” Haviland said. He and his team are assessing whether active ingredients that undoubtedly work against ants, like thiamethoxam, maintain their effects in a hydrogel system.
Unlike Hoddle's biodegradable alginate gels, Haviland is relying on acrylamide gels that are similar to the absorbing material you would find in a diaper. These gels are not organic, but are currently accessible on a commercial scale, and have been shown to be effective in wine grapes on the North Coast by a Cooperative Extension advisor in Napa County, Monica Cooper. Haviland's current research efforts are focused on citrus, table grapes and wine grapes in the San Joaquin Valley, and on lemons on the coast.
The primary challenge now is navigating pesticide regulations and registration.
“This is cutting-edge research,” Haviland said, and manufacturer labels for the products being used need to be updated to include hydrogels as an approved use. This process takes time. Additionally, adding new product uses needs to make economic sense for the manufacturer.
Hoddle and Haviland's research can provide data for adding these methods to the product labels.
“If we can show that this tech works against lots of pests, lots of ant species, in lots of different crops across California, hopefully we'll achieve a critical mass of benefits that motivates product manufacturers to make modifications to their labels,” said Haviland.
Haviland is hopeful about the process, and said he believes that UC ANR is in a prime position to lead innovation for an issue that requires collaboration among specialists, advisors and the industry.
Supply-chain crisis forces some to pivot to mechanical, biocontrol measures
Driving through her vineyards on a chilly morning in December, Hortencia Alvarado is taking comfort – for now – that the weeds she sees are all yellow. But there remains a nagging worry that, like the pesky plants, is merely lying dormant for the season.
When March rolls around, and the first signs of new green growth appear on the vines, Alvarado and other vineyard managers will again have to confront the ongoing shockwaves of the global supply-chain crisis.
Growers of grapes – the third-highest valued agricultural commodity in California at $4.48 billion in 2020 – likely won't be able to access the herbicides that they usually apply.
“I definitely need to start thinking and considering it because I don't want to be in that situation where I don't have [the herbicide] when I need it,” said Alvarado, a vineyard manager in the San Joaquin Valley.
She first noticed the effects of the shortages this past August, during the application following the harvest of early varietals. Alvarado's agricultural pest control adviser had recommended a different product, instead of their usual standby, Rely – because none of the handful of suppliers in California could find it.
Then Alvarado's foreman started reporting that the substitute wasn't controlling the weeds.
“We were using some other stuff that wasn't as good, so basically we were wasting money on stuff that wasn't doing what we wanted it to do,” Alvarado explained.
The need for more machines or labor is just one result of the herbicide shortage, said George Zhuang, University of California Cooperative Extension viticulture farm advisor in Fresno County. Zhuang has received “a lot” of calls from growers about the chemical supply issues, which are also affecting fertilizers. He's been urging them to move away from traditional herbicides to mechanical means or biocontrol such as sheep or fowl – even though they might be more expensive.
Zhuang estimates that while a weed program comprises 5% to 10% of total production costs in a normal year with the usual herbicides, the use of nonchemical alternatives could hike that percentage up to 10% to 20%. In addition to their impact on the bottom line, effective herbicides are especially crucial to grape growers because vines – unlike tree crops – cannot naturally shade out weeds with expansive canopies.
“Right now, people can still scramble around and find some limited chemicals to make sure the crop is successful for the harvest, but if the situation goes for another year, I think there's going to be a panic in farming communities,” Zhuang said.
Herbicide challenges expected to linger
Unfortunately, the availability of certain products is likely going to be “challenged” into at least the middle of 2022, according to Andy Biancardi, a Salinas-based sales manager at Wilbur-Ellis, an international marketer and distributor of agricultural products and chemicals. Biancardi said that the suppliers he talks to are advising people to make preparations.
The supply of glyphosate, the key component in products such as RoundUp (used by many Midwestern farmers), appears to be most affected, Biancardi said. As a result, that shortage has put the squeeze on alternatives such as glufosinate, used in products like Rely – the herbicide favored by many California grape growers.
“The cost of glufosinate has definitely gone up because there just isn't enough, so everyone is obviously marking it up,” said Biancardi, who estimates that prices for both glyphosate and glufosinate are up 25% to 30% for growers.
Alvarado said that while large commercial operations are able to pay the premium prices or shift to other weed control measures, some smaller growers have essentially given up the fight – simply letting the weeds take over.
“They're just letting it go wild until the dormant season,” she said. “They're hoping that – by when they do start to spray [around March] – they'll hopefully have that Rely.”
Silver lining to supply crisis?
Large-scale growers and retailers are buying up those scarcer products when they can, in anticipation of future shortages during critical times. Biancardi said that while his company traditionally runs inventories down at the end of the season, they are instead stocking up on herbicides that customers will demand.
“Careful planning and forecasting is going to be more important than ever, that's really the key,” he said. “At this point we can't guarantee ‘business as usual,' based on what we're hearing.”
Shaking off old habits might actually bring some benefits to business, according to Alvarado, as a forced shift away from chemicals could prove to be a selling point for customers, from a sustainability and marketing standpoint.
“Out of this shortage, there might be some good, some wins,” she said, “but at the same time, we're going to need some answers – I think it's going to be a bumpy road.”
Calling the confluence of drought, record heat and a shortage of chemicals a “perfect storm,” Zhuang said that consumers could start feeling those jolts as well.
“Eventually, somebody is going to eat the costs – either the farming community or the consumer is going to eat the cost, I hate to say it,” he said./h3>/h3>/h3>/h2>
Akif Eskalen, UC Cooperative Extension plant pathology specialist at UC Riverside, wants to contain this invasive bug before it spreads throughout Southern California.
"If we can't control them," Eskalen said, "they are going to wipe out all our trees."
Box elders, sycamores, American sweetgum, maple and coast live oaks are susceptible to polyphagous shot hole borer attack. In urban and suburban areas, the dead and dying trees can pose fire and limb falling dangers. In the agricultural sector, avocado trees could face huge financial losses. In the fight against the pest, the California Avocado Commission has provided Eskalen $800,000 to broaden his investigation into this mysterious species of ambrosia beetle.
In March, Eskalen and his colleagues - UC Riverside entomologist Richard Stouthamer and Huntington Library curator of woody collections Tim Thibault - spent two weeks in Vietnam, where PSHB originates, searching forests and fields for natural enemies of the fungus spread by the pest. They collected a host of possible allies, whose DNA is now being analyzed in the lab.
"I am very hopeful that we are going to find some solutions to control this fungus," Eskalen said. "We have to."
Ants can be a huge nuisance in and outside our homes, particularly if you have food lying around. But now, it turns out, they’re unwelcome, too, on citrus trees.
A year ago, UC Riverside entomologists released Tamarixia, a parasitoid wasp and natural enemy of the Asian citrus psyllid (ACP) imported from Pakistan, into a biocontrol grove in Riverside, Calif. Tamarixia can serve as an excellent biocontrol agent against ACP, a citrus pest first detected in 2008 in Southern California that is capable of spreading citrus greening disease, or Huanglongbing.
Female Tamarixia can kill psyllids also by “host-feeding.” They use their ovipositors as daggers to stab psyllid nymphs numerous times until the nymphs start to bleed. As bodily fluids ooze out of the nymph, Tamarixia sucks up this rich protein needed for developing more eggs.
An excellent way then to control ACP populations! Yes, but only until the ants come marching in. Argentine ants are threatening to disrupt the biocontrol of ACP by battling it out with Tamarixia on citrus branches. While not quite a Vader-Skywalker lightsaber duel on a precarious walkway, an “invasive meltdown” begins when the ants gang up to protect the nymphs.
“ACP nymphs produce a white, sugary waste product called honeydew, a good carbohydrate source for the ants,” explains Mark Hoddle, the director of the Center for Invasive Species Research at UC Riverside, whose research team has released Tamarixia into several Southern California citrus groves. “The ants, therefore, will protect the nymphs from Tamarixia. We have seen ants chase female Tamarixia off the psyllids, and even catch and eat them!”
“If you kill off the ants, Tamarixia can play the role of the biocontrol agent it was cast to do on citrus trees,” Hoddle says. “We’re seeing that the ants are impacting Tamarixia in two ways: they are preventing Tamarixia’s establishment in some areas; and, where Tamarixia is already established, the ants are not allowing these parasitoids to reach their full biocontrol potential.”