Citrus greening — also known as Huanglongbing — continues to devastate citrus trees across the globe. Here in California, growers have been working to keep this bacterial disease away from their orchards. One new strategy, according to Dr. Ivan Milosavljevic of the California Citrus Research Board, is effective ant management.
Species like Argentine ants have mutually beneficial relationships with sap-feeding insects like the Asian citrus psyllid, which vectors the huanglongbing disease. These insects produce honeydew, a sugary substance that doubles as one of the ants’ preferred food sources. In return, ants help protect those insects from predators, which interferes with biological control, allows psyllid populations to thrive, and enables huanglongbing to spread.
To help cut down on ant populations, Milosavljevic encourages growers to use liquid bait stations. “You can fill them with water that has a liquid sugar in it, dissolved,” he explains. “[Then add] a small amount of a pesticide — something that’s slow acting.” Ants will take that poisoned food source below the ground to the queens, who will then pass it on to other ants. Once the slow-acting poison has infected most of the ant population, the colony collapses.
Boric acid, once a favored treatment in ant management, has recently proven to be relatively ineffective in killing queens. Instead, it just kills the foragers. Milosavljevic has some advice there, too. “What we have found in our trials is Thyroxium, which is a neonicotinoid, is one of the most effective [treatments],” he says. “It’s currently our golden standard when we evaluate different chemicals to use in these baits. Spinosad is another one that has shown to promise, as well, as an organic option to the growers.”
Meanwhile, the California Citrus Research Board has been working on a new development: biodegradable hydrogel beads, which function similarly to liquid bait stations. “These beads are made of food-grade materials like sodium alginate and calcium chloride, [which] you can buy on Amazon,” he says. The beads are then soaked in water containing sugar as well as a small amount of poison, allowing ants to spread the poison to the rest of their colonies. The DPR has yet to grant its approval, however, and these poison-soaked gels are currently illegal to use. “This is still in progress,” Milosavljevic adds, “but hopefully we’ll have them for growers soon.”
In the meantime, visit one of our supply centers for your insecticide needs. We can help you identify a pest management plan that’s suitable for your unique orchards.