So if you’re going to responsibly grow citrus trees, you’ll have to be proactive and ruthless, by waging brutal insect warfare.
The University of California’s department of Agriculture and Natural Resources has created an interactive map at
For those within two miles of a hot zone, the advice is to remove your citrus trees and not plant any others until researchers find a cure. Within two to five miles of a hot zone, the advice isn’t much better: “Consider replacing your tree with a non-citrus fruit tree” or protect your citrus trees with industrial-strength insecticides, which devastate honeybees, and complicated-to-use fine-mesh netting.
In citrus-loving California, some 60% of homes already have one or more citrus trees in their yard, said UC Riverside entomologist Elizabeth Grafton-Cardwell, director of the Lindcove Research and Extension Center in Exeter.
But many homeowners treat their citrus like any other tree, which means they basically ignore them, she said, which allows HLB to spread.
The threat is serious: HLB disease devastated Florida’s citrus industry when it hit in 2005.That’s why California’s $1.7 billion citrus industry is willing to do whatever it takes to destroy the psyllids, such as spraying the trees with pesticides toxic to bees. Grafton-Cardwell sees it as a necessary evil to eradicate a terrible disease; we can then reintroduce the bees later.
But Mark Hoddle, a biological control specialist at UC Riverside, sees things differently.
The trick, he said, is to declare open warfare on the ants in your yard, which tend and protect sap-sucking insects like psyllids so they can collect the sugary sweet “honeydew” the nymphs excrete like tiny white toothpaste coils escaping from a tube.
Hoddle said: “Controlling the ants is the most important thing you can do.”
Use a bait that will slowly kill the ants over a period of days, allowing the workers time to bring the bait back to the nest, where it will be consumed by the queen and others. If the poison is too strong, it will kill the ants before they get back to the nest, Hoddle said. He recommends buying refillable liquid ant bait dispensers, such as those produced by KM Ant Pro, and mixing your own ant bait: Mix 1 cup of sugar, 3 cups of water and about 1 teaspoon of high-purity (99%) water-soluble boric acid. The mixture is relatively safe to humans and animals,Hoddle said.
Once you’ve tamed the ants, parasitoid wasps will be able to do their work without interruption, Hoddle said, but you need to entice them into your yard by planting sweet alyssum (
You won’t see the wasps. They’re about half the size of ants, but the flowers will draw them in, Hoddle said. “You don’t need a lot; just a couple of pots will provide a lot of food for natural enemies” of psyllids.
Hoddle’s biological controls require diligence. If you’re up to the task and live outside a red circle, go ahead and plant some citrus. If not, plant some other non-citrus fruit tree. There are many delicious varieties out there, and you can enjoy them without threatening other citrus.