There’s a growing threat to California’s avocado industry, and while it measures just 2 millimeters in size, its impact is potentially far-reaching. This latest menace is the avocado lace bug, a sucking insect that feeds on the underside of avocado leaves, causing yellow spots that turn brown and necrotic.
To spotlight the threat and the importance of early detection, the California Avocado Commission has debuted a new informational video for avocado growers. The video — featuring industry experts Tom Roberts, pest control adviser for California’s Ventura, Santa Barbara and San Luis Obispo counties, and Mark Hoddle, extension specialist with the Department of Entomology at the University of California, Riverside — takes viewers inside a Santa Barbara County orchard heavily infested with avocado lace bug.
From the orchard, the pair of experts explain that while avocado lace bug was first detected in Southern California in 2004, it was primarily restricted to backyard avocado plants and didn’t cause economic problems for commercial growers in California.
That changed in 2017 when reports emerged of lace bug damage in commercial orchards and groves in northern San Diego County and Riverside, Calif. By 2019, the pest began popping up in backyards in Los Angeles, and by 2023 it was present in Orange and Santa Barbara counties.
An Evil Twin?
Intrigued by the invasive pest’s more aggressive and damaging behavior, researchers examined the DNA of two different populations and discovered that the original infestation in San Diego County had come from Mexico, but the latest infestations causing problems in commercial groves appeared to come from Florida.
“There were two different genetic variants of this avocado lace bug. The Mexican variety remained well behaved in San Diego County, while the Florida variety was causing us pretty big problems,” Hoddle says in the video.
The big problems arise when the lace bug starts feeding on the underside of the leaves, the first sign of which is a little yellow spot and minor yellowing. But the damage progresses into larger necrotic patches, eventually resulting in leaf drop that exposes fruit to sunburn, which is where the financial stakes get high, Hoddle says.
To learn more about the threat of this new, “more intense” avocado lace bug and what California growers can do to get ahead of it, The Packer spoke with Hoddle in mid-March.
Economic Impact Unknown
The full economic impact of the avocado lace bug on California’s avocado industry is unknown.
“Unfortunately, those numbers are nebulous, and we have no hard data on that,” Hoddle says. “And that’s a major problem we often face when we deal with these invasive pests. We know they’re sort of broadly distributed now. The avocado lace bug is well established through parts of San Diego and Riverside counties. We know it’s in Orange and L.A. counties and in the Ventura and Carpinteria areas as well.”
As to the total number of acres infested with the pest, Hoddle says it’s unlikely anybody knows.
“But it’s probably fair to say we’re looking at many, many hundreds — if not low thousands — of acres now that have been infested to varying degrees,” he says.
What we can conclude is that avocado lace bug is going to cost growers more, Hoddle says. This is especially true when heavily infested trees defoliate, exposing fruit to the sun and causing sunburn, which results in downgrading in the packinghouse.
Another potential factor, says Hoddle, is that when an insect like the avocado lace bug is causing damage to the leaf, “it is almost certainly reducing the photosynthetic capacity of those leaves,” and as a result, there may be fewer nutrients available for fruit development.
Early Detection
In the CAC video, Roberts and Hoddle urge growers to check their leaves regularly.
“Early detection is very important, because that’s going to allow you two advantages: One, you will hit the population while it’s low, which is a good thing,” says Hoddle. “And during that low period of activity, you’ll get a sense of populations building. Then you have a window to schedule your applications.”
Hoddle says identifying avocado lace bug early allows growers to get a feel for the problem, see if it’s escalating and work with their pest control adviser to understand how much time they have before a real crisis hits.
“Contrast that to not doing anything and waiting to the last minute. The population is going to be too high. Damage will be excessive,” he says. “Defoliation will occur, and you’ll be calling around in a mad panic trying to find somebody to come and treat your orchards the next day. And that’s just not going to be possible in many instances.
“Getting your scouting and population monitoring done early allows you to tackle the populations when they’re low density,” Hoddle continues. “Damage levels to the leaves are low, and if there are scheduling issues, you’ve still got a buffer to get material or labor into your orchards to do those treatments.”
Heading into late spring and early summer, growers can expect avocado lace bug populations to increase, as phenology data shows the pest thrives in temperatures that are not too hot or too cold; mid-80s are ideal conditions for the lace bug to develop fast and lay a lot of eggs that hatch quickly.
Another reason for growers to be on high alert this spring is that once the spring defoliation is done, the leaves now sitting on the trees are going to be there long enough for lace bugs to infest, Hoddle says.
“As you move into that defoliation window, the percentage of leaves that are infested tends to be quite low because the new leaves that are coming out haven’t had time enough to acquire lace bugs,” he says. “The older infested leaves are now dropping to the ground, and that can sometimes give you a false sense of security that, oh, everything’s fine, but it’s just a matter of catch-up time. And this is probably the period when you need to be most diligent, because that’s when the lace bug could potentially sneak up on you.”
The Undeniable Threat
The California Avocado Society, in collaboration with CAC and UC Cooperative Extension, is set to hold an “Avocado Lace Bug” seminar March 24 in Oxnard, Calif., during which Hoddle is scheduled to speak. The hope, he says, is the event is well attended by growers who can provide feedback from the frontlines.
“The Carpinteria area is the emerging new hot spot, and we’re hoping growers from San Diego County and parts of Riverside will also attend that meeting so we can get input from all the affected areas,” he says. “I think there also has to be a realization that there’s going to be some customization of these emerging management plans based on the different geographic localities the avocados are growing in.”
Given Southern California’s microclimates, there probably won’t be a one-size-fits-all avocado lace bug management plan.
“Once we get that feedback, I think we’ll be in a position to start chasing down grant money from the state,” says Hoddle, who adds the ultimate goal will be to use science-backed data to help growers make well-informed decisions on monitoring and control programs for avocado lace bug.
“This isn’t a pest we can ignore anymore,” Roberts says in the video. “It’s here. It’s aggressive. But if we stay on it and stay proactive and use the tools we have, we can protect our trees, our yields and our long-term viability. Work with your PCAs [pest control advisers], know what’s going on in your orchard and take action early.”
