Researchers and pesticide manufacturers continue to make progress in their attempt to fight citrus leafminers. Two relatively new pheromone-based products— SPLAT CLM and MalEx—help control the pest without affecting non-target species.
It was back in the late 1990s when growers began spraying for Asian citrus psyllids that they inadvertently caused a resurgence of citrus canker.
The broad-scale insecticidal treatments killed off beneficial insects that had kept citrus leafminer more or less in check. That, coupled with weather and other conditions conducive to citrus canker, prompted the disease to once again become a problem.
Citrus leafminer larvae burrow into citrus leaves, creating tunnels or mines. The wounds provide an entryway for citrus canker bacteria to enter.
Leafminer feeding itself can affect yields and stunt growth of trees, particularly young ones and nursery trees, says Lukasz Stelinski, assistant professor of entomology at the University of Florida’s Institute of Food and Agricultural Sciences Research and Education Center at Lake Alford.
Two pheromone-based materials have been developed that specifically target the leafminer—SPLAT CLM, manufactured by Riverside, Calif.-based ISCA Technologies Inc., and MalEx, made by Portland, Ore.- based Alpha Scents Inc.
SPLAT CLM is a mating disruptor, and MalEx is an attract-and-kill material.
The theory behind mating disruption is you flood an area with so much synthetic female pheromone that the male insect becomes confused and can’t find a female with which to mate.
In the case of SPLAT, short for Specialized Pheromone & Lure Technology, the pheromone is contained in a mixture of non-toxic,food-grade waxes and oils that is squirted on tree trunks.
The mixture goes on with the consistency of hand cream that hardens to the consistency of crayons or wax candles in a few hours, according to product literature.
The most exciting news is the recent breakthrough in synthesizing the active ingredients, Stelinski says.
The discovery has knocked down the price from a budget-busting $300 per acre to about $40 per acre, he says.
The lower price “positions it as very affordable for growers, considering the duration and efficacy,” Stelinski says.
SPLAT CLM may now have “significant practical applications for controlling leafminer,” he says.
The manufacturer is marketing SPLAT CLM, and growers are buying it, says Stephen Lapointe, research entomologist at the U.S. Horticultural Research Laboratory in Fort. Pierce.
In fact, grove managers who worked with researchers in the testing phase now are buying the product, he says. “They’re convinced it works.”
Lapointe has been working with SPLAT CLM for several years, and he continues to test and evaluate the product.
This year, he and his research team are conducting on-farm validation trials and will monitor growers’ results.
Last year, they looked at altering coverage patterns as a way to reduce costs. They found that it’s not necessary to cover every row of trees with the pheromone.
Instead, growers can allow for “intentional gaps,” skipping rows of trees—while still protecting them—and reining in expenses.
The ongoing work on optimizing coverage patterns and validation trials is being funded by the Citrus Research and Development Foundation.
Mickey Page, farm manager for Mid- Florida Citrus Foundation in Winter Garden, has been working with SPLAT CLM and continues to be impressed.
”Their product works real good,” he says.
Last year, Page used the product with some young valencias in a project with Stelinski and reported “excellent” results.
“The pheromone confuses the male [leafminer], and he can’t find the female,” he says.
It would take at least two applications of conventional sprays to get the same results as one application of SPLAT CLM, Page says.
Since SPLAT CLM does not rely on an insecticide as its active ingredient, the registration process was fairly simple, Lapointe says.
Attract-and-kill faces more challenges
Such has not been the case with another potential leaf miner control researchers are looking at—MalEx.
“It’s taken more time than I thought” to get MalEx registered, says Darek Czokajlo, president of Alpha Scents Inc., the West Linn, Ore.-based manufacturer.
MalEx contains a pheromone that attracts male citrus leafminers. When the insects attempt to mate with the material, they come in contact with a minute amount of insecticide, which is lethal.
In early February, Czokajlo said he expected to have the registration package finished by mid-month and expected registration to be finalized within a year.
Like SPLAT CLM, MalEx is leafminer specific and doesn’t affect beneficials or other species, he says.
MalEx stays put on the trees and doesn’t move off target, Czokajlo says.
In addition, MalEx contains about 100 times less pesticide than conventional products, he says.
Lapointe says it appears that an attract-and- kill approach may work better for small trees, whereas mating disruption works better in mature groves with a closed canopy.
“We are studying why this is so as we learn how to best use these new products,” he says.
Meantime, Agenor Mafra-Neto, president and chief executive officer of ISCA Technologies, maker of SPLAT CLM, is pleased with the advances his company has made.
“We’ve made tremendous progress with SPLAT CLM in the past 12 months, to the point that it is now a commercially viable and affordable product being adopted by citrus growers,” he says.
SPLAT CLM is registered for use in California and Florida, Mafra-Neto says.
He also lauded Lapointe’s field trials for demonstrating that skipping four rows in every 10, for example, achieves virtually the same level of protection as when SPLAT is applied to every row.
In addition, “mechanical and aerial applicators have developed and successfully tested SPLAT CLM application systems, which has improved the economic feasibility and practicality of SPLAT CLM application for small to large orchards,” Mafra-Neto says.