Growers can look forward to new options for controlling Asian citrus psyllid in the next few years as pesticides in the development pipeline near the release stages.
At least two companies anticipate bringing foliar and soil drench products labeled for use in Florida citrus to market in the first half of 2013, pending registration approval by the Environmental Protection Agency and state regulators.
Asian citrus psyllid vectors the potentially devastating huanglongbing disease, also known as HLB and citrus greening.
Effective on psyllids and other insects
First out of the gate may be Indianapolis-based Dow AgroSciences' sulfoxaflor, to be marketed as Closer for psyllid control in citrus. Toni McEwan, Closer product manager, estimates EPA approval should come in 2013's first quarter.
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A foliar-applied product, Closer is effective on contact and after ingestion by the pest, McEwan says. The Insecticide Resistance Action Committee places sulfoxaflor in the newly created Group 4C mode of action. The sole member of this subgroup, it has a unique interaction with the insects' nicotinic acetylcholine receptor.
Sulfoxaflor is highly systemic in the plant, moving upward into new growth and providing a residual effect similar to that found with Delegate, another Dow insecticide. Exactly how long the product remains active in the plant varies with coverage and weather conditions, she says.
Spring applications, around bloom, are ideal, taking advantage of the product's minimal impact on bees and other beneficial insects, McEwan says. Closer will pair up well as a rotational partner with Delegate.
The company also plans to label Closer for use against citrus mealy bugs, brown citrus aphids and Florida red scale.
Foliar and drench formulations
Meanwhile, Wilmington, Del.-based DuPont Crop Protection plans to add two new products incorporating cyazypyr by midyear to its Florida citrus lineup, says Joe Mares, U.S. product launch manager for cyazypyr brands. Cyazypyr, an active ingredient in the anthranilic diamide class, falls into IRAC's Group 28 mode of action and is a ryanodine receptor modulator.
The company anticipates gaining EPA approval by late April or early May for a foliar application, to be marketed as Exirel, and a soil drench application, to be marketed as Verimark.
Florida registration likely will follow shortly after, Mares says.
Verimark is aimed at "a very focused market" to protect trees less than 4 feet tall, he says. Currently, only neonicotinoids are approved as soil applications for psyllid control on young trees.
Adding another weapon at this growth stage is particularly useful for resistance management, says Henry Yonce, president of KAC Agricultural Research in Deland, Fla.
Yonce, who participated in field trials, says the soil drench also provides "excellent" leafminer control. Depending on tree size and application rates, cyazypyr's effect on leafminers can stretch to 100 days.
Once past that growth stage, growers need to focus on protecting developing trees and leaf flush with foliar sprays, Mares says.
Timing Exirel applications early in the spring growth cycle will help protect leaf flush from both Asian citrus psyllids and leafminers. Mares also sees potential during summer flush.
Year-over-year field trials show that a strong start at spring leaf flush pays off at the end of the season in higher yields, he says.
Cyazypyr has little impact on predators and other beneficial insects, reducing the risk of secondary pest outbreaks, Mares says.
Other products in the works
Several other companies also have insecticides targeting Asian citrus psyllid in the works.
Phil Stansly, entomology professor at the University of Florida's Southwest Florida research lab in Immokalee, has tested many new psyllid control products in field trials.
Like Dow's Closer, Sivanto (flupyradifurone), under development by Bayer Crop Sciences, is similar to neonicotinoids.
Stansly says both products will be useful as foliar sprays to save neonicotinoids for soil drenches.
Nichino America Inc.'s Apta (tolfenpyrad) fits into IRAC's Group 21A insecticides.
"It's considered a miticide, but it looked quite good" in trials, Stansly says.
Marrone Bio Innovations is developing a microbial bio-insecticide derived from Burkholderia bacteria. It kills psyllids and may cause less collateral damage to beneficial insects than many conventional insecticides, he says.
More products aid resistance management
Expanding the number of available modes of action gives growers more options to rotate chemistries during the growing season, a necessary step for resistance management, Stansly says.
The new products are more selective than broad-spectrum insecticides, Stansly says. Timing their applications is important, focusing on specific life stages of the pest as well as considering impacts on secondary pests and beneficial insects.
Predatory and other beneficial insects are crucial.
"We don't realize what beneficials are doing for us until they're not there," Stansly says. "But it's hard to get them back after that."
Keeping pests in check while encouraging beneficial insects to thrive calls for added management. Tweaking such a complex equation is generally a better approach than "hitting it with a sledgehammer," he says.
"Huanglongbing has probably doubled production costs" as growers strive not only to keep the disease and the pest that vectors it out of their groves, but also to boost nutritional program, he says. "As long as prices stay high for the crop they can accept it."
The disease affects not only the current crop but also threatens trees' underlying health and future crops.
"It scared growers to death," he says. "But we're still alive and kicking here in Florida."