The War on Citrus Psyllids Still Raging

The War on Citrus Psyllids Still Raging

citrus psyllid closeup

An extreme close-up of HLB’s vaunted vector, the citrus psyllid.
Photo by Jeffrey W. Lotz

There has been plenty of talk about how high psyllid populations have been in Florida in the past year or so, and data collected by the state bears those stories out, showing historical highs for the pest. As the 2017 psyllid season kicks into full gear, growers hope populations return to more normal patterns.

“The psyllid counts throughout the summer we very high pretty much everywhere you looked,” says Brandon Page, Citrus Health Management Areas (CHMAs) Program Assistant for UF/IFAS. “If you follow population trends, the psyllids have followed historical data where they spike in the summer then start working their way down in the winter. But, for the better part of year, the pest was at record levels.”

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Perfect Storm

There were multiple factors that could attribute to the historically high psyllid counts last season. Weather was a big factor with the record-breaking rainfall during the traditional winter dry season brought on by El Niño.

“In 2015, we saw pretty high populations of psyllids, and that was followed by a really wet winter in 2016,” says Dr. Lukasz Stelinski, an Associate Professor of entomology and nematology for UF/IFAS. “So, we had a high population going into the spring and a lot of growth on the trees because of the extremely wet winter.”

Stelinski says the flush and bloom in the spring was the perfect environment for the pest to thrive and procreate. With a particularly dry winter in 2017, he says the hope would be that psyllid populations would be lower since conditions were not as ripe for the pest to proliferate.

The wet weather in 2016 might also have impacted the residual control of pesticide applications on the psyllid. “If you went out with an application in the morning, then have a 2-inch rain in the afternoon, that would definitely be detrimental to efficacy.”

Another potential factor exacerbating psyllid populations is a symptom of HLB-infected groves. Groves tend to have some level of flush year-round, which gives the pest the ability to survive through what historically would have been slower periods.

Abandoned or poorly managed groves are a constant breeding ground for the pest as well. Those psyllids can move into groves where growers are trying to manage the menace.

“Psyllids can routinely move for at least a mile,” Stelinski says. “When they do these jumps, they can use alternative hosts for brief amounts of time to remain hydrated and perhaps consume some sugar resources so they can travel further. If you have a neighbor a couple of miles away that is not controlling the psyllid or is doing the bare minimum, you are in trouble, especially in the spring when the pest is moving about more.”

Other factors include when psyllids are at their worst during bloom, the use of some key pesticides is not allowed by label restrictions to protect foraging bees. Finally, economics might be driving some growers to make fewer applications.

“With the economic situation for many growers, you have people not spraying as much as they used to,” says Henry Yonce, Owner of consulting firm KAC Agricultural Research. “Some growers can’t afford to. It is a catch 22. You have less sprays overall and groves flushing year-round with the temperatures we have. We are not zeroing the psyllids out at any time.”