Psyllid sprays have been a point of contention for Florida citrus growers. Under endemic HLB conditions, high psyllid control costs have cut into the grower’s bottom line, which has already been hit by reduced production. So, what is the right time to spray and how can a grower remain sustainable and profitable?
Lukasz Stelinski, University of Florida professor of entomology and nematology, shared research on employing a threshold approach for Asian citrus psyllid (ACP) control to maintain sustainable and profitable. He spoke during a recent University of California Statewide Integrated Pest Management Program Citrus Health Webinar.
Based on Stelinski’s findings, the concentration of Candidatus Liberibacter asiaticus (CLas), the bacterium that causes citrus greening, is not related to the frequency of inoculation. Essentially, CLas concentrations fluctuate, correlated with vegetative plant growth, or when citrus trees flush.
Stelinski discovered that psyllid density is related to tree stress, meaning the more psyllids that are present, the greater the damage to the tree. He says if psyllid populations and the resulting damage are sufficiently low, it does not pay to take control measures. As a result, growers should implement control measures once psyllid populations are high enough that taking the action to control them will pay off in greater crop yield.
According to Stelinski, one ACP per tap sample is a “working ballpark” threshold. “I think our data may decide that the threshold is going to have to be lower than that in certain instances,” he says. “I don’t think this is going to be a one-size-fits-all.”
Stelinski also shared better alternatives for current ACP spray models.
Typically, after harvest, a dormant spray is timed before major spring flush using a pyrethroid or organophosphate. Additionally, sprays are made on a schedule with intervals determined by length of efficacy of a particular insecticide.
However, Stelinski believes a better alternative is to spray at bud break at the beginning of each new flush before feather flush, which adults look to lay eggs on. He advises growers to apply a second spray on the flush as psyllids begin to reappear, which could offer more than 60 days of low psyllid populations.
Read more on ACP management.
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