Mike Roberts

Employing a Threshold Approach for Psyllid Control and Sustainability

There’s no question that citrus greening has had a huge impact on Florida citrus growers. The reduction in production means lower revenue at the end of harvest, but high psyllid control costs also eat into the grove’s bottom line. A UF/IFAS entomologist, Lukasz Stelinski, has shared research on employing a threshold approach for psyllid control to maintain sustainability in the fight against citrus greening. The aim is for Florida citrus growers to reduce spraying to control the Asian citrus psyllid and cut costs by only spraying once psyllid populations cross a certain threshold.


Employing a Threshold Approach 


Stelinski maintained that psyllid populations are related to citrus tree stress because the higher the psyllid population, the higher the damage and stress to citrus trees. Citrus growers have to knock down psyllid populations because tree stress is increased by psyllids feeding even after trees have become infected with citrus greening, but the cost needs to match the benefit. His presentation maintains that how the increase in psyllid populations is related to the increase in tree stress “explains the importance of vector suppression as part of HLB management,” but that “we need to make it more sustainable.”


Employing a threshold approach, citrus growers would only utilize control measures like spraying once the populations reached a certain point. “If the pest population (and the resulting damage) is low enough, it does not pay to take control measures,” Stelinski shared in the presentation. “As the pest population continues to rise, it reaches a point where the resulting damage would justify taking control measures;” Stelinski’s presentation maintained that a “0.7 ACP per (scouting) tap is a ‘working ballpark’ threshold.” Using this threshold, citrus growers would only spray citrus trees for psyllids when psyllid populations were higher than 0.7 psyllids per scouting tap. 


Stelinski has shared a conventional spray model versus an alternative model. In the conventional model, citrus growers time dormant sprays to coincide with after harvest and before major spring flush. In the alternative model, spraying would occur at bud break at the beginning of each new flush, making sure to spray before a feather flush, which adults look to lay eggs on, and then a second spray would be applied to the flush as psyllids began to reappear. This alternative model could offer “more than 60 days of low ACP populations,” according to the presentation. Stelinski advised that growers would hold off spraying until the psyllids hit a threshold of 0.2 to 0.7 per tap, but that any threshold below one psyllid per tap was associated with an improved yield.

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