Photo by Lyle Buss, UF/IFAS
This winter’s hard freeze may have knocked back visible Asian citrus psyllid (ACP) activity, but research shows the pest is not reliably eliminated by the cold. In lab studies, many ACP adults and nymphs survived several hours at 21 to 23 degrees, and eggs could still hatch after several hours at temperatures as low as 8 degrees. Adults can also become cold-acclimated during winter, improving their survival even further. That matters because ACP adults overwinter on hardened leaves, then rapidly rebuild their numbers on new flush growth when spring conditions return. Once temperatures rise, psyllid reproduction accelerates. Egg-laying increases above a 61 degrees threshold.
If you made a dormant spray: great. The goal is to reduce overwintering adults before bud break and before spring flush drives population growth. Florida field research showed a single mid-January dormant spray (Jan. 15) can suppress ACP populations for approximately five to six months compared with blocks that don’t get such a spray.
If you missed the dormant window: Don’t give ACP a “free pass” in March.
Scout for fresh flush (the engine that drives ACP increase). Treat only when flush is present and ACP are found. If you find psyllids on the new flush and a treatment is needed, choose a broad-spectrum material like a pyrethroid (e.g., Danitol 2.4 EC or Mustang) or organophosphate (e.g., dimethoate or Imidan 70-W), and rotate modes of action to slow resistance. Typically, the colder months are a good time to make a broad-spectrum spray because natural enemies of psyllids are not abundant and it will cause less harm than it would be during the warmer months.
The bottom line is that the freeze slowed ACP, but it didn’t eliminate it. If you didn’t get a dormant spray in earlier, a pre-bloom spray is your chance to prevent a rapid spring rebound. But it starts with scouting and timely action.
Lukasz Stelinski is a professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.
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