A complementary pest-management tool
Perimeter sprays offer an additional tool for pest management programs, Rogers says.
In general, they're best used when psyllids go on the move, starting in the spring and into the summer, he says. The practice may provide less benefit in winter when the pest isn't as mobile.
But every grove is different, rarely perfectly square or straight-edged, Youngman says. A perimeter spray may need to hit only the outer edge or perhaps go a little deeper, into the first three rows.
Some groves may abut areas that pesticide applications don't always cover or that can provide hidden refuges for psyllids, such as myrtle bushes, he says.
Those irregular shapes and other physical constraints can demand extra effort to ensure that spray machines cover only the desired depth on grove borders, Rogers says. He suggests turning off nozzles on one side of the applicator to force sprays into border trees.
Low-volume is another option
Another option is using low-volume spray machines for night applications.
"We can do a thousand acres a night when no one else is in the grove," Youngman says. "It's half the cost to apply at low volume instead the full volume."
An added benefit is the chance to use lighter machines at higher speeds, factors that combine to lower environmental impacts, he says.
Adding perimeter sprays to a control program obviously increases the number of pesticide applications. That makes rotating chemical classes for resistance management more complex, Rogers and Youngman say.
Following rotation guidelines is crucial to maintaining growers' pesticide arsenal against psyllids. "The CHMA program puts a priority on resistance management," Page says. "We can't lose any one of these tools."
Hew closely to all pest management guidelines, not only when it comes to rotations, but also in following label instructions for rates, timing and so on, Youngman says.
"We want to keep the populations down, but we don't want to create super-psyllids," he says.
The other key component is to scout groves diligently in order to understand pest population trends, tree health and grove conditions, he says.
Youngman also suggests working with neighboring growers to share experiences with your control program. For instance, one material may perform better with a surfactant.
A psyllid outbreak next door has the potential to harm more than your neighbor's grove. "Fight as a unit, not as individuals," he says.