Bactericides, Psyllids and HLB-Resistance/Tolerance

HLB, Bayer

Harold Browning

At a recent meeting of the Citrus Research and Development Foundation’s (CRDF) Commercial Product Delivery Committee, approximately half of the agenda was devoted to bactericides and HLB-spreading psyllids. Reflective mulch that keeps psyllids away and field trials for HLB-resistant or tolerant rootstocks and scions were also addressed. CRDF Chief Operations Officer Harold Browning summarizes some of the discussions.

“The issue that we continue to face is trying to understand how much benefit we’re getting from the use of these (bactericide) materials,” Browning says. “We know intrinsically they’re not as efficient when foliar-applied as may be desired.” So, he says, researchers are discussing alternative ways to apply bactericides, including through the trunk or by laser-assisted applications.

Browning notes that HLB-spreading Asian citrus psyllid populations have been increasing “over the last couple of years. It’s probably due to a number of things, including there’s more acreage that’s being unmanaged. Growers are having to make choices in their production budgets and are substituting better nutrition, for example, or the use of bactericides into a fixed budget. And in those cases, they’ve got to back off of something.”

He says there is concern that lessened psyllid control might impact yield. “But certainly the early (HLB) infection of new plantings cannot be good.” So, he says, growers want to know “how important reinfection is in young trees that are just becoming infected. But also, if you have an older block and it’s being reinfected all the time by psyllids, what impact is that having on the tree health?”

Reflective mulch studies for psyllid deterrence were also discussed at the meeting. “It’s pretty definitive now … if you put in a reflective mulch at planting, aerial insect populations, or psyllids in this case, have a hard time seeing the foliage, and so you’re repelling psyllids,” Browning says. He adds that studies also show “that trees grow faster in that mulch because you have weed control and better moisture retention and so on. So early in a tree’s new growth/life, it makes sense and we’re trying to understand the economics of: Can you afford to do it and get the return early enough to make it worthwhile?”

Finally, Browning says CRDF is contemplating how it can best help with data collection for trials into HLB tolerance of rootstocks and scions so growers can determine which scion-rootstock combinations are best for their situations.

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About the Author
Ernie Neff

Ernie Neff

Senior Correspondent at Large