Organic citrus growers continue to battle ACP

Local organic citrus growers gathered at the Pala Mesa Resort Feb. 22 to discuss their continuing battle with Asian Citrus Psyllid (ACP) and the efforts to prevent the disease Huanglongbing (HLB) from spreading to their groves.

The psyllid feed on citrus leaves and stems and can infect the trees with a bacteria that causes HLB.

"California has a bug that can transmit a bacteria that kill your trees, and there are limited ways in which we can deal with it at this time," Enrico Ferro, a pest control advisor, told the audience while providing an update on the Citrus Pest & Disease Prevention Program. "What our goal is, is to keep the industry alive and to keep the industry thriving."

Florida, which had its commercial orange groves hit with ACP in 1998 and subsequently HLB in 2004, has been devastated by the disease, according to Ferro.

"They've shown graphics of the infection moving through a grove in Florida and within a couple years it will spread throughout the entire grove," said Ferro. "That bacteria will be spread and you'll start to see the trees that had the infection earliest will start dying."

The tree is greatly weakened by the disease and production suffers.

"The fruit is smaller, the taste becomes bitter and the really hard situation to deal with is it doesn't take much for the fruit to drop off the tree," said Ferro. "You can just go up and grab a branch and give it a little shake, and if the tree is infected with HLB, the fruit will just rain off."

Ferro said Florida, by 2015, had lost "75 percent of what they produced in 1997-1998."

It is the fear of ACP and HLB that prompted Rich Hart, president of Rainbow Valley Orchards, to start organizing meetings for organic citrus growers.

"The first meeting we had on ACP was in February 2014 as a result of the statewide find of the ACP in California and the HLB citrus greening disease in Los Angeles," said Hart, who farms 30 acres in Fallbrook. "We had two meetings in 2015 and one in 2016. This is our fifth meeting."

The purpose of the meetings is to educate and update growers on the ACP situation so they be can be proactive instead of reactive, which was the case in Florida, according to Ferro.

"It's pretty amazing how much of a decline Florida has seen already," said Ferro. "And Texas and Louisiana are also starting to have this problem as well. And in all those cases, there wasn't enough being done before HLB spread throughout the area. And most of their response has been reactionary."

"Whether you're looking at it from the biological control standpoint or the conventional standpoint, there are things being done prior to HLB getting here (in California's commercial groves)," continued Ferro.

Ferro said HLB has been found in 38 residential trees in Los Angeles.

"HLB is only in a small part of Los Angeles right now," said Ferro. "It has not spread out of that Los Angeles region for a reason. We have been very proactive in California. That cannot be stated enough – how important it is that we continue to be proactive if we want to keep HLB from spreading into our citrus groves."

Proactive measures include closely monitoring ACP populations in groves, using insecticide sprays at the optimal times, and releasing beneficial insects that eat the psyllid into groves.

"The disease is controlled by preventing it from getting to your plant in the first place," said Ferro. "There's biological control that's doing a great job of suppressing populations, there's insecticide treatments. If you reduce the population to a low level when the trees are flushing, you prevent a lot of eggs being laid and you prevent a lot of adult feeding on that flush."

Jim Davis, a pest control advisor with Entomology Services, Inc., explained that having flowering plants in your grove can help with the fight against ACP since those plants can attract insects like the hoverfly, brown lacewing, and cryptolaemus (the melee bug destroyer).

"The plant species you have on your property are really important for supporting all these different types of predators that will move into your citrus grove and attack the Asian Citrus Psyllid," said Davis. "There are a lot of choices in flowering plants. The idea is that we want to create a whole ecosystem of plants and animals that make the environment in your grove so rich with predators and parasites that you don't even need to worry about the ACP. That's the ideal thing."

Baiting to eliminate the troublesome Argentine ant was also strongly recommended at the meeting.

"The Argentine ant is the most destructive ant for the control of the ACP because they'll kill the good predators and kill other ants," said Hart.

Ferro mentioned a pair of a new organic products that are currently being tested for use against ACP.

"Experimental products that have not been approved yet but have shown some promise are Surround WP (made from kaolin clay) and Envirepel (which contains garlic juice)," said Ferro. "Until something is approved we can't say definitely that it works great, but it is good to know that there's other products out there coming down the line to help us fight this insect."

Since there currently isn't a cure for ACP nor a resistant tree, Ferro said the best growers can do is to try to keep the number of psyllid in their groves as low as possible.

"Manage the population until we have a resistant tree, or something you can inject inside the tree – a systemic that would prevent the tree from dying or kill the bacteria in the tree," said Ferro. "We don't have any of that right now, so the only tool we have to prevent the HLB from getting to the trees and spreading throughout the trees is to reduce the population of psyllid, the vector, whether you do it biologically or chemically."