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Insects plague Rancho Santa Fe’s eucalyptus trees

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The lerp pysllids have taken over the red gum eucalyptus trees in Rancho Santa Fe.
(Caitlin Kreutz)

With the spring and onset of summer comes the return of the lerp psyllid insect to Rancho Santa Fe’s trees, an insect that eats up red gum eucalyptus foliage and leaves behind a big mess.

The weather being cold and rainy for the last two winters has helped—the lerp psyllid population dies down in the cold months and that, in combination with the abundant rain, has reduced the overall stress on the trees, they are able to sustain themselves a bit better, said Caitlin Kreutz, RSF Association Parks and Recreation assistant manager.

But with the return of warmer weather, the lerps are back.

“In the last three weeks, I’ve seen them explode in numbers,” Kreutz said. “Everyone expects a really bad year for pests with all the vegetation growth. We will see this become more apparent over the summer and the worst will be in the late fall.”

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The red gum lerp psyllid is native to Australia and invaded Southern California in 1998—it has also been found in Hawaii, Florida, Mexico and other similar climates. Most attracted to the red gum eucalyptus, the leaves of many Ranch trees are covered in little white dots, a baby lerp cap made of solidified honeydew and wax. Inside, the wingless aphid grows—the adult lerp psyllid looks like a tiny fly.

“They are plant juice sucking insects, they like to extract nutrients from the leaves and once they suck all the juice out of the leaves, it leads to premature leaf drop,” Kreutz said.

Kreutz said what people complain about the most is the annoying honeydew—the lerp secretes a sticky substance that gets all over people’s cars and property. A sooty black mildew can eventually form on the honeydew, “It’s nasty and a sticky mess,” she said.

“My property is now so gross with sticky fallen leaves, it’s overwhelming,” said longtime resident Gary Stadler. “I’m sure all of Rancho Santa Fe is experiencing much the same right now.”

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So what to do?

Over the years, Stadler has tried many methods to combat the lerp psyllids. He has found the most effective treatment is tree injections, which work almost instantly but can be a very expensive solution. A single tree may require as many as 10 injectors at about $5 per injection—Stadler said his one-acre plot requires about $2,000 worth and takes about two full days to do.

For Stadler, another drawback of the injections is that the main ingredient is a neonicotinid insecticide known as Iminicloprid. Used to control sucking insects, termites, some soil insects and fleas on pets it’s a heavy molecule that does not easily break down in nature and could be responsible for bee colony collapse all across the world, he said.

“Here in our neck of the woods, it’s a choice of either the trees or the bees. Neither is a win-win situation,” Stadler said.

After the recent rains, Stadler noticed that thousands of the little white lerp houses were on the ground and no longer on the leaves. He learned that the little houses soak up water like a sponge and lose their ability to stick to the leaf. As a result he has tried on a new tactic this spring—spraying his trees with water for five minutes, waiting 20 minutes and doing it again. It doesn’t get rid of all of them but he found that 90 percent of the lerps would simply soften and wash off.

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Eucalyptus trees after complete defoliation from the lerps.
(Caitlin Kreutz)

The watering method can work, Kreutz said, however, it is highly dependent on a person’s ability to a reach the higher leaves of their tree canopies—this has become a challenge for Stadler.

“I’m about ready to give up, these lerp psyllids are out of control,” said a frustrated Stadler. “I have been doing the watering thing and it works well, but I can’t get to the higher tree parts.”

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He has issued a call for help for research and development on some kind of treatment that is biodegradable and won’t hurt nature.

Kreutz said one solution is reducing the amount of red gum eucalyptus trees on your property. Over time, extensive defoliation will weaken the trees and result in reduced tree health, decline and ultimately, tree loss.

According to the RSF Association’s Forest Health and Preservation Committee’s Forest Health Study, 42,000 trees are rated as poor or dead out of the estimated 266,000 trees in Rancho Santa Fe’s forest. Eucalyptus trees were found to be in the highest level of decline.

“That is part of the reason that Rancho Santa Fe is so prone to fire,” Kreutz said.

The removal of dead and dying trees is an issue that the Covenant has been working to resolve and Kreutz stresses the importance of homeowners being proactive about their properties, maintaining defensible space and reducing fire risk by removing dead and dying trees.

If homeowners are determined to save their eucalyptus trees, the injection treatment might provide the best chance for recovery, she said.

“It can be pricey,” Kreutz said. “The alternative is planting other trees that are not susceptible to the lerp psyllid.”

For more help, contact Caitlin Kreutz at (858) 756-4652 or email caitlin@rsfassociation.org


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