Avocado Lacewing
I’ve been successfully treating the pervasive Avocado Lacewing Bug (Pseudacysta persea) infestation since June of last year. This pesky little sucker (literally!) came over to the island from Florida, but we don’t know exactly how they got here. The bug was identified on Oahu in 2019, and made it’s way over to the Puna side of Hawai’i Island in 2020. It was formally identified by the Department of Agriculture to have invaded the Kona and Kohala coast early summer of 2021.
These bugs love avocados - probably almost as much as I do. The good news is that they don’t love any other types of trees, so they only target avocado trees. The bad news is that they’re not too picky about what type of avocado, or the age or health of the tree. Adult bugs fly onto the underside of an avocado leaf, where they suck the moisture from the leaves (like what a mosquito does to us). Then they lay eggs and hatch their babies and the cycle repeats. Once a community has been established, they have no reason to leave until their host tree has dried up and dropped all it’s leaves.
So here’s what happens: the tree needs all those leaves to be working at top productivity in order to make enough energy through photosynthesis to make those delicious, creamy fruits. When the bug sucks the moisture out of the leaf, a brown spot shows up on the top side of the leaf. Those brown spots do not produce photosynthesis, so therefore they are not producing energy for the tree. When enough leaves are compromised, there’s no energy left to make flowers, or buds, or… fruit.
I’ve had customers call me to tell me their fruit hasn’t ripened, though it’s been on the tree for months. This is because the tree doesn’t have the energy stores to finish ripening. And it likely doesn’t have the energy to make itself new leaves.
The bugs CAN be treated, so you’re not out of luck. I use a fungal spore treatment that targets the bugs without damaging the tree or any other plants nearby. It does not go systemic into the tree, will not affect the fruit, and does not leach into the soil. Unlike many pesticides, it is not harmful to beneficial insects, or even to bees - however, if bees that are actively foraging are directly sprayed with the spores, it can bring them back to the hive (therefore, I will postpone spraying a tree that is actively flowering).
Beauveria bassiana is an entomopathogenic fungi, meaning that it is a pathogen for insects. It propagates inside an affected insect and infects them with white muscardine disease. When the microscopic spores of the fungus come into contact with the body of an insect host, they germinate, penetrate the cuticle, and grow inside, killing the insect within a matter of days. When timed just right, an initial spray treatment will eliminate adult and juvenile bugs (it does not kill eggs), and a second spray treatment, done 5-8 days later, will eliminate the newly hatched larvae before they reach sexual maturity.
Once the bugs are eliminated, the tree can direct energy towards new leaf growth. Usually I see improvement before the second treatment. Some large trees, or trees with very bad infestations do need a third dose to be most effective. This treatment - indeed any pesticide treatment claiming to kill these bugs - does not prevent reinfestation, due to the airborne nature of the buggies. I generally check on clients’ trees every 3 months or so, to make sure they’re doing okay.
Do you have questions? Do you think your tree is infested? Avocados do experience normal dieback on leaves, normally from the edges or tips back towards the stem of the leaf. Evidence of the bugs shows generally in the middle of the leaf, close to the main vein, and can be seen easily from casual glance. Confirmation comes from merely flipping the leaf and looking to see if there’s little black spots or bugs crawling around on there.
Feel free to drop me a line if you have more questions, or would like to schedule treatment!