- Author: Maria Murrietta
- Contributor: Dr. David Headrick
We're now seeing the aftermath of this long rainy season. The heavier than normal rain has given us velvety green hills carpeted with an abundance of wildflowers. But we cannot overlook the other less pretty things that benefit from a wet winter – lots of weeds and insects.
For now, we'll focus on insects. They're already showing up in a news-worthy fashion. KSBY did a feature story on whiteflies and spoke with UC Master Gardener Cathryn Howarth.
This story has been posted on various social media pages and people are wondering if this whitefly is a new pest, where it came from and what can be done about it. I wanted to follow up to fill in some of the gaps in information. So, I went to Cal Poly entomology professor, Dr. David Headrick who has done quite a bit of research on whiteflies over the course of his career.
Here's what he had to say after watching the news story.
"The whitefly pictured on hibiscus (in the news story) is giant whitefly which came to California from Mexico. It was first noticed in San Diego County in the early 1990s. Hibiscus is a favored host plant, but they also are seen on citrus, but more commonly on the landscape plant Xylosma. In the mid-1990s, a biological control program began with researchers at the University of California, Riverside. They successfully imported two beneficial species of tiny stingless wasps that feed exclusively on giant whitefly and achieved excellent control of giant whitefly."
"Giant whitefly and the two beneficial wasps (pictured above) all occur in San Luis Obispo County and normally the populations are all under good control. When the giant whitefly first invaded SLO county in the early 2000s, the populations were enormous and made the news then also. But the wasps soon brought whitefly numbers under control. However, in some years since then, environmental conditions have favored the giant whitefly and allowed them to outpace their natural enemies. Eventually, the wasps will catch up and population balance will be restored."
"There are many species of whitefly, most are native species that cause no serious harm to their host plants. The whiteflies that you see on broccoli, citrus, oaks, and poinsettias are all different species. Some of the invasive species of whiteflies, like giant whitefly, can indeed kill their host plants."
"As for management, spraying plants with the garden hose is a good approach when numbers are low."
Thank you, Dr. Headrick, for your insights.
UC Master Gardeners always recommend monitoring your plants regularly to catch pest populations before they become a problem. Whiteflies can be observed any time of day. Remember to flip over the leaves to look for evidence of nymphs and the waxy coating as pictured below. Insecticides, such as horticultural oils may provide some relief. However, direct contact with the insect is necessary to smother and kill them which is difficult to achieve, particularly for whiteflies that congregate under the waxy coating on the underside of leaves.
If you have questions about plant or pest issues, call the Master Gardener Helpline
Arroyo Grande: 805-473-7190
SLO Office: 805-781-5939
Or email us at firstname.lastname@example.org
Looking for more?
- Visit UC IPM for more photos and information: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7401.html
- For more information about the early biological control program and findings -
UC Riverside research paper - http://www.nhm.ac.uk/resources/research-curation/projects/chalcidoids/pdf_X/BellowMe2000b.pdf
Cal AG article - http://calag.ucanr.edu/Archive/?article=ca.v051n06p5
- And if you really want o geek out, like I sometimes do, check out this catalog of introduced species - https://bugwoodcloud.org/resource/pdf/FHAAST-2018-09_Arthropod_Biological_Control.pdf
- Author: Maria Murrietta
- Contributor: Kim Corella
Beetle borers. They are very small and they cause a lot of damage to trees, including death.
These insects have not been found yet in our County but they are very close and we are especially concerned about the ISHB which can attack over 110 tree species. Many of these are native riparian species such as Sycamore, Cottonwood, Alder, Willows, Box Elders and this insect also attacks coast live oak and valley oaks.
Cal Fire, the City of San Luis Obispo and UC Ag and Natural Resources are offering a workshop to educate the public about these two serious pests. Early efforts and education are key in preventing an attack on a wide range of tree species in San Luis Obispo County.
Here is a message from Kim Corella of Cal Fire:
I am excited to announce that we are having an invasive shot hole borer (ISHB) and goldspotted oak borer (GSOB) workshop here in San Luis Obispo on May 9th from 9:30-2:30.
This workshop will address biology, identification, surveillance, and management of infested trees, downed wood, and firewood. We'll cover these topics in the classroom, then have a hands-on lab to learn how to identify signs of shot hole borer damage, set up a monitoring program, and sample trees.
$30.00 registration fee includes lunch, a ISHB Field Guide, and ISHB Demonstration Kit. Pre-registration is required. Click here to register.
We have applied for CEU's from the Department of Pesticide Regulation and the International Society for Arboriculture.
For more information on the training and to register, visit www.pshb.org.
Kim Corella, Forest Pest Specialist, Cal Fire
Thank you, Kim, for keeping us well-informed!
- Author: Maria Murrietta
- Contributor: Dr. David Headrick
Next time you're on Higuera St. in downtown SLO, look up.
Cal Poly entomology professor, Dr. David Headrick, is taking biological control to new heights!
Here's his story:
An invasive whitefly pest is attacking our giant fig trees in downtown SLO. I got a call to help out, so we started a proof of concept experiment to release microscopic stingless parasitoid wasps that lay eggs in whiteflies. Then, their young hatch out and eat them. If these wasps do the job, we can release lots more to get control. First step is to try them out in cages on the trees. I hope this raises some awareness. I like elevating people's knowledge about biological control. It's uplifting. Raising to the occasion. (Btw, can't lie, it's totally cool being in a bucket up in a tree.)
A big thank you to Dr. Headrick for keeping us informed and entertained. We'll be checking in with him again soon so stay tuned for updates! Also thank you to Crystal Kirkland for helping with photos and keeping track of all the findings.
To see more photos of his downtown adventure, check out our Facebook page - SLO MGs
- Author: Norman Smith
Western Subterranean Termites
Western Subterranean Termites have a winter time activity period, but are year-round pests of wooden structures and dead trees. The winter activity is associated with their swarming habit. The winged adults are black/dark brown with opaque gray wings. King and queen adults will swarm the first warm day after the years first major rain fall. Some of you may have seen the winged adults emerging from a hole in the soil, one after the other, and flying off, but maybe you weren't sure what you were observing. Mating is this activity that allows the termites to spread to other favorable habits.
Kings and queens will pair up, then look for a moist soil situation with wood present, such as 2 X 4's laying on the ground next to the wall of a home, a dead tree trunk and buttress in the garden, or even decorative bark in landscape areas.These can all get a colony started, but the worker termites are seldom satisfied with their initial discovery, and will almost always send out exploratory trails and tunnels to look for other sources of wood. Unfortunately, the wood framing of your nearby house is one of their favorite habitats.
The major portion of the colony and the queen and king are in the soil. Workers must foray back to the soil each 24-hour period, to pick up dirt and certain bacteria, but will then head back up into the above ground structure. Their tunnels in the wood are always lined with dirt from the garden or below the house. The habit of the queen termite residing in the soil and not in the wood source is the main reason that fumigation is not effective for this kind of termite. Fumigation may kill some of the foraging adults in the wood foundation of the home, but not the one termite that can keep the colony going with more eggs and immatures. Termite pest control companies try to put up a toxic barrier between the nest in the soil and the wood source, hoping that as the workers pass through the barrier, they come in contact with the toxin and die. Another control method is to place some poisoned bait wood traps around the home and hope that the foraging workers will discover it and transport the poison wood to the queen.
Termite inspectors will look for the dirt tunnels plastered to the foundation or rising from the soil beneath the foundation. These tunnels should be destroyed by the inspector at the time of treatment so that if more are seen in the future they will know that they were not successful in eradicating the colony.
I saw a stark reminder of the importance of termite control while residing in Fresno. Some of you may remember the Coalinga earthquake. Some of the homes in that town were snapped off their foundations, offset by a foot in some instances. The reason was that some of the homes had weakened wood framing from termite damage and the sharp jolt from the earthquake just snapped the 2 X 4's at their base. Those homes had to be raised and rebuilt. I hope they had good insurance.
Norman Smith was the Fresno County Entomologist for 30 years. He fielded calls from the general public, pest control companies, farmers, PCA's, etc.; ran the insect trapping program, and gave presentations on insects to many different groups, including lots of schools. Norman has developed a 100,000 insect specimen collection for the county over the 30 year career. Norman earned a Ph.D. in Entomology at UC Davis in 1979.
Norman says...I now enjoy working in my garden, traveling with my wife, golfing and bowling, taking insect collecting trips in the US and overseas in the tropics, and working on some personal research of some small wasps. I also enjoy working with and for the Master Gardener program in SLO.