- Author: Ben Faber
Years go by and the regulars are out there on the trees - red scale, broad mite, citrus thrips, bud mite, leafminer and more and more Asian citrus psyllid. And then suddenly one that has seemed to be just in the background pops up all over the place. What is it about the weather, the interaction of other agents like spray programs or harvest interval or rise of others that push the balance allowing an otherwise less common pest to show up? Purple scale has generally been in the background, out there, but not prominent in backyard citrus. In the last two weeks I've gotten six calls about the "sudden appearance" of this scale. It likes cool, but not cold; warm, but not hot. Perfectly adapted to the winter this year which probably slowed down the biocontrol agents, like wasps and ladybird beetles.
You can read more about the insect and its control at the UC Integrated Pest Management website.
- Author: Ben Faber
Dr. Elizabeth Grafton-Cardwell will discuss the key stages of citricola scale and how they damage citrus, weather trends that help reduce citricola scale, chemical control choices and their relative efficacy, coverage and timing of treatments, and monitoring for resistance and methods to manage resistance.
April 8, 2020, 3 PM
This is part of the series of 1-hour webinars, designed for growers and Pest Control Advisers, will highlight various pest management and horticultural topics for citrus and avocados. During each session, a UC Expert on the subject will make a presentation and entertain write-in questions via chat during and/or after the presentation.
What Are the UC Ag Experts Talking About?
Upcoming topics:
- Invasive shot hole borers in avocado by Akif Eskalen (May 2020)
- Vertebrate pests by Roger Baldwin (June 2020)
- Ants in citrus by Mark Hoddle (July 2020)
- Use of plant growth regulators on citrus by Ashraf El-kereamy (August 2020)
Register for the Citricola Scale webinar (April 8, 2020)
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- Author: Ben Faber
It's been quiet for awhile, just odd winter weather and fire and ash and hot hot heat andsuddenly we see a beautiful insect we haven't seen in a while. Jarrell Larmon is a PCA who was nosing around in a Satsuma orchard and he turned up a Barnacle Scale, the likes we havent seen in about 4 years. Pretty little thing. Last time it came under pretty good biological control in no time.
This is the image from USDA
Jane Delahoyde,
a PCA here in Ventura, recently found an unusual scale in lemon here. It is barnacle scale with a typically long Latin name - Ceroplastes cirripediformis. It is unlikely to be any worse than other scales, but it's something to keep our eyes on. This is one of the soft scales, often called wax scales because of the wax they produce. It turns out that this has been described as being in Southern California for years, but some years they are just more present. For more on "Wax" scales see the University of Florida site:
http://entnemdept.ufl.edu/creatures/orn/scales/florida_wax_scale.htm
or our UC IPM website
http://ucipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
And this is the scale that Jane found.
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- Author: Ben Faber
Wow, woolly whitefly covered with waxy, curly filaments , Aleurothrixus floccosus.
One of the consequences of fire and the resulting ash is that the biocontrol agents that keep whiteflies, scale, mealybug and other pests in balance is that they will spend so much of their time preening that they don't have time to go after their prey. Lacewing larvae, minute pirate bug, ladybird larvae, parasitic wasps and others rely on moving around to get at their food sources. When they cant move fast, they stop and clean their joints to stay limber. Whitefly and scale insects just hunker down and don't need to do a lot of moving. They just breed, and without actively moving biocontrol agents, their populations can explode. Or that's my human analogy. In dusty areas or areas affected by ash, the particles get in their joints and they need to spend time cleaning in order to move fast.
Whiteflies suck phloem sap, which in some cases can cause leaves to wilt and drop when there are high numbers of whiteflies. However, the primary concern with whiteflies is the honeydew they produce. Honeydew excreted by nymphs and adults collects dust and supports the growth of sooty mold; large infestations blacken entire trees, including fruit, as well as attract ants, which interfere with the biological control of whiteflies and other pests. The sooty mold can also affect tree yields by reducing photosynthesis and requiring extra handling time for cleaning.
So pests under good control prior to a fire can get out of hand. This is a good example of a tree in the town of Ventura where ash was a problem. A seemingly clean tree, free of whitefly, started to defoliate with blotchy leaf spots. On the undersides of the leaves corresponding to the blotches are colonies of whitefly. And looking closely you can see that some of the nymphs have exit holes, indicating that they have been parasitized by a wasp. So nature is kicking in and taking it's course. The whitefly should get cleaned up soon too by some forager, such as lacewing larvae or pirate bug. No need to spray because it would just be a further disruption.
See more about whiteflies at:
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7401.html
Photos: Defoliating 'Meyer' lemon tree, blotches on upper side of leaf, whitefly colonies with exit holes in some of the nymphs
- Author: Ben Faber
We live in unusual times and every year is different, so we are bound to see things that are different, or see things differently. Recently a pest control advisor brought in a sample of what looked like black scale (Saissetia oleae) on the stems of avocado fruit. Along with the scale came a mess of Argentine ant and sooty mold. The PCA had not seen this scale on avocado before. It is common on citrus and, from the name, it is also found on olives and over 100 other host-plants. I hadn't seen it on avocado before, and became somewhat alarmed and sent samples off to UC Riverside for identification. I thought maybe there might have been an introduction of a new scale, riding on imported fruit. Joe Morse and crew from UCR had done a study monitoring fruit coming across the border and found several scales on fruit that were not currently in California:
http://entnemdept.ufl.edu/Hodges/als4161/Secure/PDF%20Files/Articles/AvocadoPhytosanitaryRisks.pdf
Back with the first infestations of Avocado thrips in 1996, PCA Charlie Gribble kept saying that he was finding citrus thrips in avocado. The avocado orchards where he found the thrips were next to a lemon orchard and we kept saying that the insect was probably just getting lost between the two orchards. Well it turned out, it wasn't citrus thrips, but an all new thrips previously undescribed that has gone on to cause a lot of disruption to the California avocado industry. And from here, avocado thrips has gone on to Israel and Spain to cause similar problems. It was better to find out sooner than later it this scale was something new.
I also put the word out to local PCAs and growers asking if they had seen “black scale” this year. The responses were interesting. One grower said that he had seen it occasionally on avocado trees for the last 30 years. They were on older trees and wood. They would be in small numbers in orchards some years and not others. Two PCAs said that they saw it occasionally on young trees, but they were usually parasitized, with wasp exit holes. One PCA said that the scale was only there when there were lots of ants present to fend off parasitic wasps.
Photos: parasitic wasp laying eggs and exit hole of young wasp from adult scale
And bingo, that was the case in this organic orchard with smaller trees. The Argentine ants were protecting the scale and the scale was thriving as evidenced by the sooty mold.
The black scale samples sent into Paul Rugman-Jones at UCR Entomology were identified as the scale Saissetia olea and that virtually all of them were parasitized by the Coccophagus rusti wasp. So it's not a new scale and it's under biological control.
Photos: Sooty mold on avocado leaves and fruit
Nice coverage of scales:
https://www.dialenvironmental.com/images/scales.pdf
http://ipm.ucanr.edu/PMG/r107301411.html
For a guide to the scales of California, big files and illustrations:
https://www.cdfa.ca.gov/plant/PPD/publications/tech_series.html