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
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:
or our UC IPM website
And this is the scale that Jane found.
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:
Photos: Defoliating 'Meyer' lemon tree, blotches on upper side of leaf, whitefly colonies with exit holes in some of the nymphs
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:
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:
For a guide to the scales of California, big files and illustrations:
Recently a grower called up with a beautiful scale that the PCA couldn't identify. I could just marvel at the beauty of it and wondered what in the heck it was. It didn't look like any scale I had seen in the area and others who were queried didn't know either.
I took it into the Ag Commissioner's office and they sent it off to see if it was a new species. Images were sent off to various entomologists and David Haviland in Bakersfield identified it as a Ceroplastes, possibly a Chinese wax scale or Barnacle scale. Others had identified it as Florida wax scale.
It was sent into Paul Rugman-Jones at UC Riverside Entomology for DNA identification. His identification and that of CA Dept of Food and Ag entolomogists came back as Barnacle scale, Ceroplastes cirripediformis.
All of these scales turned out to have been seen in California before, so there was no quarantine issue. It also turned out that all of the adults that were turned in for identification had also been parasitized by some wasp. So there is biological control already in place for it. The issue at stake here, though, is that it's important to be watching for new visitors in the orchard. Joe Morse now retired from UC Riverside Entomology lead a team that intercepted avocados coming into the US. They found a number of scale insects that were new to California and new to the identification world. A number of these scale are parthenogenic, meaning they can reproduce without males, and just one lone female could possible balloon into a massive population in a short time. And on a scale like that, trees would have a hard time without some serious intervention.
Argentine Ant is a very aggressive invader that disrupts native ant populations and at the same time disrupts biocontrol agents that help control, such pests as scale, aphids and mealy bugs in citrus and other tree crop species. They defend these sugar producing sources of energy from attack by predators and parasites, like parasitic wasps and predatory assassin bugs and lady bugs. They increase the threat of Asian Citrus Psyllid and HLB by protecting the psyllid from attack by parasitic Tamarixia.
A careful, well placed chlorpyrifos spray has been used to control Argentine ants. A trunk spray and/or spray on irrigation lines has disrupted their activity with minimal impact on beneficials. This protectant spray keeps the Argentine ants out of the canopies and allows the beneficials access to the pests. Controlling this one species, can have significant impact on biocontrol and the whole need for controlling pests.
Chlorpyrifos is a pesticide that might lose registration and other materials and techniques have been examined over the years as a replacement. A recent procedure has been proposed and used successfully on Santa Cruz Island to control introduced Argentine ants. The ant has caused tremendous disruption in biocontrol and it appears to have been controlled by this new technique. We are in the process of evaluating it's use in citrus. The application technique, costs and materials would need to be modified for use in citrus orchards. The current procedure would not be considered an organic practice since the pesticide material is not registered organic. It might be possible to use an organically registered material in the future.
Protocols for Argentine ant eradication in conservation areas
L.Boser1,C.Hanna2,D.A.Holway3,K.R.Faulkner4,I.Naughton3,K.Merrill5,J.M.Randall1,C.Cory1,D.-H. Choe6 & S. A.Morrison
Journal of Applied Entomology
The Argentine ant (Linepithema humile) is a widespread, abundant and ecologically disruptive invader that is present throughout major portions of coastal California and on half of the California Channel Islands. On Santa Cruz Island, the Argentine ant had invaded about 2% of the island's area in four distinct locations as of 2012. Given the negative ecological effects resulting from Argentine ant invasions,we sought to develop a cost-effective method of eradication. Here, we describe the results of large-scale, field-tested methods for Argentine ant eradication and post-treatment detection. Our eradication protocol employs a novel toxicant-delivery system: an aqueous solution of sucrose and 6 ppm of thiamethoxam mixed with hydrating polyacrylamide beads. Ants feed on the solution present on the bead's surface for about 24h after which time bead dehydration prevents feeding. We distributed hydrated beads by helicopter over 74 ha of infested areas plus a 50-m buffer on 14 occasions between June 2013 and September 2014. Treatments reduced Argentine ant activity to subdetectable levels within four months. In 2014, we conducted a high-intensity detection protocol using lures (n = 55 363) in areas treated in 2013.This effort did not detect Argentine ants. In 2015, we conducted a medium-intensity detection protocol using lures (n=2250) in areas treated in 2013 and 2014 but not searched in 2014; this sampling effort did not detect Argentine ant activity except for a single remnant infestation (c.0.3ha in area),which was retreated in2015.Thec ost of treatments was approximately $1400 per ha; this cost is comparable to other ant eradication efforts. The cost of our preferred detection method, which used lures spaced every 10m,was $500 per ha.These results demonstrate sufficient protocol efficacy to justify expansion of treatments to other infested areas in ecologically sensitive areas.
Photo: Argentine ant and scale