- Author: Neil O'Connel
Installing tree wraps on young trees provides protection to the trunk from applications of herbicides during weed management operations. Additionally, the wraps minimize light interception by trunk tissue thereby reducing sucker growth. During hot weather tree wraps provide shade to the trunk and reduce the incidence of sunburn. With the increasing incidence of earwigs, damage to young trees and the tendency for the insect to congregate under the wraps, tree wraps are being removed in some cases. Recent laboratory data from Dr. Beth Grafton-Cardwell (confirmed by observations in the field) suggests that as the season progresses adults become less and less interested in feeding on leaves (peak of feeding in March and April, declines to next to nothing by June). So, a management consideration would be to check the earwigs in the wraps in the summer, and if there are only adults present there is less concern than if there are immatures present. Another point would be to consider treatment with an insecticide such as Lorsban if wraps are to be left on for sunburn protection.
If wraps are removed a uniform coating of sun protective material should be applied to the trunk to protect against sun damage. Trunk surfaces should be monitored to ensure that a uniform coating is in place. Sun damage to unprotected trunk tissue can result in partial or complete girdling of the tree.
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 Texas A&M site
or our UC IPM website
Bob Hill, a local Ventura PCA, saw an interesting mite he had never seen before and asked if I could id it. Well, I sent it in to Mark Hoddle and UCR and he turned it over to his student Ricky Lara to id it. And this is what he says:
I started finding this type of mite infrequently in 2011, when I was sampling foliage in avocado orchards. Although seldom seen, they have a wide geographic distribution on avocado. I found them in Cambria (SLO), Santa Rosa Valley (Ventura County) and Irvine (Orange County). At the time I narrowed down the mite family to Winterschmidtiidae. I have to double check, but I believe their feeding habit is listed as fungivorous (The Manual of Acarology). They might feed directly on plant material too (no fungus on the avocado leaves I sampled) but no one has really studied them. I tried rearing them in the lab (without other mites as a food source, only pollen) but the colony only lasted for a couple of months. On avocado I have seen these mites at the leaf-vein junctions. This probably provides a natural home ("domatia") for them as it does for other mites (e.g. phytoseiids, tydeids, stigmaeids). On lemons, the calyx structure probably serves the same ecological function for these mites.
The tydeid mites are what I call the "tidy mites" since their basic function is to run around and clean up leaves, although there are some predatory and scavenging members of the family This little guy is just one of the many tidy mites found out there and its recent appearance is just a reflection of the weather/climate we have this time.
The red circled mite is the one we are talking about here. The structures next to it are some egg cases of another animal. The red dots are called opisthonotal glands which produce pheromones, the purpose of which is not clear.
At a recent avocado meeting, Carol Lovatt of the Botany Department at UC Riverside pointed out that avocado fruit take up more potassium than nitrogen, almost twice as much, and that much of that uptake occurs later when the fruit is expanding. She reminds growers that all to often, the potassium needs of the tree are overlooked.
Click on "attached files, potassium nitrogen uptake" to view graphs.
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