- Author: Ben Faber
In coastal lemons, there has been a major increase of broad mite and the damage it causes on fruit and leaves this year.
Broad mites are often found in depressions on fruit where the females lay their eggs, which are dimpled, translucent, and covered in white speckles. These mites are so small you need a hand lens to see them. Broad mites are yellowish in color and adult females have a white stripe on the back.
Broad mites feed on fruit and leaves, preferring young fruit up to about 1 inch (2.5 cm) in diameter that are located on the inside of the canopy or on the inward facing side of outer fruit. Feeding results in scarred tissue that cracks as fruit grows, leaving a characteristic pattern of scars and new tissue. Although most feeding occurs on fruit, broad mites may also feed on young expanding leaves causing them to curl. This cupping and curling of leaves can appear similar to mild damage caused by glyphosate-Roundup applications.
Broad mites are occasional pests of coastal lemons from late July through early October; infestations are enhanced by the presence of Argentine ants. This mite often occurs in conjunction with Citrus Rust Mite, with the rust mite usually predominating in number. Populations of broad mite tend to be most severe in warm, humid conditions such as found in greenhouses. No treatment thresholds have been developed for broad mite in citrus. If high and increasing populations warrant treatment, use miticides with the least toxicity to predaceous mites. The predatory mite Neoseiulus californicus appears to be a good biocontrol agent.
Check out the IPM website for a greater discussion of pesticides available for use on broad mite.
Broad mite on fruit and the damage it causes to leaves.
- Author: Gary S. Bender
The polyphagous shothole borers (Euwallacea sp.) that spreads fungal diseases (Fusarium sp. and possibly Graphium sp.) to susceptible trees in Los Angeles County have now been found in mid and northern Orange County and western San Bernardino County. Sick and dying trees are being cut down and shredded or chipped. A lot of different species of trees are affected, including avocado, box, elder, castor bean, coast live oak, Engelmann oak, sycamore, bigleaf maple, California bay laurel, white alder, olive, peach persimmon, goldenrain, mimosa, liquid amber and wisteria vine.
Why is this important to growers in San Diego, Riverside, Ventura and Santa Barbara counties? Because growers in San Diego County (and probably other coastal counties) are being offered free shipping by the waste disposal companies of wood chips and free spreading of the mulch in their groves. What a deal!! But wait a minute!
The problem lies in that the material I have seen is either not composted or poorly composted, because it heats up in the grove after delivery and starts steaming. This means that freshly shredded or chipped trees could very likely be spreading the borers right into their groves!
Growers should ask themselves “why are these trees in Los Angeles being cut down in the first place?” Trees are being pruned and cut down for a variety of reasons, but now that we have a new pest for which there is no control, we have to be very cautious about what we bring into our groves. Other problems that could be brought into groves include Phytophthora root rot and trunk cankers, oak root fungus, Dothierella cankers, and Asian citrus psyllid.
Growers should insist that only correctly composted mulch be brought into their groves. During the composting process the piles should be turned at least five times to allow the material on the outside of the pile to be turned into the middle for correct heating of the entire pile.
- Author: Akif Eskalen
This is an update on our recent findings on PSHB/Fusarium dieback. As of October 4, 2013, PSHB/Fusarium dieback was detected in Glendora in northern Los Angeles county and Laguna Niguel in southern Orange County. The infestation in Laguna Niguel Regional park appears to have arrived there within the last week. We inspected the South coast research station last week, and it was still negative. Please find attached recent distribution map.
- Author: Ben Faber
This just in from Cal Recycle pertaining to the movement of green waste in Southern California. Now with Asian Citrus Psyllid so widespread in that area and the spread of Polyphagous Shot Hole Borer, it is a good idea to consider carefully the source of green waste used for mulching.
The Oriental Fruit Fly (OFF) attacks over 230 crops, including citrus, other fruits, nuts, vegetables and berries. In August, 2013, the OFF resurfaced in the Anaheim area of Orange County and in the Artesia/Cerritos area of Los Angeles County.
To prevent the spread of the pest, authorities have established a 130-square-mile quarantine, which includes portions of Orange and Los Angeles Counties, (Quarantine zone). Many host plants for the OFF grow in the urban landscape and end up in recycled green material.
USDA, CDFA, and County Agricultural Commissioner staff, enforce the Federal Domestic Quarantine and the State Interior Quarantine. These quarantines prohibit movement of green material unless specific conditions are met. The State Interior Quarantine for OFF includes portions of Orange and Los Angeles counties.
For additional information, please contact Elena Yates (916) 341-6466, of the CalRecycle Organic Materials Management Unit./h2>/span>
- Author: Craig Kallsen
I had a chance to talk to PCA Dennis Seaton a few weeks back. During the farm call, he mentioned that he was making a survey of leaf ‘yellowing’ in his clients’ citrus orchards. He explained that he thought this would help him in the future, should HLB disease show up, in distinguishing the yellowing associated with HLB, from the other things, both biological and abiotic, that currently cause leaves to yellow in Kern County. This project sounded like a good idea to me. Currently, every time a new article appears in our local Bakersfield paper related to ACP and HLB, my phone is busy with homeowners concerned with yellow leaves. Unfortunately, we have always had a lot of ‘yellow’ leaves on Kern County citrus trees. A list of a few things (not complete) that can cause leaf yellowing is as follows:
Citrus stubborn disease - caused by a mycoplasm – also produces small, hard, green, lopsided fruit
Root rots (e.g.Phytophthora species, Fusarium species)
Alkaline soil - iron deficiency
Gas leaks, oil-field waste oil in soil
Sunburn, heat stress (tends to be on older leaves)
Nutrient deficiency – iron, zinc, manganese,
Nutrient toxicity – boron, arsenic, sodium, chloride
Trifoliate and citrange tree decline
Pre-emergent herbicide uptake
Mite feeding, citrus leaf miner feeding, citrus thrips feeding
Chemical toxicity from foliar sprays (e.g. Biuret toxicity)
Tristeza disease – caused by a virus
For those who really want to try to diagnose HLB from yellow leaves, pictures of leaves with HLB can be found at the following webs address; http://www.californiacitrusthreat.org/huanglongbing-citrus-greening.php .
If we mentally divide a leaf with HLB symptoms in half, longwise, along the midrib, the yellowing is more asymmetric than is the case with other factors that can yellow leaves. That is, one half of the leaf will have yellow areas in different locations than the other half. Yellowing from zinc deficiency, on the other hand, looks pretty similar between halves. HLB leaf yellowing often affects individual branches or shoots more than neighboring branches or shoots. If you see leaf yellowing, always looks for the presence of ACP nymphs on new, young leaves. The nymphs, about the size of aphids, produce distinctive waxy tubules. See the website at www.californiacitrusthreat.org for pictures of the nymphs and adults of ACP. The insects themselves are much better indicators of possible HLB infection than leaf yellowing. The production of small, hard, greenish-yellow, sour fruit is another indication of HLB infection (but not definitive).