VOL. 23, NO. 7
IN THIS ISSUE:
MORE HLB (GREENING)
NEW TEXT ON PATHOGENS OF CITRUS PESTS
MORE HLB (GREENING)—
On June 9, 2009, officials of USDA—APHIS—PPQ confirmed the identification of huanglongbing (greening) at a residential property in Savannah, Georgia. The tree was reported to be a mature sour orange. The property is near where the Asian Citrus Psyllid was detected last August. APHIS is presently conducting additional delimiting and detection surveys in the surrounding area.
With this detection, all of Chatham County would immediately be under a federal quarantine. It appears, however, that the State of Georgia has declined to initiate a parallel intrastate (i.e., within Georgia) quarantine, in which case APHIS will quarantine the entire state for HLB and ACP.
Both Savannah, GA, and Charleston, SC, are on the Atlantic Coast—suggesting that “hot” psyllids moved north out of Florida along the Atlantic Coast, spreading HLB as it went. A similar link does not yet appear along the Gulf Coast coming west out of Florida, since neither Alabama nor Mississippi have HLB detections to date, though both states have confirmed ACP. Officials are looking, however, as there are several citrus plantings not too far from Mobile.
Ever since the feds quarantined Florida citrus fruit for citrus canker back in 2007, fresh Florida citrus has not been permitted into markets in California and Texas. Some figure that was a boon to citrus producers in those two states, though I know of no studies showing that total fresh volumes sold by Texas or California producers increased or that prices received were significantly higher than prior to the quarantine on Florida fruit. I am certain that there are studies out of Florida showing that their shippers shipped less total fruit and had lower returns during those two seasons. Neither position, of course, makes it so.
Well, if the Texas and California citrus growers had a free ride for the last two seasons, it‘s time to pay the piper, as the feds should have posted new rules about the canker quarantine in the Federal Register this week. The upshot of the new rules is that the feds have concluded that Florida citrus fruit with canker lesions is “unlikely” to cause the disease in other states. Thus, it would seem that the upcoming season will see Florida fruit in both Texas and California markets.
There will be a 60-day public comment period following publication of the proposed rule in the Federal Register. While I fully expect that citrus officials in California and Texas will have plenty of comment, I am not optimistic that such comment will have any significant effect.
I have not seen all of the supporting research that underlies this probable lifting of the quarantine, though I am certain that it was good research, well conducted—but I don’t know if it included all of the possibilities that can happen to a piece of fruit. Obviously, I have reservations about lifting the quarantine—not because of market protection, which I don’t think really mattered anyway. Perhaps it’s part of human nature—you don’t send your kid to school if the kid has an infectious or contagious disease.
Too, I’m reminded of some unrecalled Florida official who complained that Dallas is a really long way from the Texas citrus industry in the Rio Grande Valley, implying that even if fruit with canker lesions were sent to Dallas, it wouldn’t affect citrus in the Valley. Maybe not directly, but obviously he is unaware that Dallas and Tarrant counties are among the 110 Texas counties in which Texans are growing citrus trees.
Southern Gardens Citrus in Hendry County in Southwest Florida is one of the largest citrus growers in the state and is the site of a new citrus planting that may be the long- term solution to the problems of citrus canker and HLB, not only for Florida but also for all citrus industries. Some years ago, Texas AgriLife Research of Texas A&M University initiated studies to introduce a gene from spinach into citrus, thereby hoping for resistance to canker and HLB.
In closely regulated greenhouse/laboratory conditions in Florida, the transgenic citrus plants survived challenges from both canker and HLB. Essentially, the challenges occurred by grafting transgenic plants with diseased stocks. The next step in the process is to plant the transgenic materials into a grove where they will be constantly exposed to challenges from adjacent diseased trees.
Recently, transgenic seedling trees of Hamlin, Rio Red and Ruby Red, plus non-transgenic controls of each, were planted in a strictly secured area of Southern Gardens Citrus. The projected timeline is about six years. Basically, these are transgenic plants, otherwise known as “genetically modified organisms”, so there is more involved than just citrus growers and the USDA. Add the EPA and the FDA into the mix, as both have a say in GMO plant materials, e.g., there may be allergy issues which bring in the FDA.
Thus, the projected timeline of six years for these plants to prove themselves and to be accepted as safe by all the different state and federal agencies is really quite short. If it goes as hoped, propagation of the GMO varieties could begin then.
I am told that there are transgenic Marrs and Rohde Red Valencia, with other varieties in the pipeline.
On another note, the transgenic Rio Red trees with resistance to citrus tristeza virus that were field planted several years ago have borne fruit the last couple of years. According to tests, the fruit and tree characteristics are all identical to non-transgenic Rios. There has been no serious field challenge of CTV to these trees, as we don’t often encounter CTV in Texas. Nonetheless, now that the fruit and tree characteristics of these trees are documentably identical to Rios, it shouldn’t be too long for the next step to field test propagations of these trees in citrus areas where CTV is a major disease.
Not much rain occurred in June, just a few scattered showers during the last week. I am not one to begrudge rain whenever it comes, but I was grateful that the showers last week basically stayed away from Camp Perry just north of Rio Hondo, as the resulting mud would have added even more misery to the already extremely hot days and nights of Summer Camp with the Boy Scouts. The threat of rain was such that most of us finally put up rainflys over the tents, making the nights even warmer.
Grain harvest is proceeding rapidly and corn harvest will soon follow. Thus, it is the time of year when we start to see more so-called “boll-weevil” showers as cotton begins to mature in anticipation of defoliation and picking.
The biggies in grove care at this time are irrigation and pest control. Irrigation is a no-brainer—if it hasn’t rained recently and the requisite time since your last irrigation has passed, then it’s time to water.
Pest control is another matter, as you have to physically check the trees and fruit for mites—and keep on checking every couple of weeks (more often if you’re worried because you haven’t found many yet). Citrus rust mite populations can increase to damaging levels in just a couple of weeks, and the likelihood of population increases is enhanced by the occurrence of higher humidity and scattered showers or other rain events.
Midsummer is yielding to the dog days of summer when little else is required beyond those two practices. Fruit continues to size, trees continue to grow, navels will start to split, and before you know it, harvest crews will be looking for work. In other words, you have made the crop, so just keep it watered and keep it clean until it’s finally picked.
NEW TEXT ON PATHOGENS OF CITRUS PESTS —
Pathogens Infecting Insects and Mites of Citrus is a pictorial guide to the entomopathogens of phytophagous insects and mites found on all plant parts of a citrus tree. It includes illustrations of healthy citrus insects and mites and their feeding injury. Although emphasis is on Florida, citrus growers and other interested people will find the images helpful in identifying arthropods and their diseases.
The purpose of this book is to present a comprehensive overview of the pathogens that cause disease of the various citrus arthropods, emphasizing: 1) visual recognition of a diseased host based on gross pathology, 2) identification via diagnostic characters of the pathogen, 3) visual recognition of healthy citrus pests and alternative ornamental hosts, and 4) direct injury to the plant.
The book is available from Florida Science Source firstname.lastname@example.org, who you should contact for ordering details. The price is $90.00.
JULIAN W. SAULS, Ph.D.
Professor & Extension Horticulturist
2401 East Highway 83
Weslaco TX 78596
THE INFORMATION GIVEN HEREIN IS FOR EDUCATIONAL PURPOSES
ONLY. REFERENCE TO COMMERCIAL PRODUCTS OR TRADE NAMES IS MADE WITH THE
UNDERSTANDING THAT NO DISCRIMINATION IS INTENDED AND NO ENDORSEMENT BY
THE COOPERATIVE EXTENSION SERVICE IS IMPLIED.
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