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SCALE INSECT PROBLEMS
In recent years, Florida red scale has been problematic in some groves, as has barnacle scale. Generally, these two pests have long been considered of only minor occurrence in Valley citrus, being pretty well held in check by natural controls. Many believe that the resurgence of problems with these two scales is because growers have "sprayed" themselves into the problem by using materials that do not control mature adults and that are hard on the beneficials. Consequently, it is time that you go back into your records (your records, not your memory!) and review your scale control efforts of the last two or three seasons.
One of our most commonly-used scalicides is not, nor does it claim to be, especially efficacious when applied to mature scales. You might consider giving these materials a break and use them at the most opportune time for scale control. Otherwise, I suggest you seriously consider a return to oil sprays to regain control in problem groves. Oil is very effective on adult scales, as well as on the crawlers, plus it serves as a spreader-sticker, suppresses mites, leafminers and greasy spot, while not being too deleterious to the beneficial organisms in the grove.
Several growers have long used oil in the summer spray with absolutely no phytotoxicity to the trees or fruit. For the most part, they apply it in 250 gallons of spray solution per acre, assure themselves that the tank agitator is working perfectly and carefully choose the days when it will be applied. Basically, even the thinnest layer of clouds during application is essential, while days of "white" sky conditions are to be avoided. Granted, large operations may not be able to get across all their acreage under the better conditions for oil application; but they should at least target the problem groves for priority treatment.
With years of inspecting groves after early-to-mid-July applications of oil, the only phytotoxicity that I have ever seen has been due to failure of the tank agitator. In some cases, pencil-eraser sized water-soaked spots may appear on the fruit a few days after the application of oil, but these spots always disappear within a short time.
Don't think that oil is just for summer application; in problem areas, I would not hesitate to use oil in both post-bloom and late spring applications. Naturally, the inclusion of a good miticide in all oil sprays is recommended. Too, to get a better degree of control of greasy spot, include a good fungicide with oil and the miticide in both late spring and summer oil sprays.
Texas Department of Agriculture is proposing a few changes to the existing rules regarding the citrus budwood program, as well as to those rules which establish citrus maturity standards. You can go online to http://www.sos.state.tx.us/
texreg/issues.shtml to check them out. The public comment period ends May 11.
Blame my first reply on a lapse in judgement or a senior moment. In any case, it was gratifying to get an "attaboy" from Chet Roistacher and a good letter of support from Michael Kesinger, Chief of the Bureau of Citrus Budwood Registration in Florida.
SUDDEN DEATH DISEASE-
Brazilian citrus growers have lost approximately 3 million orange trees in the last 3 years to a disease they are calling "sudden death". It initially appeared in the southern state of Minas Gerais, but has since spread into Sao Paulo, which is home to some 85 percent of Brazil's estimated 280 million orange trees. It is believed that the new disease is a mutant of CTV which only affects trees budded onto Rangpur lime stocks-which is the predominant rootstock in Brazil. Initial symptoms of infection are yellowing of the leaves, with death occurring rapidly after the yellowing.
While efforts to identify the problem are on-going, many growers are inarching other rootstock seedlings into existing trees in an attempt to prevent tree losses. Inarching is a propagation method in which one or more seedling rootstocks are planted alongside the existing tree trunk, the tops of which are then cut off at a sufficient height and angle and inserted beneath a vertical slit made in the bark of the scion above the existing bud union. After the graft takes, the new seedling rootstocks begin to grow and ultimately replace the susceptible rootstock when it is killed out by the disease. To date, some 10 million trees have been inarched.
Rangpur lime became the rootstock of choice in Brazil following the devastation caused by CTV in the early 1940's, as it was resistant to CTV and was very tolerant to dry conditions. Too, Brazil has long practiced CTV cross-protection inoculation using mild strains of the virus.
It isn't over yet, but the end of the current season is very near. Slightly more than 8 million cartons of Texas citrus have been shipped to date, which is about 20 percent below last season's 10 million plus cartons.
About 4000 tons each of grapefruit and early/mid oranges were dropped from the USDA's crop estimate on April 10, leaving about 3.5 and 4.3 percent remaining supply, respectively, as of mid-April. Remaining Valencias are estimated at about 7.8 percent.
External appearance of grapefruit has been a season-long problem leading to about half again as much grapefruit being eliminated to processing than was the case a season ago. Sheepnosing is not the culprit, though it has continued to occur. Rather, this season has been characterized by grapefruit with a very rough, coarse rind-which eliminates it from Fancy grade and often even from Choice. For the lack of a more definitive explanation, blame it on the cumulative effects of several years of inadequate rain and inadequate irrigation water.
Well, Mexico transferred ownership of waters already in storage in the international reservoirs to, belatedly, fulfill its agreement of late January. Once again, Mexico took water that rightfully should have gone to growers in northern Tamaulipas rather than to effect a physical release of water from the Rio Concho Basin-which latter was the commitment made by Mexico. While I know of no one who doesn't need the water, we all wish Mexico would keep its word, honor the treaty and quit penalizing Tamaulipas growers to pacify Chihuahua.
Somewhat unexpected rains occurred along the southern part of the Valley early in the month, and additional rains fell in west-northwest areas at the end of the month. The east-northeast area has been a little light, however. If the once-common Cinco de Mayo rains come, perhaps everybody will get a share.
Fruit droppage is still ongoing, and final set may be delayed until near the end of May. As you know, the final fruit drop period has almost always finished by about May 20, but late bloom of all varieties this spring could delay that by a week or two.
Post-bloom sprays are in progress Valleywide as growers endeavor to protect the new fruit from significant damage by citrus rust mites. Careful monitoring of rust mite populations is one of the most important aspects of grove care from now until the end of the year.
If yours was not the recipient of any of the recent rain, monitor
soil moisture carefully so as to avoid any semblance of moisture stress
in the next 30 days while the trees adjust fruit load to carrying capacity
(that's a convoluted way of saying that if the trees aren't well tended
and with good soil moisture, they will drop more of the young fruit between
now and June!).
JULIAN W. SAULS, Ph.D.
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