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TEXAS ORANGES HEADLINED
A routine news article by Rod Santa Ana in mid-September must have needed spicing up, so the newspaper put a catchy headline on it about "markings" on oranges. As usually happens with sensationalism, the story was picked up by wire-services and spread nationwide and beyond.
The "mysterious" markings are rather roundish blemishes, the largest I've seen being little more than half-an-inch in diameter, though most have been smaller. Within the spot, all of the green tissue of the rind goes from green to yellowish and then becomes completely devoid of color. It is striking in that the oil glands within the blemish are initially unaffected. In time, the affected tissue turns brownish in color, and the oil glands do, too.
The only mystery is the cause of the blemish. It isn't mechanical damage, it isn't spray burn or herbicide damage, and Dr. Mani Skaria can't find a pathogen, so it isn't a disease. Some claim that it cannot be false spider mite damage, which it greatly resembles, either because they sprayed or because they can't find the mites. Leaf-footed or other plant bugs (stinkbugs) were suggested because they were plentiful earlier. However, their feeding injury usually results in gumming within the rind-but no puncture or gumming has been observed.
Astute growers will recall that this problem occurred last year and the year before that (and probably even before that, too). Because it closely resembles nail-head rust, sometimes erroneously called leprosis, caused by false spider mites, Dr. Carl Childers of the University of Florida came over last year to check it out with Dr. Vic French. They found a lot of it and a lot of false spider mites, too.
Is this the same thing? It sure looks like it to me, though it may not be. One thing to remember, however, is that the damage you've seeing today was caused several weeks ago-and a potentially causal pest could be long gone, leaving only its damage behind.
One potential cause of the spotting is potato leafhopper, which is a rather common insect here in the Valley. Dr. Stormy Sparks called my attention to a photograph of potato leafhopper damage to citrus in a California citrus pest management publication. The damage appears identical to what we are seeing in that the cluster of oil glands is intact in a spot in which the other rind cells are devoid of color. According to the California report, potato leafhopper will move from some vegetables, pastures and cotton into citrus during late summer to early fall.
According to Dr. French, false spider mites are often opportunistic in that they will move into an already-damaged area to feed. That could explain why it is hard to find false spider mites in association with these spots until some time after the spots have developed. Could it be that the leafhopper causes the spot, then false spider mite moves onto it and causes the necrosis that we call nail-head rust?
Some are concerned about the edibility of such fruit, though I can't imagine why such concern exists. After all, the blemishes I've seen would prevent the fruit from making grade, even No. 2, so it'll wind up in PHE rather than in market channels. PHE oranges are sometimes worth more to the grower than No. 2 grade anyway, as PHE's don't incur a "pack and sell" charge.
Despite the fact that it seems to be a bit more common this season than last or in previous years, it seems to me to be much ado about almost nothing. If the facts change, then I'll be among the first to change my opinion-and you'll know that, too. Meanwhile, the damage is done and growers cannot reverse that.
AND YOU THINK WE HAVE PROBLEMS?-
In browsing through a couple of industry periodicals recently, I was struck by the number of problems our colleagues in Florida are currently battling or facing. Aside from the usual citrus pests and diseases we are familiar with, try these on for size.
The Florida industry has both a rapidly spreading brown citrus aphid population and inherent strains of quick decline tristeza virus. Growers have been battling citrus root weevil (Diaprepes) for at least three decades. The industry is still trying to eradicate Asiatic citrus canker, along with outbreaks of Oriental fruit flies and Mediterranean fruit flies.
The most recent pest is Asiatic citrus psylla, which is the principal vector of the bacterium which causes citrus greening-one of the most serious citrus diseases there is. While the bacterium has not been found in Florida, some biochemical tests of foliage from trees on which the psyllid had been feeding indicated the presence of DNA very much like that of the greening disease bacterium. That is not to imply that greening is in Florida-to date, it is not known to be.
Thanks, but I'll keep the nail-head rust or whatever "mysterious marking" we have, please.
UPCOMING CROP FORECAST-
The wait is almost over-at 7:30 Texas time on the coming Friday, the official 1999-00 citrus crop estimate will be released. If the Florida orange volume is close to the 193.8 million boxes estimated by Elizabeth Steger two months ago and if California's orange crop and Florida's grapefruit crop are down as expected, or at least not up significantly, we should see better than normal returns for both grapefruit and oranges for a second year.
PACKERS AND SHIPPERS-
I have just completed the updates of Texas citrus packers and gift fruit shippers for the current season, based on responses from those who were listed last season. Not all packinghouses or gift fruit shippers responded and I know that there are some changes that I couldn't make until I get the information.
The changes were posted on our website on October 1. The listings give company, address, sales personnel, phone, fax, E-mail and web address-at least that information that we have. We linked both your E-mail address and your website, if any-so potential customers can E-mail you directly or click to your website.
Check it out at http://aggie-horticulture. tamu.edu/citrus/market.htm. When you get there, click on Commercial Packinghouses or on Gift Fruit Shippers to see the listings. The entire site is averaging better than a million hits monthly so far this year-our citrus directory is pulling about 5,500 hits and somewhere around 1,200 user sessions per month. "User sessions" mean that the individual spent some time in the site as opposed to just hitting it and going somewhere else immediately. The average user session is running about 13 minutes. While those aren't all growers or Texans, it really ain't too shabby for a "dinosaur" like me.
While rainfall has been fairly close to average this year, the traditional September rains were rather short. The watersheds have benefitted partly from reduced irrigation demand and partly from inflows. The current levels are not comfortable by any means-only about 42 percent of capacity. Unless the situation in the watersheds improves dramatically, we will start 2000 with less water in storage than we had at the beginning of 1999.
CITRUS WATER USE-
I don't know about you, but I get really annoyed at some people widely and frequently stating to the media that citrus is a heavy water user. To compound my annoyance, they frequently "rank" citrus water use as being close to that of sugarcane.
I pretty much quit trying to refute such erroneous statements, as I was being portrayed as "uncooperative" or whatever. Still, I have regularly reported that metered flood irrigations in citrus in the last couple of years have been running from about 3.5 to about 4.5 inches of water. Fortunately, I'm getting some additional data as the result of mandatory metering in some districts.
Cooperators and I are working to obtain data and to assimilate the data we already have. We should soon be able to report typical flood irrigation rates for citrus, cane, row crops and vegetables, if all goes well. What is clear already is that citrus irrigations use much less water than district average rates-even when you tack on an additional 15 to 25% evaporation, loss and leakage charge.
As I have maintained for nearly 20 years, Texas citrus growers are subsidizing most, if not all, other agricultural water users in the Valley. Frankly, it really surprises me that many citrus growers are still opposed to water metering-metering is the only way that citrus growers will ever get their fair share of the available water. Think about it.
Would you believe a cold front in September? Compared to normal, it was downright chilly on September 29. Since there is probably only so much cold weather up in the Arctic, I wouldn't mind seen it continue moving south so early-then there won't be enough left up there to cause major crop damage in the subtropics later in the year. Yeah, I know-it doesn't work that way.
Rains in early September delayed the startup of harvesting, but virtually all houses were operating by month's end. Momentum should build through October to full throttle by November. Because of short supplies of oranges in California, the current market window is very favorable to Texas citrus. Hopefully, the October 8 forecast won't dampen the prognosis of good returns to growers.
Orchard operations include some spraying for rust mite outbreaks, catchup weed control, occasional irrigation and fall fertilization. One precaution about weed control-while Mandate (Rohm & Haas) is an excellent herbicide for citrus, it currently carries a 90-day PHI. It's 30 days in Florida and we are going to try to get it down to 30 days here.
JULIAN W. SAULS, Ph.D.
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