RAINWATER
WATER USE BY CITRUS
TOPWORKING DEMONSTRATION
RUST MITES GALORE
SCALE CONTROL
GREASY SPOT
Y2K

RAINWATER-

How sweet it is! Did you ever notice that most vegetation responds so much better to rainfall than to irrigation? Obviously, rainfall washes some of the dirt off the leaves of citrus, which does make the trees look even better-but even the weeds in the orchard seem to grow much faster and ranker after rainfall than after irrigation. It's partly a cleansing effect-a little bit of leaching of accumulated salts and replacement with salt-free water-at least for awhile.

Reservoir levels have not changed much during June-the decrease in irrigation needs and the limited inflows from rains upriver have combined to leave the U.S. share at about 35.0 percent of capacity through June, which is considerably better than the 22.7 percent at this time last year.

We still need some monsoon-like rains in the watersheds to improve the situation for everybody.

WATER USE BY CITRUS-

Many times we see quotes in the media from supposedly knowledgeable persons about how extravagant citrus water use is as compared to other irrigated crops in the Valley. Such quotes are especially disheartening to those of us who know better. Fortunately, the wider use of meters as a consequence of the drouth is providing us with factual data to counter such claims.

We are still collecting information, but for now I can tell you that flood-irrigated citrus orchards are running about 0.35 to 0.45 acre feet of water per irrigation. That's a range of 4.2 to 5.4 inches of water-which includes an "inefficiency" charge of 25 to 35 percent. Limited information or row crops is that it is taking 0.6 to 0.7 acre feet per irrigation-some 7.2 to 8.4 inches of water.

Others apparently figure that citrus uses more water because it's there all year whereas the row crops aren't (except cane). Hopefully, we will have sufficient data from citrus, cotton and cane-and perhaps some other crops-to report total water use for the entire season.

TOPWORKING DEMONSTRATION-

The topworking demonstration was conducted in spite of the threat of rain-I think there were nine to 10 people who showed up. Apparently, none of the attendees has even seen this method of grafting, especially as applied to citrus.

Success rates are looking good-11 of the first 12 trees grafted were successful, having at least one if not both scions in full growth now. We'll know about the other 10 grafts later this month.

If you are contemplating using this method to change variety in lieu of pushing and replanting, I'll be happy to visit with you about it. Ideally, I would prefer to use hedging equipment to remove most of the tops in advance of grafting. Too, I would recommend it be done from late February into April-it is cooler then and the grafts generally grow better than those inserted in the summer.

RUST MITES GALORE-

The downside of June's rains is a virtual explosion of citrus rust mite populations in orchards throughout the Valley. Damaging populations have been found in several orchards, but growers have been responding quickly to those infestations. If you haven't checked in the last week or so, you may be in for an unpleasant encounter.

Actually, the outbreak should have come as no surprise to veteran growers, as spring-applied miticides should play out about mid-June to July, depending on the weather. And mid-June this year was the start of the warm, humid, rainy weather in which citrus rust mites thrive.

SCALE CONTROL-

While California red scale seems to receive the most attention, chaff scale is usually more damaging, as fruit tissue underneath the scale does not de-green at maturity. Too, Florida red scale continues to defy growers with scattered flareups here and there.

Too many growers rely on pesticides other than oil for scale control, apparently under the delusion that such materials will kill mature armored scales. Such materials are very effective against non-armored scales and the crawler stage of armored scales-but they cannot penetrate the waxy armor of mature scales. Citrus spray oil doesn't penetrate it either, but it kills the scale by smothering it.

As well as anyone, I recognize the problems of low humidity and high temperature in oil application during late June or early July. Nonetheless, a minimum of five gallons of oil in 250 gallons of spray per acre is not likely to cause phytotoxicity, especially if good agitation in the tank is maintained. While trouble can result from spraying oil on those hot days when the sky is more white than blue, just a thin layer of wispy cloudiness is more than adequate for oil application.

According to Texas pest management guidelines, control of California red scale and chaff scale should be implemented when 5 percent of the fruit examined have 10 or more live scales. A minimum of 10 outside fruit in both east and west quadrants of the trees should be checked. Use a hand lens to verify if the scale is alive or dead (or parasitized).

We don't have established threshold numbers for chaff scale. Consequently, if chaff scale or any other scale was a problem last season, I would incorporate oil (or other scalicide, if appropriate) in the rust mite-greasy spot spray that is going out now or will be very soon.

GREASY SPOT-

Prime infection periods for greasy spot have existed since the June rains started, and spore release from those decaying, infected leaves under the tree should be intense. If you are planning to put a sprayer into the orchard for mite (and scale) control, do not neglect to include copper, oil or Benlate® (DuPont) in the spray.

Enable® (Rohm & Haas) has looked very good in local tests for greasy spot control, but labeling for Texas citrus has not yet been obtained. Similarly, Quadris® (Zeneca) has looked good in local tests, but is not yet labeled. Until either Emergency, Section 18 or full labeling of either or both of those products occurs, either copper or Benlate® alone or combined with oil are our present greasy spot control options.

Y2K BUG-

There continues to be a lot of attention to the Y2K bug that is supposed to devastate computers at the end of the year. Untold millions are being spent to test computer hardware and software and to make them compatible.

In certain applications, the problem is potentially serious because of the computer's internal calendar and internal clock. It is claimed that the computer will "think" it is in 1900 instead of 2000 (why not "think" it is year 0000?). Okay, so what's the big deal?

Well, there is a little quirk in the calendar. Leap year occurs every 4 years for 96 years of every century, but does not occur in the 100th year of any century unless such year is divisable by 400. Consequently, 2000 is a leap year because it is divisible by 400, but 1900 was not a leap year (nor was year 0000).

So if your computer isn't Y2K compatible, it is supposed to assume that 2000 is actually 1900, you will not have a February 29 and will, therefore, be a day off from then on.

While that one-day error may or may not be critical for you, this is simply one example of how so simple a problem (leaving the 19 out of the year when computers and software were developed) can become uniquely complex.

Supposedly, there are some simple tests for compliance. I tried one, didn't know exactly what I was doing, but my system passed. You can find it and other Y2K information at http://eit.tamu.edu/EITDOC/Y2K/Y2kprob4.htm

JULIAN W. SAULS, Ph.D.
Professor & Extension Horticulturist
2401 East Highway 83
Weslaco TX 78596