CITRUS PROGNOSIS
GREASY SPOT
HIGHLIGHTS OF TCM MEETING
CURRENT SITUATION

CITRUS PROGNOSIS-

Given either timely rainfall or adequate irrigation supplies, the 1998-99 Texas citrus season should realize substantial increases in grapefruit and early orange crops. Grapefruit stands to reason, inasmuch as the current season's production is down an estimated 11.5 percent from last year.

Despite the fact that we shipped nearly 27 percent more earlies and 34 percent more navels, the fact remains that the total early crop (minus fresh navel utilization) was only 44,261 tons, or about 6.8 percent more than the year previous. Looking at the 90's, the total early crop (less fresh navels) had tremendous increases in volume during 1994-95 and 1996-97, with either relatively small increases or an actual decrease during the other seasons (1993-94, 1995-96, 1997-98). Thus, the trend is for a substantial increase in 1998-99.

GREASY SPOT-

Everybody else has been talking about this disease for the last several months, so I reckon it's about time I put in my two cents worth of opinion.

When I arrived in the Valley in 1980, greasy spot was mostly a non-problem--in fact, I did not observe greasy spot in an orchard until sometime in 1981 in the Bayview area. Today, by contrast, greasy spot should be considered a major problem in many orchards across the Valley.

Why has greasy spot become so widespread and severe? Frankly, I think there are several reasons. On one hand, more widespread use of herbicides and less disking has resulted in increased levels of infected leaf litter on the orchard floor. Too, greater use of microsprayer irrigation has undoubtedly resulted in earlier infections than under flood irrigation.

Our pest control program has changed significantly since the early 80's. On the one hand, the use of Temik® precludes ground rig sprays during the spring--which was a time when virtually all groves were receiving one or two copper sprays to control melanose. Too, the severity of the two freezes in the 80's have resulted in considerably less melanose pressure since that time.

Finally, the reduction is spray volume from 500 to 250 and even 125 gallons per acre has caused many growers to abandon summer oil sprays because of potential phytotoxicity problems.

So, the upshot is that we don't spray much copper in the spring and we don't use much oil in the summer, so greasy spot just keeps getting worse and worse.

Because it has taken years to get into this situation, one shouldn't expect to get through it overnight. I firmly believe that it will take multiple applications over a couple of years to bring greasy spot under better control.

Copper is so effective against greasy spot that I would advocate its use in every spray from spring through the summer. And most of you know that I like oil in the summer (plus copper).

Other than copper and oil, Benlate® is the only other labeled material for greasy spot control. Rohm & Haas is working to get fenbuconazole labeled, since it appears to be very effective. Zeneca also has a product (Quadris) that may be labeled in the near future. Both have looked good in tests in Florida and Texas.

Regardless of the limited availability of greasy spot fungicides, growers should get out of the mindset that greasy spot can be controlled by a single, well-timed summer or fall spray. Indeed, greasy spot control starts with the first trip through the grove with a sprayer and continues through the last trip.

HIGHLIGHTS OF TCM MEETING-

The Annual Mid-Year Meeting of Texas Citrus Mutual was a good one. In addition to Dr. Pete Timmer's discussion of citrus greasy spot, other speakers addressed the use of oil for greasy spot as well as scale control in relation to potential phytoxicity from oil use. The key to oil use safety is good agitation, high humidity and a little bit of cloudiness to offset the higher temperature effects of mid-summer spraying.

Bob Thornton highlighted some of TexaSweet's goals and accomplishments, while Ben Abbitt enlightened us about TCX. It is noteworthy that the price for by-products is down, as is the value of juice--even though total juice sales are up. It is interesting that TCX has to purchase about 2.0 pounds of solids to blend with every pound of solids from our earlies--because of the poor color and quality of our Marrs juice. And if you ever needed to know, overall Texas orange yields are about 130-135 pounds of solids per ton of fruit while Texas grapefruit has jumped from about 90 to 109 pounds of solids per ton of fruit processed.

Bob Smith highlighted the Growers League's efforts to enhance the price of choice grapefruit by way of a $0.50 rebate per carton to retailers to handle choice fruit. In another vein, the League would like to see a return to more cash sales rather than the so-called participation plans under which most of the independent fruit is handled today. In that regard, it should be noted that the current system is not a true "participation plan", as the handler takes a commission on gross sales plus the cost of pick, pack and sell. Under a true participation plan, the handler would more directly share in the risk of lower prices than he does under commission sales.

The afternoon panel and the breakout discussion groups came up with some good ideas. Of most interest to me was that a retail produce manager will stock an item if only two customers request it--which may help move more Texas grapefruit if we can convince people to demand it of their local grocers.

In value-added, the not-from-concentrate juice market is booming--but it requires a lot of storage capacity for the single-strength juice and TCX is farming out the dairy pack procedure to a company which has the necessary equipment to package single-strength, chilled juice.

Under cost reduction in citrus production, Jason Johnson basically recapped articles I wrote in this newsletter a couple of years ago--and the discussion group basically concluded that there was very little room for savings in the current citrus production program.

Under research needs, the group came up with more work on sheepnosing, continued work on leafminer control, spacing trials for Rio, continued CTV work, marketing work and further research on the health benefits of citrus.

Also, Dr. Bhimu Patil highlighted preliminary results of his work on sheepnosing. It is interesting that sheepnosing was much less severe in Bayview than in Mission and that sheepnosing was worse with the larger sizes of fruit. Sour orange produced less sheepnosing than did Swingle which caused less than Carrizo. It surprises me that flood irrigation resulted in less sheepnosing than did microsprayers--so you know that I am glad that these results are only preliminary. Dr. Patil will be continuing his work on sheepnosing.

There were some other presentations, also, but I missed them or didn't make notes and therefore cannot recap them here.

CURRENT SITUATION-

The winds of March have been fierce--damaging the bloom and new flush, as well as taking its toll on the remaining unharvested crop. In addition, the drying effect has more rapidly depleted the available soil moisture, thereby shortening the cycle between the last rainfall or irrigation and the next irrigation. Pan evaporation levels have been exceedingly high in March. Not exactly what we need in view of the severely curtailed water availability for irrigation.

March and April are not noted for copious rainfall--and this March produced virtually none. And if we must irrigate now, as is true for most orchards, then I would just as soon the traditional Cinco de Mayo rains come on time.

With limited water, the choice of when to use it is not really a difficult one--the time from bloom to about the third week of May is most critical in terms of fruit set. Good soil moisture at this time will maximize fruit set (and will establish potential fruit size). Water after June 1 is involved in tree growth, which directly affects the sustained development of this crop and determines the ability to flower and set a crop next spring. Too, summer water is directly involved in expansion at the cellular level, which thereby determines whether or not the fruit attains its potential size.

In other words, all cell division within a developing fruit occurs before summer, and it is the number of cells that determine potential fruit size. From then on, the growth of the fruit is wholly dependent upon cell expansion and not on the addition of new cells.

So, use your water to set the crop and if you still have some, use it in summer to help the crop attain its total size potential.

The Texas citrus IPM program will start biweekly scouting very soon--you should already be signed up if you plan to participate. April is traditional post-bloom pest control time, whether you use Temik® or other materials in a spray machine program.

On a Temik® program, schedule the Temik® application in conjunction with the need to irrigate, i.e. let the need for irrigation dictate when you apply the Temik®--not the other way around. The window of application of Temik® is sufficiently wide that it should be no problem to delay (or advance) the application to take full advantage of irrigation for the good of the orchard as well as for incorporation of the Temik®.

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