IN THIS ISSUE:
If warmer than normal temperatures during pre-bloom through fruit set are responsible for sheepnosing in grapefruit, we should be in for a bad year, as average daily maximum, minimum and mean temperatures have been rather higher than normal since November.
As you may recall, the indicators in 1996-97 were mixed-but only Rio had sheepnosing. Those in 1997-98 indicated no sheepnosing-yet Rio still showed some degree of sheepnosing. The current season is comparable to 1989 and 1995-96 in terms of temperature departure from normal, especially in the January to May period.
Obviously, we are not sure about which temperature variable nor which period is most reliable as an indicator of sheepnosing, if any. Regardless of what happens this season, the occurrence or lack of sheepnosing, especially in the Ruby-Sweet types, will provide a little more information which may shed a little more light on the subject.
Through the end of August, 1996, Valley irrigators used a total of 487,133 acre feet of water in excess of inflows during the same period. During the last four months of the year, inflows in excess of withdrawals totaled 207,704 acre feet-so 1996 finished with a net loss of 279,429 acre feet of water.
Through the end of August, 1997, Valley irrigators used only 49,131 acre feet above inflows, in spite of 221,167 acre feet having been used during June, July and August of last summer. During the rest of 1997, inflows exceeded withdrawals by only 69,215 acre feet-so 1997 finished with a net increase of 20,084 acre feet of water.
Ironically, 1996 was a dry year which saw a net loss of 279,429 acre feet of water, while 1997 was a wet year that generated a net gain of only 20,084 acre feet.
By any logic, 1998 is a dry year so far-and we have taken 229,073 acre feet of water out of the reservoirs (above inflows) during the first five months of the year. Reservoir levels have fallen below 24 percent; several irrigation districts have already quit pumping water for irrigation and several others will run out very soon.
Regardless of allocations, the winter-spring vegetables were irrigated and are gone, the sorghum that was irrigated (much was not) is harvested, harvest of irrigated corn is starting, soybeans are finished insofar as irrigation is concerned and cotton is either in its last irrigation or will be soon. That leaves cane, fall crops and citrus without much water.
Cane yields are sure to be down from limited water use to date, while planting of fall crops will depend upon a significant increase in water supplies.
Citrus is still looking good-but we will need some rainfall soon in order to finish this crop in many orchards where the water supply is gone or about to be. Since it hasn?t rained much in the first half of the year, maybe the last half will be generously wet.
1997-98 CITRUS CROP DATA-
According to data from the Texas Valley Citrus Committee, total grapefruit production was down by 7.7 percent from the previous season. Processed grapefruit declined 16.9 percent, resulting in a fresh grapefruit utilization that was down only 1.1 percent.
The total early orange crop was up 10.4 percent, with processed diversions being down 17.2 percent. Fresh navel orange shipments were up 34.1 percent while other early oranges were up 26.5 percent.
Valencia production was up some 54.0 percent, with processed Valencias up 37.0 percent and fresh shipments up 70.7 percent.
It is a credit to the industry that fresh grapefruit sales were down only 1.1 percent when the total grapefruit crop was down 7.7 percent. For early oranges, it is certainly commendable that fresh utilization was up substantially (28.4 percent) on 10.4 percent more production.
While a few showers have begun to pop up along the coast at the end of June, the four plus months without rainfall is taking its toll in Valley citrus.
Several irrigation districts have stopped delivering irrigation water, others will soon follow. Some growers in districts that still have water have already used their allocation, so they are in the same boat as those in districts which have closed.
Water stress is becoming apparent in several citrus orchards across the Valley. Too many groves are showing limited growth and too many have potentially smaller fruit size; some have reduced fruit load, also.
The overall crop for 1998-99 has been adversely affected already- hopefully, the rains will come soon enough that we can mature what we have and support tree growth sufficiently for next year's crop, also.
CITRUS PEST UPDATE-
The past few months have been very hot and dry which has kept rust mite populations at non-detectable levels. However, a few groves do have very low populations of rust mites which could rapidly increase with any marginal showers that may pass in July.
The citrus leafminer has hardly been detected since very few strong flushes have occurred during this season. Also, the armored scale complex that caused serious problems last year has yet to make any significant appearance. The citrus blackfly populations continue to increase in those groves that have had citrus blackfly problems but are still at low levels. Problems with false spider mites have been reported and this is not unusual during very hot and dry summers like the one we are experiencing. The false spider mites can cause serious damage on grapefruit and should be quickly treated; little to no damage generally occurs on oranges. Texas citrus mites, mealybugs, and whitefly are present and increasing but these populations have been at very low levels. With spring applications of copper in some groves and the dry weather, much of the greasy spot and melanose problems from last year have been tremendously reduced in a relatively short period of time.
SUPPLY AND SALINITY-
Back in January, I discussed water management for citrus orchards for the season-pointing toward a dry spring and reduced allocations that would start to run out in June and July. I also discussed some of the options for citrus growers, including microsprayer, drip irrigation, partial abandonment of less profitable varieties and other factors.
In the intervening half-year, it has not rained since February, many growers are using drip, microsprayers, meters, strip borders and other conservation methods. Some Ruby-Sweet acreage has been semi-abandoned to use the water on more profitable Rio blocks.
Still, some growers used their allocations and are out of water, other haven?t completed their allocation-but they are still out of water because the respective irrigation district used its total allocation and quit pumping except for municipal use. Citrus growers in at least eight districts are without water as of June 30.
Because hopes for rainfall, either in the Valley or in the watersheds, have not been realized, citrus growers have come to that bridge that I indicated we would have to cross-or watch our groves slowly dry up.
Some growers are pumping from wells, others are putting in wells. Obviously, there is a lot of concern about the quality of well water, particularly its salinity and especially its boron content. While I have reviewed the research and recommendations about using saline water in citrus-and I know that excess boron can salt-out the soil-the reality of the situation may override some concerns about water quality.
In other words, if the grove is going to dry up anyway, would it be better to try to keep it going with water that is twice or more as salty as our usual irrigation water? If boron levels are less than 1.0 ppm, the answer is probably ?yes?-as the trees can tolerate the added salinity for awhile and surely we will receive leaching rains before any serious and more permanent harm results.
On the other hand, what if boron levels are greater than 1.0 ppm? Conventional logic suggests that such water not be used at all unless it is blended a with sufficient quantity of water of low boron content so as to maintain a total boron level below 1.0 ppm in the blended water.
JULIAN W. SAULS, Ph.D.
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