|IN THIS ISSUE:
While some growers have already done it and others are thinking about it, most growers seem to be ignoring the need for pruning groves. If you look around, too many groves have middles that are only 4 or 5 feet wide, which impedes culture, harvest and pest control. Such overcrowding also causes shading and dieback of the lower canopy and lowers production. Moreover, to hedge the canopies back to the necessary space necessitates cutting larger wood, which significantly reduces production for the following year or two.
The decision is not whether your grove should be hedged, rather it is when, how and how often it should be done. Generally, if you aren't quite sure that it needs hedging yet, it probably does.
Using middles width as the key, hedging should be implemented as soon as the canopies begin to encroach into the space designated for the middles so that not more than one foot of foliage has to be removed from each side of the middle. The hedging angle should be at least 5 degrees to no more than 25 degrees from vertical-10 to 15 degrees is most common and will usually be more satisfactory for culture, harvest, production and pest control.
Topping is also critical, as fruit in the tops of overly tall trees is usually of smaller size and poorer quality, is harder to spray and harder to pick. Topping should be lower than desired so that subsequent topping is restricted to the new growth above the original cuts. Topping angles range from flat to as much as 25 or 30 degrees from horizontal. As a general rule, a greater angle aids in brush removal from the tops. A common scenario is to top so that the shoulder is 12 to 14 feet high, with a topping angle of 15 degrees, which puts the peak at about 13.5 feet, 20 degrees makes it about 14 feet, 25 degrees puts it at 14½ feet while 30º tops the peak at just over 15 feet (for a 12-foot high shoulder, hedged at 15 degrees-at the same hedging angle but higher shoulder heights, the peak height would increase by about the difference between 12 feet and the actual shoulder height).
If you have trouble visualizing this, at a 25-foot row spacing and an 8-foot middle, the base of the tree row will be 17 feet wide, the shoulders (at 15º hedging and 12-foot height) will be 10.5 feet wide, and the peak (30º topping) would be at just over 15 feet high. In other words, it looks like an angle-sided (or flared) camping tent with a slightly pitched roof.
Now comes the hard part-what time of year should you prune? The answer is simple-during the winter months after harvest and before spring flush. Unfortunately, harvest of grapefruit and Valencia oranges usually isn't finished until after bloom, so what do you do-prune anyway and cut off some mature fruit or wait until after harvest and cut off some fruit that have just set? If the decision comes to that, the latter is usually the more desirable option (and really the only option for Valencias). For grapefruit, visit with the packer to try to arrange cleanup harvest before bloom.
The next hard decision is to determine the hedging-topping program that you are going to follow. Back in the days of wider spacings, a three-year cycle for vigorous orchards or a four-year cycle for less vigorous varieties was common. With today's tree spacings, two-year and three-year cycles may be more appropriate.
With a vigorous variety like Rio Red, a two-year program would entail hedging odd-numbered middles in the first year, even-numbered middles in the second year and start over in the third year. For the sake of spreading the load, I would probably be inclined to top the same middles that are hedged. For a less vigorous variety, hedge odd-numbered middles in the first year, even-numbered middles in the second year, top both sides in the third year and start over in the fourth year.
Remember that you want to cut only twig-sized growth and only about a foot into the canopy in any maintenance hedging and topping program. In theory, subsequent hedging and topping will cut at or just outside the original cuts. Thus, a maintenance pruning program will also maintain optimal production from season to season.
Unfortunately, many groves have become so crowded that the initial operation is going to cut into one-inch or larger wood, thereby significantly reducing production on the hedged side for at least one, maybe two, seasons. Under that scenario, hedging alternate middles is about the only way to go, as the non-hedged middle will compensate somewhat for the greatly reduced production on the hedged middle.
In the case where the orchard is crowded and where alternate heavy and light crops occur, it is better to prune after the light crop is picked and before the heavy crop is set. Thus, pruning will reduce the number of fruit in the heavy year, increasing fruit size and helping to attenuate alternate bearing.
Finally, what about fertilization levels following pruning? If started on time and maintained as a regular program, there should be no change in the fertilizer program. If, however, pruning has been delayed until severe crowding exists, the fertilizer level should be reduced in order to avoid excessively rank regrowth of the pruned sides.
Remember a reduced crop and heavy nitrogen results in severe sheepnose in Rio-since delayed pruning is going to reduce the set, normal fertilization will blow it up.
As I read back over this article, it occurs to me that some might wonder why I talk about middles rather than rows. The simple answer is that during my early citrus career in Florida, most hedging machines were double-sided. Both sets of blades were set at the appropriate angle and distance, then all the operator had to do was drive straight down the center. The other reasons reflect the operation itself-first, you are trying to open up the middles to facilitate orchard operations and second, it puts all the brush into one middle for easier flailing or shredding.
Ron Muraro, Farm Management Economist at Lake Alfred, FL, has recently published the 1999-00 Comparative Citrus Budgets (Citrus Industry, July, pp. 23-34). The one of perhaps most interest to Texas growers is Indian River grapefruit for fresh market (on page 26), which averaged $951.47 in production costs per acre. To make it more interesting, I totaled his results into broader categories.
Weed control totaled $211.91 per acre, while pest control amounted to $322.08. Nutrition was $118.01, while irrigation averaged $169.80. Pruning averaged $55.48 and tree replacement cost $74.19.
In addition to production costs, interest on operating costs and on capital investment, plus management and taxes added another $634.92 to the pre-harvest costs-for a total of $1,586.39 per acre total cost. At his average production, converted to tons, the average cost per ton came out at $79.59.
CITRUS CAPITALIZATION TAX CASE-
You might recall that a little more than a year ago, I was subpoenaed to U.S. Tax Court in Florida to testify in a case in which a citrus grower was trying to expense rather than capitalize the pre-productive period costs of establishing new orchards. The bone of contention was that because the grower was able to produce and sell a modest amount of fruit in the year after planting, he should be allowed to deduct pre-productive expenses in the tax year that they were incurred rather than having to capitalize those costs starting in the fourth year after planting.
The judge issued his opinion in late May, which basically denied the grower's claim and upheld the position of the IRS-which had disallowed over $1.4 million in deductions over a three-year period. The possibility of an appeal does exist, the basis being that when Congress passed the existing law in 1986, IRS and Treasury were mandated to establish national weighted average pre-productive periods for a number of perennial crops, including citrus, but that that has not been done. In one sense, this tax court trial may have defined the national weighted average pre-productive period for citrus.
The weather has been hot, dry and windy-with virtually no rainfall during July except for a couple of scattered thunderstorms over the last week. Potential rain activity is forecast to pick up, but then it usually does at this time of year. Reservoir supply dropped 1 percent in July to 37.7 percent of conservation level.
The weather has been hard on the trees-more stress than we would like to see, but the flip-side is that rust mites have finally been controlled. Sunburned fruit is more common than I can remember. Navels are likely to experience severe splitting as soon as the rains start, as the current weather has severely restricted elasticity of the rind, which won't be able to stretch fast enough to accommodate the infusion of fresh rainwater.
Since summer sprays are about finished, as are summer herbicide applications, most growers can relax a little and wait for the rains to start. Then, greasy spot, mites, stinkbugs and other problems will have to be carefully monitored. And, whether you are ready or not, the first oranges of the new season will probably be harvested just about five weeks from now.
CITRUS PEST UPDATE-
With the last Valley rains being several weeks ago, citrus rust mite populations have been brought under control with spray applications and the extremely hot, dry weather. There was much concern with chemical control failures back in April and May but the tremendous rust mite pressure that over-wintered probably set the stage for all the problems that were experienced this spring. Many producers have as many as three or four rust mite applications thus far, making this season as costly as last year even though it has been much drier this year.
The armored scale complex, especially Florida red scale, has been at relatively low levels this year in contrast to last year at this time. Several groves that were experiencing Florida red scale problems last year still have none to speak of because of the beneficial parasitoids and predators that were released through the course of last season. However, the armored scale complex (all of them) has been increasing in the last four weeks and expect these populations to increase in August. Esteem® has proven to be effective against California red scale and there are field demonstrations looking at its effectiveness against Florida red scale.
Greasy spot and melanose continue to be a problem and these diseases have to be managed in a manner that incorporates a strategy that looks at the health of the trees for the next year or so. Copper is an excellent product for control and a summer oil application (5 gallons/acre) helps suppress greasy spot. A Section 18 for Enable® on grapefruit for greasy spot control exists until October 1, 2000, and a package has been resubmitted. Enable® has proven to be an excellent product for greasy spot control and should be part of a strategy that is used in rotation with copper to help delay/prevent any resistance problems that may surface.
JULIAN W. SAULS, Ph.D.
| Valley Citrus Notes Index | Aggie Horticulture |