IN THIS ISSUE:

NEW FRUIT FLY BAIT
CITRUS PESTS & THAILAND
CROP DISPOSITION
POTENTIAL CITRUS WATER USE
POST-HARVEST LOSSES
TEMPORARY RELIEF
CURRENT TOPICS
FREEZING GRAPEFRUIT SECTIONS

NEW FRUIT FLY BAIT-

Scientists at USDA’s Subtropical Horticulture Research Laboratory in Miami, FL, are testing a bait of sugar, yeast and abamectin as an alternative to malathion bait spray for Caribbean fruit fly control in citrus and other crops. They plan to test the bait against Mediterranean fruit fly, also. The efficiency of this product on Caribe fly suggests possibilities for use on Mexican fruit fly in citrus in Texas, but such testing has not been announced.

The USDA is applying for a pate nt for this bait and is seeking a cooperative research and development deal to commercialize the product. Abamectin is the active ingredient in Merck’s Agri- Mek® currently being used for mite and leafminer control in citrus.

CITRUS PESTS & THAILAND-

I have recently had requests from both TDA and USD A about an annotated listing of insects and diseases that presently ex ist in Texas citrus. The TDA request was apparently initiated in response to the USDA request. While the reasons for these inquiries were neither offered nor requested, subsequent conversation with Dr. Vic French and others suggested a possible link to Thailand.

More recently, I learned that Sunkist Growers began shipping navel oranges to Thailand back in January a fter years of effort by U.S. and Thai officials to work out some problems of phytosanitary regulations and import tariffs that were effectively excluding any citrus importation into Thailand. Hopefully, Texas citrus can make the grade for export to Thailand in the coming season.

CROP DISPOSITION-

The industry heard an aw ful lot about sheepnose last season, with real horror stories of packouts as low as 30 percent on some orchards. But the problem was not so severe as one would th ink, at least based upon market disposition of the crop. Fresh market Texas grapefruit accounted for 64.26 percent of productionin 1995-96, with 35.74 percent processed. By contrast, fresh utilization in the 1994-95 season was only 68.67 percent, with 31.32 percent processed. Thus, it would appear that sheepnose and all other grade-lowering factors accounted for a decline of only about 4.4 percent.

Early oranges, including navels, were marketed 81.16 percent fresh and 18.84 percent processing; while Valencias went 91.96 percent fresh and 8.04 percent processing.

If you have the inclination, and the records, you can compare these values to your packouts, since these are the industry average packouts.

POTENTIAL CITRUS WATER USE-

Based upon historical records, I indicated that citrus would average needing about 1.2 inches of water per week during May. Because of higher maximum, minimum and mean temperature averages during May, pan evaporation was higher than normal. Since pan evaporation was up, so was potential evapotranspiration, i.e. citrus water requirement during May was up about 0.2 inch (weekly average).

Data for June indicates about 1.5 to 1.6 inches of water use weekly by citrus, with 1.6 to 1.7 inches per week in both July and August. If temperatures remain slightly higher than normal, so too will citrus water use during these months. Because of June rains in the lower Valley, both evaporation and evapotranspiration should be at or below normal for the month in that area.

POST-HARVEST LOSSES-

The Texas citrus industry has experienced some significant losses to post-harvest decay over the last few years-some years being worse than others. Probably no one in the industry fully appreciates the magnitude of the problem exc ept shippers and a couple of researchers who have studied the problem over the last couple of years.

In the June newsletter from the Citrus Center, Dr. Mani Skaria reported the results of a test last seas on involving ‘Rio Red’ grapefruit fr om a single orchard and a single harvest. Basically the harvest was divided among four packinghouse and an in-the-field pack. All lots were shipped UPS to six interstate and four intrastate locations, then returned to the Citrus Center for evaluation.

Intrastate shipments of the control fruit (packed directly in the field) suffered 19 percent de cay, while interstate losses were 15 percent. Th e four packinghouse lots suffered 37 to 50 percent decay instate and 35 to 73 percent decay out-ofstate.

Regardless that this test occurred in late season and the fruit was not refrigerated, the losses are appalling-a minimum of one-third of the fruit from the packinghouses rotted. While the numbers were not as bad, I consider the15 to 20 percent l osses that occurred on field-packed fruit to be excessive.

To summarize this work, the losses from the field-packed fruit occurred from damages sustained by the fruit while still on-tree, during harvest and boxing and during transit. The four lots from the packinghouses experienced those same damages on-tree, during harvest and during transit, plus additional damages that occurred during hauling and during packing.

Thus, if you subtract the losses sustained by the field-packed fruit from that of the packinghouse, you still get 15 to 20 percent loss (minimum) that is solely due to hauling and packinghouse operations (the maximum would be in the range of 30 to 60 percent).

TEMPORARY RELIEF-

The rains across the middle and lower Valley during the last half of June provided much-needed relief for our dwindling water reserves, but such relief is short-lived at best since there was no significant rain in the watershed. Moreover, many orchards in the upper Valley were not blessed with even a little rainfall.

From an over all agricultural irrigation standpoint, demand should be in a lull anyway, as grain is completed, corn should be finished and there’s’s little in the way of vegetables, leaving only pasture, cotton, cane and citrus until planting of fall vegetables and corn starting in August. However, several irrigation districts are already out of water or are very close to it. In addition, there’s talk of a possible negative allocation, i.e., we may have to give back part of the allocation that hasn’t been used as yet.

Too bad we can’t capture and store the runoff from last week’s rai ns for future irrigation use.

CURRENT TOPICS-

While irrigation demand has slackened a little in the middle and lower Valley, unless rains return during July, irrigation of those orchards will resume shortly, given water availability.

Some orchards were in serious trouble at mid-June, as I noted several orchards that were wilting daily and a couple with trees in permanent wilt (from which they will not recover). Hopefully, the rains hel ped some of those with daily wilt sufficiently that they can go another several weeks in hopes of additional rains.

Asian citrus leafminer damage this year continues to be relatively inconspicuous, even on the current flush of orchards that were being regularly irrigated. Stressed orc hards should push a growth flush in response to the recent rain, but it’s anybody’s guess as to whether leafminer will explode on it.

Other pests need monitoring regularly, inasmuch as it is nearing the time when post-bloom Temik® and other miticides should start to break, so rust mites could increase quickly. Too, July is the usual time when red scale starts to build.

For the summer spray, when it becomes necessary, oil is hard to beat for cost and effectiveness if applied properly with respect to weather. It works very well on mites, scales and greasy spot , while being environmentally friendly. To reduce potential phytotoxicity and to enhance th e summer spray, lower rates of oil can be supplemented with a miticide, scalicide and/or fungicide. Oil should not be applied to droug ht-stressed trees.

FREEZING GRAPEFRUIT SECTIONS-

I credit Dr. Bill Grierson for this idea to preserve grapefruit in the freezer for later enjoyment, which was recently printed in Citrus Industry (May, 1996, p. 26). A couple of Winter Texans indicate good success with the method, though they claim no proprietary rights to the origin of the idea.

Freezer bags work nicely, though they can be a bit troublesome to fill. To obtain the grapefruit sections, either use the serrated grapefruit spoon to extract them just as you would if you were going to eat a grapefruit half. Another way to get sections is the commercial way of sectioning-cut off both ends, then cut off the remaining rind with several knife strokes (each cutting into the section slightly to remove the outer membrane). Then separate the sections from the membrane.

Place the spoon-sized or the commercial-sized sections into plastic freezer bags, pour the extra juice over the sections, and seal the bags. Remove the air from the bag at closure for best results. Freeze, then thaw when you want them. They’ll last for months with no discernible flavor loss.

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