RAINS
FINAL HARVEST REPORT
CURRENT SITUATION
POSSUM GRAPE

RAINS-

Two rain events finally occurred across parts of the Valley during May; the first on the 16th was less than an inch, mostly in Hidalgo County, the second during the middle of the night early on May 30 was heavier and more widespread. The latter was accompanied by strong winds, much lightning and thunder, and some hail. Because of the wind, my rain gauge at home showed only 1.3 inches, but the water level in a nearby swimming pool went up more than 2 inches. Still, not every area of the Valley recorded significant rainfall, as it apparently tapered off towards the north, with one gauge north of Santa Rosa showing barely a quarter inch total.

Prior to the last rainfall, storage levels in the reservoirs had dropped from over 100 percent of conservation level to the 98 percent range as irrigation demand was quite high during May. In as much as various row crops including sunflowers, melons, cukes and cantaloupes have matured, sorghum is maturing and corn is on its last stages, irrigation demand should drop significantly in June.

FINAL HARVEST REPORT-

The Texas Valley Citrus Committee issued its final report for the 2004-05 season as of May 21. Overall, fresh utilization was only 93 percent of the previous season, despite a near four-fold increase in export shipments of grapefruit. Early orange volume was up about 5 percent, navels about 10 percent and Valencias about 13 percent.
Domestic fresh grapefruit volume finished at only about 77 percent of the previous season's volume and that despite a 16 percent increase in the total grapefruit crop. Combining both domestic and export volumes of fresh grapefruit, the final was about 88 percent of the prior season. Obviously, sustained high prices combined with continued concerns about the interactions of grapefruit with certain medications served to dampen the demand for grapefruit significantly.

CURRENT SITUATION-

Reports of scattered light bloom in some oranges and grapefruit continue to occur, but there has been no indication of any major bloom in grapefruit. Grapefruit size varies from slightly larger than normal to fairly small, depending upon when bloom occurred. Despite later bloom in some oranges, overall orange size appears to be about normal for this time of year.

Weed control has remained fairly good to date, in part because of the lack of major leaching rains, though that could change if prevailing weather patterns turn towards more rains of greater frequency.

Rust mites have not been a major problem, probably because of timely control applications in combination with generally unfavorable (to rust mites) weather conditions. Still, periodic scouting efforts should be maintained, as the situation can change rather quickly.

POSSUM GRAPE-

During the last couple of years, I have been involved in trying to control possum grape and other vines in citrus orchards. In the main, goatsbeard and morningglory have succumbed to a combination of Roundup (1.5 percent), Hyvar X (4 lbs per acre) and Solicam (2.5 lbs per acre). Milkweed vine has been retarded, but not eliminated as yet.

Possum grape has not responded very well to this combination, even following hand cutting and pulling prior to application. Inclusion of 2,4-D in the mix has shown a little better retardation of growth, though 2,4-D is not labeled in Texas citrus.

Ray Prewett recently inquired of USDA for any suggestions to control possum grape. He passed along to me a copy of the responses most interesting being those from Craig Ramsey at the National Weed Management Lab in Fort Collins, CO. Of the products mentioned, Roundup at a 2 percent solution applied from June to September is the only labeled possibility for control as a foliar spray. However, there were some recommendations involving other (non-citrus labeled) materials that may be effective when used as a basal stem application.

One of the suggestions included application in basal oil instead of water to facilitate the penetration into the bark of the vine, so I am trying to find out exactly what ?basal oil? is so that I can apply it with a higher percentage of Roundup to see if better efficacy can be obtained. As you know, the bark and foliage of possum grape resist the penetration and absorption of Roundup.

In general, it appears that a good pre-emergence herbicide program can suppress new infestations of possum grape, especially if existing infestations can be prevented from fruiting so as to reduce the number of seed dispersed both beneath the infestation as well as to new trees and sites from the activities of birds feeding on the mature fruit. To date, the prevention of fruiting has been almost exclusively as the result of hand pulling prior to the vines blooming.

That still leaves the problem of a long-term solution to existing infestations, as pulling alone just doesn't get rid of the large, tuber-like underground part of the vine. The practice of some growers to manually pull/dig the tubers when the ground is wet, such as immediately following irrigation, isn't totally effective. Hopefully, the USDA information about 2 percent Roundup in oil during the summer months will prove more effective, and perhaps the oil may also enhance the contact action of Hyvar X. Beyond that, I intend to test some of the suggested, non-labeled, herbicides on trees that can be sacrificed in the event that such products prove to be particularly harmful to citrus trees.

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