WEATHER AND WATER
C-PROBE SOIL MOISTURE MONITORS
PEST UPDATE
END OF SEASON
NEW CROP, NEW SEASON
SUDDEN DEATH DISEASE

WEATHER AND WATER-

With the exception of mostly southern Cameron County, very little precipitation occurred in the Valley during May, so irrigators have had to crank it up a notch. Despite the increase in irrigation demand over the last few weeks, reservoir levels have remained high-U.S. share just under 70 percent of conservation level, Mexico share nearing 45 percent of conservation level.

Part of the reason for the levels staying up is that Mexico has been releasing water into the Rio Grande (below Rio Grande City) from its dams on the Rio San Juan. These reservoirs have been overly full, so caution dictates that they be drawn down in preparation for the start of hurricane season, which was June 1, I think. This water has been available to virtually all users on both sides of the river in what is called "free pumping", i.e., water districts have been using this water to fill irrigation requests without having to order water releases from the reservoirs. This deal will probably end later this month.

Waters of the Rio San Juan belong entirely to Mexico by terms of the 1994 Water Treaty. Because it enters the Rio Grande below the reservoirs, excess flows cannot be effectively captured for the future, only utilized for current water needs and for filling the resacas or other storage facilities of the various irrigation districts. To probably no one's surprise, U.S. authorities are reportedly going to credit much of this "free pump" water toward the water debt. I wonder how they expect to quantify how much was taken from the river by U.S. interests, how much by Mexican interests, how much flowed on into the Gulf of Mexico, et cetera?

Meanwhile, the weather has definitely turned hot, dry and windy, as is typical for the season. Triple digit temperatures closed out May and ushered in June. Coupled with strong daytime winds, evaporation rates are soaring and soil surfaces are drying rapidly. Irrigation will be the main grove activity in June, unless rains visit us again.

C-PROBE SOIL MOISTURE MONITORS-

Chet Townsend of AgriLink, Intl. was in the Valley in early May to discuss a relatively new soil moisture sensor apparatus and related software. In addition to visiting with a number of people at the Research and Extension Center and the Citrus Center, he also visited with a number of citrus growers and with Hi-Tech Irrigation, Inc., which has signed on as a distributor.

In a nutshell, the C-Probe is a device that continuously measures soil moisture at various depths in the soil and transmits the information via cell phone to a web server in Australia, which then graphs the data and displays it on the world wide web-access to which is password protected, since there is an annual service fee involved. The soil moisture status graphs for each device and sensor depth are updated every 15 minutes and are on-line within about 20 minutes, 24-7.

I have two instruments installed, but am still in the process of learning how to read and interpret the data, especially with regard to specific soil moisture capacities of the sites. Dr. Juan Enciso (that's Enciso, the irrigation specialist, not Anciso, the vegetable specialist) will be working with me over the next few weeks to accomplish this. I'll keep you posted as we learn to use this technology in Texas citrus groves.

PEST UPDATE-

Because May was a very full month for me, I did not have the usual opportunities to visit a lot of different groves nor even growers to get a feel for what's happening in the citrus pest management world. Consequently, I checked with Dr. Vic French to see what he could share with us on this subject. In truth, I would rather rely on what Vic reports anyway.

Black scale is not a pest you normally encounter in Texas citrus, but Vic reports that some black scale is becoming problematic in the Lower Valley. Because it is an unarmored, soft scale, the usual scalicides such as Lorsban® do provide control. Normally, however, this scale has been kept at very low to non-existent levels biologically. Tests last season with Lorsban® and Esteem showed pretty good control, but the scale is returning this season. If you are not familiar with black scale, its young look a lot like brown soft scale, the adults have a distinctive "H" marking on the back.

Vic also reported the occurrence of some pretty bad blackfly levels north of Donna, so this pest is apparently spreading into the mid-Valley. He indicated that parasitism is apparent in this grove, so that's certainly good news. Regardless of where you encounter blackfly, you can help disseminate the parasites. Just collect 40-50 infested leaves, place them in a sealed plastic bag overnight and check for the presence of the "smaller than gnat-sized" parasites. If parasitism exists, the parasites should be obvious. If you have them in the bag, take it to the field, hang it in a citrus tree and open it up to allow the parasites to escape. Collect more leaves at the release site and repeat the process until you have spread active parasites all over the area where you find blackfly.

Citrus rust mite is not as bad as it was back when we were getting rain every couple of weeks, but it is starting to pick up in some groves. Just continue to monitor, monitor and monitor some more, as spring-applied controls may be playing out.

By popular demand, the Citrus Center is readying its laminated pest guide that has always been a grower favorite. The new edition is a little larger than in the past; especially for disease controls, as there are several relatively new fungicides available. The guide should be available shortly.

END OF SEASON-

The Texas Valley Citrus Committee's Final Fresh Fruit Utilization Report No. 32 shows shipments through May 18. According to the data, fresh shipments of all citrus from Texas were up 6.7 percent over the 2002-03 season. Grapefruit was up 7.9 percent and earlies were up 8.9 percent while navels were down 11.1 percent and Valencias were down 1.8 percent.

In terms of total production, grapefruit was up 0.9 percent above last season and 5.1 percent above the final USDA revised crop estimate of April 8. Early and navels were up 5.2 percent for the season, but 2.9 percent below the April 8 revised crop estimate. Similarly, Valencias were up 4.4 percent for the season, but 1.3 percent below the April 8 revised crop estimate.

How do the season finals compare to the original USDA crop estimate of October 10, 2003? Grapefruit was up 5.1 percent, earlies and navels were up 8.4 percent but Valencias were down by 10.0 percent.

In terms of processing, tonnage of grapefruit processed was down 2.7 percent from 2002-03, but early and navel tonnage processed increased by 8.4 percent. Processed Valencia tonnage increased 10.6 percent.

External quality of our grapefruit was better than in recent seasons, but was still not as good as anticipated. Excellent fruit shape across the Valley at the start of the season indicated the potential for a banner year, but then the rains of September and October (and November in some cases) resulted in significant citrus rust mite damage as growers could not put spray machines into the groves.

NEW CROP, NEW SEASON-

Despite the delays in flowering and fruit set brought about by cooler weather, it seems that the trees have made up the time already. Typically, the final fruit drop ends about May 20, give or take a few days. From what I can see, final drop may have occurred about May 25, give or take a couple of days. The point is, what you have there now is what will be there for harvest, as very little fruit drop occurs from now on. As usual, a disclaimer must be made for navels, as they are subject to a couple of additional fruit drop periods during the summer ending with the end of the late summer fruit splitting period that always seems to occur.

It is far too early to make serious predictions about the coming crop, as it is really hard to reliably estimate the number of green berries present in a world of lush green leaves on a citrus tree. Try if you like, but I'll wait until the fruit is much larger. What does it look like for sheepnosing of Rio's? The lateness of bloom suggests the possibility of severe sheepnosing, but cooler temperatures that prevailed soon after bloom may have been sufficient to ameliorate that potential somewhat. Time will tell.

In any case, the total volume for the 2004-05 season has been set, as has the potential fruit size and the potential for sheepnosing of grapefruit. For those factors, growers have very little influence from now on through harvest. From this point on, grower efforts are directed to pest control to keep what you have clean, plus timely irrigation through the summer to enable the fruit to achieve its size potential. Everything else including irrigation and pest control will impact growth and flowering for the spring of 2005.

SUDDEN DEATH DISEASE-

Since about 1999, Brazilian citrus growers have lost about 3 million citrus trees to a problem that they are simply calling "sudden death". It began in the northern state of Minas Gerais, but has moved southward into Sao Paulo state, which is the giant citrus production state in Brazil.

No causal agent has been identified, but its pattern of spread appears to be that of an infectious disease, possibly insect vectored. It appears to be predominant in groves on Rangpur lime rootstock, which accounts for the vast majority of Brazilian citrus-but Volkamer lemon rootstock is affected to some degree.

According to reports from Brazil, the disease causes a rather quick general decline of the tree. A yellowish stain in the inner bark of the lower trunk is characteristic.

Is this important to Texas growers? Even though we don't use Rangpur lime or Volkamer lemon rootstocks in Texas, and even though Brazil is a long ways off, the fact is that whatever malady there is that kills citrus trees anywhere in the world is important to Texas growers, whether we realize it or not. In the modern age, it only takes one tourist who doesn't know or care about such matters to smuggle (they don?t look upon their action as smuggling, of course) infected plant material from one place to another and in less than a days time.

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