NOVEMBER, 2010      

VOL. 24, NO. 11                                                                             

IN THIS ISSUE:

EFFECTS OF GREENING ON ORANGE FRUIT
THE TROPICS AND OUR AREA
AREA-WIDE PSYLLID CONTROL MEETINGS
ULV SPRAYER CALIBRATION
OTHER GREENING NEWS
CROP ESTIMATES
MORE SWEET ORANGE SCAB REPORTED

CROP ESTIMATES

The official crop estimates for the 2010-11 season were released on October 7.  First, let’s look at Florida.  The estimate is for 69 million boxes of earlies and 77 million of Valencias, for a total of 146 million boxes.  If you recall, the pre-season private estimates were 149 and 154 million boxes by Louis Dreyfus and Elizabeth Steger, respectively.  Florida is also expected to produce 6 million boxes of white grapefruit and 14 million boxes of colored grapefruit, for a total of 20 million boxes.

Texas growers are expected to produce about 59,500 tons of earlies and 12,325 tons of Valencias, for a total of 71,825 tons.  For grapefruit, the estimate is 220,000 tons.  In terms of last season’s final production, this season is pegged at almost exactly the same for grapefruit and up only 3.87 percent for oranges.  If you follow the TVCC reports, these numbers translate into 2800 carlot equivalents for earlies, 580 for Valencias and 11,000 for grapefruit.

FLOODWAY BACK DOWN

In the last newsletter, I indicated that although IBWC had been diverting water into theFloodway for   nearly a week, it had not reached the Expressway crossing at Mercedes.  As soon as that newsletter was posted, the water at the Mercedes crossing had risen substantially.  On October 18, the water level at the Mercedes crossing was back to near normal, being almost entirely confined to the normal streambed. 

News is that Lake Amistad is sufficiently above conservation level that IBWC is stepping up releases there to lower the lake to conservation level.  It is unknown how this might impact subsequent water levels in the river below Anzalduas Dam, if at all.

CITRUS BLACK SPOT REGULATIONS

Because of the presence of citrus black spot in parts of Collier County and Hendry County, the USDA has implemented quarantine regulations for that disease.  Basically, no fresh fruit from the quarantined areas (i.e., within one mile of a positive detection) nor the regulated areas (within 8 miles of a positive detection) can be shipped to other citrus-producing states. 

It is interesting that USDA allows lemons from Argentina into the US, even though citrus black spot occurs in Argentina, because there is only a medium risk of disease spread via fruit.  One has to wonder how the disease came to be in Collier and then Hendry County, especially only a few months after mandarins carried by Canadian tourists entering the US in North Dakota were found to be infected with the disease.

SWEET ORANGE SCAB

The more they look, the more they find.  Sweet orange scab has now been confirmed on a large number of dooryard trees in the Valley, from Willacy to Cameron to Hidalgo to Zapata and Webb Counties—somehow skipping over Starr County (for the time being?).  So far, there have been no reports of the disease in orchards, suggesting that it either isn’t there or that it is fairly easily suppressed by the regular orchard spray program.

We have seen scab in dooryards trees, especially in East Texas, for about as long as I have been here—but we always considered it to be sour orange scab, since sweet orange scab was not known to be present in the US.  In addition, sweet orange scab was supposed to be limited to fruit, but what we have always called scab was present on fruit, leaves and twigs.  So, by elimination—the scab we saw was sour orange scab.  Now, it looks like we were wrong, as it appears that the old literature was wrong and that sweet orange scab also attacks the twigs and leaves.  It now appears that we were seeing sweet orange scab way back then without realizing that it was the sweet version rather than sour.

In addition to the five counties in South Texas, both Harris County (the initial confirmation) and Orange County have yielded positive samples.  Add to that about 15 parishes in
Louisiana and it looks like the disease has been around for years, if not for decades—just misdiagnosed.

Finally, although the disease has not been detected in commercial orchards in the Valley, training in the recognition of the disease was provided to all packinghouses on October 28 to assure that fruit that might have the disease is eliminated on the packingline.

ACP/CG TESTS

From Laurie Elizalde of USDA-APHIS comes the summary data for the ACP/CG Residential Survey results through October 8, 2010.  The survey team has accumulated a total of 26,563 psyllid samples and 18,933 plant tissue samples, with all psyllids and 5,252 tissue samples forwarded for PCR testing.  All samples reported negative for the greening bacterium.

In the last couple of months, this group has also been collecting samples for sweet orange scab, the results of which are reported in the previous section.  In addition, 4 psyllid and 8 plant samples collected by CBP, SITC and PPQ were tested at Manhattan, KS, all negative for the CG bacterium.

It is reassuring to note that of over 26,000 psyllid samples sent for testing in the last couple of years, there have been no “hot” psyllids found.  Moreover, of over 20,000 plant samples collected and screened (including those by growers and the Mexfly trappers), and just over 7,300 of those tested, there have been no positives.

AREA-WIDE SPRAY FOR ACP

The targeted fall spray for ACP is the first three weeks of November, which you should all know as a result of the various meetings held across the Valley in early October.  Because of the variety of materials available and the means of application, there should be no serious problems in trying to coordinate the applications and pre-harvest intervals with harvesting operations.

GROVE CARE AND CITRUS FLUSHING

Under usual and customary grove management in South Texas, citrus groves flush in March, May, July and September—year after year after year.  Basically, the spring flush starts in late February and finishes by mid-March—every year, though it may be delayed or advanced a few days from year to year.  Each subsequent flush does not occur until the previous flush has matured—which usually takes about two months.  Weather can and does affect the exact timing of all the flushes, primarily as it affects the maturation of the prior flush.  It’s really that simple.

So why do we sometimes hear that rains result in a new flush? Or that Temik use causes flush?  The only time I have seen rains trigger a flush is in non-irrigated groves. This is somewhat common in tropical areas where the groves go into severe drought stress due to the absence of rain in the first half of the year.  Indeed, it is that drought stress that induces flowering, so the groves don’t bloom and flush until the drought is broken—usually about May or June.

As for the assertion that Temik causes flush, that will soon be a moot point, even though it

isn’t true.  Temik can be applied from as early as November to as late as April, so when during that time frame do groves flush?  Think about it. 

If Temik is applied prior to the flush, the trees still flush at the same time as non-Temik groves. Post-bloom application of Temik also does not cause a new flush to occur—the spring flush is still maturing and the next flush is going to come along at its usual time whether or not Temik was applied. About the only relation between Temik and flush is that the flush in a Temik grove might be a bit greater than in a non-Temik grove. But there is no “cause and effect” relationship between the use of Temik and the emergence of growth flushes.

Pruning (hedging and topping) is another matter, however.  Pre-bloom hedging is least likely to change the timing of the spring flush, as climatic conditions are usually not conducive to early flushing.  However, post-bloom hedging can and does result in new flush emergence.  The mechanism is pretty simple—the flush that results from hedging comes from buds that were formed, but did not grow, on much older flushes than the most recent one.  How much older depends for the most part on how large the hedging cuts are—the larger the limbs cut off, the older the buds that will begin to grow.

And now you know.  Why bring it up?  As an industry, we are trying to encourage citrus psyllid control as the best means to limit the potential spread of citrus greening.  As part of that effort, the industry is committed to November and January-February area-wide psyllid control efforts, as those two sprays can essentially eliminate overwintering psyllids in the groves.  With no overwintering psyllids, the spring flush should come and go before psyllids from outside the grove can move in, which means that you have essentially protected one of the four major flushes from potential psyllid feeding and egg-laying activity.

FLORIDA TRIP

Next week, I will be spending Monday in the Plantation/Fort Lauderdale area, Tuesday in the Fort Pierce area, Wednesday in Polk/Hillsborough Counties and Thursday in the Immokalee area.  The principal object of my trip is to see and take pictures of citrus greening, citrus canker, brown citrus aphid, and hopefully citrus black spot.  In addition, I will visit an “open hydroponics” grove to see firsthand how this intensive management project is progressing.  I will also be working with a couple of Extension citrus agents over there along with Bruce Sutton and his scouts to see how they scout a grove for citrus greening, the objective being to try to develop a training/educational effort for Texas growers in the near future.

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