FEBRUARY, 2010      

VOL. 24, NO. 2                                                                             

IN THIS ISSUE:

THE FREEZE
WHAT TO EXPECT
WHY FRUIT AND NOT LEAVES/TWIGS?
FLORIDA DAMAGE REPORTS
GREENING MEETING
BUD PUSH
AREA-WIDE PSYLLID CONTROL
TEXAS CITRUS FIESTA YOUTH SHOW RESULTS

THE FREEZE

Early reports were that the Valley’s citrus mostly escaped significant damage during the freeze event of January 8-9.  There were only a few reports of ice in the fruit on the morning of January 8; most of those were attributed to colder locations.  Reported temperatures and durations suggested that there should have been damage, however.

After about a week, some leaf burn on the tops of trees in some orchards was being observed.  Next, there were reports of peel damage to grapefruit, soon followed by reports of softening of earlys and mids, then increased drop of earlys and mids.  There has been some leaf drop, though all the fallen leaves that I have examined were affected by insect or disease damage—mites, leafminer, greasy spot, et cetera.  
Last week, there were more and more reports of fruit damage, so I set out to check more closely.  I cut quite a few grapefruit and Valencia oranges over the weekend and the results are not altogether what I expected, to say the least.

First, grapefruit— all large fruit and all interior fruit, without regard to size, show no indication of freeze damage.  Small fruit exposed to the sky, however, do show drying out of the stem end, usually no more that about a quarter inch into the flesh.  Exposed, sheepnosed fruit do not show drying, either, probably because of size and thicker peel at the stem end.  For the most part, I confined my visits to grapefruit groves in western Cameron County, so results further west may be different.

Next, Valencias—all interior and non-sky-exposed fruit were okay, but any small fruit exposed directly to the sky were showing drying.  Over near Edinburg, the situation was that many exterior fruit were drying, while the interior ones seemed mostly okay.

Temperatures in my own grove dropped to 28 degrees at 3:00 am on that Saturday morning, and returned to that level just after 7:00 am, with a minimum reading of 26.  According to the prevailing experience, 28 degrees for four hours is the threshold for icing in oranges, but the only ice I cut was on exterior, sky-exposed, small-sized fruit.  I ran microsprayers from about 4:00 pm Friday until about 10:00 am Saturday. 

The extensive rains of December put most groves in a good soil moisture situation, so the storage of radiant energy in the soil before the front was about as much as one could expect under the generally overcast skies of the previous six weeks.  Obviously, the more radiant energy stored in the soil, the more that’s available to attenuate freezing temperatures.

And for the record, the temperatures only slowed down psyllid activity for a while—they were not killed.

WHAT TO EXPECT

Damaged earlys and mids are likely to continue to soften, dry out and drop.  Grapefruit and Valencias are more likely to stay on the tree.  In fact, there is a good chance that Valencias will “heal” as the undamaged juice vesicles and segments enlarge to fill in the space created by drying.  For the most part, that will depend on how long the fruit stays on-tree before harvest.  

Some groves will undoubtedly be picked straight to juice, particularly any remaining earlys and mids, as well as some grapefruit that has more damage than what I saw.  For the rest, there is a possibility that packinghouses may have to consider using freeze separators, along with pre-sizers and pre-grading to eliminate most of the oversized, undersized, sheepnosed and other fruit that is not likely to pack anyway.

There is some leeway in packing regulations that allows limited freeze damage for fresh grades.  For example, if the damage extends no further than a quarter inch into the flesh from the stem end, the fruit could still make Combo grade.  If the damage extends more than a quarter inch but less than one-half inch into the flesh, the fruit could still make Choice grade.  If the damage extends deeper than half an inch into the flesh, the fruit will go to juice.

WHY FRUIT AND NOT LEAVES/TWIGS?

The fruit is less hardy than the leaves and twigs, obviously.  Too, the timing of the front was about as good as it gets for Valley citrus.  Because citrus hardiness increases with increasing exposure to cold temperatures, I suspect that the trees had about as much hardiness as they could attain because of the relatively low temperatures experienced through most of December and January.

Why do some groves show damage to the upper leaves?  Likely, the fall flush on these trees was not fully matured as yet, thereby leaving them less hardy.

The non-sky-exposed fruit were the recipients of radiant energy from the soil, which basically was absorbed and re-radiated back and forth between the fruit, the leaves, the wood and the soil all night long, keeping them from freezing.  The sky-exposed fruit, however, received radiant energy to the bottoms (blossom end) and sides, but the tops of such fruit did not, so the tops of the fruit simply lost heat to the sky all night long, as once the skies cleared, there was nothing above them to absorb and re-radiate that heat.

FLORIDA DAMAGE REPORTS

The initial damage reports coming out of Florida indicate that Florida citrus growers in the north, central and west had more damage than they would have liked.  Harvest operations went into overdrive to get early and mid oranges to the juice plant before cold damage could affect juice and solids content.  Still, I have seen no definitive estimate of potential loss, and it is really too early to expect one.

GREENING MEETING

TCM is conducting a meeting on citrus greening on February 16 at the TAMU-K Citrus Center.  The main thrust of the meeting is how to scout/survey for the disease in Texas groves.  This effort will be delivered by Bruce Sutton and his wife, who have experience in this effort in Florida.

Texas AgriLife Extension is hoping to tie in to this meeting with additional information on psyllid survey methods, on sampling protocols for the disease, and on the symptoms of greening and how to distinguish symptoms that are not caused by the greening bacterium.  Stay tuned for more details as we try to work them out.

BUD PUSH

Temperatures returned to more normal levels after the freeze (and preceding six weeks of cold/cool weather), and the warmer temperatures have resulted in trees that are about ready to push out the new flush.  Navels are usually the first to flush, and this year is no exception, as they are already showing the first signs of bud break.  At this pace, navels could be in full bloom by mid-February, with other oranges soon to follow. 

AREA-WIDE PSYLLID CONTROL

Well, all the grower meetings have been held across the Valley.  Reaction at the one in Weslaco appeared favorable to this volunteer effort to try to reduce psyllid numbers before the spring flush commences.  There are some groves/growers that may have to rely on aerial application to get across the acreage; others will use traditional ground rigs to spray.  In this regard, most seem to prefer to go with a full spray for mite cleanup and include something for psyllid control.  Others may opt for psyllid control only, boosting the speed of the sprayer substantially in order to get across the grove at the least possible cost in terms of gallonage and time.  Finally, some growers are hoping to utilize the ultra low volume rigs at relatively high speed.

For the low volume advocates, two considerations are necessary.  The first is that because of very small particle size of the spray, night spraying is the best alternative, as that is when one would normally expect the lowest wind speeds, thereby increasing the effective coverage of the outer canopy.  The other problem with low volume is that most of the materials that can be used for psyllid control do not yet have 24c labels for low volume application.  This situation is subject to change any day, so the best bet is to contact Mamadou Setamou at the Citrus Center for the latest news in that regard.

If I am not mistaken, the presently labeled materials list was to have been made available to attendees at the four grower meetings held a couple of weeks ago.

TEXAS CITRUS FIESTA YOUTH SHOW RESULTS

I believe there were over 850 entries in this year’s show, which is really quite good in terms of the number of entries and youth interest in this event.  It certainly didn’t hurt that the weather during the week before the show was rather nice and mostly dry, which made it a lot easier to get out and collect specimens. 
Fruit quality was pretty good and I was especially impressed that participants have apparently learned that the judges will not tolerate fruit with scale insects or dirt.  Almost all participants did a great job of cleaning the fruit and removing any scale insects.

For the record, Clayton Stevens with the Los Fresnos FFA took Grand Champion with his Valencia orange entry, which was collected at Thompson’s Grove in Weslaco.  Reserve Grand Champion was awarded to Clarissa Chapa of Sharyland FFA for her exhibit of Rio Red grapefruit collected at one of Healds Valley Farms orchards.

In addition, Kenneth Miller of Los Fresnos FFA amassed the most points for exhibit placings, thereby garnering the Sweepstakes Award.

Congratulations to them and to all of the contestants.

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