|IN THIS ISSUE:
CITRUS RUST MITE PROBLEMS
The rainy weather of June-July has resulted in serious rust mite control problems-partly because of the inability to put equipment into wet groves to spray and partly because some control efforts have been less effective than expected. As July progressed, orchards dried out enough to initiate controls in order to minimize the damage that was occurring.
In some cases, growers are experiencing problems with Temik® again this season. No one seems to have good explanations as to why Temik® apparently isn't doing what growers expect. My comments on the use of Temik® are presented in the following article.
THOUGHTS ON TEMIK® USE-
According to early work on Temik® some 20 years ago, Dr. Leon Smith determined that the best results were obtained from applications early in the post-bloom period. The same was true in work conducted by Dr. Pete Timmer and by Dr. Vic French. I was working in Florida when Temik® was introduced to the citrus industry and was in Texas when it was labeled here-so my opinion about the best time to apply Temik® was predicated on early post-bloom, i.e., March-April.
Consequently, I have always been somewhat astounded to learn that some growers apply Temik® in late May or even June, ostensibly to carry the groves through the summer and hopefully to preclude the need for late-summer mite control. Is it coincidental that some of the problems that are being reported with Temik® use are with these late applications?
Have growers who practice such late Temik® applications forgotten all about the need for armored scale insect control during the summer months? Sure, the pressure washers in use in packinghouses today will remove the scale from the fruit, but that's after the scale has been feeding on the fruit and tree for several months. And the spots under chaff scale don't degreen, so that fruit goes PHE. It's a sure bet that Temik® has very little effect on scale populations.
So, I'm still trying to understand why anyone would apply Temik® much beyond mid-April. With 90 (to 120) days of rust mite control, even mid-April application is probably late, as scale control should normally be initiated about the first of July. You can do the math-90 days from mid-April is mid-July.
I know that the Temik® label does not preclude May-June applications (except in Florida!). Yet, I would think that prudent growers would use it during the time shown to be most favorable by research in Texas-and get full benefit from it before they have to treat for scale (and greasy spot and other problems).
REVIEW OF TEXAS CITRUS PEST MANAGEMENT-
Back at the time Temik® was labeled for Texas citrus, the typical spray program involved four sprays-early post-bloom, late spring, summer and late summer-fall. Granted, the last one wasn't always necessary in every grove every season. Melanose was a major problem on grapefruit, requiring copper in the first three sprays. That wasn't so bad, as copper wasn't terribly costly and you had to spray anyway since the miticides of the day wouldn't give much more than 6 weeks of control-if that much.
Too, the standard spray volume was 500 gallons per acre, with many managers, caretakers and custom applications pushing for 250. We used a lot of oil in those days, too, with little or no phytotoxicity.
Not surprisingly, greasy spot was practically non-existent in our groves-what with all the copper and oil we were using. I'll probably never forget that I had been here two years before I saw a grove with greasy spot-and it was over at Los Fresnos.
So, what has changed in the last 20 years? Well, Temik® came along, giving growers 90 to 120 days of rust mite control that carried the groves into mid-summer (plus its nematicidal activity). Because of its duration of control, Temik® use obviated both the early post-bloom and the late spring sprays-which made it comparably priced to the two sprays. Too, the 1983 freeze pretty much eliminated the need for intense melanose control, thereby increasing grower acceptance of Temik®.
In addition, Temik® applicators could cover three to six times as much acreage in a day as could a sprayer. Spray volume was halved again to 100-125 gallons per acre-after all, the trees weren't terribly large during the rest of the 80's and most of the 90's-and ground speeds starting inching upward.
With such low volume, some problems with oil phytotoxicity occurred-although most phyto was caused by failure of the tank's agitation system and/or failure to heed the weather precautions about oil use. Lorsban® was introduced for scale crawler control, and more and more growers started using it instead of oil. Unfortunately, too many growers expect Lorsban® to kill mature armored scale insects-which it won't do because it cannot penetrate the waxy covering of mature armored scales.
Better miticides such as Vendex® and Agri-Mek® were introduced, affording a good 60 or more days of rust mite control-if you included a knockdown material in the spray. And Agri-Mek® is about the only product around that will suppress Asian citrus leafminer, which came along in the mid-90's.
Certainly, other changes have also occurred, but their impact on citrus pest management has not been so dramatic as those mentioned. On the one hand, the use of Temik® or the better miticides during early post-bloom, along with little or no melanose problems, has eliminated the late spring spray, thereby taking us from four sprays to three, as a rule-and one less copper application (two in the case of Temik®).
On the other hand, increased reliance on scalicides other than oil has been harder on the beneficials complex that was helping to reduce armored scale populations (note the increasing occurrence of Florida red scale in the last few years). Aside from the fact that some applications are too late to control scale crawlers, these scalicides do not provide any greasy spot control, as does oil.
The overall consequence is that greasy spot has now become a major problem throughout the industry. Currently, copper, Benlate® (only during the summer) and oil are the only materials available for greasy spot control. Hopefully, Enable® and/or Quadras® will soon be labeled in Texas citrus, as preliminary tests show both products to be superior to copper and oil for greasy spot control.
So, basically, we have gone from four sprays to three (or even two sometimes), with lower volumes per acre, and considerably less use of both copper and oil. The availability of some products has changed the way some growers approach the overall pest management program, sometimes to their detriment. Thus, we now have Valley-wide greasy spot problems, shocking PHE levels from chaff scale damage and resurging Florida red scale problems.
Maybe it's time to re-examine the basics of pest management-apply a good, residual miticide early post-bloom, come back with oil and another miticide for the summer spray and finish with a scalicide and miticide in the fall. Every spray should include something for greasy spot-copper in post-bloom, Benlate® and oil in summer and copper again in the fall. If you're worried about oil, check out the tank agitation system thoroughly, use 250 gallons of spray per acre and heed the precautions about temperature, humidity and drouth.
CITRUS PEST UPDATE-
With the June and July rains, citrus rust mite populations have really exploded with some groves having to spray multiple applications to get control. There is some concern of chemical control failures but with all of the showers falling, it probably caused much of the chemicals to wash off or deteriorate. So, if you have not sprayed for rust mites in the last eight weeks be sure to inspect your grove very carefully.
The armored scale complex, especially Florida red scale, has been at relatively low levels this year in contrast to last year at this time. However, the armored scale complex (all of them) has been increasing in the last four weeks and expect these populations to increase in August. Currently, Florida red scale beneficial insects have been released with more numbers expected to be released in August. If you would like to participate or enroll your grove(s) please call me at 1-800-638-8239. The citrus leafminer continues to increase in the new growth flushes, with many groves having the new flushes completely devastated by the leafminer. Generally, no control is recommended for leafminer in mature, producing groves unless they are affecting the fruit. So far, very little damage has been observed on the fruit. However, in nursery citrus, the leafminer can cause such serious leaf damage that control is necessary. On May 5, 1999, we received a section 18 for Admire® and Provado® on nursery citrus for leafminer control. The Citrus Center guide recommends these products as well as Agri-mek® and Spintor® for leafminer control.
The water situation has improved slightly, with the U.S. share of reservoir levels at about 38.5 percent of the total. As we enter the last month of summer, we should be in good shape with irrigation water supplies. If good rains don't occur in the next week or two, growers will have to irrigate in advance of the normal September rains.
It's hard to believe that the new season is less than six weeks away, especially since shipping of last year's crop didn't finish until about seven weeks ago.
The Texas Produce Convention is on-tap in San Antonio for August 25-28. In addition, I am scheduled to accompany a group of local packinghouse managers to Florida during August 16-20. We'll be touring some Florida packinghouses and attending the annual Florida Citrus Packinghouse Day program at Lake Alfred, as guests of Elf-Atochem.
JULIAN W. SAULS, Ph.D.
| Valley Citrus Notes Index | Aggie Horticulture |