TEXAS CITRUS FIESTA
CITRUS BLACKFLY
PESTICIDES AND BLACKFLY
COLLECTION AND DISSEMINATION OF PARASITES
VINE CONTROL UPDATE

TEXAS CITRUS FIESTA-

As usual at this annual event, I had the pleasure of overseeing the judging of exhibits and setup of the identification and judging contests for the Texas Citrus Fiesta Youth Show. Unfortunately, one of the judges was not feeling well at the last minute, so I filled in and helped judge the exhibits for the first time in many years (No, my children did not participate this year, otherwise we would have been short one judge).

There were approximately 700 entries this year, from some 65-70 young exhibitors. The overall quality of the entries was not quite as good as we expected, based on the quality of the crop this season. Since half of our judges (one on each of the four teams) are with the Cooperative Inspection Service, they are very much aware of the quality of fruit going into the carton at the packinghouse. Vo-ag teachers and others who traditionally support the Youth Show indicate that there were quite a few first-time exhibitors this year, so perhaps these youth haven't yet learned how to select and prepare citrus exhibits. But we'll work on that for the coming year.

A "Marrs" orange exhibit entered by Brice Warnecke and collected from Warnecke Citrus Farms took home the Grand Champion Trophy, while a "Rio Red" grapefruit exhibit, also entered by Brice Warnecke, collected from one of Tommy Thompson's groves was selected as Reserve Champion. About 25 exhibitors received awards (ribbons and/or trophies) and prize money in this year's show.

CITRUS BLACKFLY-

Texas Citrus Mutual and Texas Cooperative Extension collaborated on a short-notice meeting on the citrus blackfly problem last week at the TCM offices in Mission. Dr. Rod Summy and Dr. Vic French discussed the biological control and chemical possibilities, and had scopes and monitors set up to show the emergence of blackfly parasites. In addition, personnel from USDA-APHIS reported on the efforts and progress to rear the Amitus parasite, while USDA-ARS reported on their aerial photography work that clearly shows the presence and extent of blackfly infested orchards.

To recap, there are two blackfly parasites; Encarsia and Amitus. Both are effective in reducing and maintaining blackfly populations below damaging levels. All of the parasites that have been documented currently in Valley orchards and dooryards are Encarsia?it has a four to six week adult cycle and is well adapted to Valley weather. Amitus adults, on the other hand, usually live only four to six days and are not terribly well adapted to our hot, dry conditions. In the past, Texas has been able to obtain Amitus from Florida, but sufficient numbers for release are no longer available. Consequently, USDA-APHIS has begun a rearing program, starting with Amitus from Florida.

Meanwhile, Texas Cooperative Extension and the Citrus Center are collaborating to see if descendents of the Amitus that were released in the Corpus Christi area a few years ago are still around. If so, it is possible that some might be brought back to the Valley to aid in controlling the current situation until the USDA-APHIS program begins to produce sufficient numbers of parasites some months from now.

PESTICIDES AND BLACKFLY-

That pretty well recaps the current situation, so what can growers do for themselves at this point? First, there is absolutely no indication that biological control has failed?rather, the current infestations are considered to have occurred because of some disruption event. In most cases, you can read that as parasites being killed by pesticides used in the grove to control normal pests.

Lorsban, Supracide, and Danitol are all very good at controlling all stages of citrus blackfly, but they are all highly toxic to the beneficial complex. Nexter does nothing for blackfly, but it is moderately toxic to beneficials. Vydate has both some contact and some systemic action on blackfly, but it too is moderately toxic to beneficials.

On the other hand, Admire, Provado, Esteem and Temik are pretty good on the immature stages of blackfly-the first three are non-toxic to beneficials, while Temik has low toxicity to beneficials. Miticides such as Agri-Mek, Vendex and Micromite don?t do anything for blackfly, but they are non-toxic to beneficials.

Citrus spray oil is effective on all stages of citrus blackfly, including the eggs, and is relatively easy on beneficials. Moreover, with the exception of Nexter, oil typically enhances the control of other chemicals.

While some growers would prefer to spray to control current blackfly outbreaks, no spray application will be completely successful, you'll never get them all, you may disrupt the beneficials, and you'll see an in-migration of blackfly adults from adjacent orchards. If you look again at the chemicals that aid in the control of blackfly without killing all the parasites, with an eye toward the control program for our primary pests, rust mites and scale insect, Admire, Provado and Esteem don't control mites, though the latter does control scales. Temik does control mites and offers some control of blackfly and other pests.

In other words, without specifically targeting blackfly, yet trying to provide some suppression while controlling our major pests, some of the better options for post-bloom pesticide applications include Temik or Agri-Mek and oil or Vendex and Vydate. While Vydate is moderately toxic to beneficials, it works well with Vendex (to provide quick mite knockdown) and provides some blackfly control.

For late spring or summer pest control, the choices include Esteem for scale (and blackfly) plus Agri-Mek or Micromite or Vendex for mites. Oil should be included with all three miticides to provide better mite control, good scale control and better blackfly suppression. Other materials may be available and/or preferred-it is the grower's responsibility to compare materials and control options in light of the pest situation in the grove. However, if blackfly is a problem in the grove, those materials that are highly toxic to beneficials should not be used.

COLLECTION AND DISSEMINATION OF PARASITES-

The next thing growers should consider is the collection and dissemination of existing parasites. Whether you are aware or not, Texas Citrus Mutual has CD's with the color infrared aerial photography taken by USDA-ARS of all groves west of 281. All you have to do is make arrangements with Billy Lyckman at the TCM office to locate your grove(s) on the appropriate CD so you can compare the extent of blackfly infestation in your grove(s) and surrounding groves. This will give you a much better idea of the extent of the problem in your grove(s).

If you believe that parasite collection and release is required, it is really very simple. Go into the grove and locate some heavily infested trees, collect 40 or 50 leaves with lots of blackflies, place them in a one-gallon Ziploc bag and set them aside in a cool place overnight. Frankly, I would make several such collections. If there are active parasites, there should be literally hundreds of the adults emerging over the next couple of days, they will be very obvious as they tend to gather at the corners of the bags.

If you don't have parasites in any of the bags, you need to find another grove from which to collect leaves. If growers cooperate, TCM will develop a list of growers who do have parasites and will let you collect. If you have parasites in some of the bags, but not all, obviously you should take the bags with parasites to those trees from which you collected leaves that did not produce parasites. Finally, if you have parasites in all of the bags, consider taking them to other groves to help spread them around. In all cases, I would repeat the collections every week or so, at least until every bag of collected leaves has parasites emerging.

This isn't rocket science-anybody can do it. You don't have to squint through a lens at blackfly-encrusted leaves to see if there are exit holes. You don't have to be concerned with the shape of the parasite exit hole to identify which parasite you have (they are all Encarsia at present, anyway). About the hardest thing required is to figure out how to attach the plastic bag inside the tree canopy and keep it propped open so the adult parasites can fly out over the next few days.

VINE CONTROL UPDATE-

Based on recent observations, last season's vine control project is showing some results. The combination of Roundup, Hyvar X and Solicam has given some control of existing infestations of morningglory, milkweed vine and goat's beard, but not much help on possum grape. The 2,4-D and Roundup mix as a directed spray, injected into stems or painted onto scraped surfaces of stems of possum grape made them a little sickly, but did not kill them.

Morningglory is more or less an annual vine, so the results are not surprising. The Hyvar X and Roundup combination killed out the younger vines, with old age and frost getting those that had canopied over. Both the Hyvar X and Solicam should preclude the germination of morningglory seeds, which we should be able to confirm in the next couple of months.

Pretty much the same results occurred on goat's beard, except that frost did not affect the canopied vines. Too, the preemergence combination of Hyvar X and Solicam is expected to reduce new germinations.

Results with milkweed vine were not as good except on small young vines that had not yet reached into the trees. Too, it is expected that the preemergence combination will reduce new germinations.

For the near term, we have done some hand cutting and pulling of possum grape in preparation for spring tests. Because technicians at the Citrus Center used Hyvar X, Solicam and MSMA at high rates with pretty good effect (not elimination, however) on possum grape, I intend to incorporate MSMA into the basic mixture in tests this spring. In addition, it is hoped that Encore Technologies will produce DeVine this year so that I can incorporate it for milkweed vine control.

As some of you know, this work was supported in part by a grant from the Texas Citrus Producers Board in late 2002. With the exception of the purchase of a backpack sprayer and a few trips to the groves, none of the grant funding was used, as Fred Karle and Steve Flowers provided the herbicides at no cost.

While I am not quite ready to make a specific blanket recommendation, the results with Roundup, Hyvar X and Solicam are good enough that I will repeat it this spring?and I will incorporate MSMA for potentially better contact activity. After all, this is a two-pronged program?the control of existing vines, if possible, and the prevention of new germinations.

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

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