Program to be Held in Weslaco to Address Critical Issues for Valley Vegetable Growers
The Hidalgo County Extension Vegetable Program Committee is sponsoring "Weeds, Water, and the Laws that Affect You". This program will cover current laws and regulations, weed control in the valley, and the water situation and how to manage what we have (or don't have). The program will be held on February 25, 1996 at the Hoblitzelle auditorium at the Weslaco Extension Center. Presentations will begin at 9:30 a.m. with the final program beginning at 12:30 p.m. Lunch will be provided. A registration fee of $5.00 will be payable at the door. To R.S.V.P. for this event, or if you would like an informational flyer mailed to you, please contact Brad Abrameit at the Hidalgo County Extension Office at 383-1026. CEU and CCA credits will be given.
What's News With CEU's: Brad Abrameit
This news is not really new, but sometimes these things take a while to get around. As of September 17th, 1996, private pesticide applicators are required to attain two CEUs in IPM (up from one). This new requirement applies to license cycles which started on or after January 1, 1996. There is still a requirement for 15 CEUs to be earned during a 5 year period as well as two units in laws and regulations. Commercial and noncommercial license holders must obtain two separate units from any of three required topics: IPM, laws and regulations, or drift minimization, which is a new addition.
Drift minimization is a practice of reducing chemical movement other than that applied directly to the target area. By preventing chemical drift, you ensure that you: 1) are applying the calculated rate to your crop for proper pest control, 2) are not wasting chemical and thus saving money, 3) are preventing damage of non-target areas, and 4) are protecting the environment.
The most obvious application practice to prevent drift occurrences is to spray when wind speeds are minimal. There are however many other practices you can adopt to prevent drift from occurring. The following tips are reprinted from an article published by Dr. Bryan W. Shaw in the Texas Agricultural Extension Service CHEMOGRAM.
1. Select pesticides with low volatility to reduce vapor drift.
2. Read and follow the pesticide label. Approximately 65% of drift complaints involve application in violation of the label.
3. Avoid spraying with susceptible areas down wind or when the wind speed is above 10 miles per hour (5 miles per hour when applying regulated herbicides).
4. Consider leaving a 200-300 foot buffer zone between the field being sprayed and sensitive areas.
5. It is best to spray early and late in the day when winds die down, temperatures are low, and relative humidity is high. Use additional caution when relative humidity is below 50%.
6. Consider using larger orifice sizes to increase droplet size.
7. Operate at the lower end of the recommended pressure range with a low boom height. Keep the boom just high enough to assure proper coverage.
8. Consider using drift reduction nozzles to produce larger droplets.
9. Consider using drift control additives "thickeners". If used properly, they can reduce drift 50-80%. If not used properly, they can cause non-uniform spray patters and/or incorrect application rates.
10. Use shields to reduce drift caused by wind.
New Host for The Watermelon Fruit Blotch Bacterium: Tom Isakeit
An outbreak of a bacterial disease causing lesions on honeydew fruit occurred in the fall of 1996 in one field in Frio county. The causal bacterium was identified as Acidovorax avenae subsp. citrulli. This bacterium is more commonly referred to as the watermelon fruit blotch bacterium (WMFBB). Isolates of the bacterium, identified by Dr. Jeff Jones of the University of Florida, were highly identical with known WMFBB isolates in his collection. Isolates were obtained from fruit samples submitted by Dr. Mark Black (extension plant pathologist for the Winter Garden area) and seed company representatives, as well as from samples that I collected myself. All of these isolates caused typical WMFBB symptoms when inoculated on watermelon seedlings and fruit. The symptoms produced were identical to those produced by isolates of the WMFBB obtained from watermelon fruit. Bacterial isolates from honeydew fruit produced the same symptoms on developing honeydew fruit when they were inoculated at the time of pollination. This is the first known incidence of the WMFBB infecting honeydew.
The initial symptoms of this disease on honeydew fruit are small, water soaked, circular spots. These spots enlarge to about one-half inch in diameter. The skin becomes rough and light brown in the center of these spots and have a scabby appearance. This rough area enlarges and these lesions become cracked, dry and sunken. A water soaked area still surrounds these lesions. Spots may be quite abundant on fruits and coalesce, resulting in large, irregular, scabby, dark brown areas. Some of the fruits with well-advanced lesions may be invaded by secondary fungi. At the time I examined the field, I was not able to determine if the bacteria produced symptoms on the foliage. The bacteria do not produce severe symptoms when inoculated on honeydew seedlings, as compared with watermelon seedlings.
The disease was wide-spread on fruit in one field, but no symptoms were seen on honeydew grown in two other, nearby fields. Several cultivars were grown in the affected field. The origin of the bacteria in the honeydew field is not known. The disease on watermelon is known to be seed-borne. It is not known whether the WMFBB in honeydew is seed-borne; this needs to be determined. Seed lots of some of the cultivars planted in the affected field were tested for blotch and found to be negative. Furthermore, the carry-over of the WMFBB from a previous crop has not been ruled out.
Carry-over of the WMFBB in the field is an issue that needs to be addressed in south Texas. In 1996, citron melons infected with the WMFBB were found in Frio county. These melons were found in a field that had a previous crop history of fruit blotch-infected watermelon. (There is no evidence of "native" infections of citron melons with WMFBB, i.e., without any prior involvement of an infected watermelon crop). Thus, in south Texas, it appears that citron melons can serve as a weed reservoir for the WMFBB, once it is introduced into a field via infected watermelon plants. However, so far, no fruit blotch epidemic has been documented to originate from infected citron fruits. Nevertheless, it is necessary to aggressively control citron and other cucurbit weeds as part of a fruit blotch management program.
The factor which I feel led to the severe disease incidence in the honeydew field was the use of overhead watering, which served to spread the bacteria throughout the field. I regard overhead watering as a critical factor for fruit blotch development in south Texas. Although the timely use of copper sprays will limit the spread of the bacteria within a field, their effectiveness can be reduced when overhead watering is used.
For example, in one sprinkle-irrigated watermelon field that had 10-20% incidence of fruit blotch, copper sprays were applied as recommended. This doesn't reflect a failure of the copper sprays, only that they can not be fully relied upon if conditions are very favorable for disease. According to Dr. Don Hopkins (University of Florida), had copper sprays not been used in this field, the grower would have likely experienced an incidence of approximately 90%. In contrast, this grower had the same batch of watermelon plants (i.e. also likely to be contaminated with WMFBB) growing under drip irrigation in a nearby field. He did not find any fruit blotch in this field. This example clearly illustrates the significant contribution that overhead irrigation can make in initiating an epidemic.
This outbreak of fruit blotch of honeydew hopefully does not signal the start of a new, major disease problem. There are several things that can be learned from it. The new piece of information is that other cucurbits should not be used as rotation crops to follow watermelon. My experiments so far indicate the bacterium can survive only a few weeks in soil under south Texas conditions, so it would be more likely that carry-over would occur with infected seed of volunteers and cucurbit weeds; these need to be thoroughly controlled between crops. Finally, overhead irrigation presents a risk factor that may not be overcome by using copper sprays.
Southern Pea Variety Trial Report: Lynn Brandenberger
Nine varieties of southern pea were trialed this past fall in the Falfurrias area. Information on earliness of flowering, maturity and yield are provided in this report, (Table 1 & 2). If you would like to receive a copy of the full report, contact either Jaime Lopez/Brooks County Ag Agent, Rogelio Mercado/Jim Wells County Ag Agent or Lynn Brandenberger/Vegetable Specialist.
| Table 1. Flowering data for fall 1996 southern pea variety trial, Falfurrias, Texas area. | |||||||
| Cultivars | Average % flowering on 10/28/96z |
Average % flowering on 11/04/96 |
Average % flowering on 11/06/96 |
Average % flowering on 11/11/96 | |||
| Early Scarlet | 58.8 | a | 71.3 | a | 76.3 | bc | 96.3 |
| Excel | 37.5 | bc | 71.3 | a | 83.8 | ab | 100.0 |
| AR 87-435-69 | 36.3 | bc | 76.3 | a | 87.5 | a | 100.0 |
| AR 87-435-68 | 50.0 | ab | 73.8 | a | 83.8 | ab | 98.8 |
| Arkansas Blackeye # 1 | 16.3 | d | 48.8 | b | 67.5 | cd | 100.0 |
| Pink Eye Purple Hull BVR | 13.8 | d | 43.8 | b | 61.3 | d | 98.8 |
| Coronet | 10.0 | d | 51.3 | b | 68.8 | cd | 98.8 |
| Quick Pik | 56.3 | a | 77.5 | a | 90.0 | a | 100.0 |
| Texas Pinkeye | 21.3 | cd | 52.5 | b | 67.5 | cd | 96.3 |
| Average | 33.3 | 62.9 | 76.3 | 98.8 | |||
| zNumbers within a column followed by the same letter are not statistically different where P=0.05. | |||||||
| Table 2. Maturity and harvest data for fall 1996 southern pea variety trial, Falfurrias, Texas area. | ||||||
| Cultivars | Maturity rating on 11/19/96 z | % Moisture of peas on 11/25/96y | Net yield lbs./acre | Imbibed wt. % increase in weight | ||
| Early Scarlet | 50.0 | abc | 10.9 | 1078.6 | b | 234 |
| Excel | 52.5 | ab | 10.3 | 1169.2 | ab | 245 |
| AR 87-435-69 | 52.5 | ab | 10.6 | 1015.9 | b | 226 |
| AR 87-435-68 | 57.5 | a | 10.4 | 1183.2 | ab | 244 |
| Arkansas Blackeye # 1 | 50.0 | abc | 11.1 | 1170.9 | ab | 229 |
| Pink Eye Purple Hull BVR | 45.0 | bc | 11.1 | 1409.7 | a | 219 |
| Coronet | 40.0 | c | 11.1 | 1395.7 | a | 217 |
| Quick Pik | 42.5 | bc | 10.7 | 1017.6 | b | 228 |
| Texas Pinkeye | 52.5 | ab | 11.0 | 993.2 | b | 221 |
| Average | 49.2 | 10.8 | 1159.3 | 229 | ||
zNumbers within a column followed by the same letter are not statistically different where P=0.05. yNumbers not followed by a letter were not statistically analyzed. | ||||||
Section 18's on Melons: Stormy Sparks
The current section 18's for use of Admire and Capture on melons for control of sweet potato/silverleaf whitefly are scheduled to expire on January 26, 1997. TDA submitted a request for renewal of these section 18's on November 18, 1996. The new regulations controlling the registration process (Food Quality Protection Act) puts everything in the questionable area, but we should hear something soon. Given the performance and safety of these products under previous section 18's I would expect approval, but we will have to wait and see.
Lynn Brandenberger/Editor
The information given herein is for educational purposes only. References to commercial products or trade names are made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.