Control of Gummy Stem Blight With Fungicides by Tom Isakeit

A field trial recently conducted by Dr. Marvin Miller at the Texas A&M University Agricultural Research Center in Weslaco has identified a couple of effective fungicides for control of gummy stem blight of cantaloupe. These fungicides are intended to replace Benlate, which no longer is recommended for control of this fungal disease because of the prevalence of resistant strains in the Rio Grande Valley. In this trial, fungicides were sprayed onto the stem of young cantaloupe plants growing under drip irrigation with plastic mulch. In the Rio Grande Valley, gummy stem blight typically occurs early in the spring growing season, causing lesions on the lower stem. With periods of rain throughout the growing season, the infection can spread to the vines, leaves and even fruit, which, in the 1997 spring season, resulted in a catastrophic loss of $15 million to Valley growers. To simulate the development of the disease epidemic in the field trial, spores of the fungus were sprayed onto the stems of plants after the first application of fungicides, and sprinklers were used to maintain conditions of leaf wetness and high humidity.

Three weeks after inoculation, the incidence of stem lesions on plants with no fungicide application was 97% and with Benlate treatments, 90%. Additionally, there was substantial development of leaf and fruit infections. In contrast, stem lesion development was 3% with treatments of Quadris SC (0.8 pts/acre) and 7% with Bravo WS (3 pts/acre). Fruit and leaf infection was significantly suppressed by these treatments, too.

Based on these results, we have requested a Section 18 for Quadris. Bravo is already labeled. Both of these fungicides are intended for use early in the season to prevent gummy stem blight development. The advantage of Quadris is that it has some systemic activity and so, it can protect portions of the plant that would not get covered by a protective fungicide such as Bravo. If Quadris is approved, applications of it should be alternated with a protectant fungicide to prevent development of fungicide resistance.

In the field trial, we found that Bravo was more effective in suppressing gummy stem blight than Dithane. However, in growth chamber tests, where plants were grown under constant, high humidity, both fungicides were equally effective. It is possible that Bravo had a higher persistence on plants in the field subjected to the washing from the sprinklers. Under conditions of low disease pressure, Dithane could be used as well.

These results should be used as a starting point for disease management, they are not the final recommendations. There is much research that still should be done to optimize fungicide use. We still would like to see other systemics available for control. Although some of the systemics that performed well in growth chamber tests did not do as well in the field trial, we think that some of these fungicides do have utility for gummy stem blight control in areas other than the Rio Grande Valley, where the disease is more important on foliage.

Good fungicide coverage early in the season will be the key to preventing an epidemic if weather conditions remain favorable for disease development. However, these fungicides would be more effective if coupled with a two-year rotation of the field out of cucurbits, to reduce the amount of the fungus initially present.

Vegetable IPM Program Set to Begin by Juan Anciso

The Vegetable IPM Program is organizing vegetable producers for the 1997-98 season. This program is intended to establish an integrated pest management scheme to assist local vegetable producers in making economically and ecologically sound pest control decisions. This is intended to be an educational program and not intended to replace the service of professional consultants. However, participating producers will have information (reports) on pest densities within their fields and such information should lead to judicious use of pesticides as well as cost-effective control of pests. Hopefully by taking this approach, the participating producer will see an increase in his profitability margin and justify this IPM scheme in his future farming program. As well as helping all producers with pest control knowledge, it is intended that the consumer and environment benefit by keeping pesticide usage required for production down to a minimum. The program has been successful in reducing insecticide and fungicide use in cabbage and carrots and further expansion into the cucurbits is the goal of the program for the year. Also, disease forecasting information will be provided to the participants.

The number of reports received per field range from 12 to 16 for carrots while 20 to 24 for cabbage, cucurbits or onions. The program for cabbage, carrots and onions will run from November 3rd to March 31st. A program for spring cucurbits (cantaloupes, pickling/cucumbers, watermelons) will run from February 16th to June 30th. Fees for cabbage, carrots, and onions are $8.50/acre and should be similar for cucurbits. The fees for this season should remain nearly the same depending on the committee's decision. The program will be limited to the first 1,000 acres that sign up. If you have any questions about the program please call or write Dr. Juan Anciso at the Hidalgo county Extension Office (383-1026 or 1-800-638-8239).

Third Lower Rio Grande Valley Irrigation Conference

Time to mark your calendars and make plans to attend the third Lower Rio Grande Irrigation Conference on Thursday December 4, 1997. The conference will be held at the Harlingen Community Center and will feature topics dealing with all facets of irrigation and water management and will include simultaneous Spanish translation. For more information on the conference contact either Terry Lockamy (956) 399-7757 or Brad Cowan at (956) 383-1026.

IR-4 Food Use Workshop by Stormy Sparks

The annual IR-4 Food Use Workshop was held in New Orleans on October 14 and 15. Texas had good representation at this years workshop, with at least 8 representatives at the entomology session. The purpose of this workshop is to prioritize proposed IR-4 projects for the coming year. Each group (vegetable entomology, vegetable plant pathology, and vegetable weed control) is allowed about 10% of their proposed projects as 'A' projects that will get worked on in the coming year, about 25% as 'B' projects that will probably get worked on, and the rest fall through the cracks. Obviously, the more representatives you have present, the more votes you have. Texas did well in the vegetable entomology session. We went in with 6 projects as high priorities for Texas, and all six received A or B rankings.

With the cost of registering pesticides for minor use crops, and the potential loss of pesticides because of new regulations, you have to believe that IR-4 will likely play an even bigger role in minor use registration in the future. Texas' role in the program is increasing, but we could probably utilize these resources even better. If you have pesticide registration needs that may fit this program, give us a call and we can get the ball rolling. Or even if you have specific pest control needs, but do not know the best potential product for use, that information alone will help guide this program toward maximizing benefits for producers.

World Wide Web site addresses by Lynn Brandenberger

This past spring we discussed in a series of articles (Valley Vegetable Notes for May, June & July) how to get geared up to retrieve information from the World-Wide-Web i.e. WWW. Suggestions were made regarding equipment, software and how to find information on the WWW, but since that time we've had several requests for Web-site addresses. The table included in this newsletter lists Web-site addresses that may be of interest to the commercial vegetable industry.

Experience with browsing the Web for information on agriculture and specifically commercial vegetable production web-sites has increased my desire to cut through all the fluff and to get to useful web-sites as quickly as possible. I have found that if I can go to a web-site that has links to other useful web-sites and then use those links to find the information that I'm after, I'm a lot happier camper than trying to use a general search engine that tends to dredge up hundreds if not thousands of unusable web-sites.

In a web-browser such as Netscape, at the top of the page there is an address box where you can type in the web-site address and once typed, you hit the enter key and the browser will take you to that specific web-site. Sounds pretty simple and it actually is and that's why it's important to know where a few good web-sites are located. Once you find a useful web-site you'll want to create a bookmark in your web-browser so you don't have to type in the address next time and for goodness sakes you won't have to hunt the darn thing down again. You create a bookmark for a web-site by clicking the left button of your computer's mouse on bookmark and then clicking on add bookmark while you are in the particular web-site that you want to have a bookmark for. Next time you want to go to that book marked web-site you just click on bookmarks and then on the desired web-site bookmark and you're there.

World Wide Webb (WWW) site addresses
Webb Site	Address
Aggie Horticulture	http://aggie-horticulture.tamu.edu
South Texas Vegetable Web	http://extension-horticulture.tamu.edu/southtex
Vegetable Improvement Center	http://vic.tamu.edu
Texas Subtropical Agricultural Center	http://primera.tamu.edu/
Global Agribusiness Information Network	http://www.milcom.com/fintrac/prices.asp
Texas Ag. Extension Serv. Publications	http://agcomwww.tamu.edu/agcom/
TAMU Home Page	http://www.tamu.edu
AgriNet - Texas A&M University	http://agrinet.tamu.edu
Texas State Agency - Agriculture, Dept. of	http://www.texas.gov/agency/551.html
Agonline Discussion Group	http://agriculture.com/agtalk/agonline
Texas Agricultural Experiment Station	http://taeswww.tamu.edu
TAMU Department of Entomology	http://entowww.tamu.edu
TAMU Plant Pathology & Microbiol.	http://plantpathology.tamu.edu/PLPA/dept_toc.html/
U.S. Department of Agriculture	http://www.usda.gov
TNRCC	http://www.tnrcc.texas.gov/
Texas Agricultural Market Research Cntr.	http://agrinet.tamu.edu/centers/tamrc/
Texas State Data Center/	http://www-txsdc.tamu.edu/
Texas Vegetable Association	http://www.tva.org
Ag Links - Links for the Ag. Industry	http://www.gennis.com/aglinks.html

 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.

Return to Newsletters

Return to South Texas Vegetable Web