IN THIS ISSUE: Introducing Jason Johnson South Texas Vegetable WebSite Open for Business Grower/Shipper Survey Results on Spring 1997 Rain Damage Texas Guide for Controlling Insects on Commercial Vegetable Crops Available Now Managing Diseases Caused by Fungicide Resistant Pathogens |
Jason Johnson is our new Extension Agricultural Economist for the South Texas area. Jason hails from Lubbock, Texas and Texas Tech. He grew up near Jacksboro, Texas and has been involved with his family's ranch throughout his life time.
Jason received his B.S. in Agricultural Economics from Texas Tech University in 1991. He earned his M.S. in Agricultural Economics from Louisiana State University in 1993 and his Ph.D. in Agricultural Economics with a minor in Consumer Economics from Texas Tech University in 1996.
His primary interests lie in farm and financial management, production economics, agribusiness management and marketing. Specific topics that he is responsible for include the preparation of area crop enterprise budgets, economic analysis of regional and state programs and the presentation of information to clientele on related economic issues. As the area economist for the South Texas region, Jason is officed out of the Texas A&M Research and Extension Center in Weslaco and can be contacted through your local County Extension Office.
South Texas Vegetable WebSite Open for Business: Lynn Brandenberger
We've been as busy as South Texas ground squirrels during the building phase of an Internet website for commercial vegetable production in South Texas, and finally we're ready to announce it's opening. The South Texas Vegetable Web is open for business and is located at the following address on the Internet
http://extension-horticulture.tamu.edu/southtex. This website has been developed to serve as an information source to the commercial vegetable industry through the efforts of Texas A&M Extension and Experiment Station personnel. A special thanks to Dr. Daniel Lineberger for his assistance in developing this website.
The South Texas Vegetable Web provides direct access to information about the vegetable industry in South Texas, research and result demonstration reports, this newsletter and much more. Currently we have completed the home pages within the website relating to Texas A&M staff in South Texas and also general information about the vegetable industry in the area. Feel free to browse through the website and we'll do our best to complete construction on the remainder of the home pages that will be included in it.
Grower/Shipper Survey Results on Spring 1997 Rain Damage: Jason Johnson
This report summarizes the results of a June grower/shipper survey to assess the extent of vegetable crop damage incurred from the untimely rainfall in the Spring. The results from this survey were used to assist county officials and USDA personnel in their efforts to procure state and federal disaster declarations and to provide economic assistance to eligible Valley producers. In many cases, the planted acreage of vegetable crops for 1997 was below historical levels as a result of both uncertain market factors and water availability. The loss estimates reported herein do not reflect the effects of reduced acreages resulting from these
circumstances. These estimates are meant solely to depict reduced production and economic losses for selected crops resulting from untimely excess rains in the Rio Grande Valley.
Survey response from producers in Hidalgo, Starr, Cameron and Willacy Counties totaled 19,000 acres. The South Texas Onion and Melon Committee was contacted to evaluate the survey participation rate and corroborate damage estimates. It was determined that the grower/shipper survey response accounted for 70 percent of the Valley Onion acreage and over 90 percent of Valley cantaloupe and honeydew melon acreage. Other crops reported include: carrots, cabbage, peppers, potatoes, watermelon, cucumbers, squash, celery, kohlrabi, green onions, beets, Swiss chard, spinach, mustard greens, turnip greens, kale, cilantro, collard greens, parsley, leek, dill and dandelion.
Estimated Losses from Excess Rain - Spring 1997 - Rio Grande ValleyHidalgo, Starr, Cameron, & Willacy Counties
| Crop | Est. Planted Acreage |
Damage Est. % of Crop Lost |
Est. Loss to Producers Million $'s |
Est. Loss to Valley Economy Million $'s |
| MELONS | ||||
| Cantaloupe | 5791 (1) | 68 % | 15.0 | 23.1 |
| Honeydews | 2256 (1) | 36 % | 5.5 | 8.5 |
| VEGETABLES | ||||
| Onions | 9200 (1) | 46 % | 14.5 | 21.2 |
| Carrots | 5400 (2) | 16 % | 2.5 | 3.7 |
| Cabbage | 6500 (2) | 56 % | 17.0 | 24.8 |
| TOTAL | 54.5 | 81.3 |
2/ Texas Agricultural Extension Service, Jason Johnson, Extension Economist
Texas Guide for Controlling Insects on Commercial Vegetable Crops Available Now: Stormy Sparks
The 1997 revision of B-1305, "Texas Guide for Controlling Insects on Commercial Vegetable Crops" , is currently available. This guide primarily consists of registered insecticide listings for 22 of Texas' major vegetable crops or crop groups. The table for each crop lists the products labeled for use on the crop, the more common pests included on each product label, and labeled rates for each of these crop-pest-product combinations. Additional label information (pesticide class, re-entry interval, pre-harvest interval, etc.) Is included for each product to aid in pesticide selection for various conditions.
The revised guide includes major changes, with the addition and removal of many crop-pesticide combinations as a result of pesticide label changes. Old guides should be discarded immediately. Copies of B-1305 are available from your County Extension office.
Managing Diseases Caused by Fungicide Resistant Pathogens: Tom Isakeit
This past season has seen problems caused by several fungicide-resistant vegetable pathogens in the Rio Grande Valley: the appearance of a Ridomil-resistant genotype of Phytophthora infestans (US-8), the fungus that causes late blight of potato; failure of Bayleton to control the cucurbit powdery mildew fungus (Sphaerotheca fuliginea); and a catastrophic fruit rot problem caused by Benlate-resistant strains of the gummy stem blight fungus (Didymella bryoniae). The wet spring played a major role in launching the late blight and gummy stem blight epidemics. The initial build-up of the pathogens could have been suppressed if effective systemic fungicides were used. However, although systemic fungicides are an important management tool for foliar diseases, they need to be used properly to prevent the development of pathogen resistance.
Generally, systemic fungicides target a narrower spectrum of pathogens and control them very effectively in comparison with protectant fungicides. The potential downside of systemic fungicides that they tend to have such a narrow mode of action that resistant mutants can develop after only a few years of use. In contrast, protectant fungicides have multiple modes of action, with the consequence that there is little chance that resistant mutants can develop.
Mutants resistant to fungicides can be naturally present in low levels in a pathogen population. The constant use of a fungicide can select for these mutants. If the pathogen has a high reproductive rate, which is the case for many fungal pathogens of foliage, then these resistant members of the population can quickly increase in proportion to the original population. If these mutants have the same fitness in the environment as the original population, and if environmental conditions favorable to their reproduction occur (including management practices), then the obvious consequence is the failure of a fungicide to control the disease. Furthermore, these mutants may persist in the environment long after use of the fungicide ceases. In some instances, a mutant resistant to one fungicide is resistant to other fungicides that are similar in chemical structure and mode of action. This is known as cross-resistance.
With these thoughts in mind, the solution to gummy stem blight and other epidemics is not simply to substitute a new systemic fungicide with a different mode of action. This will work for a limited time, but resistance will likely occur with the new fungicide as well. The new fungicides must be used in such a manner as to minimize the build-up of resistance.
Systemic fungicides should be applied in the very early stages of a disease epidemic, when symptoms are first noticed in a few plants. With some diseases, such as late blight of potato, they should be applied when conditions favorable for disease development exist and if the disease has been reported in the vicinity. (Otherwise, in the absence of disease in the area, protectant fungicides will suffice). If these fungicides are applied after the disease has become well-established in the field, with the erroneous expectation that they will cure the disease, there is an increased risk of selecting for resistant pathogens. The systemic fungicides should be used in combination with protectant fungicides. Also, a particular systemic fungicide should not be applied back-to-back; it should either be alternated with a protectant fungicide or another systemic fungicide with a different mode of action. The fungicide should not be used at below label rates and it should be applied over the whole field.
Thus, for future gummy stem blight control, we are proposing the use of three new systemic fungicides, each with a different mode of action. During the season, their use would be rotated. Furthermore, when a particular fungicide is applied, it will be applied along with a protectant fungicide. This strategy will maximize effectiveness of the fungicides and minimize the chances that strains will become resistant to these chemicals. Testing of three proposed replacement fungicides for effectiveness are currently underway.
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.