Pesticide Residues and Food Safety - ACS Publications - American

Chapter 8

Integrated Pest Management in the Southwest Ray Frisbie and Jude Magaro

Downloaded by TUFTS UNIV on June 12, 2018 | https://pubs.acs.org Publication Date: December 31, 1991 | doi: 10.1021/bk-1991-0446.ch008

Department of Entomology, Texas A&M University, College Station, TX 77843 Integrated pest management (IPM) in the Southwest has intensified in the last 15 years as a rational approach to controlling pests for major crops. A public mandate exists to provide food and water reasonably free of pesticide contamination. In order to meet this mandate, IPM must evolve to its next step and become much more biologically intensive in its approach for the future to prevent pesticide pollution. Biologically intensive IPM program proposes multiple tactics to reduce dietary risk from pesticides. Economic validity of both cotton and cabbage biologically intensive IPM systems are provided. The Southwest has a rich history of developing and delivering IPM to farmers and ranchers. Texas A&M University and Oklahoma State University accelerated research and Cooperative Extension Service education programs beginning in the early 1970s. Integrated pest management systems using multiple control tactics were designed to keep pest populations below those causing economic damage while at the same time reducing negative environmental impacts caused by pesticides. Technology has been developed to implement IPM programs at the farm level for a variety of crops including cotton, sorghum, livestock, hay, corn, peanuts, pecans, wheat, rice, soybeans, citrus, sugar cane and a variety of vegetable crops. Specific management tactics developed for IPM programs have included pest resistant varieties, cultural techniques, the preservation and use of biological control agents, crop and pest computer forecasting models, pest monitoring techniques, and economic thresholds that relate pest abundance to plant damage for selectively timing pesticide applications. EPM: a System for Pesticide Pollution Prevention Recent concerns over pesticide contamination of water and food, as well as negative impacts on wildlife, have spawned a renewed interest in IPM. Integrated pest management is a rational approached for dealing with pesti0097-6156/91A)446-0068$06.00/0 © 1991 American Chemical Society

Tweedy et al.; Pesticide Residues and Food Safety ACS Symposium Series; American Chemical Society: Washington, DC, 1991.


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Integrated Pest Management in the Southwest

cide pollution prevention. In fact, IPM has a proven track record for reducing the source of pesticide contamination through focusing on pesticide alternatives for managing a wide range of pest species while maintaining profitability in agriculture. Integrated pest management is far from a perfect system in terms of dealing with the wide range of pests attacking crops; however, IPM systems, when properly designed, have shown substantial reductions in pesticide use for major cropping systems in the Southwest and other areas. There are outstanding regional examples of IPM successes on major cropping systems in the Southwest as well as the Southeast (i). Insecticide use on cotton, sorghum and peanuts has been significantly reduced since the introduction of IPM by the Cooperative Extension Service in the early and mid-1970s. For example, in 1971 (pre-IPM) U.S. insecticide use on cotton, grain sorghum and peanuts was 73.4, 5.7, and 6.0 million pounds, respectively. By the early 1980s, and after 10 years of intensive educational work by the Cooperative Extension Service, based on State Agricultural Experiment Station research, insecticide use dropped to 16.9, 2.5 and 1.0 million pounds, respectively, for cotton, grain sorghum and peanuts. During this period, acres for these commodities remained relatively constant. Not only was the total amount of insecticide reduced, but the proportion of acres treated was also significantly reduced. Cotton, grain sorghum, and peanuts experienced a decrease in acres treated by 46%, 48% and 54%, respectively. The IPM tactics used to achieve these reductions were resistant or tolerant crop plants, field monitoring to preserve natural enemies and carefully time selective insecticide applications, and cultural practices such as optimum planting and harvest that disrupted the life cycle of the insect pests. Another outstanding example of the use of careful pest monitoring and treatment thresholds is the processing carrot IPM program developed by the Texas Agricultural Experiment Station and provided to producers through the Texas Agricultural Extension Service IPM program. Processing carrots are used for baby food, soups and for a variety of other canned foods. The Texas carrot IPM program was operated in cooperation with Gerber Foods, Inc., and Campbell Foods, Inc., for farmers growing carrots under contract. In the first year of this program (1988) insecticide use was reduced by 66% (from 6 to 2 applications) without loss in yield or quality. A fresh market cabbage IPM program using similar technology reduced insecticide use by 44%. There are several other good examples of similar pesticide reductions for other commodities in the Southwest. Biologically Intensive IPM: The Future Despite the many successes of IPM, IPM programs still rely perhaps too heavily on pesticides as a primary tactic for managing pests. The IPM systems developed and delivered in the next twenty years will rely to a much greater extent on biologically based IPM tactics rather than agricultural chemicals. These systems will become biologically intensive (bio-intensive)


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PESTICIDE RESIDUES AND FOOD SAFETY

in their approach. The rationale for bio-intensive IPM is based on the assumption that fewer conventional pesticides will be available in the future. The choice of available pesticides will diminish not only because of public concern over food and water quality and wildlife conservation, but also because of associated costs of pesticide registration and reregistration, increased incidence of pesticide resistance by pests, and as some pesticides for numerous food and speciality crops will be considered "minor use" by pesticide manufacturers and not constitute a sound market investment. Therefore, the reduced availability of pesticides will result from both environmental concerns and crop production economic concerns. The future course of agriculture in the Southwest and the U.S. will depend on how quickly bio-intensive IPM systems can be developed. Creative and bold steps must be taken to develop and deliver IPM systems that insure a constant and safe food and fiber supply without complete reliance upon agricultural chemicals; to ignore this precept would be foolhardy. It is important to note, however, that there are many instances where pesticides are necessary to protect human health. Mycotoxins, for example, are highly toxic compounds produced by fungi that infect grain, oil seed and other crops. The careful use of fungicides to control mycotoxin producing fungi is easily justified to protect human health. There are other examples where there can be little choice but to use pesticides at this time in order to produce a safe food supply. Pesticide alternatives may be available in the future to address these critical problem areas. Bio-Intensive IPM will rely on three primary tactics to meet its objectives: biological control, host resistance and cultural management. These three tactics are the cornerstones on which bio-intensive IPM will be constructed. Bio-intensive IPM builds on the same philosophical tenets as traditional IPM except agricultural chemicals are considered secondarily and their use in bio-intensive IPM must be nondisruptive and environmentally safe. Biotechnology, along with classical breeding, will provide opportunities to alter plants and animals to be resistant to pests. Biotechnology must take advantage of ecological theory applied to agriculture to delay or prevent pest resistance to genetically engineered plants. Host resistance and biological control form a powerful combination for pest suppression. For example, if host resistance can be developed for even one key pest of a particular crop, pesticide use will be reduced and several unique opportunities will be available for biological control. Biotechnology also offers tremendous potential for genetically engineered microbial pesticides that would fit well into bio-intensive IPM systems. Historically, biological control has made significant advances in controlling pests in perennial cropping systems. These advances must now be extended to include greater biological control activity in annual crop systems. As the theoretical basis for biological control in annual crops is developed and emphasis on biological control expands, more success is predicted. This challenge must be met before biological control can reach its true potential and be useful over the large acreages of annual



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71 Integrated Pest Management in the Southwest

crops grown in the U.S. Likewise a creative, scientific revolution must take place in the area of weed control. Weed control, due primarily to high labor and fuel costs, depends most heavily on herbicides. In some areas, conservation tillage systems have forced producers to rely even more heavily on herbicides for weed control. Some biological herbicides have been successfully developed, but more work must be done if solutions to these problems are to be found. Cultural management options, such as crop rotation, varietal selection, planting dates, tillage practices and water and fertilizer management have provided the agronomic base for IPM. Under bio-intensive IPM, even greater demands will be placed on cultural management requiring an increased understanding of the ecology of annual cropping systems. Systems science will be important for developing bio-intensive IPM systems that meet the biological, economic and environmental objectives of modern agriculture. New tools, such as knowledge based systems, e.g., expert systems, will emerge that integrate crop, pest and economic data to provide critical management information for decision making. Field monitoring (scouting) and computerized forecasting models will continue to be used to evaluate the systems and anticipate future events upon which mangement decisions will be based. A Transition to Bio-Intensive IPM: A Case Study of Cotton Cotton in the Southwest serves as a good example of how all of the characteristics of a production system must be evaluated to develop a pest management system. Cotton production in Texas had reached a crisis phase in the late 1960s due to extreme reliance on pesticides that resulted in insecticide resistance by a secondary pest, the tobacco budworm (Heliothis virescens). Ever increasing insecticide costs and declining yields forced researchers to carefully reevaluate the Texas cotton production system if disaster was to be avoided. After a thorough analysis, a major, timely breakthrough came in the early 1970s with the commercial release of the Texas A&M University Multi-Adversity Resistant (TAMCOT) cotton varieties. The TAMCOT varieties, along with commercial selections from these varieties, were capable of fruiting and maturing so rapidly that they could escape much of the mid-to-late season insect damage from boll weevil (Anthonomus grandis), bollworm {Heliothis zed) and the tobacco budworm. Shortseason cottons became the cornerstone around which a new IPM system was designed for Texas cotton. The Texas short-season cotton IPM system serves as a good organizational paradigm for examining a crop production system to seek pest management strategies alternative to insecticides. This system also represents an excellent start or transition toward a more bio-intensive IPM approach. Short-season cotton IPM systems were developed for the Blacklands, Coastal Plains, Winter Garden, and Lower Rio Grande Valley Production regions of Texas (2). The essential tactics that comprised the short-season cotton IPM system for these regions were: (1) early and uni-



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form planting for short-season cotton varieties; (2) reduced application of uniform nitrogen and irrigation where appropriate; (3) intensive field (scouting) for early season insect pests such as the cottonfleahopper(Pseudatomoscelis seriatus) and the boll weevil to carefully timed insecticide applications could be made if economic damage was anticipated, pheromone trapping of adult bollwornVbudworm as input variables to a computer simulation model to predict future population trends; (4) terminate insecticide applications 2-3 weeks prior to the bloom period to allow natural enemies to build up and gain biological control of bollworm and insecticide resistant tobacco budworm; (5) continued intensive field scouting of key insects and application of insecticides based on appropriate economic thresholds; (6) early harvest; and (7) complete, area-wide crop residue destruction shortly after harvest to reduce the number of insect pests entering overwintering quarters. This IPM system, in effect, nearly eliminated the need for multiple (10—12), expensive insecticide applications during the mid and late season. Environmental and Economic Impact of the Short-Season IPM System. As short-season IPM systems were introduced and adopted by Texas cotton farmers, there were substantial reductions in insecticide use statewide. Insecticide use in Texas was estimated at about 19 million pounds in the mid1960s. Ten years later, after the introduction and farmer acceptance of short-season cotton IPM systems, insecticide use had dropped to about 2.3 million pounds. Acreage remained relatively constant during this period. The same classes of insecticides were also used during this time frame. Today, it is estimated that approximately 90 percent of Texas and Oklahoma farmers use a short-season or modified short-season IPM production system. A specific example of the economic and environmental success of a short-season cotton IPM system is seen in the Lower Rio Grande Valley of Texas, a 350,000-400,000 acre cotton producing region. Major emphasis is placed on valley-wide post harvest crop residue destruction to prevent cotton regrowth that could serve as a food and reproduction host for the boll weevil. Crop residue destruction allows an extended cotton host free period that greatly reduced winter survivorship of the boll weevil. This nonchemical, cultural tactic has no added costs and has had a high degree of success in reducing boll weevil populations. As a result of this program, net farm income for cotton has increased by as estimated $270 per acre with a regional valley-wide economic impact of $31 million (2). Of equal importance is the 650,000 pound annual reduction of insecticide used. This represents a significant reduction in pesticides that could contaminate water as well as the many food crops that are produced in the valley. The use of the short-season cotton IPM strategy was particularly successful in the Coastal Bend area of Texas which produces cotton on about 300,000 acres. This program resulted in direct farmer profits of $11 million per year and an annual increase in economic activity for the region of $94 million (5). The number of per acre insecticide applications was reduced from an average of twelve before the program was initiated in 1973 to five


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by 1976, and averages around 4 applications today. Steady progress has been made in keeping insecticide applications to an absolute minimum. Completing the Transition to Bio-Intensive IPM for Cotton. Although signi ficant progress has been made toward a bio-intensive IPM system for cotton in the Southwest, there is still much to be done. Future research must be accelerated to find non-pesticide management alternatives. Owing to past experience, the cotton system in the Southwest is well understood. The boll weevil remains the key for solving insect problems in cotton. There is clear evidence that the multi-adversity resistant (MAR) cotton germplasm may possess a degree of resistance to the boll weevil (Κ. M. El-Zik, personal communication). MAR germplasm forms the genetic base for the TAMCOT varieties. If MAR cottons can tolerate 30-40% more boll weevil damage without loss in yield or quality, a tremendous window of opportunity will open that will enhance the already powerful short-season IPM cotton sys tem. Research must be accelerated for identifying host resistance to the boll weevil and other key pests. More efficacious strains of Bacillus thuringiensis (B.t.), used as microbial insecticides, could provide a nondisruptive, environmentally safe tactic for managing the bollworm and tobacco budworm. Natural enemies for the cotton fleahopper and boll weevil could add to mortality, particularly in the southern, more temperate areas of Texas. Given higher levels of host resistance in short-season cottons, com bined with existing cultural practices, enhanced by microbial insecticides bollworm/tobacco budworm along with increased emphasis on natural enem ies, cotton in the Southwest could be produced under a bio-intensive IPM system. Bio-intensive IPM does not mean no pesticides. Rather the careful use of non-disruptive pesticides can support a bio-intensive IPM system. Designing a Bio-Intensive IPM System for a Food Crop: Cabbage Fresh market cabbage is a good representative crop to evaluate potential of developing a bio-intensive IPM system. Cabbage in the Lower Rio Grande Valley of Texas is expensive to produce and carries with it a high risk due to rapid shifts in market prices along with risks from intense insect attack. The Lower Rio Grande Valley annually produces fresh market cabbage on about 11,000 acres. The crop has a yearly value of $30-60 million depend ing on market prices. In evaluating production costs, mediated by possiblerisksof dietary and direct human exposure, insect control represents a substantial portion of variable production costs at about $244.00 per acre. Insecticide applications range between 8-15 in one cabbage production cycle with several overlap ping cycles during the nine month growing season. The three key insect pests are the cabbage looper (Trichoplusia ni), diamondback moth (Plutella xylostella) and the beet armyworm (Spodoptera exigua). Although all of these pests pose an economic threat to cabbage production, the diamondback moth is particularly critical. Owing to heavy insecticide use on cabbage, the diamondback moth has developed high levels of resistance to all classes of


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synthetic insecticide. The cabbage industry in the Lower Rio Grande Valley and in several other areas of the U.S. and the world is in a crisis phase because of insecticide control failures due to resistance by the diamondback moth. The diamondback moth will be the focal point for proposing a research and extension education program for a bio-intensive IPM on cabbage. Elements of a Bio-Intensive IPM Program for Cabbage. As in the case of cotton, all elements of the production system must be examined before alternative management strategies for diamondback moth can be proposed. Cabbage is a fall-winter crop in the Lower Rio Grande Valley with multiple plantings. Historically, insecticides have been applied on a schedule with little consideration of insect population levels and damage. To the point, cabbage has depended almost enitrely on chemical insect control. The first element in designing a workable bio-intensive IPM program for cabbage requires the reduction of heavy chemical use on cabbage. Cartwright (4) developed a sampling system and composite action threshold for the key lepidopterous pests of cabbage. This system provides the quantitative base for relating insect population numbers to economic damage. Use of this system through the Texas Agricultural Extension Service IPM program has demonstrated that insecticide applications can be reduced by 44%. Use of this sampling system is only the first step in the reconstruction of the cabbage-IPM system. A second element involves accelerated research and demonstration of nondisruptive biological insecticides. Considerable work has been done using Bacillus thuringiensis as a biological insecticide. New strains of genetically engineered B.t. offer higher levels of control that could be used in a cabbage-bio-intensive IPM system. More research is needed to determine the potential for commercialization of entomopathogenic fungi, Erynia blunckii, Zoophthora radicans and Beuvaria spp., a granulosus virus and one or two polyhedrosis viruses (5). The use of microbial insecticides could allow existing natural enemies to operate at greater levels of efficiency. The third element involves expanded biological control. Several species of parasites exist in other places in the world that have shown to be effective control agents of the diamondback moth. Apanteles plutellae, Diadegma cerophaga, D. fenestrate, D. collaris and D.tibialisare parasites that have been effectively introduced and established in Australia, Trinidad, Indonesia, and New Zealand (6). High rates of parasitism and complete or near complete biological control of diamondback moth were achieved in New Zealand, Australia and Indonesia using single or multiple species of the above parasite complex. The introduction and establishment of any biological control agent depend on either elimination or careful use of synthetic chemical insecticides so as not to disrupt biological control. Biological control is a pivotal element in this bio-intensive IPM system. The first two elements of the system must be in place in order to foster biological control. A fourth element for consideration involves expanded research for host resistance in cabbage and other crucifers (7—8). As with cotton, marginal



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levels of tolerance or resistance may be sufficient to reduce synthetic insecticide use and allow biological control agents, specifically parasites and predators, to operate with greater efficiency. The fifth element involves cultural management of the cabbage system to further suppress or discourage diamondback moth population development. A host free period of at least three months should be established where diamondback moth is not able to reproduce at high levels on cabbage. This may require destruction of cabbage that has been abandoned because of low market prices or for other reasons. Sufficient wild hosts are available for diamondback moth survivorship during a host free period; however, overall populations should be significantly reduced using this tactic. It is also important that a residual diamondback moth population be available during the off-season in order to allow the parasite complex to survive and increase in the succeeding season. Also, some cabbage is sprinkler irrigated. The diamondback moth is a weak flyer and is active at dusk. Sprinkler irrigation can physically kill the adults or disrupt mating if irrigations are timed during peak flight periods (9). Sprinkler irrigation also drowns the larval stage. The use of timed sprinkler irrigations should be investigated as a possible mechanical control technique. Expected Benefits of a Cabbage Bio-Intensive IPM System. The above proposed cabbage Bio-Intensive IPM system when fully developed has the potential of near elimination of synthetic pesticide use. The system has the potential for greatly reducing insecticide use on cabbage. Other insect pests, such as an aphid complex, would have to be taken into consideration. However, it is anticipated that once insecticides are removed from the system, greater biological control of aphids will be achieved by parasites and predators. The economic benefits of synthetic insecticide free cabbage will be substantial. Losses in yield or quality are not expected. The market value of synthetic insecticide free cabbage should increase. Consumer risk of dietary exposure to insecticides could be significantly reduced or eliminated under the cabbage bio-intensive IPM system. Additionally, human exposure to insecticides by field workers and managers would be greatly reduced. Bio-Intensive IPM: A Template for Other Crops Cotton and cabbage are but two examples of crops where a balanced biointensive IPM system could be established. Both crops have a heavy dependency on synthetic insecticides. Although significant progress has been made toward a bio-intensive system for cotton in Texas, there is still some progress to be made. The cabbage system is illustrative of many food crop systems where there is a great dependence on synthetic insecticides and other chemicals. Bio-intensive IPM is not exclusive of other pest classes. In fact, a complete bio-intensive IPM system must include alternative approaches for the management of plant pathogens and weeds. Many opportunities exist.


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Literature Cited

1. Frisbie, R. E.; Adkisson, P. In Biological Control in Agricultural IPM Systems; Hoy, M. A .; Herzog, D., Eds.; Academic: New York, NY, 1985; p 41. 2. Frisbie, R. E.; Crawford, J.; Bonner, C.; Zalom, F. In Integrated Pest Management Systems and Cotton Production; Frisbie, R. E.; El-Zik, K.; Wilson, L., Eds.; John Wiley and Sons: New York, NY, 1989; pp 389-412. 3. Lacewell, P. D. and Masud, S. In Integrated Pest Management Systems and Cotton Production; Frisbie, R. E.; El-Zik, K.; Wilson, L.; John Wiley and Sons: New York, NY, 1989; pp 361-388. 4. Cartwright, B.; Edelson, J.; Chambers, C. J. Econ.Entomol.1987, 80, 175-81. 5. Wilding, N. Proc. 1st International Conf. Diamondback Moth, 1986, p 219. 6. Lim, G. Proc. 1st International Conf. Diamondback Moth, 1986, p 159. 7. Eckenrode, C. H.; Dickson, M.; Lim, G. Proc. 1st International Conf. Diamondback Moth, 1986, p 129. 8. Dickson, M. H.; Eckenrode, C.; Lim G. Proc. 1st International Conf. Diamondback Moth, 1986, p 137. 9. Takelar, N. S.; Lee, B.; Huang, S. Proc. 1st International Conf. Diamondback Moth, 1986, p 145. RECEIVED

August 19, 1990


Pesticide Residues and Food Safety - ACS Publications - American

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