DEVELOPMENT OF AN INSECT SPECIFIC FUNGUS (NATURALIS–L®) FOR CONTROL OF COTTON INSECTS

Abstract                                                                         Back to Table of contents

The insect specific fungus, Beauveria bassiana (Balsamo) Vuillemin, ATCC 74040, formulated as Naturalis–L®, was highly effective for control of cotton insects in an integrated pest management system (IPM) for cotton in the Lower Rio Grande Valley of Texas. Naturalis–L® effectively controlled  populations of the boll weevil Anthonomus grandis Boheman, cotton fleahopper Pseudatomoscelis seriatus (Reuter) and silverleaf whitefly Bemisia argentifolii. Naturalis–L® was effective as an ovicide and as a larvicide on the tobacco budworm Heliothis virescens (F.) and the bollworm Helicoverpa zea (Boddie).  Population of beneficials was significantly higher in cotton fields treated with Naturalis–L® than in fields treated with conventional insecticides.  Full season control of insects was obtained in fields treated with Naturalis–L® only and in Naturalis–L®/IPM programs. Lint yields were equal to or better than yields of cotton  fields treated with conventional insecticides.

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NOVEL BIOLOGICAL AND CONVENTIONAL INSECTICIDES: WHAT’S NEW?

Abstract                                                                         Back to Table of contents

In recent years, with the continuing burden of increasing development and registration costs, the agricultural community has been facing the loss of a number of products from its portfolio of insecticides.  Furthermore, as different governments enact upgrades to their regulatory procedures or bring in tough new re-registration laws, there will be additional pressure on minor products that fit niche markets and specialty use opportunities, some of which are of significant importance to cotton growers.  This trend affects the whole agricultural industry, but is particularly noticeable in cotton where perhaps the broadest range of products is used on a wide variety of pests in cotton producing countries around the world.

It is encouraging, therefore, to see that despite the increasing costs that the multi-national agricultural chemical companies are incurring to support their international registrations, there has not been a time in recent years when so many new insecticide developments are finding their way into the hands of the cotton grower.  These new developments cover new chemistries with novel modes of action, both contact and systemic, such as the nicotinyls, pyrroles, phenyl pyrazoles, amino triazinones and the quinazolines.  In addition there are several new insect growth regulator products, both benzoyl phenyl ureas as well as novel structures, hormone analogs and a range of new products and improvements in the field of biologicals and natural products. In terms of resistance management, such developments could not come at a better time to fit into integrated programs around the world.  Some of these new products will undoubtedly find utility in helping overcome control problems due to resistance.

These new developments, from a wide variety of agricultural chemical companies, and their potential for the control of various pests around the world, are reviewed.  Opportunities that some of these discoveries might offer in terms of resistance management are also discussed.

Conclusion

It is clear from the above that there is significant potential for the expansion of the global arsenal of new insecticide products.  Not all the products discussed will end up with cotton registrations in all or even some countries.  Different governments regulate the registration of new pesticides in different ways, thus certain products may mature with disjointed use patterns on a global basis.  Some others, such as the new chemistries that possess novel modes of action, may very well obtain registration in all the major cotton markets.  Most of the products discussed will find great utility in the handling of resistance concerns, adding new opportunities for the development of more effective management programs.

After the paucity of new developments over the last decade, we are entering into an exciting future of integrated pest control that bodes well for the long term survival of global agriculture.

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PEST MODELS FOR DECISION SUPPORT – DEVELOPMENT AND APPLICATIONS

Introduction                                                                Back to Table of contents

In cotton crop management, there are many solutions to problems relating to insects, weeds, irrigation, fertilization, harvest, etc.  Almost every expert has a different solution.  How can we know which solution or recommendation is best?  One way is to evaluate the objectivity of the decision–making process.   Is there any conflict of interest?  Did the process fairly evaluate several, rational, crop management solutions to determine which is best for the farmer, the environment, and the decision–maker?  The advice of experts is important, but objectivity may be enhanced using complex, crop systems models…

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MANAGEMENT OF THE COTTON BOLL WEEVIL WITH ATTRACT-AND-KILL-DEVICES

Abstract                                                                         Back to Table of contents

Poison baits such as molasses laced with arsenic were employed against the cotton boll weevil, Anthonomus grandis grandis Boheman, soon after the pest entered the United States in 1893 but were never effective. The search for an effective attracticide continued for nearly a century. New interest in attracticide research was spurred by the discovery and synthesis of Grandlure®, the boll weevil pheromone, in 1969. Grandlure® has been employed in traps for monitoring boll weevil populations and is highly attractive to both sexes early and late in the growing season. Scientists at the Boll Weevil Research Unit, ARS, USDA, Mississippi State, Mississippi, have developed an attract-and-kill device that incorporates Grandlure®, feeding stimulants and a toxicant. Laboratory and field tests with the device, the Boll Weevil Bait Stick (BWBS), have been carried out for the last four years. Area-wide field tests in Tennessee and Georgia have demonstrated significant suppression. Improvements in the BWBS and the methods of use are ongoing. The technology has been granted a U.S. Patent and is registered for commercial use by the Environmental Protection Agency. The attract-and-kill concept may prove to be an economical, effective and environmentally sound approach to a major pest problem.

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INSECTICIDE RESISTANCE IN MAJOR COTTON PESTS WORLDWIDE: INCIDENCE, MECHANISMS AND MANAGEMENT

Abstract                                                                         Back to Table of contents

Management of insect pests is required for successful cotton production in most of the world’s cotton producing areas.  For many years insecticides have played the primary role in management programs.  The occurrence of resistance is now limiting their effectiveness.  In this presentation we will review the major mechanisms of insect resistance to insecticides and describe the principles determining which mechanisms of resistance are likely to occur in various insect pests.  In addition we report on which resistance mechanisms are likely to occur with each of the different types of conventional insecticides.

Resistance monitoring techniques and restricted insecticide use strategies have become major components of successful resistance management programs.  New strategies involving use of Bacillus thuringiensis and other less toxic chemicals as pest management agents are being developed.  Future successful pest management programs may involve primary reliance on Bacillus thuringiensis as an insect growth regulator with conventional insecticides as important, but secondary components.

Conclusions

  1. The development of restricted insecticide use strategies in conjunction with resistance monitoring has greatly extended the useful life of pyrethroid insecticides in cotton production.
  2. Occasional failures in the strategy might have resulted from the use of highly toxic pure isomer pyrethroids in place of mixed isomer pyrethroids rather than from inadequacies in the strategy.
  3. A strategy based on the use of a low dose mixture of insecticides may be an effective way to continue insecticide use and lessen selection for resistance.
  4. Alternate strategies based on the use of noninsecticidal controls such as Bacillus thuringiensis, juvenile hormone analogs and crop oils may significantly reduce the need to control cotton insect pests with insecticides in the future.
  5. The cotton ecosystem normally contains beneficial insect predators and parasites in numbers that frequently provide partial to satisfactory pest control. The use of soft strategies which maximize the effectiveness of beneficials seems to be the most effective way to manage insect pest populations in cotton.

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FIPRONIL: A NEW SOIL AND FOLIAR INSECTICIDE FOR COTTON

Abstract                                                                         Back to Table of contents

Fipronil [(+)-5-amino-1-(2,6-dichloro-a,a,a-trifluoro-p-toly)-4-tri-fluoromethylsulfinylpyrazole-3-carbonitrile] is a new pyrazole insecticide that provides excellent control of many foliar insects on cotton.  Fipronil at 100 g a.i./ha applied in-furrow at planting to the soil effectively controls thrips, Frankliniella spp.  Fipronil applied at 50-65 g a.i./ha to foliage controls boll weevil, Anthonomus grandis grandis.

Conclusions

Field trials conducted between 1989 and 1993 demonstrated that fipronil is very effective at low use rates on economically important cotton pests:  thrips and boll weevil.  Fipronil, a phenyl pyrazole, represents a new class of chemistry, with a unique mode of action.  The product can effectively control thrips as a preventive spray applied in-furrow or as a curative treatment applied as a foliar spray for thrips and boll weevil.  Fipronil use to control the above mentioned insects during early season would slow insecticide resistance development to the organophosphate class of insecticides, which have been the primary products used as foliar sprays to control early season insect pests.

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CHEMICAL CHARACTERIZATION OF COTTON INSECT HONEYDEW AND ELIMINATION OF STICKINESS OF HONEYDEW-CONTAMINATED LINT

Abstract                                                                         Back to Table of contents

Cotton fiber stickiness due to honeydew from insect infestations is a severe problem in many cotton producing countries.  In the southwest United States, honeydew secreted by the sweetpotato whitefly (Bemisia tabaci Gennadius) or cotton aphid (Aphis gossypii Glover) onto cotton fiber is a major detriment to lint quality and marketability.  These honeydews have been analyzed by gradient anion high performance liquid chromatography and found to consist of at least 30 different sugars, some of which have quite unusual structures.  Results of enzymic digestion studies indicate that many of these sugars in B. tabaci  honeydew consist entirely of  a-D-glucose and contain both the trehalose moiety [a-D-glc(1´1)a-D-glc] and the maltose moiety  [a-D-glc(1Æ4)a-D-glc] in their structure. From a knowledge of the chemical composition of this sugar mixture, an enzyme preparation was identified which, when sprayed in an aqueous solution on honeydew-contaminated seedcotton, significantly reduced the stickiness of the resulting lint as measured by either the minicard or the thermodetector tests.

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AREA–WIDE MANAGEMENT OF HELIOTHIS/HELICOVERPA IN THE DELTA OF MISSISSIPPI

Abstract                                                                         Back to Table of contents

Utilizing an entomopathogenic virus on alternate hosts as the main pre–crop treatment, a pilot test was conducted in 1990 and 1992 to manage Heliothis virescens (F.) and Helicoverpa zea (Boddie) in cotton in a 259 square kilometer area in the Mississippi Delta.  The results of these two programs are reviewed.  In addition, this program will be expanded in 1994 to a 1,036 square kilometer area.  In-season control measures in cotton within the treated area will also be evaluated for additive effects.  These include the use of transgenic cotton, nectariless cotton, release of parasites, and pre–square treatments with Bacillus thuringiensis, virus, and/or entomopathogenic nematodes.  This program is designed to reduce pesticide output and aid in resistance management while maintaining grower profitability.

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IMPACT OF BOLL WEEVIL ERADICATION ON COTTON PRODUCTION AND INSECT MANAGEMENT IN VIRGINIA AND NORTH CAROLINA, USA

Abstract                                                                         Back to Table of contents

A boll weevil (Anthonomus grandis [Boheman]) eradication program was begun in September 1978 as an approximately 6,000 ha upland cotton (Gossypium hirsutum L.) trial in the northeast counties of North Carolina (NC) and the southeast corner of Virginia (VA), the northeastern-most cotton growing area of the US and was subsequently expanded in 1983 to include the remainder of NC and all of South Carolina (SC) (48,900 ha total).  Primarily due to the elimination of the boll weevil, foliar insecticide use in NC has dropped from a mean of 10.2 applications ha-1 of primarily organophosphate insecticides employed at rates varying from 0.56 to 3.4 kg a.i. ha-1 for the five year period preceding 1978, compared with the post-eradication (1979-1993) mean use of 2.6 applications of mostly pyrethroids at rates varying from 0.02 to 0.067 kg a.i. ha-1.  Planted cotton acreage in NC has increased from an all-time low of 18,200 ha in 1978 to a high of 188,000 ha in 1991.  Employing a linear yield model based upon 20 years of data from 19 NC counties, a yield increase of 77 kg ha-1 resulted from eradication, in addition to a 71% drop in total insect control costs (compared with a 39% drop outside the eradication area) and a greater return on investment to land which was converted from less profitable crops such as corn and soybean to cotton because of reduced costs achieved by the eradication.  Despite the finding of occasional, passively-transported boll weevils into the “weevil free” area (two weevils were found in 1993, one in 1992 and none in 1991 in approximately 200,000 total Grandlure®-baited traps) and an elevation in the pest status of the European corn borer (Ostrinia nubilalis [Hübner]) and the green stink bug (Acrosternum hilare [Say]) in the weevil-free area, the subsequent elimination of these transported localized weevils and the greater ease of managing the bollworm/tobacco budworm complex Helicoverpa zea (Boddie) and Heliothis virescens (F.), respectively, and other pests, such as the cotton aphid, Aphis gossypii Glover, has allowed the development and deployment of an inexpensive, biocontrol-oriented, threshold-based, pest-specific system of managing cotton insects unique to the Southwest and the mid-South.

Conclusion

Fifteen years of post-eradication research, survey information and grower experience in NC suggest that the benefits of eliminating the boll weevil from the cotton ecosystem and the present ease of tobacco budworm and cotton bollworm control far greatly outweigh the negative impact of species which have been elevated in status following eradication, such as the European corn borer and the green stink bug.  Without the disruptive treatments once required to control boll weevils, NC’s cotton producers can now manage cotton insects relying largely upon:-

  • a minimal 2.75 foliar applications per year for all insects (except the at-planting treatment)
  • naturally occurring predators and parasites for early season aphid and tobacco budworm control
  • avoidance of late “cutout” to shorten the late season protection window by avoidance of organophate insecticides
  • pathogenic fungi to reduce or eliminate aphids in opening cotton.

If the Boll Weevil Eradication Program continues to expand, the relative contributions of boll weevil eradication in other cotton production regions will likely vary and await quantification.  However, the dynamics of insect-related changes in the various regional cotton agroecosystems induced by the elimination of the boll weevil and its requirement of organophosphate insecticides for control in many situations likely will be positive and place a greater premium on beneficial arthropods and less reliance upon insecticides.

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PYMETROZINE (CGA 215,944) – A NOVEL NEW CONTROL FOR SUCKING PESTS IN COTTON

Abstract                                                                         Back to Table of contents

Pymetrozine is a novel insecticide for the control of aphids and other sucking pests in cotton and represents a new class of control agents.  The compound interferes in the feeding behaviour of insects and controls insects resistant to standard chemistry.  Because of its unique mode of action, pymetrozine does not harm beneficial insects and is very useful in Integrated Pest Management (IPM) programs.  The compound exhibits low acute toxicity to mammals and has favourable environmental properties.  Use rates are 100-300 g a.i./ha.  Full development is underway around the world.

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