Secondary Pest Outbreaks Research Articles

Nontarget Impact of Spinosad GF-120 Bait Sprays for Control of the Mexican Fruit Fly (Diptera: Tephritidae) in Texas Citrus

Bait sprays containing the toxicant spinosad (GF-120) were applied to citrus groves in the Rio Grande Valley of Texas where Mexican fruit flies were detected in surveillance traps. The sprays were applied as a supplement to a continuous sterile insect release program. Sterile fly captures were 47-63% lower in the treated groves compared with control groves. Eight of 10 secondary pest populations declined in the test groves subsequent to spray applications, but they also declined in the control groves, suggesting that the decline was a seasonal phenomenon rather than a result of the bait sprays. Citrus whitefly, Dialeurodes citri (Ashmead), populations increased modestly and citrus blackfly, Aleurocanthus woglumi (Ashby), populations remained unchanged compared with pretreatment levels. Thus, no outbreaks of secondary pests occurred as a result of the spinosad bait sprays in this instance, as has been reported for malathion bait sprays in citrus. The bait sprays had no detectable effect on populations of specific indicator species of parasitoids (including Aphytis spp. and Comperiella bifasciata Howard), or on numbers of beneficial insects in general, in the treated groves.

Tritrophic Effects in Bt Cotton

Transgenic insecticidal Bt crops are being increasingly used worldwide, and concern is increasing about resistance and their effects on nontarget organisms. The toxin acts as a weak pesticide and, hence, the effects are subtler than those of chemical biocides. However, the toxin is ever present, but concentrations vary with age of plant and plant subunit, causing varying lethal and sublethal effects on pest survival, developmental time, and fecundity. Refuges for susceptibility to Bt occur spatially in non-Bt hosts and temporally within the crop because of time-varying toxicity and pest tolerance. Natural enemies feeding on Bt-intoxicated prey may have reduced longevity and, likely, fecundity that reduces their efficacy in controlling pest populations, and pest resurgence and secondary pest outbreaks may occur that may require insecticide use. System modeling is proposed as an efficient tool for examining the use of extant and future biotechnologies in pest control.

TOXICITY OF BACILLUS THURINGIENSIS CRY1-TYPE INSECTICIDAL TOXIN TO GEOGRAPHICALLY DISTANT POPULATIONS OF TOMATO PINWORM

The tomato pinworm (TPW), Keiferia lycopersicella (Walsingham), is an important pest of tomato in southern California (Oatman 1970), Texas (Wellik et al. 1979) and Florida (Poe 1974). In Florida this insect pest increases to tremendous numbers late in the tomato season (namely in spring) when the plants mature. In a number of instances, dense populations (2 to 10 larvae/leaf) have resulted in large scale death of the plants, despite frequent insecticide applications (D.R.S, field observation). Currently growers use chemical insecticides to manage TPW in commercial fields; but the degree of control is not satisfactory in large measure because of the deficiencies in the current spray programs and detection method. The use of broadspectrum insecticides for TPW control may induce development of resistance, or induce outbreaks of secondary pests (Smith 1970; Brown & Pal 1971). Cultural practices such as burning of crop residues, crop rotations, manipulation of planting dates, etc. helped suppress the TPW population (Elmore & Howard 1943; Poe 1974). However, insecticides are the only tool for pest management that is reliable for emergency action when insect pest populations approach or exceed the economic threshold (Metcalf 1975). Therefore, efforts are needed to evaluate less detrimental insecticides for control of TPW. Bacillus thuringiensis has become an effective insecticide in the management of various insect pests (Burgerjon & Martouret 1971); however, resistance to B. thuringiensis toxin has been documented through laboratory studies in 12 species of Lepidoptera, 2 species of Coleoptera and 5 species of Diptera (Tabashnik 1994). When compared to the response of a fully susceptible strain the level of resistance observed in most instances did not exceed 50to 100-fold. For coping with resistance to B. thuringiensis protein toxins, it will be very important to determine the level of resistance that a given population can develop, and the cross-resistance spectrum of this resistance. Considerably more information of benefit to management would be obtained if the mode of inheritance of the resistance could also be determined. The overall objective of the present study was to characterize the toxicity of a selected B. thuringiensis toxin to a number of geographically diverse populations of the TPW. Insects. The study was conducted in a private quarantine facility at Labelle, Florida. Mixed instars of TPW were collected from tomato over a period of time from 4 locations in Florida (Tropical Research and Education Center, Homestead; commercial field, Homestead; BHN Laboratories Naples; commercial field, Naples); three commercial locations in California (Cameron, Hurron, California-South) and three commercial locations in Sinaloa, Mexico (2 locations at Guasava on two dates, and LaPalma). TPW larvae from each location were shipped to Labelle in strict accordance with quarantine procedures. All shipments were secured in the quarantine facility to separate the live TPW larvae. A colony from each geographic population was established on 'Flora-Dade' tomato transplants within the quarantine facility in a separate room to prevent any intermixing. The escape of live insects was prevented by not handling any insects outside the quarantine facility. Each colony was maintained for 2 generations prior to use in the bioassay study. Sufficient numbers of the required developmental stage of TPW were collected from the cultures to run bioassays using the selected B. thuringiensis toxin. At the end of each bioassay all live specimens were destroyed by heating in an autoclave. Bacillus thuringiensis toxins. Sufficient amount of selected toxin of B. thuringiensis var. kurstaki (Cry 1, Monsanto) was supplied by BHN Research, Bonita Springs, Florida. The toxin was stored in a refrigerator at 6?C at Tropical Research and Education Center, Homestead, Florida for future use. Bioassay procedure. A leaf-dip bioassay was conducted in the laboratory. Five concentrations of the selected B. thuringiensis toxin (0, 6.25, 12.50, 25.00, 50.00 and 100.00 ,ug/ml of water) were prepared in 0.02% Tween 20 (Sigma St. Louis, MO). The concentrations of B. thuringiensis protein were prepared following a serial dilution method, where a factor of 0.5 was used in each dilution step. Each concentration was made up to a total volume of 20 ml in a test tube. Freshly cut tomato leaflets (eight leaflets/concentration) were immersed in each suspension for one minute. The leaves were removed and air dried. To avoid leaf desiccation, the petiole of each leaf was wrapped with moist cotton, which was kept moist by adding a drop of distilled water daily.

Managing the pepper maggot (Diptera: Tephritidae) using perimeter trap cropping.

A perimeter trap crop barrier of hot cherry peppers, border-row insecticide applications, and a combination of the two management strategies were evaluated to see if they could protect a centrally located main crop of bell peppers from oviposition and infestation by the pepper maggot, Zonosemata electa (Say). In large plots, the main cash crop of bell peppers was protected from the majority of the oviposition and infestation by all three barriers. The combination sprayed/trap crop barrier provided the best protection against both oviposition and infestation and resulted in over 98% pest-free fruit at harvest. Maggots infested only 1.7% of the main crop fruit when protected by a sprayed or unsprayed trap crop barrier, compared with 15.4% in control plots. The perimeter sprayed/trap crop strategy was employed in three commercial fields in 2000 and 2001. The combination barrier resulted in superior insect control and reduced insecticide use at all commercial locations, compared with the same farms' past history or to farms using conventional and integrated pest management (IPM) methods. Economic analysis showed that the technique is more cost effective and profitable than relying on whole-field insecticide applications to control the pepper maggot. Farmer users were surveyed and found the perimeter trap crop technique simple to use, with many hard-to-measure benefits associated with worker protection issues, marketing, personnel/management relations, pest control and the environment. Use of the perimeter trap crop technique as part of an IPM or organic program can help improve crop quality and overall farm profitability, while reducing pesticide use and the possibility of secondary pest outbreaks.

Insect pest management in African agriculture: Challenges in the current millenium

Pest management on a global scale experienced a total revolution after World War II when synthetic organic compounds were in agriculture and public health. However, it soon became apparent that there were many limitations in the use of chemicals for pest management. In agriculture, problems of pest resurgence, secondary pest outbreaks, pest resistance and adverse effects of pesticides on the environment, including human poisoning and toxicity to other non-target organisms, led to the search for alternative approaches to the pest outbreak problem. The 1960s produced new ideas on integrated pest management (IPM) strategies, followed by intensification of the search for biological control agents, which could be incorporated into IPM programmes. New application technologies were developed in the 1970s and 1980s and ecological approaches to the pest problem were spearheaded in the developed world in the 1990s, with extensive studies focused on the whole ecosystem. Important advances in crop production have also taken place in Africa in this century, involving adoption of high yielding varieties, fertilizer application, intensification of crop protection approaches, less shifting cultivation and more mono-cropping systems. However, these advances have led to increasing pest problems which unless tackled imaginatively and intelligently, they could become the most important constraint in crop production in the present millennium. Africa has entered the current millennium with relatively underdeveloped agriculture on a global scale and little investment in research on new pest management technologies that could be used to reduce crop losses. We are still highly dependent on pesticides for pest management. Therefore, the greatest challenges in agriculture in Africa will be the switch from a pesticide based mode of reducing losses due to pests to one that is ecosystem based, making use of insect management techniques which are ecologically and economically sound. Specifically, some of the major challenges in pest management in agriculture in Africa include; (i) reducing the dependence on pesticides, thus avoiding the limitations observed in the past 50 years; (ii) overcoming ignorance of the pest species and their associated community of parasites and predators which has dire consequences on the whole ecosystem; (iii) keeping out exotic pests, which in this millennium have had a devastating blow on the production of some crops and (iv) developing indigenous technologies for pest management (IPM, biocontrol, etc.) and making available to farmers materials for pest management which are affordable, safe, effective and environmentally friendly (e.g. microbial, botanicals, pheromones, genetically engineered products etc.). Both legislative and quarantine measures will have a significant role to play in pest management in the next millennium, but only when practised on a wider geographical area. Information technology (IT) will affect the way we acquire and make use of pest management strategies. Africa is therefore faced with the challenge of building up and improving its infrastructure and expertise on IT if it is to benefit pest management on the continent.

Agricultural implications of pesticide-induced hormesis of insects and mites.

Resurgence of pest insects and mites and secondary pest outbreaks are commonly observed following pesticide applications on agricultural commodities. Reduction of natural enemy populations is the major factor blamed for these phenomena but insect or mite hormesis is a second, often overlooked factor which may be partially responsible. A major impact of hormesis is that it often leads to the need for additional pesticide treatments and can result in a spiralling increase in the use of pesticides, a term labelled in entomological literature as the 'pesticide syndrome'.

Susceptibility of Predaceous Hemipteran Species to Selected Insecticides on Soybean in Louisiana

Toxicity of selected insecticides to hemipteran predators [i.e., Geocoris punctipes (Say), Nabis capsifonnis Germar, Nabis roseipennis Reuter, and Podisus maculiventris (Say)] was evaluated by contact with foliar residues and indirectly through the consumption of prey [i.e. soybean looper, Pseudoplusia include118 (Walker)] previously exposed to insecticides. Methyl parathion and permethrin generally were more toxic than newer insecticides after predators were exposed to treated foliage. Chlorfenapyr caused contact toxicity equal to permethrin and methyl parathion. Exposure to foliage treated with emamectin benzoate resulted in lower mortality as compared with chlorfenapyr. Foliage treated with Bacillus thuringiensis Berliner subsp. kurstaki had the lowest contact toxicity to hemipteran predators of all insecticides tested. Standard insecticides (i.e., methyl parathion and thiodicarb) caused low indirect toxicity to hemipteran predators after consumption of treated prey. Chlorfenapyr caused significantly greater indirect toxicity than emamectin benzoate, permethrin, and thiodicarb to adult N. roseipennis. Consumption of chlorfenapyr-treated prey also caused significantly greater mortality than imidacloprid, permethrin, spinosad, and thiodicarb to G. punctipes adults. These results demonstrate that most of the newer compounds were more selective than older insecticides. This greater selectivity will enable soybean producers to combat pests but conserve resident beneficial arthropod populations that help restrain pest resurgence and prevent secondary pest outbreaks.

Seeking the root of insect resistance to transgenic plants.

Bt was first formally described from Thuringia, Germany, in 1911 and has been available in commercial formulations for insect control since the 1930s (3); yet until recently, it remained a minor component of pest management. Three factors set the stage for the emerging importance of Bt: evolution of resistance to insecticides in more than 500 species of insects and mites (4), rising concerns about environmental hazards of conventional insecticides, and breakthroughs in biotechnology. Genetic engineering has created transgenic varieties of many crops that express Bt toxins; such cultivars of transgenic corn, cotton, and potatoes were grown on a large scale in the United States for the first time during 1996. Transgenic plants armed with Bt toxins are defended against some of the most notorious pests, which reduces the need for insecticidal sprays. Because Bt is not toxic to arthropod natural enemies, opportunities for biological control are enhanced and the secondary pest outbreaks often caused by conventional insecticides are avoided. Thus, this new technology could yield enormous benefits for food production and environmental quality worldwide. Will the advent of Bt-expressing transgenic plants herald a new era of environmentally benign insect control? Or will the pests quickly adapt?

Evaluation of Color Sticky Panels for Monitoring Megastigmus spermotrophus (Hyntenoptera: Toryntidae)

Four colors and 3 types of colored sticky panels were tested for effectiveness in monitoring adults of Megastigmus spennotrophus Wachtl. Panels (gold Rebell) were used to catch chalcids in 44 seed orchard blocks over a 4-yr period. Although the relationship between number of M. spermotrophus captured and subsequent seed damage was weak, a threshold of a cumulative average of 1 female per panel (until 10 d after cone pendency) accurately predicted damage in 89% of the cases. This monitoring system could be used as part of a decision process that includes other factors such as cone crop size, tree phenology, seed value, and the likelihood of a secondary pest outbreak.

Integrated citrus thrips control reduces secondary pests

Citrus growers are very concerned about scarring of the rind caused by early-season pests such as citrus thrips, katydid and various Lepidopterous larvae because heavily scarred fruit is downgraded in the packing house. Citrus growers who use a broad-spectrum pesticide program for early-season pests experience problems with pest resurgence and pesticide resistance, but generally have low levels of fruit scarring. Growers who use both selective pesticides and natural enemies have fewer secondary pest outbreaks of citrus red mite, but don't always effectively control citrus thrips scarring.

The role of biodiversity in the dynamics and management of insect pests of tropical irrigated rice—a review

AbstractBiodiversity relevant to pest management of tropical irrigated rice pests is discussed in terms of variation within rice plants, rice fields, groups of rice fields and rice associated ecosystems. It is concluded that, in the unique cropping conditions and stable water supply of tropical irrigated rice, the manipulation of a relatively few manageable components of diversity can confer stability such that pests are mostly kept at levels which do not justify the use of insecticides. Durable rice plant resistance, including moderate resistance, together with ability to compensate for damage by certain key pests, are regarded as fundamental to successful biological control by the natural enemy complex. Reliable natural enemy action is also considered to depend on all-year-round continuity of prey or hosts made possible by the relatively short fallow periods between staggered two to three rice crops per year and by proximity of certain non-rice habitats, notably the vegetation-covered bunds (levées) surrounding each field. In contrast, synchronous cropping could upset stability by destroying the continuity needed for natural enemy success. Such conclusions are supported by the experience of farmers who use little or no insecticide. Much evidence on destruction of natural enemies by certain insecticides supports the contention that insecticide use, especially early in the crop season, upsets natural enemy control of insects such as Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) and also creates heavy selection pressure for strains of pests that can overcome previously resistant rice cultivars. Such circumstances create outbreaks of secondary pests and impair biological control of some key primary pests such as stem borers. It is concluded that pest management of much tropical irrigated rice must be based on natural controls rarely supplemented by insecticides. The success of this approach depends in particular on further research on dynamics of natural enemy and pest communities in rice ecosystems, especially where climatic conditions and water supply are marginally stable. Much more needs to be known about the nature and utilization of rice plant compensation for damage, particularly by defoliators and stem borers. The justification for, and supplementary use of, insecticides needs to be radically reassessed. There is no evidence that a natural control-based approach, as recommended in this review, is incompat ible with farmer practicability or with future developments in rice production technology, except perhaps the possible mechanization-driven increase in field size which would decrease bund area. In contrast, the insecticide-based approach is not only harmful to natural controls but is costly and mostly demands impracticable decision making by farmers on need-based use.

Integrated pest management in Swiss apple orchards: Stability and risks

AbstractIn recent years, a system of Integrated Pest Management (IPM) has been introduced in many Swiss apple orchards. It is based on monitoring pests and natural enemies, on a package of selective pesticides and on biological control of phytophagous mites by typhlodromids. Some natural control has also been introduced for aphids and leafrollers. Stability of this approach is offered by natural control and by monitoring. Risks exist in two fields: Selective pesticides may disappear due to resistance and to other undesirable side effects. Outbreaks of secondary pests occur and will continue to do so in the future. In the past few years populations of scale insects and of Grapholita prunivorana (Rag.) have built up to damaging levels in some regions.

The ecological basis of boll weevil ( Anthonomus grandis Boheman) management

The boll weevil ( Anthonomus grandis Boheman), generally considered to be native to Mexico or Central America, spread into the southern United States of America in the late 1800s and seriously threatened the cotton industry. As there were no effective alternatives, pest control specialists studied the insect's ecology and advocated cultural practices that would disrupt its environment and maximize the benefits of natural biological and environmental controls. An ecologically orientated pest management scheme founded on cultural practices emerged well before suitable chemical control technology became available and allowed farmers to live with the weevil problem. Despite the ingenuity of the early management scheme, it frequently did not provide satisfactory boll weevil control gauged by present standards. Control of the pest thus shifted largely from an ecological to a chemical approach as effective synthetic organic insecticides became available after World War II. The chemical approach was successful for a number of years, but problems of insecticide-resistant strains of pests, secondary pest outbreaks, environmental quality, and increased costs of the insecticides have forced pest control specialists to re-emphasize the nonchemical techniques used widely against the boll weevil before World War II and to revive the ecological approach to weevil management. This article examines boll weevil ecology as related to management of the insect and reviews the status and prospects of ecologically-based weevil management techniques in the United States.

The boll weevil in North America: Scientific conflicts over management of environmental resources

This paper is a historical and philosphical reconstruction of how U.S. entomologists attempted to mitigate the depradations of the boll weevil on cotton, the world's most important natural fiber. The boll weevil caused severe losses in the U.S. after 1892. Early control methods were based on altering the cultural practices of cotton growers. The discovery in 1917 that calcium arsenate was an effective insecticide for boll weevils eventually allowed some farmers to rely on chemical control. Development of synthetic, organic insecticides allowed many U.S. growers after 1945 to rely heavily on insecticides for boll weevils. By the 1960s, resistance of boll weevils to insecticides, induction of secondary pest outbreaks, and environmental health hazards threatened cotton production practices based on insecticides. U.S. entomologists devised two new strategies to rescue cotton production from its insecticide crisis: integrated pest management (IPM) and total population management (TPM). Eradication of key insect pests such as boll weevils was envisaged by TPM entomologists with adequate technology. E.F. Knipling, the USDA entomologist who designed TPM, gave 1968 as a target for possible boll weevil eradication. The pilot boll weevil eradication experiment (PBWEE) was conducted in 1971–1973. IPM entomologists argued the futility of attempting to eradicate the boll weevil from the U.S.A., but TPM adherents argued for a second test, which was held in Virginia, North Carolina and South Carolina (1978–1980). A new controversy erupted over how to interpret the fact that a few boll weevils were found at the end of the second test. IPM and TPM entomologists were once again pitted against one another on three major issues: defining eradication; explaining secondary pest behavior; and drawing conclusions about the wisdom of a national boll weevil eradication program. Currently, entomologists have reached a stalemate over boll weevil eradication in the U.S. Some entomologists are attempting to synthesize opposing views in the hope of reaching a professional consensus on appropriate boll weevil suppression methods. Significant distinctions separate IPM and TPM and will make it difficult to achieve an agreement. Budgetary problems in the U.S.A. argue for a management rather than eradication stance against boll weevils. The split in the U.S. entomological profession could have adverse effects on efforts to develop insect-control science outside of the U.S.

Expected Benefits from Nonchemical Methods of Alfalfa Weevil Control

The problem of managing insect pests has been receiving increased interest as a part of the technological revolution that has dramatically increased agricultural output.' During the past few decades, several biological and cultural methods of pest control have been conceived and/or implemented, e.g., DeBach, Huffaker (1971, 1980), Huffaker and Messenger, Metcalf and Luckmann, Reichelderfer and Bender. However, contemporary technology has analyzed and relied heavily on the use of synthetic chemical pesticides (Hall and Norgaard; Regev Gutierrez, Feder; Talpaz and Borosh; Talpaz et al.). The preference for chemical control is derived, in most cases, from its achievement of satisfactory control at relatively low costs. However, the intensive, as well as extensive, uses of synthetic organic pesticides, in particular a few persistant insecticides such as DDT and BHC, have had detrimental effects on the quality of the environment. Prolific use of chemical pesticides develops genetic pest resistance, changes pest complexes by affecting nontarget populations and allowing outbreaks of secondary pests, and affects the ecosystem with its residues in feeds, foods, and organisms (Shoemaker). Policymakers have reflected the concern of society for environmental contamination by legislation restricting pesticides, suggesting that future pest control cannot solely depend upon routine applications of insecticides. This note investigates the potential gains that may be derived from the use of biological means of control as well as the introduction of a host plant with added resistance (antibiosis) against the alfalfa weevil (Hypera postica). This insect contitutes one of the more important insect pests of alfalfa and can cause large losses in yield or even death of the crop if uncontrolled (Armbrust and Gyrisco). Model Description and Procedure

An Evaluation of Some Natural Enemies of Cabbage Looper 1 on Cotton in California 3

A comparative life-table analysis of Trichoplusia ni (Hubner) populations on cotton in California revealed that, where predators were suppressed with properly timed applications of dimethoate insecticide, increases in larval survival of T. ni occurred. When the populations of predators were allowed to reach density levels comparable to those in the nontreated control, survival rates for T. ni larvae did not differ significantly between nontreated plots and previously treated plots. The results suggest that predators, particularly adults and nymphs of Orius tristicolor (White), Geoeoris pallens Stal, Nabis americoferus Carayon, and larvae of Chrysopa carnea Stephens, inflict a major intrageneration mortality on T. ni larvae on cotton, and that, when these natural enemies are suppressed, a secondary pest outbreak of T. ni can occur. Rates of parasitization and polyhedrosis of T. ni developmental stages were not, in general, adversely affected by the dimethoate sprays. A nuclear polyhedrosis virus and an egg-larval parasite, Copidosoma truncatellum (Dalman), appeared to cause mortality which was density related. Two apparently new parasite records for T. ni are recorded: Chelonus texanus Cresson and Patrocloides montanus (Cresson).

The integration of chemical and biological control of arthropod pests.

The desirability of integrating chemical and biological control of arthro­ pod pests is not a new idea in the field of applied entomology. Recurrently over the years, investigators have expressed a need for the preservation, augmentation, and utilization of entomophagous and entomogenous organ­ isms in overall pest control programs involving chemical control (14, 34, 63, 69, 70, 76, 77, 88, 109, 116, 117, 119). However, these were sporadic pleas and it was not until the last decade that the call for integrated control swelled to a chorus. Now, a band wagon of rather respectable proportions seems to have developed in support of this approach to arthropod pest con­ trol. As a point of illustration, in the most recent numbers of the Journal of Economic Entomology, a significant percentage of the articles have dealt with or alluded to integrated control. (Six of 51 papers in Volume 54, No.1.) The factors contributing to this trend seem directly related to the mani­ fold secondary problems associated with the extensive use of the new, widely toxic synthetic organic insecticides. Prior to the organic insecticide era, entomologists working with the arsenicals, botanicals, petroleum oils, lime sulfur, and the few other materials available to them, inadvertently effected large-scale integrated control. This came about because the methods of entry and chemical and physical characteristics of these materials limited their toxicity to a relatively small number of arthropods, and they did not have the disruptive effects to arthropod ecosystems that the new broad spectrum synthetic chemicals do. As a result, the problems of insecticide resistance, pest flarebacks, and secondary pest outbreaks that have come to plague the organic insecticides were not nearly as severe and general as they are today. Consequently, there was no great concern over, or even aware­ ness of the potential disruptiveness of insecticides to arthropod ecosystems. Thus, with little reason for apprehension other than matters related to mammalian toxicity, pollinator mortality, and possibly resistance, the organic insecticides were almost universally accepted as unmixed blessings. With rare exceptions, those persons associated with arthropod pest control crossed