Pest Management Decisions Research Articles

Fall Armyworm, Spodoptera frugiperda (J.E. Smith) Management Strategies: A Synopsis

Fall armyworm (Spodoptera frugiperda) is a polyphagous pest with a host range, native to North and South America. This pest was formally reported for the first in January 2016 in Africa and in May 2018 in India. On 9 May 2019, this pest was first noticed in Nawalpur Nepal. 20-35% losses have been reported in maize crops. Since the outbreak of this pest from Africa, entomologists are working for their strategic management. This review aims to compile the fall armyworm (FAW) management works carried in the world and discuss their relevancy in Nepalese context. Of the various practices, chemical pesticides are one of the most commonly used tools followed by habitat management and other cultural practices. Insect pheromones are used for pest monitoring, and thereby to improve pest management decisions. Trap cropping, cover cropping, intercropping, maintaining floral diversity are some examples of habitat pest manipulation. Push-pull strategy uses Napier crop as a ‘Pull’ component and Desmodium crop as a ‘Push’ crop. These agro-ecological strategies change the behavior of FAW and able to trap or manage them in a certain area or certain crop, where pest can be managed manually or using other non-insecticidal strategies. This review work will be useful for the academicians, extension workers and plant protectionist to design a sustainable FAW management protocol.

Historical trends of the ecotoxicological pesticide risk from the main grain crops in Rolling Pampa (Argentina).

We showed the results of the first long-term analysis (1987–2019) of pesticide (herbicides, fungicides and insecticides) impact in the Rolling Pampa, one of the main agricultural areas of Argentina. Using a clear and meaningful tool, based not only on acute toxicity but also on scaling up the results to total sown area, we identified time trends for both pesticide impact and the ecoefficiency of modal pesticide profiles. By the end of the time series, soybean showed a pesticide impact four times greater than maize crop in the studied area. However, the time trend in the subperiod (2012–2019) showed a sustainable pattern of pesticide use in soybean crop, with an improvement in its ecoefficiency. Oppositely, maize showed a relatively constant ecoefficiency value during most of the time series, suggesting a possible path towards an unsustainable cropping system. Findings from this study suggest that some efforts have to be made to improve the pest management decisions towards a more efficient pesticide profiles in maize crop and to keep improving the ecotoxicity pesticide profile in soybean crops because of its large sown area in the studied area.

Characterizing the Feeding Injury Caused by Phylloscelis rubra (Hemiptera: Dictyopharidae) to Cranberries.

Due to changes in pest management practices, farmers’ reports of severe feeding injury to cranberries, Vaccinium macrocarpon Aiton Ericales: Ericaceae, caused by the cranberry toad-bug, Phylloscelis rubra Ball, have increased in recent years in New Jersey (United States). Currently, however, limited information is available on the effects of P. rubra feeding or density of individuals needed to cause injury to cranberry vines and fruit. In 2015‒2017, we conducted studies to characterize injury to cranberry at a range of P. rubra densities by using cages in a screen-house and field, to establish a correlation between P. rubra density and crop injury in an open field experiment, and to measure the effects of P. rubra injury on the nutritional content (i.e., amounts of macro- and microelements) of cranberry vines. Phylloscelis rubra feeding on cranberry vines produced typical injury symptoms at relatively low densities (i.e., 2 individuals per vine in field cages or <10 individuals per sweep net sample in open fields), which included discolored (yellowish or reddish) or dead (brown) vines. This vine injury could lead to reductions in fruit mass and total fruit number. However, P. rubra injury to cranberry vines did not alter their nutritional composition. In general, this study highlights the ability of P. rubra to cause substantial injury to cranberry vines even when population densities were relatively low, which could result in declines in fruit production (quality and quantity). Therefore, infestations by P. rubra in cranberries must be considered when making pest management decisions in regions where this insect is present.

Distribution, Survival, and Development of Spotted Lanternfly on Host Plants Found in North America.

Studies were conducted from 2015 to 2018 to evaluate spotted lanternfly (SLF) distribution and developmental suitability of different plant species in the U.S. Tree bands on 283 trees spanning 33 species captured 21,006 SLF in 2 yr. More SLF per tree were trapped on tree-of-heaven Ailanthus altissima (Mill.) Swingle (Sapindales: Simaroubaceae) than on other species, on average, and most adults were captured on tree-of-heaven. Frequency of detection of adult SLF was higher on tree-of-heaven than on other species but was actually equal or lower on tree-of-heaven than on all other species combined for younger SLF stages in 2015. An enclosed choice test between tree-of-heaven and black walnut Juglans nigra L. (Fagales: Juglandaceae) revealed nymphs showed little consistent preference, whereas adults consistently and significantly preferred tree-of-heaven. No-choice field sleeve studies evaluated SLF survivorship on 26 host plant species in 17 families. Ten plant species supported SLF for an average of ≥45 d, with the rest unable to support SLF for >30 d. Eight species were able to support development from first instar to adult: black walnut, chinaberry Melia azedarach L. (Sapindales: Meliaceae), oriental bittersweet Celastrus orbiculatus Thunb. (Celastrales: Celastraceae), tree-of-heaven, hops Humulus lupulus L. (Rosales: Cannabaceae), sawtooth oak Quercus acutissima Carruthers (Fagales: Fagaceae), butternut Juglans cinerea L, and tulip tree Liriodendron tulipifiera L. (Magnoliales: Magnoliaceae). The ability of SLF to develop to adult on hosts other than tree-of-heaven may impact pest management decisions.

Sharpening the Precision of Pest Management Decisions: Assessing Variability Inherent in Catch Number and Absolute Density Estimates Derived from Pheromone-Baited Traps Monitoring Insects Moving Randomly.

During a trapping study interval, each target insect is either caught or not caught. Therefore, the current analysis treats trapping as a binomial process. Data from a binomial calculator, along with computer simulations of random walkers, documented that the inherent variance associated with estimates of absolute population density generated by a single catch number in a pheromone-baited monitoring trap becomes very high when catch probability averaged across the trap's sampling area falls below 0.02, as is the case for most insect trapping systems operating in the open field. The imprecision associated with interpretations of single catch numbers renders many current pest management decisions risky and unsatisfactory. Here we reinforce how single-trap, multiple-release experiments can and should be used to measure catch probability, plume reach, and trap sampling area. When catch probability lies in the danger zone below 0.02, steps are suggested for how multiple traps might be deployed to raise composite catch probability to a level where estimates of absolute pest density become reliable. Heat transfer is offered as an appropriate conceptual model for the mechanics of trapping. A call is made for a radical rethinking in the designs of insect monitoring traps in light of their significant current deficits highlighted by this study.

Effectiveness of varietal resistance and risk prediction for the control of ramularia leaf spot of barley under Irish growing conditions

Ramularia leaf spot (RLS) of barley, caused by the fungal pathogen Ramularia collo-cygni, is a significant threat to the viability of spring barley production in Ireland. As a relatively new disease of barley, limited information is available on the development and impact of the disease under Irish conditions. RLS symptoms often only develop after anthesis and the final fungicide application, therefore some decision support is required for growers to be able to make sound integrated pest management (IPM) decisions. In the present study field trials were conducted on spring barley in 2016–2018 to determine if environmental conditions during stem extension, specifically leaf wetness, could be used to aid decisions relating to the intensity of fungicide control required later in the season for the control of RLS. The trials were conducted on four spring barley varieties subjected to one of five fungicide treatments at awn emergence 1) untreated control 2) pyraclostrobin 3) prothioconazole and chlorothalonil 4) decreased/increased rates of prothioconazole and chlrothalonil depending on risk of RLS development and 5) exclusion of prothioconazole or addition of bixafen depending on risk of RLS development. In 2018, although moderate-high levels of disease were predicted, a prolonged dry period post-stem extension resulted in no disease development. In 2016, 2017 moderate levels of disease developed in the trials, with various significant (P < 0.05) interactions recorded between site, year, variety and fungicide treatment, depending on specific variable assessed: visual leaf symptoms, pathogen load in the leaf or grain as determined by qPCR or final grain yield. This was further evident in the relationships between visual symptoms and detectable R. collo-cygni biomass in the leaf with yield, these contrasted between seasons with weak relationships detected in 2016 (R2 = −0.019 and R2 = 0.176 for visual and biomass respectively) and strong relationships detected in 2017 (R2 = −0.748 and R2 = −0.5 for visual and biomass respectively). The variability in responses to the variety and fungicide treatments and the relationships between visual disease symptoms and biomass further highlight the unpredictability of RLS.

The value of insect management to US maize, soybean and cotton farmers.

Most US maize, soybean and cotton farmers use Bt crops, insecticidal seed treatments, soil-applied insecticides, and foliar sprays to manage insect pests. Given the global economic importance of these crops, we examine farmer benefits of this insecticide use. Using a telephone survey, we document pest management practices and concerns, estimate adoption and farmer perceived values for these practices, and determine factors besides yield and cost that impact adoption and perceived value. Seed-based technologies (Bt seed, seed treatments) dominated insecticide use. Almost 80% of respondents' planted hectares used Bt crops and more than half used seed treatments, while about one-sixth used soil insecticides and one-sixth to one-third used foliar insecticides. Perceived farmer values per treated hectare were greatest for Bt cotton and foliar insecticides in cotton, especially after first bloom. Values for maize and other cotton insecticide uses were greater than for soybean. Aggregating over treated areas, the largest total values for each crop were for seed-based technologies. In addition to yield and cost, farmers showed significant concern for economic risk and human and environmental safety when making pest management decisions. These non-monetary concerns significantly affected the likelihood farmers used these practices and their perceived value. For these crops, seed-based insecticides dominate farmer insecticide use and the value they derive from insecticides. Because seed purchase is months before planting, farmers rely on risk-based integrated pest management to make pest management decisions, weighing both monetary and non-monetary factors when deciding whether the risks are sufficient to justify the use of insecticides. © 2020 Society of Chemical Industry.

Physiological and behavioral interactions of a predator with its prey under indirect exposure to the insect growth regulator lufenuron

Growth regulating insecticides, such as lufenuron, are recommended for pest management due to their action on the ecdysis process and low toxicity to non-target species. However, these insecticides affect some non-target insects, such as Podisus nigrispinus Dallas, and can interfere with the control of lepidopteran pests by this predator. This study evaluated the impacts of indirect ingestion of lufenuron on the nutritional and histological characteristics of P. nigrispinus, as well as this predator's consumption rate, prey preference, and the weight and nutritional aspects of the prey, Alabama argillacea Hübner. Fourth and fifth instar P. nigrispinus nymphs preying upon A. argillacea larvae fed on cotton leaves that were either untreated or treated with lufenuron were evaluated. For the prey analysis, third instar A. argillacea larvae that had fed on cotton leaves treated or untreated with lufenuron were used. Exposure of P. nigrispinus to lufenuron resulted in a reduction in lipid, sugar, and glycogen contents in fourth instar nymphs; a greater number of treated than untreated prey was chosen by fourth instar nymphs, in a no-choice test; increased lipid content in fifth instar nymphs; histological alterations, such as cellular disorganization and desquamation, lysis of the epithelium; and decreased survival were observed in both evaluation instars. Prey preference was not affected. Lufenuron-treated A. argillacea larvae exhibited a reduction in glycogen content, while prey weight was not affected. These results provide an important resource for pest management decisions, since lufenuron induced biochemical and histological alterations in the midgut epithelium of P. nigrispinus, affecting its survival and possibly compromising its potential as a biological control agent.

Modelling the tri-trophic population dynamics of a host crop (Triticum aestivum; Poaceae), a major pest insect (Sitodiplosis mosellana; Diptera: Cecidomyiidae), and a parasitoid of the pest species (Macroglenes penetrans; Hymenoptera: Pteromalidae): a cohort-based approach incorporating the effects of weather

AbstractThis paper describes a tri-trophic analysis of the ecological dynamics of a crop, an insect pest, and a natural enemy of the insect pest. Worldwide wheat (Triticum Linnaeus) (Poaceae) production in 2018–2019 was estimated at over 700 million metric tons in 2018–2019. Wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), a serious insect pest of wheat, is widely distributed in many parts of the world where wheat production occurs. Macroglenes penetrans (Kirby) (Hymenoptera: Pteromalidae), a parasitoid of S. mosellana, has successfully established in most wheat midge-infested areas. Mechanistic, or process-based, population models were used in this study to assess the interactive population dynamics of the three species, based on their respective life cycles and meteorological factors. The models were validated with survey data from multiple sites over numerous years (1991–2016). These simulation models helped to detail our understanding of the tri-trophic population dynamics and will help guide pest management decisions both prior to the growing season and until wheat heading, when wheat is no longer susceptible to S. mosellana. The associated models also help identify gaps in system knowledge, provide a foundation for evaluating future innovative management options, and evaluate the potential impact of a changing climate.

Assessing the Potential Distribution of Asian Gypsy Moth in Canada: A Comparison of Two Methodological Approaches

Gypsy moth (Lymantria dispar L.) is one of the world’s worst hardwood defoliating invasive alien species. It is currently spreading across North America, damaging forest ecosystems and posing a significant economic threat. Two subspecies L. d. asiatica and L. d. japonica, collectively referred to as Asian gypsy moth (AGM) are of special concern as they have traits that make them better invaders than their European counterpart (e.g. flight capability of females). We assessed the potential distribution of AGM in Canada using two presence-only species distribution models, Maximum Entropy (MaxEnt) and Genetic Algorithm for Rule-set Prediction (GARP). In addition, we mapped AGM potential future distribution under two climate change scenarios (A1B and A2) while implementing dispersal constraints using the cellular automation model MigClim. MaxEnt had higher AUC, pAUC and sensitivity scores (0.82/1.40/1.00) when compared to GARP (0.70/1.26/0.9), indicating better discrimination of suitable versus unsuitable areas for AGM. The models indicated that suitable conditions for AGM were present in the provinces of British Columbia, Ontario, Quebec, Nova Scotia and New Brunswick. The human influence index was the variable found to contribute the most in predicting the distribution of AGM. These model results can be used to identify areas at risk for this pest, to inform strategic and tactical pest management decisions.

Neonicotinoids in global agriculture: evidence for a new pesticide treadmill?

Bakker, L., W. Van der Werf, P. Tittonell, K. A. G. Wyckhuys, and F. J. J. A. Bianchi. 2020. Neonicotinoids in global agriculture: evidence for a new pesticide treadmill? Ecology and Society 25(3):26. https://doi.org/10.5751/ES-11814-250326

The Economic Challenges of Dealing with Citrus Greening: The Case of Florida

Abstract While pest management decisions are made at the farm level, a distinctive characteristic of the pest management of invasive species is its public-good nature. Here, we examine the challenges that a vector-disease pathosystem such as Diaphorina citri Kuwayama (Hemiptera: Liviidae)—citrus greening, creates for the adoption of prevention and collective management practices from an economic perspective. Those economic challenges originate from the choices and behavior of individual growers, which can impact not only their own payoff but also the choices, behavior and payoffs of other growers; influencing, for example, the spread of the disease, the vector population dynamics, and the adoption of proposed scientific solutions. While for most people the economics of invasive species is limited to calculating damage or control costs, economics is more than that. Economics can provide insights on the interactions between human behavior and natural processes, enabling a better understanding of the rationale of individual growers’ choices, which are key for the design and implementation of effective public policies to deal with invasive pests and diseases.

Seasonal Occurrence of Potato Psyllid (Bactericera Cockerelli) and Risk of Zebra Chip Pathogen (Candidatus Liberibacter Solanacearum) in Northwestern New Mexico.

Potato psyllid (Bactericera cockerelli) is one of the most important pests in potatoes (Solanum tuberosum L.) due to its feeding behavior and the transmission of a bacterium (Candidatus Liberibacter solanacearum) that causes zebra chip disease, altering the quality of the potato tuber and the fried potato chip or french fry. This pest is thus a threat to the chip potato industry and often requires preventive measures including the use of costly insecticides. The objectives of this research were to monitor the variation in B. cockerelli adult abundance and to evaluate the risk of zebra chip disease in northwestern New Mexico, USA. Yellow sticky traps were used to collect the pest at the Agricultural Experiment Station at Farmington, NM and in nearby commercial fields at the Navajo Agricultural Products Industry (NAPI) and Navajo Mesa Farms during the 2017–2019 period. The collected adult pests were analyzed at Texas A & M University for the presence of Candidatus L. solanacearum (Lso). The results showed field infestation by B. cockerelli in early June and that the population peaked during the second half of July and decreased as the potato growing season progressed. However, a second less important peak of the pest was revealed around mid- to late-August, depending on the growing season and field. While the B. cockerelli population increased linearly with average air temperature, it showed strong third order polynomial relationships with the accumulated thermal units and the Julian days. The test of B. cockerelli for the Lso infection revealed a low incidence of the pathogen varying from 0.22% to 6.25% and the infected adult B. cockerelli were collected during the population peak period. The results of this study may be helpful to potato growers in pest management decision-making and control. However, more study is needed to evaluate zebra chip disease in terms of its prevention and economic impact, and to develop economic thresholds and pest management programs for northwestern New Mexico and neighboring regions.

How much is too much? Quantifying pesticide overuse in vegetable production in Southeast Asia

This paper quantifies the extent of pesticide overuse in vegetable production systems in Southeast Asia. Pesticide overuse was defined as levels of use in excess of an economic (profit-maximizing) optimum. A production function with an exponential damage abatement term was estimated. Data come from a representative sample of 1000 farmers producing leaf mustard and yard-long bean in Cambodia, Laos and Vietnam. The results show that 100% of the sampled farmers in Vietnam, 73% in Cambodia and 59% in Laos overused pesticides. Pesticide expenditure in excess of the economic optimum was 96% for Vietnam, 92% for Cambodia, and 42% for Laos. Pesticide overuse was positively associated with men in charge of pest management decisions, farmers seeking advice from pesticide sellers and a strong belief that pesticides are effective. It was negatively associated with the use of non-chemical methods of pest control. These results imply that farmers in Southeast Asia are spraying excessively and inefficiently and could increase their profits by applying fewer pesticides.

Development and Field Testing of a Spatial Decision Support System to Control Populations of the European Cherry Fruit Fly, Rhagoletis cerasi, in Commercial Orchards

The European cherry fruit fly, Rhagoletis cerasi (Diptera: Tephritidae), is a key pest for the cherry production industry in Europe and west Asia that has recently invaded North America. Insecticide applications are frequently employed to control this devastating pest, often without considering its population trends. We developed a novel decision support system (DSS), and field tested it in commercial sweet cherry orchards in central Greece. The DSS includes two algorithms that predict the timing of adult activity in the wild and support pest management decisions, based on R. cerasi population trends and pesticide properties, respectively. Preparatory monitoring of the testing area during 2014, using adult traps, revealed high population densities of R. cerasi in non-managed sweet cherry orchards and low densities in commercial ones. Implementation of the DSS during 2015 resulted in low R. cerasi adult population densities and zero fruit infestation rates in commercial cherry orchards. Similar population and infestation rates were recorded in conventionally treated plots that received on average two insecticide applications compared to the one-half that the DSS treated plots received. Simultaneously, high population densities and fruit infestation rates were recorded in non-managed cherry orchards. Apparently, the implementation of the simple DSS we developed reduces the cost of R. cerasi management and minimizes the chemical footprint on both the harvested fruit and the environment.

Detection of Ceratitis capitata Wiedemann (Diptera: Tephritidae) using trimedlure versus enriched ginger oil in citrus orchards

Successful fruit fly control requires effective monitoring to make pest management decisions. Ceratitis capitata (Medfly) is typically monitored in Tunisia with parapheromone commercialised as trimedlure (TM). Chemical treatment is applied when the economic threshold (3 flies/trap/day) is reached. In this study, C. capitata populations in a commercial citrus orchard captured in McPhail traps baited with TM or enriched ginger oil (EGO) were compared over two seasons (2011 and 2012). Females of C. capitata were not attracted to TM or EGO. Trimedlure was significantly more attractive to C. capitata males than EGO under low and high population densities over sampling dates. The TM used in McPhail traps was adequate to attract male medflies in citrus orchards under a wide range of Medfly population levels. The use of the best attractant can help to make control decisions when population levels of flies are low, thus preventing unnecessary application of insecticides and/or other control methods.

“The Role of Strategic Uncertainty in Area‐Wide Pest Management Decisions of Florida Citrus Growers” – Authors' Response to Comment

“The Role of Strategic Uncertainty in Area‐Wide Pest Management Decisions of Florida Citrus Growers” – Authors' Response to Comment

Development of a Species-Specific PCR for Detection and Quantification of Meloidogyne hapla in Soil Using the 16D10 Root-Knot Nematode Effector Gene.

The Northern root-knot nematode (Meloidogyne hapla) is an important soilborne pathogen of numerous agricultural crops in temperate regions. Accurate detection and quantification is vital to supporting informed pest management decisions. However, traditional methods of manual nematode extraction and morphology-based identification are time-consuming and require highly specialized training. Molecular methods may expand the diagnostician's toolkit beyond those methods that rely on this disappearing specialized skillset. However, molecular assays targeting the internal transcribed spacer region may lead to inaccurate results because of intraspecific variability. The Meloidogyne spp. effector gene 16D10 was assessed as a target for a SYBR Green I quantitative PCR (qPCR) assay for detection and quantification of M. hapla. M. hapla-specific qPCR primers were developed and evaluated for specificity against five M. hapla isolates and 14 other plant-parasitic nematodes. A standard curve was generated by relating the quantification cycle (Cq) to the log of M. hapla population densities artificially introduced into soil. The influence of soil inhibitors on quantitative amplification was assessed by generating a dilution series from DNA extracted from pure nematode cultures and inoculated soil. Extracts from soil produced significantly higher Cq values than those produced from pure culture extracts. The utility of the qPCR was evaluated using soil samples collected from three naturally infested potato fields, resulting in a significant positive relationship between populations estimated using qPCR and populations derived from manual counting. The qPCR developed in this study provides a useful method for detecting and quantifying M. hapla in soil and demonstrates the utility of effector genes in plant-parasitic nematode diagnostics. The ability to use effector genes as targets for qPCR and other molecular detection and quantification methods may open additional avenues of novel research and support development of improved species-level diagnostics.

Methods for the Identification of Microclimates for Olive Fruit Fly

The support and development of the primary agri-food sector is receiving increasing attention. The complexity of modern farming issues has lead to the widespread penetration of Integrated Pest Management (IPM) Decision Support Systems (DSS). IPM DSSs are heavily dependent on numerous conditions of the agro-ecological environment used for cultivation. To test and validate IPM DSSs, permanent crops, such as olive cultivation, are very important, thus this work focuses on the pest that is most potentially harmful to the olive tree and fruit: the olive fruit fly. Existing research has indicated a strong dependency on both temperature and relative humidity of the olive fruit fly’s population dynamics but has not focused on the localised environmental/climate conditions (microclimates) related to the pest’s life-cycle. Accordingly, herein we utilise a collection of a wide-range of integrated sensory and manually tagged datasets of environmental, climate and pest information. We then propose an effective and efficient two-stage assignment of sensory records into clusters representing microclimates related to the pest’s life-cycle, based on statistical data analysis and neural networks. Extensive experimentation using the two methods was applied and the results were very promising for both parts of the proposed methodology. The identified microclimates in the experimentation were shown to be consistent with intuitive and real data collected in the field, while their qualitative evaluation also indicates the applicability of the proposed method to real-life uses.

Comment on “The Role of Strategic Uncertainty in Areawide Pest Management Decisions of Florida Citrus Growers”

Comment on “The Role of Strategic Uncertainty in Areawide Pest Management Decisions of Florida Citrus Growers”