Pest Density Research Articles

Integrated pest management of plant sucking bugs (Hemiptera: Miridae) in Australian cotton: back to the future.

Creontiades dilutus (green mirid) and C. pacificus (brown mirid) are major hemipteran pests of transgenic (Bt) cotton in Australia. Current integrated pest management (IPM) guidelines for mirids in Australian cotton, based on economic thresholds and sampling recommendations, were developed and disseminated to industry at the start of the 2005-06 growing season and have remained largely unchanged since then. However, adoption of mirid IPM guidelines by industry has been highly variable and generally well below expectation. Annual surveys of crop protection practices across the Australian cotton industry, from 2010 to 2017, indicate that a third of all mirid sprays are applied below the recommended thresholds each year. More than half of all survey respondents in the 2017 survey indicated lack of confidence in the mirid thresholds due to highly variable and disproportionate damage, a phenomenon best described as the 'mirid enigma'. A critical review of RD&E outputs since 1998 shows that potential contributors to the mirid enigma include but are not limited to biological, ecological and methodological factors. Mirid feeding damage is likely to vary with developmental stage, gender and reproductive status. Ecological factors including trophic effects and multiple host plant usage are potential modifiers of mirid feeding damage. Methodological and technological constraints and shortcomings are evident in the threshold research done to date. Inadequate commercial sampling that results in unreliable estimates of pest density in the crop is a major contributor to the mirid enigma. Failure to account for the complexity of factors that can influence the nature and severity of mirid damage to cotton often results in fruit loss due to non-mirid related factors being incorrectly attributed to mirids. An alternative approach to mirid management based on modelling the dynamics of net fruit load (production-loss) proposed over 15 years ago is discussed.

Influences of Insect-Resistant Genetically Modified Rice (Bt-T) on the Diversity of Non-Target Insects in an LMO Quarantine Field

This study was conducted to develop environmental risk assessments and biosafety guides for insect-resistant genetically modified rice in an LMO (Living Modified Organism) isolation field. In the LMO quarantine area of Kyungpook National University, the species diversities and population densities of non-target insects found on insect-resistant genetically modified rice (Bt-T), rice resistant to Cnaphalocrocis medinalis, and non-GM rice (Dongjin-byeo and Ilmi-byeo) were investigated. The Bt-T plants were, therefore, evaluated under field conditions to detect possible impacts on above ground insects and spiders. In 2016 and 2017, the study compared transgenic rice and two non-GM reference rice, namely Dongjin-byeo and Ilmi-byeo, at Gunwi. A total of 9,552 individuals from 51 families and 11 orders were collected from the LMO isolation field. From the three types of rice fields, a total of 3,042; 3,212; and 3,297 individuals from the Bt-T, Dongjin-byeo, and Ilmi-byeo were collected, respectively. There was no difference between the population densities of the non-target insect pests, natural enemies, and other insects on the Bt-T compared to non-GM rice. The data on insect species population densities were subjected to principal component analysis (PCA) without distinguishing between the three varieties, namely GM, non-GM, and reference cultivar, in all cultivation years. However, the PCA clearly separated the samples based on the cultivation years. These results suggest that insect species diversities and population densities during plant cultivation are determined by environmental factors (growing condition and seasons) rather than by genetic factors.

Population Density of some Insect Pests Infesting Fallen Soft Dates and their Associated Natural Enemies in Giza Governorate, Egypt

This study aimed to determine the population density and survey the insect pests infesting fallen dates fruits of soft cultivars (Zagloul, Samani and Amhat) in Giza Governorate, Egypt and associated natural enemies, parasitoid and predatory species during two successive seasons 2016/2017 & 2017/2018. Ten insect pests belongs to three insect orders (Lepidoptera, Coleoptera, and Homoptera) were recorded. Lepidopterous insects were,Batrachedra amydraula Meyrick (Fam.: Cosmpterigidae), Arenipses sabella Hampson (Fam.: Pyralidae), Ephestia calidella Guenee (Fam. Pyralidae),Ephestia cautella Walker (Fam. Pyralidae), Ectomyelois ceratoniae Zeller (Fam.Pyralidae) and Stathmopoda auriferella (Walker) (Fam. Stathmopodidae). Coleopterous pests were Coccotrypes dactyliperda (Fabricius) Fam. Scolyitldae, Carpophilus spp. (Fam. Nitidulidae) and Oryzaephilus surinamensis Linnaeus (Fam. Silvanidae). The Homopterous insect was Parlatoria blanchardi Targioni (Fam. Diaspididae).one predatory species, Labidura riparia Pallas, (O.:Dermaptera: Fam.: Labiduridae )and one parasitoids species bracon hebetor (Say) (Hymenoptera: Braconidae ) were found. Results showed that there was no significant difference between the numbers of insects in the two years of study or between the three tested cultivars. While there were significant differences between the inspection dates and between the recorded insect's species numbers. In addition, the results showed that the highest average number of the insect species were Carpophilus spp. followed by E. calidella, P. blanchardi and E. cautella respectively. Mean daily temperature &RH had a low and negative effect on insect population density, while there were differences between the insect pests numbers in different date of inspection. In addition, there was a significant difference between the insect pests numbers, which belongs to order Homoptera and each of (Lepidoptera and Coleoptera).Regarding infestation, percentage, there were significant differences between the averages infestation percentage for the three tested cultivars as well as between the two years of study. Bracon hebetor (Say) was the only recorded parasitoid during the period of study. Percentages of parasitism had no significant difference between the two years of the study, while it had a significant difference between the three date palm cultivars.

Spatial Distribution of Euschistus heros (Hemiptera: Pentatomidae) in Cotton (Gossypium hirsutum Linnaeus).

Recently, the Neotropical brown stink bug, Euschistus heros (Pentatomidae: Hemiptera), has been detected in cotton in the Brazilian Cerrado. Several reliable surveys have been conducted on the spatial distribution of stink bugs in soybean; however, few studies have examined the behavior of this insect in cotton in Brazil. Thus, this study examined the spatial distribution of E. heros in cotton using aggregation indices based on the variance-to-mean ratio, Morisita index, exponent k, Poisson and negative binomial distributions. Inverse Distance Weighting interpolation maps were also used to represent insect density. The study was conducted in a 1.1 hectare experimental cotton field in which 64 equally-sized plots were sampled on a weekly basis. Our findings revealed that stink bugs presented an aggregate distribution in 2 sampling weeks based on aggregation indices, and this pattern was best described by a negative binomial distribution. Maps showing the density of pests can be an important tool for sampling pests in crops and control measures in early stages of infestation, when there is an edge effect on the distribution of E. heros, can be an efficient strategy in cotton.

When managers forage for pests: Implementing the functional response in pest management

In this study, we explore how the functional response framework can be implemented in pest management. Here, managers take the role of predators foraging on pests and facing monetary costs for survey and control in a spatial domain where the pest distribution and control strategy do not have to be random. To investigate this framework quantitatively, we simulated various management processes on different pest spatial distributions using a spatially-explicit individual-based model and Monte-Carlo simulations, and also confirmed some of the results analytically. By graphing the number of pests controlled versus pest density, we obtained management functional response curves. Whether the management functional response was shaped like a type I, type II or type III functional response depended on the management costs and the search area. However, the management spatial strategy and the pest spatial distribution had little effect on the functional response. We applied our model to the management of mountain pine beetle epidemic in Cypress Hills, Saskatchewan, Canada, with simulations matching the real number of attacked trees controlled by managers. We showed how to make an analogy between functional responses in predator–prey interactions and in human–pest interactions and thereby, apply insights from the functional response framework to pest management.

Role of farming awareness in crop pest management - A mathematical model

Control of pest attack is an important aspect in agriculture to obtain healthy crop as well as high yield. Farming awareness is also equally important in pest management. Awareness campaign are made for making people aware of damages due to the pest and protect the crop from pests which ultimately leads to high crop yield. In this article, a mathematical model is proposed to study the effect of awareness among the people in crop pest management using plant biomass, pest and aware population. Pest population is divided into two compartments: susceptible pest and infected pest. We assume that the growth of awareness level is assumed to be proportional to the density of healthy pest in the crop field. Global source such as radio, TV etc. can increase the level of awareness. It is further assumed that aware people will adopt biological control methods like integrated pest management. Susceptible pests are made infected by this process as infected pest are less harmful to crop. Moreover, there may be some time delay in measuring the healthy pests in the crop field i.e. some delay may take place in taking necessary steps while controlling the pest attack. Thus we developed the model incorporating time delay into the system. The existence and the stability criteria of the equilibria are obtained in terms of the basic reproduction number. The Hopf-bifurcation analysis has been done at the endemic equilibrium considering time delay as the bifurcation parameter. Numerical simulations are carried out to justify the analytical results.

Регулирование состояния насаждений на антропогенно преобразованных территориях: принцип дендрологического разнообразия

In low-forest areas with a poor natural of woody vegetation, the ecological capacity of the territory is increased by the introduction of the forest plantations for various purposes, which contribute to the regulation of phytosanitary conditions and the preservation a biodiversity of the regional. Among the ecological-adequate methods for the preservation of ecological optimum in the systems of multifunctional plantations of various purposes are importance of fundamentally: the inclusion of adapted entomophilic and fruit-bearing tree and shrub species, the creation of ecotonic zones of abundant flowering herbs and other landscape-ecological elements. Optimization of the phytocoenotic situation expands environmental preferendum beneficial insects, their attracted by the possibility of additional supply and new safe havens creation for the entomophages its expanded a food range and the use in foods not typical for them types of pests. Collection of material was carried out in the forest plantations of various a special purposes. The objects of the study were useful insects. A samples have been taken by the mowing trees of crowns by the nets of entomological , a visual inspection of the model branches and the manual collecting of predators and phyllophages with species of parasite with the subsequent by cultivation of adult insects in the laboratory conditions. Stabilization of the ratio of harmful and useful insects in the communities is facilitated by the introduction of forest plantations into the landscapes. In this regard, many atypical species of insects in the forest-equipped areas is expand their food spectrum, using non-specialized a species of pests. The number of individuals of parasitic insects here increases by an average of 4.0 times, the abundance of predators increases by three times, the density of economically dangerous pests is reduced by 1.5-4.0 times. Against field pests (harmful bugs and grain flea beetles) the biocenotic role of forests plantation is most pronounced. Their number on forest-protected crops is reduced by 4.0 and 3.5 times, respectively. The increase in dryness of the climate provokes an increase in the density of pests (by 41-96%) and a reduction in the number of their natural enemies (by 16-28%), with the total number of insects increasing by 11-31%. The diversity of dendroflora is determines the effectiveness of action the parasites and predators. Most of the entomophages (28.0% of the total number of useful arthropods) are concentrated in the plant crowns сем. Rosaceae. Attractiveness of plants Sambucus и Lonicera for the parasites and predators are less pronounced – their number here is on average 4.0-10.0 times lower. The complexity of the structure of phytocenosis with the inclusion in the composition of landings blooming profusely woody species increases a exchange the faunal by the facies and strengthening of the complex of the entomophages in the gradient of vertical. Optimization of phytosanitary conditions in the forest stands of different purpose is based on the selection of adapted tree species, positively changing fitered and contributing to the preservation and enhancement of biocenotic relations, biodiversity, restoration of natural mechanisms of self-regulation and, as a result, stabilety functioning of the forest reclamation complexes. Increasing dryness of the climate in the southern direction affects the diversity and abundance of faunal communities of forest reclamation complexes. Zonal of affiliation the communities of entomofaunal to the more arid areas leads to an increase in the total number of insects on 11-31%. Positive effect for a harmonious the entomofauna of community, with an adequate ratio of harmful and useful component, is fold to the areas adjacent to planting - the state of ecological stress. On remote site from the direct influence the forest plantation areas is manifested ecological regression.

The Spider Mite Schizotetranychus spireafolia (Acari, Tetranychidae), Specific Pest of Spiraea in the A. V. Fomin Botanical Garden

Abstract The spider mite Schizotetranychus spireafolia Garman, 1940 is found on plants of the genus Spiraea L. in A. V. Fomin Botanical Garden, Kyiv (Ukraine). Th is is the second record of the species in Ukraine. Th e species diagnosis with measurements of body, legs and dorsal setae for male and female mites was given. New data on distribution, ecology of mites is obtained, and damage to plants was described for the first time. Th e pest density was different on various species, forms and sorts of Spiraea L. plants, and did not depend on leaf pubescence.

Evaluation of pest control efficiencies for different banker plant systems with a simple predator–prey model

AbstractThe banker plant system has been introduced for the biological control of various pest species in Japanese greenhouses. With the banker plant system, non‐crop plants infested with a host insect (a non‐commercial crop pest) are placed in the greenhouse to provide alternative resources for the parasitoids or predators. We want to evaluate the effectiveness for controlling pests on the crop in a quantitative way by immigrating predators from the banker plant. Therefore, we developed a simple model for the interaction of the pest and predator in the crop and included the banker plant only as a source for predators. For three different pest‐predator systems we parameterised the model and used these models to predict under what conditions biological control in a banker plant system is successful. We defined successful as keeping the pest below the economic injury level of the crop estimated from damage analysis. Because the crop is mostly grown during a period that lasts less than a year our analysis should not only focus on the equilibrium dynamics. In contrast, it should also focus on the transient dynamics. Our main analytical result, from the equilibrium analysis, is that for successful control the maximum lifetime consumption of immigrating predators should exceed the daily prey growth at half the value of the maximum consumption rate. For practical purpose this translates into the fact that the immigration of predators at a low initial pest density is crucial for successful control.

Population analysis of white grubs (Coleoptera: Melolonthidae) throughout the Brazilian Pampa biome

The replacement of natural grassland by cultivated areas might favor the increase in abundance of some root-feeding species such as the white grubs, which may become a constraint for field crop production. This research aimed to assay the population density and geographical distribution of white grubs pest and other species in natural grassland and cultivated areas throughout the Brazilian Pampa biome. White grubs were sampled in 18 locations in both landscape use types and identified. Population density (number of larvaem−2) was calculated for each recorded species and sorted within two groups (pest species and other species), compared between natural grasslands and cultivated areas, as well as among locations. A dendrogram to evaluate species similarity among locations was built based on combined data obtained from both landscape use types throughout the region. In total, 31 species were found in the Brazilian Pampa, and four of them are considered as crop pests: Diloboderus abderus (Sturm, 1826), Euetheola humilis (Burmeister, 1847), Lyogenys fusca (Blanchard, 1830), and Phyllophaga triticophaga Morón & Salvadori, 1998. The average population density of pest species in cultivated areas was less than five larvae m−2, at most of locations. Some species had a wide geographical distribution (e.g. D. abderus and Cyclocephala modesta Burmeister), while other melolontids occurred at only one location. The knowledge of which white grub species are present in a field and its population densities assist farmers to take proper management decisions.

Landscape configuration, organic management, and within‐field position drive functional diversity of spiders and carabids

AbstractAgricultural management intensity and landscape heterogeneity act as the main drivers of biodiversity loss in agricultural landscapes while also determining ecosystem services. The trait‐based functional diversity approach offers a way to assess changes in community functionality across agroecosystems. We focused on carabids and spiders, because they are an important component of crop field biodiversity and have significant biological control potential.We assessed the effect of small‐ vs. large‐scale agricultural landscapes, organic farming, and within‐field position on functional diversity of spiders and carabids. We sampled pairs of organic and conventional winter wheat fields in small‐scale agricultural landscapes (former West Germany) and in neighbouring large‐scale agricultural landscapes (former East Germany). We sampled arthropods with funnel traps in transects at field edges, field interiors (15 m from edge), and field centres.The gradient from field edges towards the centres played an important role: spider body size decreased; ballooning ability increased, and hunting strategy switched from active hunters to more web‐builders—presumably, due to higher microhabitat stability in the field centre. Higher trait diversity of spiders in field edges suggested higher biocontrol potential in small‐scale agriculture. In contrast, carabid feeding switched from herbivores to carnivores, presumably due to higher pest densities inside crop fields. Furthermore, small‐scale agricultural landscapes and organic management supported larger, i.e., less dispersive carabids.Synthesis and applications. In our research, spiders were more sensitive to edge effects and less sensitive to management and landscape composition than carabids. Smaller fields and longer edges, as well as organic management increase carabid functional diversity, which may increase resilience to environmental change. Since many spider species are confined to field edges, the effect of within‐field position on functional diversity is more important in small‐scale agricultural landscapes with more edge habitat than in large‐scale agricultural landscapes. Our findings suggest that European Union policy should acknowledge the high benefits of small‐scale agriculture for the functional role of major predators such as spiders and carabid beetles, as the benefits are equal to those from a conversion to organic agriculture.

An assessment of the non-target effects of copper on the leaf arthropod community in a vineyard

Bordeaux mixture has been used for more than 150 years in viticulture and other agricultural applications because it is the most effective fungicide against grape downy mildew. However, the copper present in these mixtures is not degradable and can have environmental consequences. Even though the effect of Bordeaux mixture on downy mildew is well known, the non-target effects of this fungicide on leaf arthropod communities are poorly understood. In this study, we simultaneously monitored the direct effect of Bordeaux mixture on three grapevine leaf diseases and five leaf arthropods (beneficial and pest species) in the field over a four-month time period. We found a strong interaction between sampling year and treatment for all tested organisms. Overall, the presence of copper generally decreased both the occurrence of disease and densities of leaf arthropods. Thus, copper reduces some pest densities but also biological agent densities which might interfere with biological control. The effects and results presented here should prove valuable when implementing future crop management strategies and pest control procedures.

Modeling effects of ecological factors on evolution of polygenic pesticide resistance

Widespread use of pesticides has resulted in the evolution of resistance in many insect pests worldwide limiting their use in pest control. Effective pest and resistance management practices require understanding of the genetics of resistance and of the life history of the pest. Most models for pesticide resistance assume that resistance is monogenic, conferred by a single gene. However, resistance could evolve as a polygenic quantitative trait resulting from the action of several genes, especially when pesticide dose is low. Further, fitness of the pest could be density-dependent and might depend upon abiotic factors such as temperature. It is not known how these factors affect the evolution of polygenic resistance or pest population dynamics when resistance evolves. We use the western corn rootworm, Diabrotica virgifera virgifera, as a case study and use data on density-dependent survival, heritability and survival rates on the transgenic Cry3Bb1 toxin and corresponding LC50 values, to model polygenic resistance to Cry3Bb1. We found that LC50 increased rapidly even at doses that produced a mortality of less than 99.9%. However, survival reached 100% only when mortality was as high as 99.9%. Fast response to high selection pressure produced cyclical larval densities while lower selection pressures produced equilibrium densities. Interestingly we found that a relatively low density observed in a population may not be evidence for a low survival to the pesticide. As a consequence we found that larger refuges might not necessarily help in reducing pest densities especially when pesticide mortality is low. This effect, arising from the tradeoff between response to selection and density dependence, calls for careful assessment of the evolution of resistance based on change in survival as well as on pest densities. When selection pressure is low a lower initial density resulted in a larger response to selection. Finally, we showed that populations with shorter developmental times developed resistance faster initially irrespective of selection pressure. However, when selection pressure is low survival eventually became higher in populations with longer developmental times. Since developmental time depends on degree days spatio-temporal variation in temperature could be an important factor in polygenic resistance evolution.

Caractéristiques de l’évolution spatio-temporelle de Thaumatotibia leucotreta Meyrick (Lepidoptera : Tortricidae) dans les zones de production cotonnière de Côte d’Ivoire

In order to update knowledge on the spatio-temporal evolution of Thaumatotibia leucotreta, the geographical areas and seasons of predilection of adult and larval populations have been studied in the last six years from 2012 to 2017. Monitoring of natural adult populations revealed that populations were more abundant in the southern cotton production area as compared to the north. A Monitoring of larval infestations showed that infestations occurred on cotton at the end of august (0.10 larvae/100 bolls) and increased gradually during october-november (0.31 to 0.93 larvae/100 bolls), indicating a strong relationship between evolution of adult and larval populations and cotton phenology. Early sowings exhibited higher infestation levels (0.87 larvae/100 bolls). Annual variations of pest infestation levels increased from years to years, from 0.23 to 0.49 larvae/100 bolls over the study period. Mapping the geographic distribution of infestations showed highest pest densities in the southern zone, mostly in surrounding areas of Boron (1.52 larvae/100 bolls). With regard to the emerging status of T. leucotreta over recent years, the current pyrethroid resistance management strategy deserves to be improved on the basis of the pest geographic and seasonal profiles.

The Effect of Weather Factors on the Population Density of <i>Oxycarenus </i>spp. (Hemiptera: Lygaidae) on Roselle and Kenaf

Roselle, Hibiscus sabdariffa and Kenaf, Hibiscus cannabinus are two important fibre crops in most parts of Africa. Insect pests are one of the major constraints in the production of these crops. The cotton seed bug Oxycarenus spp. attacks Roselle and Kenaf during the seed formation stage and cause reduction in seed viability. This study examined the effect of weather factors namely, relative humidity, temperature, sunshine and soil evaporation on the population density of Oxycarenus spp. on Roselle and Kenaf during the planting seasons 2012 and 2013. The treatments consisted of two types of Roselle (Green-calyxed and Redcalyxed) and Kenaf. The experiment was laid out in the field using Randomized Complete Block Design and the treatments were replicated four times. The results showed that the population of Oxycarenus spp. was significantly (p<0.05) higher on green-calyxed H. sabdariffa and red-calyxed H. sabdariffa than on Kenaf in 2012 and 2013. The differences in the density of the bug per fruit on green-calyxed H. sabdariffa and redcalyxed H. sabdariffa were significant in the two planting seasons. Relative humidity in the morning and maximum temperature correlated positively and negatively, respectively with the density of Oxycarenus spp. during the two planting seasons. Sunshine hours per day correlated positively, while soil temperature and soil evaporation had a negative correlation with the bug density. This information on the seasonal variation in the bug density and its relationship with weather factors could be used in pest forecasting for these fibre crops which is an important tool in formulating a successful pest management programme.Keywords: Malvaceae, Fibre crops, weather factors, Oxycarenus spp., pest management, planting seasons, pest density.

Effect of Liriomyza huidobrensis (Diptera: Agromyzidae) density on foliar leaf damage and yield loss in potato

Liriomyza huidobrensis (Blanchard) is a key pest of potatoes worldwide and an emerging pest of potatoes in Korea. To understand the nature of the damage caused by this pest and the potential for yield loss, potato (Solanum tuberosum), cv. Superior was exposed to different pest infestation levels (0, 2, 5, 10, 20, and 50 individuals/cage) for 27 days and the relationship between pest density and crop damage assessment was determined using both laboratory cage studies and field cages. Leaf stippling, number of mines per leaf, % leaf area mined, and yield loss varied significantly with infestation density level in both the laboratory and field. The greatest leaf area mined and yield loss were associated with the 20- and 50-individual infestation rates in both the laboratory and field. There was a significant relationship between female choice (as shown by stippling, caused by adult feeding and oviposition) and larval performance (as reflected by the number of mines, damaged leaf area, and yield loss). It is important to understand the nature of the damage caused by L. huidobrensis and to determine its economic threshold for potato in order to optimize the management of this leafminer and minimize management costs.

Scale invariant behavior of cropping area losses

This paper shows how crop losses, display Self-Organized Critical Behavior, which implies that under a wide range of circumstances, these losses exhibit a power-law dependence on frequency in the affected area whose order of magnitude approximates those reported for extreme climate events. Self-Organized Critical Behavior has been observed in many extreme climate events, as well as in the density and distribution of pests linked to crop production. Empirical proof is provided by showing that the frequency-size distribution of the cropland loss fits the Pareto and the Weibull models with scaling exponents that are statistically similar to the expected value. In addition, the test included comparisons of the expected value and the predicted value of the scaling exponents among different subsystems and among systems of the same universality class. Results show that the Pareto model fits the heavy-tailed distribution of losses mostly caused by extreme climate events, while the Weibull model fits the whole distribution, including small events. The analyses show that crop losses adopt Self-Organized Critical Behavior regardless of the growing season and the water provision method (irrigated or rainfed). Irrigated systems show more stable behavior than rainfed systems, which display higher variability. The estimation is robust not only for calculating model parameters but also for testing the proximity to a power-law-like relationship.A long-term risk index by growing season and water provision method is derived as an application of this power-law behavior. The index is flexible, comparable between geographical units regardless of their size and provides an indirect measure of the probability of losing a cropping area of a given size.

Orius albidipennis (Rueter) as an effective biocontrol agent against Tetranychus urticae Koch on pepper crops in greenhouse in Egypt

The present study was carried out in greenhouses, on sweet pepper crops, during the winter plantations 2015–2016 and 2016–2017 in a commercial farm located at Berkash district, Giza, Egypt. During the first season, three acariphagous biocontrol agent species, the predatory mite, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) (at a rate of 2 individuals/m2), and two of predatory insect, Macrolophus caliginosus Wagner (at a rate of 1 individual/m2) and Orius albidipennis (Reuter) (at a rate of 1/2 individual adults/m2), were applied to control Tetranychus urticae. The obtained results showed that T. urticae was controlled successfully using A. swirskii and O. albidipennis. Releasing of A. swirskii and O. albidipennis caused 26 and 24% yield increases, respectively, as compared to control treatment. During the second season of 2016–2017, the efficiency of O. albidipennis at a rate of 1/2 per m2 was compared to three recommended pesticides, for controlling T. urticae. The obtained results revealed that applying O. albidipennis proved to be the most efficient control method against T. urticae on sweet pepper, with the lowest remaining pest density of T. urticae (2.9 mites/leaf); while with chemical control, the remaining density of T. urticae reached 20.13 mites/leaf at the end of the season. Thus, results demonstrated that the released insect predator, O. albidipennis, was the most effective method to control T. urticae under greenhouse conditions for two reasons. On the one hand, it resulted in a 31.36% yield increase, and on the other hand, it could reduce the chemical application, to improve food safety and environmental pollution reduction.

Estimating Monitoring Trap Plume Reach and Trapping Area for Drosophila suzukii (Diptera: Drosophilidae) in Michigan Tart Cherry

Central-monitoring trap, multiple point release-recapture experiments were used to interpret Drosophila suzukii (Diptera: Drosophilidae) catch in a monitoring trap baited with a Scentry Biologicals commercial D. suzukii lure deployed in Michigan tart cherry orchards. The plume reach was found to be short (<3 m), while the maximum dispersive distance for 95% of the released D. suzukii was projected to be ca. 90 m, so as to yield a trapping area of 2.7 ha. These data were consistent across two growing seasons and provide the first information about the dispersal distance and monitoring trap efficacy in a fruit crop setting for D. suzukii. Catch data per single monitoring trap can now be used to estimate absolute pest density in cherries. Alarmingly, catching one D. suzukii in a monitoring trap translates to approximately 192 D. suzukii per trapping area of 2.7 ha (26 per acre). Thus, by the time D. suzukii catch becomes detectable, it is very probable that the population is already above the tolerable damage threshold, suggesting control measures should immediately be taken if the fruit is in a vulnerable stage. Caution should be taken when extrapolating these results from cherry because the measured values may differ in other crop systems.

Herbivore regulation in urban agroecosystems: Direct and indirect effects

Urban agroecosystems can provide habitat for biodiversity and can benefit human communities through urban food provisioning. Moreover, urban agroecosystems could be managed so as to optimize ecosystem services like natural pest control provided by trophic interactions between natural enemies and herbivores. As in other ecosystems, predation and parasitism regulate herbivores in urban settings, but less is known about the relative importance of direct and indirect effects at local and landscape scales in highly managed urban agroecosystems. We collected data on herbivore (cabbage aphid) density and parasitism ratios (proportion of parasitized aphid “mummies”) in 25 community gardens in three counties in the California central coast, USA. We used structural equation modeling to examine the effects of direct factors (host plant characteristics and parasitism) and indirect factors (soil, garden, and landscape characteristics) on herbivore density changes at two time points in the growing season (June and August). Aphid density, but not parasitism, varied across counties over the season, and there was a strong negative relationship between aphid density and parasitism. Direct effects were strong drivers of aphid density but not parasitism. In June, aphid density increased with host plant volume but decreased with greater floral density, while parasitism was only influenced by aphid density. In August, host plant volume similarly positively affected aphid density, and soil water holding capacity increased host plant volume. In addition, host plant density had a strong negative effect on parasitism. Urban gardeners may be able to reduce aphid pest densities by increasing floral resource density and strategically spatially distributing host plants throughout garden beds, though these processes depend on the season. The indirect effects of soil water holding capacity on aphid densities further suggest a critical role of human management on pest populations and pest control services through soil amendments and irrigation.