Analytical methods for detecting pesticide switches with evolution of pesticide resistance

After a pest develops resistance to a pesticide, switching between different unrelated pesticides is a common management option, but this raises the following questions: (1) What is the optimal frequency of pesticide use? (2) How do the frequencies of pesticide applications affect the evolution of pesticide resistance? (3) How can the time when the pest population reaches the economic injury level (EIL) be estimated and (4) how can the most efficient frequency of pesticide applications be determined? To address these questions, we have developed a novel pest population growth model incorporating the evolution of pesticide resistance and pulse spraying of pesticides. Moreover, three pesticide switching methods, threshold condition-guided, density-guided and EIL-guided, are modelled, to determine the best choice under different conditions with the overall aim of eradicating the pest or maintaining its population density below the EIL. Furthermore, the pest control outcomes based on those three pesticide switching methods are discussed. Our results suggest that either the density-guided or EIL-guided method is the optimal pesticide switching strategy, depending on the frequency (or period) of pesticide applications.     

Impact of Lygus spp. (Hemiptera: Miridae) on damage, yield and quality of lesquerella (Physaria fendleri), a potential new oil-seed crop

Lesquerella, Physaria fendleri (A. Gray) S. Watson, is a mustard native to the western United States and is currently being developed as a commercial source of valuable hydroxy fatty acids that can be used in a number of industrial applications, including biolubricants, biofuel additives, motor oils, resins, waxes, nylons, plastics, corrosion inhibitors, cosmetics, and coatings. The plant is cultivated as a winter-spring annual and in the desert southwest it harbors large populations of arthropods, several of which could be significant pests once production expands. Lygus spp. (Hemiptera: Miridae) are common in lesquerella and are known pests of a number of agronomic and horticultural crops where they feed primarily on reproductive tissues. A 4-yr replicated plot study was undertaken to evaluate the probable impact of Lygus spp. on production of this potential new crop. Plant damage and subsequent seed yield and quality were examined relative to variable and representative densities of Lygus spp. (0.3-4.9 insects per sweep net) resulting from variable frequency and timing of insecticide applications. Increasing damage to various fruiting structures (flowers [0.9-13.9%], buds [1.2-7.1%], and seed pods [19.4-42.5%]) was significantly associated with increasing pest abundance, particularly the abundance of nymphs, in all years. This damage, however, did not consistently translate into reductions in seed yield (481-1,336 kg/ha), individual seed weight (0.5-0.7 g per 1,000 seed), or seed oil content (21.8-30.4%), and pest abundance generally explained relatively little of the variation in crop yield and quality. Negative effects on yield were not sensitive to the timing of pest damage (early versus late season) but were more pronounced during years when potential yields were lower due to weed competition and other agronomic factors. Results suggest that if the crop is established and managed in a more optimal fashion, Lygus spp. may not significantly limit yield. Nonetheless, additional work will be needed once more uniform cultivars become available and yield effects can be more precisely measured. Densities of Lygus spp. in unsprayed lesquerella are on par with those in other known agroecosystem level sources of this pest (e.g., forage and seed alfalfa, Medicago sativa L.). Thus, lesquerella production may introduce new challenges to pest management in crops such as cotton.     

信息化学物质在害虫监测中的应用

种群监测是害虫种群预测与防治决策制定中十分重要的环节,而利用信息化学物质进行昆虫成虫种群监测,与其他各虫态或寄主被害率等的抽样调查方法相比,具有简便、省工、费用低、具种特异性、在低虫口密度下灵敏、监测范围广等特点。信息化学物质的应用主要包括昆虫种类和分布区检测、害虫发生期监测和发生量或为害水平监测。前两个方面的应用没有争议,而害虫发生量监测比较复杂,具有正反两方面的事例,其可靠性存在争议。本文在总结国内外研究结果的基础上,对如何提高利用信息化学物质进行监测和预测的可靠性进行了探讨。影响信息化学物质监测和预测害虫危害程度的因素很多,包括信息化学物质的成分、组成、剂量、释放速率,诱捕器种类和林间设置方法,监测对象的生物学、种群动态和发生阶段,害虫的生活环境条件(包括生物学因素如寄主种类、组成、年龄和密度等以及非生物因素如气候因子等),危害损失的估计方法,以及预测模型的类型和建模方法等。研究分析表明,正确的信息化学物质组成和比例、适当的信息化学物质用量和诱芯载体对信息化学物质的持续稳定释放是监测可靠性的基础,诱捕器的种类、设置方式、密度也需要进行测试并规范化,另外还需根据所监测对象的特性及其所处的环境研究制定特定的种群密度水平或寄主被害率统计方法及预测模型,建立系统的监测规范和程序。只要建立了符合所监测害虫特性和所处环境条件的监测方案,基于信息化学物质的害虫监测是可靠的。     

Monitoring insect pests in retail stores by trapping and spatial analysis

Stored-product insects are a perennial problem in retail stores, where they damage and contaminate susceptible merchandise such as food products and animal feed. Historically, pest management in these stores has relied heavily on chemical insecticides, but environmental and health issues have dictated use of safer methods, and these require better monitoring. A monitoring procedure that employs an array of moth and beetle traps combined with spatial (contour) analysis of trap catch was tested in three department stores and two pet stores. The rate of capture increased with the level of infestation but was essentially constant over 4- to 5-d trapping periods. Contour analysis effectively located foci of infestation and reflected population changes produced by applications of the insect growth regulator (S)-hydroprene. The most abundant insects were Plodia interpunctella (Hiibner), Lasioderma serricorne (F.), Oryzaephilus mercator (Fauvel), Tribolium castaneum (Herbst), and Cryptolestes pusillus (Sch?nherr). The results indicate that contour analysis of trap counts provides a useful monitoring tool for management of storage pests in retail stores. It identifies trouble spots and permits selection, timing, and precision targeting of control measures to achieve maximum pest suppression with minimum pesticide risk. It permits managers and pest control operators to visualize pest problems over an entire store, to monitor changes over time, and to evaluate the effectiveness of control intervention. The contour maps themselves, along with records of control applications and stock rotation, provide permanent documentation of pest problems and the effectiveness of pest management procedures.     

An improved integrated pest management model under 2-control parameters (sterile male and pesticide)

The object of the present paper is to study an integrated pest management (IPM) problem in an agroecosystem (paddy-fish culture) through mathematical modeling and analysis, where release of sterile males and spraying of pesticide have been used as control measures for pest population. Using optimal analysis of the model, we have shown that restricted and proper use of control measures might enhance the crop production of the system in an economically viable way. The paper also considers the vulnerability of the underlined ecosystem due to the effect of temperature on the pest growth. Using Liapunov-like function, we have found out a suitable range of temperature, where this IPM strategy remains effective. Some important remarks have finally been made on the basis of numerical simulation.     

Optimum timing for integrated pest management: Modelling rates of pesticide application and natural enemy releases

Many factors including pest natural enemy ratios, starting densities, timings of natural enemy releases, dosages and timings of insecticide applications and instantaneous killing rates of pesticides on both pests and natural enemies can affect the success of IPM control programmes. To address how such factors influence successful pest control, hybrid impulsive pest-natural enemy models with different frequencies of pesticide sprays and natural enemy releases were proposed and analyzed. With releasing both more or less frequent than the sprays, a stability threshold condition for a pest eradication periodic solution is provided. Moreover, the effects of times of spraying pesticides (or releasing natural enemies) and control tactics on the threshold condition were investigated with regard to the extent of depression or resurgence resulting from pulses of pesticide applications. Multiple attractors from which the pest population oscillates with different amplitudes can coexist for a wide range of parameters and the switch-like transitions among these attractors showed that varying dosages and frequencies of insecticide applications and the numbers of natural enemies released are crucial. To see how the pesticide applications could be reduced, we developed a model involving periodic releases of natural enemies with chemical control applied only when the densities of the pest reached the given Economic Threshold. The results indicate that the pest outbreak period or frequency largely depends on the initial densities and the control tactics.     

Non-linear effects of pesticide application on biodiversity-driven ecosystem services and disservices in a cacao agroecosystem: A modeling study

Growing concerns have been raised regarding the effects of disturbance due to agricultural practices on associate biodiversity and on the ecosystem services that biodiversity provides. Surprisingly little is known about the effects of such disturbances on complex agroecosystems with multiple interacting species. The aim of this study was to assess the effects of management by pesticide spraying on the productive outputs and the ecological functioning of a cacao agroecosystem. We built a mechanistic dynamic model including the dynamics of the crop, a pest (Cacao Pod Borer, Conopomorpha cramerella) and two beneficial insects: a hymenopteran egg–parasitoid and a ceratopogonid pollinator. Using this model, we tested the effects of a range of pesticide types characterized by their impacts on both the Cacao Pod Borer and the beneficial insects. Our results showed that yield strongly varies according to both pesticide type and timing of pesticide application. The type of pesticide had a strong influence on the flexibility of management. No simple spraying decision rule led to maximal yields for all types of pesticide. Although optimal spraying strategies differed with the type of pesticide used, they all showed a similar pattern, i.e. they limited and postponed the Cacao Pod Borer population peak while limiting the negative impacts on beneficial organisms. The results highlight the non-trivial effects of pesticide application in complex agroecosystems where associated biodiversity provides both ecosystem services and disservices. They illustrate the critical importance of providing good information to farmers on pesticide management because the use of pesticides can have a negative effect on production by decreasing ecosystem services such as pollination.     

Effect on radish pests by application of insecticides in a nearby spring oilseed rape field

Chemical control of insect pests is often necessary to ensure high yields of field crops. The aim of the present study was to study whether field pesticide use influences amount of pest damage in neighbouring garden crops. Spring oilseed rape, OSR (Brassica napus L.), was established in Southern Sweden as an example of an agricultural field crop. One half of the OSR field was treated with insecticides to control flea beetles (Phyllotreta spp., Chrysomelidae) and pollen beetle (Meligethes aeneus Fab., Nitidulidae). Radish (Raphanus sativus L.) was used as an example of a common garden crop and it was sown as four replications at three different distances and on four occasions during the season. Care was taken to protect the radish plots from pesticide due to wind drift during applications. Damage to the radish by flea beetle and cabbage root fly (Delia radicum L., Anthomyiidae) along with unspecified leaf damage was recorded. Significantly lower damage by flea beetles was found on cotyledons of radish adjacent to the insecticide treated side of the OSR field compared to the untreated side in radishes from the first sowing. Unspecified damage to true leaves was also less abundant on radishes at the treated side of the OSR field as compared to the untreated side, in all three of the radish harvests analysed. However, radish plot distance from the OSR field did not influence leaf damage. Root fly damage rates in radish did not differ significantly between those adjacent to the treated and untreated sides of the OSR. Damage rates were, however, higher in the radish plots closest to the OSR field in the first sowing, which coincides with the appearance of the first ovipositing females after overwintering as pupae elsewhere. Generally, insecticide treatment in the agricultural field appeared to influence overall damage in the neighbouring garden crop, despite the fact that the garden crop was protected against wind drift of the insecticides during applications.     

Within‐generation dynamics of leatherjackets (Tipula paludosa Meig.)

Larvae of Tipula paludosa (leatherjackets) are pests of grassland and cereals, and important prey items for a range of farmland birds. Their population dynamics from year to year have been the subject of study, but within‐generation dynamics have received much less attention. The duration and occurrence of instars and size of the population is important to both pest management and bird conservation. Leatherjackets were collected monthly from four grass fields over five generations (October to September). Count data were analysed for sources of variability and used to estimate the timing and duration of instars and population changes over a single generation. Instar durations were correlated with temperature. From the first to third instars, sample counts were strongly influenced by the location of the site and the generation. Fourth instar larvae showed a similar decline in numbers across all sites and generations. The duration and timing of first to third instars was more variable than that of the fourth instar, but there was limited evidence that this was influenced by temperature. Only the durations of the third and fourth instars were correlated. The population decline from April to September coincided with the onset of the fourth instar. Our results show that the factors influencing leatherjacket numbers change over the life cycle, but by the fourth instar, these are biotically driven. The predictability of its numerical decline indicates defined windows for crop damage and availability as prey. The stability of its timing suggests that day length may synchronize the annual cycle. Fixed timing of the fourth instar will have important consequences for the timing of crop damage and the conservation of farmland birds as climate changes.     

农作物虫害的机器检测与监测技术研究进展

在早期发现并准确定位害虫, 对其未来的发展趋势作出评价, 可提高施药处方决策和综合防治的针对性和准确性。在作物虫害信息的获取中, 传统的检测和监测方法不但耗时、费力, 而且导致的预报滞后会进一步增加损失程度, 很难较好地满足现代农业的精准生产要求。本文介绍了国内外学者在田间作物上开展害虫及其危害状况的机器检测和监测技术研究取得的进展, 包括声特征检测法、雷达观测法、图像识别法以及光谱监测法等, 讨论了现有技术的局限性, 指出了未来作物虫害机器检测和监测技术的可能发展方向是采用多种技术相结合的组合式检测和监测方法, 从多个角度获取特定虫害的相关信息, 相互进行实证检验, 以提高作物虫害机器检测和监测的精度及效率。     

Modeling and optimal control of insect pest populations

A distributed-parameter population dynamics model is developed specifically for use with variational optimization techniques. The objective is to develop a modeling/ optimization technique that will permit the development of optimal control policies which minimize combined costs of pest control and economic-yield loss. The model results and optimal control policies are continuous and distributed in time and in insect age. The technique is applied to a study of control by pesticide of the southern green stink bug, Nezara viridula (Linnaeus), a major pest of soybeans in the South. In this case study, the model results agree well with field-survey results, while the optimal control trajectories are reasonable and suggest several avenues for further study.     

Biological pest control by investing crops in pests

We propose a biological pest control system that invests part of a crop in feeding a pest in a cage. The fed pest maintains a predator that attacks the pest in the target area (i.e., the area for storing or growing crops). The fed pest cannot leave the cage nor the target pest cannot enter the cage. The predator, however, can freely attack both the fed and target pests in the target area. By introducing a refuge in the cage against the predator for the fed pest, the fed pest and predator may be stably sustained. In this study, we analyzed the potential performance of this system by modeling the population dynamics of the target pest, fed pest, and predator as differential equations. First, we show analytically that the target pest can be suppressed at extremely low abundance by adjusting both refuge efficiency and crop investment. Second, we show numerically that crop damage by the pest may be effectively suppressed by investing only small amounts of the crop. Third, we show numerically that the magnitude of required crop investment can be estimated by an index comprising of the predator's searching cost for prey and the relative growth efficiency of the predator with respect to the pest. Even if the system structure is changed or its population dynamics is modeled based on host–parasitoid interactions, crop damage can be suppressed effectively by small amounts of crop investment.     

具有天敌捕食的鼠害综合防治模型研究

鼠害综合防治是以生态学为基础综合考察各种措施的有机结合与协调 ,综合运用生态学、经济学、环境保护学、系统工程学的观点 ,充分利用自然因素控制鼠害 ,以取得较好的经济效益、生态效益和社会效益。害鼠种群动态、天敌类群动态以及植物群体生长动态是综合防治的基本理论问题 ,确定经济阈值是实现害鼠种群数量科学控制的重要前提[1] 。在综合防治过程中 ,如何最大限度地发挥天敌的作用 ,并将这种作用与其他自然限制因素以及人为防治措施相互协调 ,共同作用 ,是鼠害防治实践中最重要的课题之一 [2 ]。本文先简要综述天敌控制鼠害的研究成果 …     

年龄-龄期两性生命表及其在种群生态学与害虫综合治理中的应用

生命表是种群生态学与害虫治理的重要工具,由于传统雌性生命表无法正确描述昆虫的变态且忽略雄性个体,近年来国内外学者普遍采用年龄-龄期两性生命表。本文首先从昆虫种群的龄期分化、性比对种群增长的影响、总产卵前期与成虫产卵前期的差异、产卵期与产卵日数的差异4个方面概述了年龄-龄期两性生命表(age-stage, two-sex life table)的基本原理,进而阐明了基于bootstrap技术的生命表分析技术及其主要优点,然后介绍了年龄-龄期两性生命表各软件(TWOSEX-MSChart, CONSUME-MSChart, TIMING-MSChart)的主要用途,即预测种群的增长与防治适期、正确分析天敌的捕食率与害虫的取食量、预测天敌的种群增长与捕食潜能以及指导天敌的大量繁育。昆虫生命表作为一种强有力的分析技术,不仅在研究种群生态学和害虫治理方面已有广泛的应用,展望未来,这项技术还可以用于昆虫生理、抗药性、亚致死剂量、共生菌等方面的研究。     

A More Realistic Approach to Pest-Management Problem

The paper deals with integrated pest management (IPM) of a single density-dependent pest affecting a single crop. The model is basically a prey–predator model, predator being the natural enemy of the pest. In addition, it also contains the growth equation of the affected crop. This dynamic model is subjected to biological control in the form of release of additional predators and chemical control in the form of spraying of pesticides. To consider the natural side effect of pesticide on fish living in the soil water, the model is further improved to accommodate the growth equation of the fishes in the soil water. The paper considers the optimal analysis of the model under two control parameters, one is the spraying of pesticide and other one is the release of predators; such optimal analysis under multi-control parameters is completely new of its kind. The paper was presented by S. Bhattacharyya in the conference “Joint AMS-India Mathematics Meeting,” 17–20 December 2003, India.     

The potential of crop management practices to reduce pollen beetle damage in oilseed rape

A major problem associated with agricultural intensification over recent decades has been the development of insecticide resistance in crop pest populations. This has been a particular issue for control of the pollen beetle (Brassicogethes aeneus syn. Meligethes aeneus), a major pest of oilseed rape throughout Europe. Sustained and often prophylactic use of pyrethroid insecticides has led to the development of insecticide-resistant beetle populations, and alternatively, more environmentally benign integrated pest management strategies are sought for the pest. The population dynamics of pollen beetles and their natural enemies, and the damage caused by the pest, are influenced by processes acting at multiple scales, from the regional or landscape scale down to the local field or within-field scale. In this review, we focus on the within-field scale, and how crop management factors, including tillage, crop plant density, crop nutrition and crop rotations may be optimised and incorporated into integrated pest management strategies for more sustainable and effective control of the pest.     

害虫种群动态模型的燕尾突变分析

在农田生态系统中,以作物状况、气象因素及天敌分别为3种控制变量,以害虫种群数量动态为状态变量,建立了燕尾突变模型,并用燕尾突变模型的性质分析害虫种群数量动态中产生的突变现象.具体对燕尾突变的分歧点集所分各个控制区域的系统势函数形式和平衡点情况进行了分析,说明了害虫种群数量发生突变的条件和机理,为实际应用提供理论依据.同时利用燕尾突变的性质直观描述了害虫种群数量变化中的突跳和滞后等现象.     

昆虫杆状病毒流行病模拟模型及Java模拟软件

研究昆虫杆状病毒流行病模拟模型,对确定基因工程改造杆状病毒的主攻方向,明确病毒病田间流行的机制与关键因素,以及制定生物防治策略,均具有重要的理论与实践意义.本研究研制了用于昆虫杆状病毒流行病模拟的数学模型和Java模拟软件,该模型包括描述种群动态的一个微分方程组,描述气温变化、作物生长及病毒动态的若干模型等.模拟软件用...     

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.