Errors Incurred When Using Iwao's Sequential Decision Rule in Insect Sampling

Sequential decision rules based upon defining a relationship between the mean and variance of a population and using this relationship in a confidence interval about a sum of counts on sample units have been developed and used for sampling insect pests. The actual error rates that arise from the use of these rules are much larger than the nominal ones. This occurs for three reasons: The confidence interval is incorrectly used as a sequential decision rule; it is assumed that random variables are normally distributed; and variances are not constant. If these sequential decision rules are to be used, we suggest that actual error rates be determined through simulatio

Temporal and Spatial Activity Patterns of an Adult Parasitoid, Glypta fumiferanae (Hymenoptera: Ichneumonidae), and their Influence on Parasitism

Temporal and spatial activity patterns of adult Glypta fumiferanae (Vierick) were assessed through use of malaise traps placed in tree canopies and on the forest floor. Many parasitoids were trapped in the tree canopies while none was caught on the forest floor. A model that related malaise trap catches to weather was used to draw inferences from these data. It was concluded that cool wet weather inhibited activity of the parasitoid. Historical data on interaction between G. fumiferanae and its host were used to illustrate the possibility that reductions in parasite activity due to weather factors led to reductions in rates of parasitis

Simulation of How Jack Pine Budworm (Lepidoptera: Tortricidae) Affects Economic Returns From Jack Pine Timber Production in Michigan

The impact of jack pine budworm on economic returns from jack pine timber production in Lower Michigan and management actions that might be taken to reduce this impact were evaluated with a simulation model. Results indicate that current jack pine rotation ages arc excessive and should be reduced. Insecticide application is not a viable strategy for reducing jack pine budworm impact

Moisture, a Vital but Neglected Factor in the Seasonal Ecology of Insects: Hypotheses and Tests of Mechanisms

Of the major physical factors that influence insect seasonal ecology, moisture is least understood and least appreciated. It is our premise that experimental probing of insects from diverse zones and various habitats would reveal general patterns of insect responses to moisture that are as striking as those for photoperiod and temperature. Using the paradigms of photoperiod and temperature as ecophysiological determinants of insect seasonality, we hypothesize that moisture influences insect life cycles via one or more of three mechanisms—as a token stimulus for diapause, modulator of developmental or reproductive rates, or behavioral cue for vital seasonal events. For heuristic purposes, we offer each of these hypotheses in close association with approaches for testing their validity in insects that undergo dry-season dormancy. The approaches appear appropriate for examining the role of moisture in the life histories of terrestrial invertebrates other than insects, as well as plants and microbes that have a seasonal resting stage. Elucidating moisture's role in insect seasonal cycles is critical to the development of comprehensive phenological models, improved insect management systems, and identification of novel evolutionary mechanisms for adaptation to wet-dry seasons, especially in tropical, subtropical, and Mediterranean region

Binomial Sampling of Western Flower Thrips Infesting Flowering Greenhouse Crops Using Incidence-Mean Models

Accurate assessments of thrips density are important for effective thrips management programs. Complicating the development of sampling plans for western flower thrips (WFT) Frankliniella occidentalis (Pergande) in greenhouse crops are the facts that they are small, difficult to detect, and attack a variety of crops, which may be grown concurrently within the same greenhouse. Binomial sampling was evaluated as an alternative to sampling plans based on complete enumeration. This work included comparison of incidence-mean models across diverse plant species (impatiens, cucumber, and marigold) to determine the possibility of using a generic model for sampling WFT in mixed crops. Data from laboratory-processed flower samples revealed that infestation rates calculated using a tally threshold of three thrips per flower provided the best estimates of thrips population densities in each tested crop and in the combined crops (composite data set). Distributions of thrips populations were similar across the three plant species, indicating potential for development of a generic sampling plan for mixed floral crops. Practical sampling methods for simple and complex flowers tested in the greenhouse (in situ) were evaluated via construction of binomial count operating characteristic functions. In the case of simple flowers (impatiens), visual inspections provided adequate estimates of thrips infestation rates at a low tally threshold, which ultimately enabled accurate estimation of thrips densities. However, visual inspection and tap-sampling of complex flowers (marigold) provided unreliable results. These findings indicate that use of binomial sampling methods in mixed floral crops will require development of more accurate sampling technique

Neonicotinoid Insecticide Imidacloprid Causes Outbreaks of Spider Mites on Elm Trees in Urban Landscapes

BACKGROUND: Attempts to eradicate alien arthropods often require pesticide applications. An effort to remove an alien beetle from Central Park in New York City, USA, resulted in widespread treatments of trees with the neonicotinoid insecticide imidacloprid. Imidacloprid's systemic activity and mode of entry via roots or trunk injections reduce risk of environmental contamination and limit exposure of non-target organisms to pesticide residues. However, unexpected outbreaks of a formerly innocuous herbivore, Tetranychus schoenei (Acari: Tetranychidae), followed imidacloprid applications to elms in Central Park. This undesirable outcome necessitated an assessment of imidacloprid's impact on communities of arthropods, its effects on predators, and enhancement of the performance of T. schoenei. METHODOLOGY/PRINCIPAL FINDINGS: By sampling arthropods in elm canopies over three years in two locations, we document changes in the structure of communities following applications of imidacloprid. Differences in community structure were mostly attributable to increases in the abundance of T. schoenei on elms treated with imidacloprid. In laboratory experiments, predators of T. schoenei were poisoned through ingestion of prey exposed to imidacloprid. Imidacloprid's proclivity to elevate fecundity of T. schoenei also contributed to their elevated densities on treated elms. CONCLUSIONS/SIGNIFICANCE: This is the first study to report the effects of pesticide applications on the arthropod communities in urban landscapes and demonstrate that imidacloprid increases spider mite fecundity through a plant-mediated mechanism. Laboratory experiments provide evidence that imidacloprid debilitates insect predators of spider mites suggesting that relaxation of top-down regulation combined with enhanced reproduction promoted a non-target herbivore to pest status. With global commerce accelerating the incidence of arthropod invasions, prophylactic applications of pesticides play a major role in eradication attempts. Widespread use of neonicotinoid insecticides, however, can disrupt ecosystems tipping the ecological balance in favor of herbivores and creating pest outbreaks

Predatory Mites

NYS IPM Type: Fruits IPM Fact SheetPredatory mites can provide consistent biological control of pest mites such as the European red mite (Panonychus ulmi), (ERM), and two-spotted spider mite (Tetranuchus urticae), (TSSM). Pure or mixed populations of several predatory mites occur in New York tree and small fruit plantings. The most important of these predators are the phytoseiids Typhlodromus pyri and Amblyseius fallacis. Metaseiulus occidentalis, another phytoseiid, is capable of controlling pest mites, but it occurs only sporadically in New York orchards. Its behavior as a predator is similar to A. fallacis. Zetzellia mali, a Stigmaeid or yellow mite, can be found in almost any orchard in the state, but provides biological control by itself only when ERM numbers are relatively low

Use of Double Sample Plans in Insect Sampling with Reference to the Colorado Potato Beetle, \u3ci\u3eLeptinotarsa decemlineata\u3c/i\u3e (Coleoptera: Chrysomelidae)

When used in a pest control decision-making context, protocols for obtaining sample information on insect numbers can be evaluated via three properties: the operating characteristic (OC), the average sample number (ASN), and the availability of methods for calculating the OC and ASN. On the average, sequential sample plans have lower ASN\u27s, and OC\u27s are comparable to fixed sample-size procedures. The two most commonly used sequential procedures for insect sampling are Wald\u27s probability ratio test and a test proposed by Iwao. Each of these methods has limitations. An alternative to sequential procedures is double sampling. Double sample plans developed for the Colorado potato beetle, Leptinotarsa decemlineata (Say), on Long Island, N.Y., have OC\u27s comparable to a modified form of Iwao\u27s sequential method and fixed sample size methods. They also have ASN\u27s that at times are lower than those of the sequential method

Achieving Biological Control of European Red Mite in Northeast Apples: An Implementation Guide for Growers

NYS IPM Type: Fruits IPM Fact SheetEuropean red mites (ERM), Panonychus ulmi, feed on leaves of apple trees and thereby interfere with photosynthesis and production of carbohydrates. At high levels, ERM damage to apple leaves reduces fruit yield and quality. As a general rule, keeping ERM numbers below 2.5 per leaf before July, below 5 per leaf during July, and below 7.5 per leaf in August will prevent economic losses from this pest