Foci Of Infestation Research Articles

Spatial distribution of Frankliniella occidentalis (Thysanoptera: Thripidae) in greenhouse crops: location of infestation foci and distribution patterns

The spatial distribution of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) was analysed in ornamental crops (roses and spray-type carnations) and horticultural crops (pepper and strawberries), inside greenhouses, using sticky traps. In ornamental crops, at low population densities, during the winter, there was not a constant location of the isolated foci of infestation, from one week to the next, or a specific pattern of variation in that location. In spray-type carnations, pepper and strawberries, at higher population densities, in spring and summer, the basic units of distribution were the individuals, and they were aggregated. For roses, at those population levels, a random distribution was observed, with a tendency for aggregation. The number of traps needed to estimate population densities, in each crop, was evaluated for two fixed levels of precision (0.10 and 0.25) and results are indicated and discussed.

LASIODERMA SERRICORNE (COLEOPTERA: ANOBIIDAE): SPATIAL RELATIONSHIP BETWEEN TRAP CATCH AND DISTANCE FROM AN INFESTED PRODUCT

The cigarette beetle, Lasioderma serricorne (Fabricius), was selected as a representative stored-product beetle to test the validity of contour mapping of trap catch for pest monitoring in warehouses and retail stores. Three experiments, each replicated 5 times, were conducted in a 3.2 x 9.0-m aluminum shed. Each experiment involved releasing beetles at a single point and recording the numbers captured after 6, 24, and 48 h in each of 14 baited pitfall traps distributed over the floor of the shed. The experiments differed only with respect to the point of release. Beetles were released passively from rearing boxes placed at one of 3 release points, and consecutive contour maps of trap catch tracked their dispersal from each point. As the beetles dispersed and total trap catch increased, the outlying traps captured increasingly more insects, but cumulative trap catch remained highest near the release points. The rate of capture was highest immediately after release and declined with time, rapidly at first and then more slowly until it became nearly constant. The cumulative numbers captured by any trap after 6, 24, and 48 h decreased exponentially with distance from the point of release. The observed spatial patterns of trap catch relative to sources of infestation and the inverse relationship of trap catch to distance from a source support the validity of contour mapping as a means of monitoring stored-product insects and locating foci of infestation.

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 (Schönherr). 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.

Development and Evaluation of Sampling Methods for Fields with Infestation Foci of Potato Cyst Nematodes (Globodera rostochiensis and G. pallida)

ABSTRACT A computer program, SAMPLE, was developed to evaluate existing and create new sampling methods for the detection of infestation foci of the potato cyst nematode (Globodera rostochiensis and G. pallida). By combining a model for the medium-scale distribution of cysts that provides the expected population densities at each position within the focus and a model for the small-scale distribution within square meters, sampling procedures can be simulated. The importance of the parameters of the two distribution models-the length and width gradient for the medium-scale distribution and the aggregation factor k of the negative binomial distribution for the small-scale distribution-was investigated by sensitivity analysis. Parameter k proved to be less important when calculating the average detection probability of a focus than were the length and width gradient parameters. Several existing versions of the statutory sampling method used in the Netherlands were tested for their performance on a standard infestation focus with a central population density of 50 cysts per kg of soil, which is small enough to use resistant potato cultivars as a control measure without noticeable yield reductions in a 1:3 year cropping frequency with potato. These methods did not perform with the desired average detection probability, set at 90%; therefore, SAMPLE was used to develop several new sampling methods for focus detection. SAMPLE is a tool to develop sampling methods on demand for every possible combination of characteristics required for use by seed and ware potato growers (recommendations for optimum control measures leading to maximum returns and integrated pest management) and by governments (legislation, quarantine, and export protection).

Alterações do peridomicílio e suas implicações para o controle do Triatoma brasiliensis

A total of 9,906 annexes from 1,541 rural dwellings of Boa Viagem County, Ceará, Brazil, infested by Triatoma brasiliensis and Triatoma pseudomaculata were investigated and immediately sprayed with pyrethroid insecticide, followed by revisions at 6, 12, and 18 months. The initial infestation rate of annexes was 4.0%, with predominant infestation in animal shelters (7.0%). Mean insect density was low, regardless of triatomine species or type of annex. A progressive decrease in the number of initial annexes was observed (66% of remaining annexes), mainly those classified as "piles of materials". Only 3% of the annexes were modified by the population. New constructed annexes were important as new foci of infestation. Some 25% were infested at the end of observation period, significantly more than the "old" annexes (4.0%), a difference attributed to insecticide spraying at the beginning of the intervention. Reinfestation occurred slowly and was more frequent in animal shelters No differences were observed between traditional pyrethroid and slow-release organophosphate formulations. Selective spraying of "new" annexes is recommended.

A Model for Infestation Foci of Potato Cyst Nematodes Globodera rostochiensis and G. pallida

ABSTRACT Infestation foci of potato cyst nematodes (Globodera rostochiensis and G. pallida) in the provinces of Zeeland, Friesland, Groningen, and Drente of the Netherlands were sampled to validate a model describing infestation foci based on data from Flevoland. Eighty-two fields were presampled to locate infestation foci using a coarse sampling grid (8 x 3 m). Parts of 37 fields containing one or more foci were sampled intensively by extracting at least 1.5 kg of soil per square meter (1.33 x 0.75 m). Forty foci were analyzed for spatial distribution characteristics of cysts using multiple regression with generalized linear models and classical linear models. The results showed that the data from all investigated cropping areas fit well to an exponential model with two parameters, the length and width gradient parameters. Significant differences in these parameter values between cropping areas could not be demonstrated. As both parameters follow a normal distribution, the probability of any combination can be described by a bivariate normal distribution. Gradient parameters were correlated, but significant correlations between these parameters and certain variables such as the nematode species involved, the time interval between sampling and the last potato crop, soil type, cropping frequency, and cyst density in the focus center could not be demonstrated.

Natural prevalence of infection with Ehrlichia ( Cytoecetes) phagocytophila of Ixodes ricinus ticks in Scotland

Ixodes ricinus nymphs and adults were collected from vegetation and from sheep at four sites in Scotland typical of areas endemic for tick-borne fever in sheep caused by infection with Ehrlichia ( Cytoecetes) phagocytophila (Rickettsiales). The great majority of ticks examined was from woodland sites adjacent to sheep farms where there was a high probability of them feeding on roe deer ( Capreolus capreolus) in a non-domestic focus of infestation and infection. Ticks were examined for infection by five methods. Batches of ticks were examined either by feeding on susceptible sheep or by feeding on rabbits and then prepared as stabilate which was inoculated into susceptible sheep. The sheep were monitored for clinical signs of tick borne fever. Batches of ticks were examined by polymerase chain reaction for Ehrlichia phagocytophila. Salivary glands were dissected out and stained by the Feulgen method to detect Ehrlichia masses, and were examined by indirect fluorescent antibody test. Each of the methods detected infection in ticks and the prevalence of infection in nymphs with the various methods ranged from >0.25% to 2.0%. Small samples of adults examined by Feulgen staining of salivary glands indicated infection prevalences of 2.1% in males and 1.6% in females. It is considered that these low infection prevalences may be typical of natural foci of infection where deer could be a major host of ticks and E. phagocytophila.

Survival and Extinction of Xanthomonas campestris pv. campestris in Soil

Carry-over of inoculum of X.c. pv. campestris in the soil from one cropping season to the next was studied in field experiments over three years. These studies were supported by laboratory and greenhouse experiments on quantitative assessment of bacteria by bioassay using the Most Probable Number technique, and on recovery rates of bacteria from the soil. The mean recovery rate from artificially infested soil was 58%. Extinction of X.c. pv. campestris in soil infested with infected plant debris proceeded exponentially and extinction rates depended on temperature, as did the decomposition of plant debris. In replicated field plots, over three years, infection foci of black rot disease were established. At harvest time, all plants were chopped and resulting plant debris was rotovated into the soil. The resulting soil infestation was sampled and showed clear infestation foci reflecting the original infection foci of the crop. These infestation foci decreased with time and disappeared after the winter. Follow-up crops remained virtually uninfected. The results show that in The Netherlands good crop and soil management impedes survival of inoculum from one year to the next, so that cabbage can be grown continuously. Polyetic carry-over of inoculum by debris in the soil can be avoided in The Netherlands.

A new sampling method for the detection of low population densities of potato cyst nematodes ( Globodera pallida and G. rostochiensis)

To reduce the use of nematicides in The Netherlands, a new sampling method for the detection of potato cyst nematodes has been developed. The method detects small infestations with a predefined probability so eliminating the need for precautionary soil fumigation by farmers. Moreover, when a focus is detected, the area where a control measure has to be applied can be minimized. As many infestations are still quite small at the time of detection, other control measures than soil fumigation, which has a poor cost to benefit ratio, can successfully be applied. Analysis of intensive sampling data from 40 patchy infestations representing all growing areas in The Netherlands produced a simple exponential model describing expected cyst numbers within infestations. Differences in parameter values of the model between different growing areas were sufficiently low to enable one detection method for small infestation foci to apply to all potato growing areas. A pilot version of the method was introduced in 1989 in the Flevopolders and applied in all the seed and ware potato growing areas in the following years. In 1992, soil fumigation was decreased by 90% in the Flevopolders, where the sampling system was introduced first. Since 1992, the sampling system has been used as a basis for an advisory system. In 1994, an 80% reduction was realised in all seed and ware potato growing areas and a 90% reduction is estimated for 1995. As a result the total reduction of soil fumigants in The Netherlands (including the starch potato growing areas) was 75% in 1994. Current research is directed to improvements in the estimation of the size of potato cyst nematode infestation foci using sampling data originating from these new detection methods to generate improved advisory systems for farmers.

Economic Impact of Sugarbeet Root Aphid (Homoptera: Aphididae) on Sugarbeet Yield and Quality in Southern Minnesota

The economic impact of sugarbeet root aphid, Pemphigus betae Doane, infestations on sugarbeet yield and quality was studied during 1990 and 1991 in 11 commercial sugarbeet fields in southwestern Minnesota. Fields with one or more obvious infestation foci were selected for study. Severe aphid infestations were characterized by elliptical-shaped foci of stunted or wilted plants that averaged 14.8 m long and 9.0 m wide; average foci area was 104.6 m2 (0.0105 ha). Lengths of infestation foci were always parallel with row direction. An at-harvest, beet root rating system was developed to measure the impact of P. betae on yield and quality. Though gross yields were variable, sugar content and recoverable sugar per hectare were significantly reduced in 64% (seven of eleven) and 73% (eight of eleven) of the fields studied, respectively. Aphid-induced effects on quality parameters, other than sucrose, were characterized by lower levels of harmful amino nitrogen and potassium. No consistent relationship was observed for sodium. Negative effects of these factors, however, proved minimal when computing total sucrose losses to molasses (average 1-2%). Loss to molasses actually was less for aphid-infested beets in seven of eleven infestation foci. Therefore, sucrose content was the primary source of quality loss in this study. Losses in sucrose content and final recoverable sugar per hectare during the 2-yr study averaged 31 and 54%, respectively. In contrast to the 1990 season, maximum recoverable sucrose yields were significantly higher in 1991, and the rate of yield loss was initially lower (where root rating ≤2.0). Final yield loss rates for heavily infested beets (i.e., root rating ≥4.0), however, were similar. Results between years partially were explained by differences in precipitation (83 cm in 1991 versus 62 cm in 1990). Thus, separate yield loss formulas were developed to estimate monetary losses and an approximate economic injury level for P. betae.

The distribution of the tsetse flies Glossina morsitans submorsitans and G. palpalis gambiensis (Diptera: Glossinidae) in The Gambia and the application of survey results to tsetse and trypanosomiasis control

AbstractA country-wide survey of the distribution of tsetse flies Glossina morsitans submorsitans Newstead and G. palpalis gambiensis Vanderplank was carried out in The Gambia, during 1989–1990, using box traps at 1654 sites over an area of 10,000 km2 The general distribution of tsetse had changed little during the last 45 years. G. m. submorsitans was present in dry, canopied woodland throughout most of the country, but was absent from an area south of the River Gambia stretching from the coast to some 100 km inland. G. p. gambiensis occurred in evergreen forest and woodland near the coast, and in riparian habitats along the length of the River Gambia and its major tributaries. Nowhere in the country was more than 20 km from tsetse-infested areas. Five major foci of G. m. submorsitans infestation were identified. Demographic, climatic and environmental factors affect tsetse populations in The Gambia, but it is expected that these foci of infestation will persist for at least the next 5–10 years. The numbers of tsetse trapped, expressed as relative densities, were used to assess the extent and severity of losses from trypanosomiasis to different categories of livestock. Survey results such as these could be used to assess whether control measures to reduce tsetse challenge are likely to be economically viable by using techniques such as insecticide-impregnated targets, pour-ons or chemotherapy.

Geostatistical analysis of cyst nematodes in soil

SUMMARYThe numbers of cyst nematodes that live in agricultural soil vary both in time and space with important consequences when devising procedures for inspection and strategies for their control. We have examined the distributions of two species, Globodera rostochiensis and Hererodera avenue, in fields in the east of Scotland by counting their live cysts in the topsoil. Nested sampling and analysis showed that most of the spatial variation occurs within distances of 5 m to 50 m. Experimental variograms computed from transects and grid surveys appeared to be isotropic and bounded with a range of approximately 60 m. Both species are strongly aggregated. H. avenue occurred in large patches. Indicators for cyst counts of 1, 4 and 10 were created from the data. The experimental auto and cross variograms of these indicators were computed and models fitted to them. All of these variograms had the same spherical form as that of the original counts but shorter ranges, and the cross variograms had more structure, suggesting a border effect. Biologically, the distribution can be explained by the nematodes being spread by cultivation from initial fortuitous foci of infestation or control by nematophagous fungi or both.

Infestations ofCryptotermes brevis(Walker) (Isoptera: Kalotermitidae) in Queensland, Australia 1. History, detection and identification

Summary The history of the exotic West Indian drywood termite, Cryptotermes brevis (Walker), in Queensland, Australia is discussed. Survey and eradication work during the late 1960's was complicated by the presence of a common endemic drywood termite pest, Cryptotermes primus (Hill). Methods used to detect infestations of C. brevis, and features used to distinguish the two species, in particular drywood termite frass, are also discussed. The methods and results of surveys and public awareness campaigns, conducted to determine the distribution and abundance of C. brevis in Queensland, are presented. The results indicate that infestations in buildings are restricted to two areas of south-eastern Queensland and that the rate of discovering additional foci of infestation within these areas is decreasing. The programme of public awareness campaigns, surveys and treatment is considered successful in discovering and containing infestations. While total eradication has not yet been achieved, the major threat posed by C. brevis in Queensland has been substantially diminished.

Evaluation of the eradication program forAmblyomma variegatum (Acari: Ixodidae) on Puerto Rico

A cooperative effort between the United States Department of Agriculture, Animal and Plant Health Inspection Service, Veterinary Services, the Agricultural Research Service, and the Department of Agriculture, Commonwealth Government of Puerto Rico has been successful in eradicating Amblyomma variegatum (Fabricius) from the islands of Puerto Rico and Vieques (an island municipality of Puerto Rico). Application of acaricides to livestock and dogs at 14-day intervals for an 18-month period eliminated foci of tick infestation on 188 farms in four different locations without additional aerial or ground treatment. Reasons for the success and some of the costs associated with the eradication program on Puerto Rico are presented.

Control of Primary Infections of Subterranean Clover Red Leaf Virus, a Luteovirus, in a Broad Bean Crop With the Synthetic Pyrethroid Deltamethrin.

Australasian Plant Pathology Vol. 13 No.4 December 1984 further pods after the symptoms of Infection become apparent (4). The greatest losses have occurred in spring-sown crops. These emerge either during, or Just prior to, the main peak of aphid flight activity and are therefore particularly susceptible to infestation by alate aphids. Alates of the vector of SCRLV (Aulacorthum solani) mainly originate from the most important source of infection, white clover plants (Trifolium repens) in perennial pastures. Primary infections resulting from the activity of vector alatae have not been amenable to control with conventional aphtcldss such as the organophosphates in the past (5). The approach to control has therefore been to advance the sowing date from the spring to late autumn or early winter (4). Although few aphids are flying during the early growth and development of these crops, a few foci of infestation and infection are generally established within them soon after they emerge. Considerable spread from these foci may occur due to movement of apterous aphids but these secondary infections can be controlled with aphicides such as demeton-S-methyl (5). The necessity to sow in the late autumn/early winter period can cause problems in Tasmania. Low temperatures and wet conditions during this period sometimes cause long delays in land preparation and sowing. These conditions also favour the development of chocolate spot, caused by Botrytis fabae, which is another important disease of broad bean in Tasmania (7). A recent report Indicated that the synthetic pyrethrord deltamethrin had a particularly rapid knockdown action or repellant effect against aphids; it substantially reduced infection of plants with a persistent, a sermpersistent and a non-persistent virus transmitted by Myzus persicae (1). An experiment was therefore designed to test whether deltamethrin would control primary infections of SCRLV in spring-sown broad beans in Tasmania. Broad beans (cv. Cotes Dwarf Prolific) were sown at Forth in August 1983 in rows set 500 mm apart to establish 30 plants/m'. Plots measuring 2 m (4 rows) x 8 m were sprayed fortnightly from emergence until harvest with either deltamethrin (25% e.c.; 50 mi per 100 L) or with demeton-S-methyl (25% e.c.; 100ml/100 L); unsprayed plots were also included. The plots were randomized in blocks and replicated four times. Immediately prior to each spray application, counts were made of the number of plants with SCRLV symptoms in a buffered zone (6 m long) in the central two rows of each plot. Randomly selected plants were also sampled from each plot to assess aphid mtestation

Control of subterranean clover red leaf virus in broad bean crops with aphicides

SUMMARYTrials at three sites in north‐western Tasmania monitored the spread of subterranean clover red leaf virus into and within broad bean crops with movement of its vector, Aulacorthum solani. Records indicated that almost all infections within the crops resulted from secondary spread by apterae following the establishment by migrant alatae of a very few foci of infestation and infection soon after crop emergence. Spread of the virus within the crops was reduced by sprays of demeton‐S‐methyl. Incidence of infection in sprayed plots at harvest was 23%, 13% and 23% at the three sites compared with 80%, 31% and 84% respectively, in unsprayed plots. Yield increases as a result of spraying were 980, 420 and 540 kg/ha.

Control Measures Towards Colorado Beetle Eradication in Sweden

Sweden suffered a heavy invasion of Colorado beetle in 1972, leading to the establishment of numerous infestation foci in the southern part of the country. The central campaign organized in the following years culminated in the eradication of the beetle by 1978. The beetle has the potential to survive and cause economic damage in Sweden.

Aggregated distribution of Ditylenchus dipsaci on broad bean seeds

SUMMARYThe distribution of Ditylenchus dipsaci (Kühn) Filipjev between seeds in infested samples of broad bean seed was skewed so that the nematodes were concentrated on a few seeds. Such aggregation increases the likelihood of reproduction by the nematodes in infested plants and the consequent establishment of foci of infestation in the soil. These foci will be small and scattered giving the nematode the best chance of a finding a favourable environment in the field. The numbers of foci of infestation introduced by seed tend to be nearly constant, independent of the numbers of nematodes on the seed and therefore provide a stable unit of population.

Methods of Monitoring Rat Infestations, and Approval Schemes for City‐wide Deratization Operations1

ABSTRACTAn account is given of the program for deratization of Budapest (city and suburbs) and the maintenance of a rat‐free state. A single contractor, the Babolna Disinfecting Station, was entrusted with carrying out the 3 phases of the program, which consisted of large‐scale poisoning of rats with Racumin 57 (3 [α‐tetralyl] ‐4‐hydroxycoumarin), in houses, factories and sewers. Use was made of the mass media to encourage the public to help in reporting infestation foci. Between January 1971 and December 1972, rat infestation levels were reduced from 43% to 0.065%. Continued vigilance has ensured that this acceptably low level has been maintained. There were no indications of resistance to the rodenticide used developing.

Studies of the bladder defense mechanism. II. Postoperative cystitis in the elderly.

AbstractChronic postoperative cystitis in the elderly patient is a difficult problem, and is especially annoying if all obvious anatomic abnormalities have been corrected. This study of 20 such patients who underwent bladder surgery indicates that several local resistance factors may be related to this continued urinary infection. In elderly postoperative patients with chronic cystitis the bladder defense mechanisms have reached such a state of imbalance that they cannot cope with the invading organisms either by the mechanism of voiding or by vesical‐wall defense factors. The relative importance of the various cellular and serologic local defense mechanisms in resisting bacteria in bladder urine and the bladder mucus layer, mucosa or submucosa is not known.There is no apparent quantitative histologic defect in the local bladder cellular response of the elderly patient. Therefore, a decreased quality of response is implied. In addition, trauma created by indwelling catheterization or by surgery destroys the anatomic integrity of the bladder wall and may thereby encourage the development of deep‐seated infection by permitting tissue invasion. Foci of tissue infestation by E. coli were demonstrated in 1 of 2 patients in whom it was possible to make such a study. These foci are not subject to the normal voiding defense mechanism and the antibacterial factors within the bladder or urine; they can be eliminated only by inflammatory cells, antibodies, or antibacterial agents capable of attaining bactericidal tissue levels.Two axioms were confirmed by this study: 1) any period of preoperative indwelling catheterization should be as brief as possible, and 2) specific antimicrobial therapy should be planned preoperatively so that surgery takes place at a time when the urine and tissues are sterile; this sterility should be maintained until all foreign bodies, such as catheters, are removed from the urinary tract.