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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). 相似文献
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Daub Matthias Hakl Ulrike Molendijk Leendert PG Schomaker Corrie Been Thomas H van Beers Thea G Jivishova Sevda Jivishov Emil Keusgen Michael Bluemel Roman Fischer Daniel Grundler Florian MW Reuther Marie Cappel Sabrina Bauer Harald Lang Christian Watrin Cliff den Nijs Loes JMF Van Bruggen Anne-Sophie Karssen Gerrit Kiewnick Sebastian Büchler Urs Roth Irma Frey Jürg 《植物病害和植物保护杂志》2015,122(4):189-193
Journal of Plant Diseases and Protection - 相似文献
3.
J. W. Seinhorst A. Oostrom T. H. Been C. H. Schomaker 《European journal of plant pathology / European Foundation for Plant Pathology》1995,101(4):457-465
Curves according to the equationPf=M (1-e
–aPi/M
) fitted well to the relations according to Seinhorst's (1993) modelPf=y
e
y
h
M(1-e
–aPi/M
) between initial egg densities of potato cyst nematodes (Globodera rostochiensis, G. pallida)Pi up to 5T
h
(T
h
=the tolerance limit of haulm weight) andPf at the end of the growing season (a=maximum rate of reproduction,M, M=different theoretical maximum egg densities). Variation of estimates ofM, due to variation of the parameters of the submodelsy
e
andy
h
for the effect of weight reduction of haulms (and, therefore, of roots) on cyst production and damage to root tissue on egg production, respectively, was small enough to be ignored relative to experimental error. Therefore, ratios of values ofM, determined in simultaneous pot experiments with different potato cultivars, are reliable measures of the relative host status of these cultivars at initial egg densitiesPi of these nematodes up to about 5T
h
. Variation between potato cultivars of growth reduction and damage to root tissue by the nematodes reduces the reliability of ratios of rates of relative susceptibility of these cultivars.The ratios between the maximum rates of reproduction ofG. pallida, pathotype Pa 3, on 8 out of 9 cultivars and one breeder's clone of potatoes and this rate on the susceptible cvs Bintje and Irene (relative susceptibilitiesrs
a
) could be considered to be equal to the ratios of maximum population densitiesM on these cultivars (relative susceptibilitiesrs
M
) (relative susceptibilities independent of initial egg density). The latter ratios were 0.59 times the first (relative susceptibilities negatively correlated with initial egg density) in one cultivar and one breeder's clone. Relative susceptibilitiesrs
a
andrs
M
of the tested cultivars and breeders clones suggest the existence of continuous ranges of both relative susceptibilities between 0.50 and 0.15 with, in a great majority of cases,rs
a
=rs
M
. 相似文献
4.
ABSTRACT The vertical distribution of Pratylenchus penetrans was monitored in four fields cropped with maize, black salsify, carrot, or potato. Soil samples were collected at 21-day intervals from May 2002 until April 2003 from five plots (2 x 5 m(2)) per field. Per plot, 15 cores were taken to a depth of 70 cm and split into seven segments of 10 cm each. Within the plots, segments from corresponding depths were pooled. After mixing, 200-g subsamples were taken and nematodes were extracted by zonal centrifugation from the root fraction and the mineral soil fraction separately. In most crops, the root fraction contained more than 50% of the total number of P. penetrans. Because the ratio between the numbers of nematodes in the root fraction and mineral soil fraction changes during the growing season, numbers of P. penetrans found in the mineral soil fraction cannot be used to estimate the total number in the soil. Therefore, both fractions have to be processed to obtain a reliable estimate of the density. No nematodes were recovered below 50 cm soil depth, except in the maize field where nematodes were found at 70 cm. The optimum sampling depth for maize, black salsify, carrot, and potato was 45, 25, 25, and 35 cm, respectively. The percentage of nematodes per soil layer was independent of the sampling date, indicating that a defined optimum sampling depth will be applicable throughout all seasons. The cumulative vertical distribution, modeled with a logistic equation, can be used to estimate the sampling error when samples are collected at different depths. 相似文献
5.
A Monte Carlo approach was utilized to calculate the size of the demarcation unit, necessary to cover infestations with Globodera rostochiensis and Globodera pallida (PCN), detected with the new EU-sampling method. Results from 90 sampled fields were used to obtain frequency distributions of the central population density (CPD), the length and width gradients of infestation foci and the distance between 'primary' and 'secondary' foci within one field section in the direction of cultivation. With a simulation model written in R, a free software environment for statistical computing, the dimensions of the demarcation unit were calculated, based on the dimensions of the sampling unit, the position of the 'primary' infestation within the sampling unit and the size of the infestation focus. It is concluded that a demarcation of 90% of possible foci positions and dimension, analogous to the specified detection probability of the EU sampling method, provides sufficient security to demarcate any infestation. With the preferred sampling unit of 11 m width and 300 m length (1/3 ha sampled), used in The Netherlands, only 0.61% of the cyst numbers will be situated outside the demarcated unit. These cyst numbers compare to 0.17% of total amount of cysts in the EU infestation model: 1 focus with a CPD of 100 cysts kg−1 and three foci with CPDs of 50 cysts kg−1 . The required demarcation area has a width of 36 m and a (maximum) length of 402 m and covers an unit of 1.5 ha. The methodology described can be applied to all proposed sampling methods and sampling unit dimensions. 相似文献
6.
G Thomas C H Schomaker T H Been M J van den Berg H J Prijs 《Veterinary parasitology》1985,18(3):209-221
Hydrotaea irritans is commonly considered to be the primary vector for the bacteria which cause summer mastitis in cattle. A behavioural physiology approach was used to investigate potential host odours (kairomones) that may be used by the fly in finding its host and to determine which substrates or sites on the host may be utilised in feeding. Attractant odours include CO2 and butyric, propionic and acetic acids: the latter three are also produced by the bacteria causing summer mastitis. When milk, slaver, nasal secretion, mastitis secretion and blood were offered to flies as feeding substrates only the last three produced significant increases in feeding duration in comparison to controls offered distilled water. 相似文献
7.
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. 相似文献
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