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TIMING OF SAMPLING |
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CONTENTS
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While it is possible to take nematode samples any time that soil is not excessively wet, dry or frozen, most samples should be taken at the time of peak nematode density to optimize the chance of detection. However, the population densities of nematodes cycle through the season and the timing of these cycles differ between different nematode species. Therefore, something needs to be known about the population dynamics of the nematodes in mint to optimize sampling time (see section on Nematode Biology). Additional considerations include the timing of management options. For example, if the optimum time to apply Vydate nematicide is in early April, it does not make sense to wait until nematodes reach their peaks in May or August to take samples. Therefore, there are two sampling strategies mint growers can consider. The first is to take samples in late summer when populations are high and make plans for applications the following spring based on some expected nematode survival rate through the winter. The second option is to sample in March and base application decisions on damage thresholds determined for nematode densities at that time, i.e. before they have begun to increase towards maximum levels (see section on Threshold Levels). If the latter strategy is to be utilized, the grower should determine when he would put on Vydate, if he should need to, and sample the field at least two-four weeks before that time. This gives adequate time for the samples to be processed, the results to be returned to the grower, and the grower to seek consultation, if necessary, before application must be made. In addition, during March, root-lesion nematode population levels will be relatively constant, making economic injury estimates more reliable. Sampling when populations are rapidly changing can lead to errors in estimates of potential nematode damage (Pinkerton, 1983). |
