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Seasonal population cycles of pin nematodes from Central Oregon and the Willamette Valley. Data were collected by taking cores to 4-6 in, weighing the core and determining the number of nematodes which resided in 500 g of that soil.

Very few studies have been conducted on control of pin nematodes but there are some limited data from studies designed for other nematodes which contained pin nematodes in the samples as well. Spring applications of Vydate 2L in Central Oregon significantly reduced populations of pin nematodes. However, while both mid- and late April applications (1/2 GPA) significantly reduced densities, there was a trend for mid-April treatments to be more effective, reducing populations to 37 and 28% of those in nontreated plots sampled in late May and early August, respectively (Ingham 1987, Ingham et al, 1988). Yields were not determined, however. In the Willamette Valley, pin nematode populations at harvest (July 27) were least in plots treated in mid- April than before or after that time. Early plus late April split applications (1 GPA each) reduced populations over 95% but were not more effective than a single application (1 GPA) on either date. Single applications at 1 or 2 GPA were also equal (Ingham, 1990).

Weight of fresh hay following a fall application of Vydate at 1/2 GPA in the Willamette Valley was 26% higher than in nontreated, plots but this difference was not statistically significant. Spring applications at 1 GPA had no effect on yield (Ingham unpubl.).

In contrast to most other nematodes which attack mint, pin nematode populations are much higher in the fall than in the spring (see Figure above) and therefore may be responsible for more winter injury in fields with high populations. Thus, a fall application may provide better yield response than a spring application when pin nematodes are the major nematode pest in that field. Fields with pin and root-lesion nematodes may benefit from a fall-spring split application but no trials of this nature have been conducted Considerable work remains to be done to optimize management of pin nematodes in mint.