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Redbacked Cutworm



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[Redbacked Cutworm]

[Insect Management]


Redbacked Cutworm: Sequential Sampling Plans in Peppermint

Department of Entomology, Oregon State University, Corvallis 97331

© 1978 Entomological Society of America

J. Econ. Entomol. 71:323 - 328

Seventy - two stratified random 929 - cm² soil samples were sufficient to estimate density of Euxoa ochrogaster (Guenée) in commercial - sized peppermint fields of 3 different age classes. Larvae were contagiously dispersed in most fields sampled, but when the density was <0.50/ 929 cm², dispersion appeared random. Sequential sampling plans were developed for newly planted fields <1 yr old (class I) and declining fields >= 6 yr old (class III). A plan could not be developed for class II fields (2 - 5 yr old) because cutworm densities were too low to determine the EIL in this study. These plans will provide growers with procedures to determine whether or not control is justified for redbacked cutworm in 2 different - aged peppermint fields.

The redbacked cutworm, Euxoa ochrogaster (Guenée), has caused serious losses in peppermint in central Oregon in the past (Berry 1975a, b) . Its occurence is erratic, and growers continued to make unnecessary insecticide treatments, partly because of the time required to take samples.

Sampling programs have been described to study cutworms in small plots (Berry 1975a, Frank 1971, King and Atkinson 1927, Klostermeyer 1952, Pfadt 1956, Pruess 1961, Walken 1943), but these programs are not suitable for growers to determine cutworm densities in commercial - sized fields. A possible solution to this problem was presented by Waters (1955) in a discussion of sequential sampling. Sequential sampling is especially suited for use in pest management because it allows rapid classification of insect populations into broad levels of infestation (Ruesink and Kogan 1975, Onsager 1976) . Generally, growers do not need exact estimates of population density, but they do need to classify populations as to whether or not control is needed. The primary advantage of using sequential sampling compared with other sampling programs is the saving of time and labor costs (Harcourt 1966a). Sequential sampling plans for the green cloverworm on soybeans (Hammond and Pedigo 1976), for the southern potato wireworm on potatoes (Onsager 1974), and for cabbage loopers on cauliflower (Harcourt 1966b) were designed to provide growers with practical sampling procedures.

A sequential sampling plan requires a reliable sampling technique, a description of the dispersion of the population, and the economic injury level (EIL). Our study was conducted to develop sequential sampling plans for redbacked cutworm in peppermint to assist growers in deciding whether or not densities were high enough to justify treatment with insecticides.