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Redbacked Cutworm:
Sequential Sampling Plans in Peppermint
STEPHEN D. DANIELSON and RALPH E. BERRY
Department of Entomology, Oregon State University, Corvallis 97331
© 1978 Entomological Society of America
ABSTRACT
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. |
