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Variegated Cutworm Economic Loss

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Variegated Cutworm: Leaf Consumption and Economic Loss in Peppermint

Ralph E. Berry and Elson J. Shields
Department of Entomology, Oregon State University,
Corvallis, Oregon 97331

1980 Entomological Society of America
J. Econ. Entomol. 73: 607-608

ABSTRACT

Mean total consumption of peppermint foliage for Peridroma saucia (Hubner) instars 3-6 was 2.3+1.2, 7.2+2.5, 31.5+5.0, and 133.6+25.4 cm2, respectively. Total consumption of 174.4 cm2 was equivalent to 26.7 peppermint leaves. Instars 5-6 consumed 94.5% of the total foliage consumed during development of instars 3-5 (25.3 leaves). Mean number of days for development of instars 3-6 was 3.2+0.4, 3.9+0.4, 4.8+0.9, and 10.0+2.0, respectively. Peppermint plant samples (1000 cm2 soil surface area) were used to estimate mean leaf size (6.5+1.4 cm2), total leaf area/1000 cm2 (6247+1105 cm2, and mean oil yield/1000 cm2 (0.8+0.1 ml).

It was estimated that 0.9 5th and 6th instars/1000 cm2 would cause a 2.4% defoliation which was equivalent to the economic injury level for variegated cutworm on peppermint based on an oil value of $22/kg and a total cost of insecticide treatment of $45/ha.