Pulsed ultrasonic sound was broadcasted over lettuce and broccoli crops to determine its effectiveness in reducing oviposition by the cabbage looper moth, Trichoplusia ni (Hübner). Three frequencies were used: 20, 30, and 40 kHz. Each was doubly pulsed: a low-frequency pulse (duration I second, interval 5 seconds), and a high-frequency pulse (duration 25 mseconds, interval 50 mseconds). The high-frequency pulse was generated during the on-time of the low-frequency pluse. Overall reductions in oviposition of 41, 23, and 30% were obtained in plots treated with 20, 30, and 40 kHz sound, respectively. However, sound intensities within each plot ranged from 30 or 40 to 80 or 90 db (re 0.0002 dynes/cm2). Linearregression analyses indicated that the greatest reduction in oviposition-up to 66%-occurred on plants receiving the highest sound intensities (70 to 90 db) .
Document Type: Research Article
Publication date: February 1, 1968
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