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Performance Evaluation - OFB Eden Pesticide against Cabbageworm
Performance Screen
Efficacy screens of "OFB Eden" against the imported cabbageworm, Pieris rapae
July 10, 2000
by
Brook C. Murphy, Ph.D.
Consulting Entomologist, Ornamentals
Summary
Evaluations were conducted to test the performance of "OFB Eden" against the imported cabbageworm, Pieris rapae a common pest of crucifers and other row crops. Laboratory bioassays and small plot trials were conducted to test and evaluate the potential for using "OFB Eden" against caterpillar pests.
The laboratory bioassays revealed that "OFB Eden" dilutions of 150 and 300:1 (6,666 and 3,333ppm) resulted in significant mortality of cabbage worms feeding on kale. The early instars (1st through 3rd) appeared most susceptible. Cabbage worm mortality was not significantly affected by differences in "OFB Eden" concentration.
From the results of this preliminary screen it can be concluded that "OFB Eden" demonstrated consistent effectiveness against a significant caterpillar pest at both concentrations and under the different environmental conditions of the trials. These results also suggest "OFB Eden" may be effective against other economically significant caterpillar species in other agricultural crops.
Procedures
I. Laboratory Bioassays
"OFB Eden" Treatments:
1)0.333% "OFB Eden" (3,330 ppm or 300:1 dilution)
2)0.666% "OFB Eden" (6,660 ppm or 150:1 dilution)
3)Water only control.
Potted kale plants were grown from seed in 3 x 3 inch pots. At the forth leaf stage plants were exposed to natural populations of adult Pieris rapae which oviposited from the fifth to seventh leaf stage. When 10 or more eggs were oviposited on each test plants, the seedlings were covered to prevent further egg laying and the larvae allowed to develop for 10 days (figure 1). Two plants were randomly assigned to each of the treatments listed above. Treatments were applied using a hand held atomizer until runoff on 14 April 2000. The seedlings were left covered for 48 hours and the numbers of live and dead cabbage worms recorded.
II. Whole plant evaluations
"OFB Eden" Treatments:
1)0.333% "OFB Eden" (3,330 ppm or 300:1 dilution)
2)0.666% "OFB Eden" (6,660 ppm or 150:1 dilution)
3)Untreated control.
Kale and radish plants (12 and 10 of each respectively) grown in a garden bed became naturally infested with cabbage worm larvae. When an even larval age distribution became established among the radish and kale plants, plants containing larvae were randomly assigned one of the treatments listed above and the material applied using a hand held atomizer on 30 June 2000. Plants and larvae were monitored hourly for 12 hours before the number of live and dead larvae were recorded.
Results
I. Laboratory Bioassays. Results of the laboratory trial showed significant mortality of 1st through 3rd instar larvae 48 hours after treatment application (Table 1). Late instar larvae (n = 3) showed arrested feeding behavior for several days but otherwise appeared to recover and pupate normally. Pupae were not examined to determine adult viability. During the trial it was noted that early instars showed arrested feeding and either fell from the host plant or hung from the leaves or stems. None of the young larvae recovered.
II. Whole plant evaluation. Results of the whole plant evaluation was similar to the laboratory bioassay above. Virtually 100% of the 1st through 3rd instar larvae were killed with a single application at both concentrations. Most showed toxic effects within 2 to 4 hours after the "OFB Eden" applications (figure 2). Some 4th instar larvae did show toxic symptoms, and several were killed by the applications. However several other recovered and pupated normally.
Conclusions
The preliminary screens suggest that "OFB Eden" had activity against a major caterpillar pest. Although the greatest impact was seen for the early instars, from a pest management point of view this is the most important stage to achieve economic control over this and other important caterpillar pests. Furture trias will need to more closely examine both the lethal and sublethal effects on this and other caterpillar species.
Observations during this trial suggest that similar to the aphid and leafhopper trials the mode of action is not just a physical effect, but appears to affect movement and feeding behavior some time prior to death. The effects on the caterpillars resembled physiological poisons similar to that caused by some conventional pesticides.
Table 1. Laboratory bioassay (trial 1) comparing mortality of the imported cabbage worm at two concentrations of "OFB Eden" with a water only control (WOC) 12 hours after treatment application.
Table 2. Small plot test (trial 2) comparing two concentrations of "OFB Eden" against the imported cabbage worm feeding on kale and radish 12 hours after treatment application.
Figure 1. Egg (above) and 1st instar imported cabbage worm (below) used in the laboratory bioassay. "OFB Eden" applications resulted in virtually complete mortality of early instar larvae.
Figure 2. Early instar imported cabbage worm larvae immobilized within 4 hours of the "OFB Eden" applications (above). Late instar larvae were much less susceptible to the "OFB Eden" treatments, although some, as shown here became immobilized and were killed (below).