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Lab test of OFB Eden Pesticide for use against Leafhopper
Performance Screen
Efficacy screens of "OFB Eden" against the grape leafhopper, Erythroneura elegantula
July 5, 2000
by
Brook C. Murphy, Ph.D.
Consulting Entomologist, Ornamentals
Summary
Evaluations were conducted to test the performance of "OFB Eden" against the western grape leafhopper, Erythroneura elegantula a common pest of table, raisin and wine grape. Laboratory bioassays and small plot trials were used to test and demonstrate the potential for using "OFB Eden" against the grape leafhopper and possibly other leafhopper pests.
The laboratory bioassays revealed that "OFB Eden" dilutions of 150 and 300:1 (6,666 and 3,333ppm) resulted in virtually 100 percent mortality of all stages of the grape leafhopper including the adult stage. It was also observed that nymphs succumbed to the "OFB Eden" applications within 36 hours under indoor conditions and less than 12 hours under field conditions. Grape leafhopper 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 leafhopper 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 leafhopper species in other agricultural crops.
Cover photo: The fifth instar of the western grape leafhopper feeding on a merlot grape leaf.
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.
Laboratory trials were conducted in Davis and Sacramento, CA. Merlot leaves infested with the grape leafhopper were collected from commercial wine grape vineyards near Healdsburg, California. Twelve Merlot grape leaves (trial 1) and six grape leaves (trial 2) were placed individually in 50 ml vials filled with distilled water. Grape leafhopper nymphs were transferred to test leaves using no. 1 brushes. From ten to twenty second through fourth instar nymphs were placed on each test leaf (figure 1). Vials with leaves were randomly assigned one of the three treatments listed above. All applications to leaves and insects were made using a hand held atomizer. Leaves were sprayed to drip and allowed to air dry at room temperature for trial 1 (780F, 62% RH) and allowed to dry 3 hours under outdoor conditions for trial 2 (840F, 48% RH). Trial 1 was conducted on 28 June and trial 2 on 5 July 2000.
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)Water only control.
Evaluations were conducted using potted grapevines in Davis and Sacramento, CA. Nymphs were transferred to potted vines as described for the laboratory assays above. Nymphs were allowed to settle for 24 hours on leaves before treatment. Two grape vine canes with the leafhoppers established were assigned randomly to each of the treatments listed above. Applications were made using a hand held atomizer until the material dripped from the leaves. The trial was conducted on 6 July 2000. The numbers of live and dead nymphs were recorded 24 hours after treatment application. Applications were made at 3:00pm, at 860F and 52% RH.
Results
I. Laboratory Bioassays. Results of trial 1 showed significant mortality of 2nd through 5th instar nymphs 24 hours after treatment application (Table 1). Under room temperature conditions many of the nymphs were slow to succumb to the "OFB Eden" treatments. Over the course of 36 hours though, almost all of the nymphs eventually died and most of these fell from the grape leaves. Several of the survivors in the 300:1 treatment (see Table 1) showed abnormal appearance (figure 2) and I suspect would not survive under field conditions. During the first trial it was also observed that recently emerged adults were also killed by the "OFB Eden" treatments.
Trial 2 was intended both as a repeat of trial 1 using a different field population of leafhoppers and a test of the effects of outdoor conditions on time to leafhopper death. After the "OFB Eden" treatments test leaves were subjected to dryer and presumably more stressful outdoor conditions for 3 hours and then returned to indoor conditions. As before, most leafhoppers were killed within 24 hours at both concentrations tested. However, in this trial it was also observed that most died within 6 hours of application as evidenced by the dried cadavers remaining on some leaves (figure 3).
II. Whole plant evaluation. Results of the whole plant evaluation was similar to both of the previous laboratory bioassays. Reductions of near 100% of the leafhoppers were achieved with a single application at both concentrations. Most of the leafhoppers were killed 4 to 6 hours after application.
Conclusions
The preliminary screens suggest that "OFB Eden" has activity against the grape leafhopper similar to that seen for many aphid species previously tested. Observations during the trials suggest that the mode of action is not just a physical effect, but appears to affect leafhopper movement and feeding behavior some time prior to death. The effects on the leafhopper nymphs resembled physiological poisons similar to that caused by some conventional pesticides . The activity seen here suggests "OFB Eden" may be effective against other leafhopper pest species in other cropping systems and should be investigated as time permits.
Table 1. Laboratory bioassay (trial 1) comparing mortality of the grape leafhopper at two concentrations of "OFB Eden" with a water-only control (WOC).
Table 2. A second laboratory bioassay (trial 2) comparing mortality of the grape leafhopper at two concentrations of "OFB Eden" with a water only control (WOC).
Table 3. Small plot test (trial 3) using potted grape vines comparing two concentrations of "OFB Eden" against the grape leafhopper.
Figure 1. The laboratory bioassays used Merlot grape leaves infested with leafhopper nymphs and placed individually in 50 ml vials filled with distilled water for testing "OFB Eden" efficacy.
Figure 2. Prior to death, many of theArgi-50 treated leafhopper nymphs in the laboratory bioassays appeared deflated (dessicated?) and showed abnormal behavior (above). Adult grape leafhoppers also succumbed to "OFB Eden" applications.
Figure 3. Fifth instar grape leafhopper, just prior to molting to the adult stage, showing arrested movement and a dessicated appearance six hours after treatment with "OFB Eden" (above). The same nymph twenty-four hours after treatment showing complete dessication as indicated by the brownish coloration.