Progress 08/01/06 to 07/31/08
Outputs
OUTPUTS: Year 1 methods: We did our project at the State Historic Citrus Park, Riverside, CA. We tested 2 different insecticides using 1.6 acre plots. Within each plot we randomly selected 25 trees for monitoring of ant numbers. Within each area KM AntPro bait stations were placed in a 100-ft grid pattern. The bait stations in one of the plots contained Gourmet Liquid Ant Bait, which is 1% disodium octaborate tetrahydrate. Bait stations in the other plot contained Impetus liquid ant bait, 0.0051% imidacloprid (Bayer). The control plot (0.8 acres) was in another block of oranges that was separated by a paved road. Twenty trees in this control plot were randomly selected for monitoring. Monitoring of ant numbers was done by taping 50 ml centrifuge tubes containing 25% sugar water onto the trunks of the monitored trees for 24 hrs. The tubes were weighed before and after they were put on the trees, so we knew how much the ants consumed. We also know that a single ant can consume 0.3 mg of liquid, so that 1 ml of consumption corresponds to about 3,300 ant visits to the tube. Consumption of sugar water is therefore an indirect measure of ant numbers. Post-treatment evaluation of the plots was done at 2, 4, 6, and 8 weeks. Year 2 methods: Field study. The location was the same as the above. Three 1.5 acre treatment plots were set up, each containing over 250 trees. In each of these plots we randomly selected 25 trees for monitoring of ant numbers. In addition, a control plot that was at least 1,000 ft from the treatments was set up (0.65 acres and containing about 120 navel oranges) in another block of oranges. Twenty trees in this control plot were randomly selected for monitoring. KM AntPro liquid bait stations were used for the treatments. One plot received Gourmet Liquid Ant Bait (see above) and the bait stations were placed using a 200-ft grid pattern . A second plot received Vitis liquid ant bait (0.001% imidacloprid, Bayer) using the bait stations in a 100-ft grid pattern. The third treatment plot received bait stations in a 100-ft grid pattern containing Tango (4.9% methoprene, an insect growth regulator, Wellmark) diluted with 25% sugar water to make a 0.25% concentration of methoprene. All bait stations were re-filled as necessary every 2 weeks. The monitoring of ant numbers was done as in year 1 above. Post-treatment evaluation of the plots was done at 1, 2, 5, 8, 10, 11, 12, and 14 weeks. Tango Laboratory study. We took a large laboratory colony that had been collected from the control plot. Two g of workers and 15 queens from this colony were put into each of 6 boxes. Three of these colonies received 25% sucrose water and roaches. The other 3 colonies received 0.25% methoprene in 25% sucrose water and roaches. We then periodically counted the number of dead workers and queens in each of these boxes up until week 16. Symposia: March 14, 2007. Invited speaker, CA Association of Pest Control Advisors-UCR Entomology Conference, Santa Paula. "Control of Argentine ants with bait stations in organic citrus." April 1, 2008. Gave talk at Pacific Branch ESA meeting, Napa, CA. "Control of Argentine ants with bait stations in citrus groves." PARTICIPANTS: PIs John Klotz and Mike Rust were involved in overall planning and execution of project. PI Les Greenberg directed the daily activities in the field and laboratory. Graduate student Kris Tollerup assisted in field setup and collection of data. Senior Research Associates Clint Allison and Paul Flores participated in the field studies in data collection and setup. Technician Edna Diaz also assisted with laboratory preparation and field data collection. Joe Barcinas and Chris Boisserranc, Pest Control Advisors who manage the citrus groves we were using, helped us find suitable plots for the study. The State Historic Citrus Park, Riverside CA., allowed us to use their citrus groves for the study. Ken Kupfer provided the KM AntPro bait stations and the Gourmet Liquid Ant Bait. Bayer provided the Impetus and Vitis products for the study, and Wellmark supplied the Tango. TARGET AUDIENCES: Our project targeted one of the priorities of the California Citrus Board, namely Argentine ant control in citrus production. We are also demonstrating the usefulness of bait stations for ant control in agriculture, one of the priorities of IR-4, with whom we have been collaborating by getting permission to use bait stations in agriculture. We have also been working with the Bayer, KM AntPro, and Wellmark corporations to get products labeled for use in the bait stations. Results from our studies have been presented in symposia and will be promulgated in future publications. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Year 1: For the Gourmet bait over these time intervals the reductions in ants were 38, 30, 88 and 91%, respectively. For the Impetus bait the respective reductions were 40, 42, 87, and 88%, respectively. Ant numbers in the controls increased through week 8. Year 2, Vitis field study: Ant numbers in the Vitis bait plot were significantly lower than the controls for all weeks except for the Pretreatment and Week 5. Ant numbers in the controls increased through week 8. The greatest reduction of ants with respect to controls was 74% at week 10. After that there began a seasonal decline in overall ant foraging activity which lowered the control values. Therefore, week 10 is the best indicator of the products' reduction in ant numbers. Tango field study: Ant numbers in the control plot peaked 2 weeks after treatment. However, in the methoprene plot ant numbers continued to rise through week 8, probably reflecting the fact that these ants are being fed sucrose water ad libitum all that time and the insect growth regulator has not yet had an effect. At week 8 the Tango plot had about twice as many ants as the control plot. In the treatment plot ant numbers crashed starting at week 10, when they were almost the same as the numbers in the control plot. Ant numbers continued to decline in the treatment plot during weeks 11 and 12, and were significantly lower than the controls for those 2 weeks. The reductions in ant numbers with respect to the control plot for weeks 11 and 12 were 51 and 52%, respectively. For week 14 the reduction was only 13% and not significant. The latter probably reflects the overall decrease in ant foraging at the end of the summer season, making it more difficult to show differences between treatments and controls. Given the sudden crash in ant numbers in the methoprene plot, we decided to collect ant samples from the treatment and control plots to help evaluate the results. We collected ants from 10 nests in each of the plots. There were only 10 queens in the methoprene plot whereas the control plot had 142 queens for a similar weight of workers. There were 0.395 queens per g of workers in the methoprene plot, while there were 5.13 queens per g of workers in the control plot. Tango laboratory study: Beginning Week 9 the mortality in the methoprene boxes was significantly greater than in the controls (by ANOVA or Mann-Whitney U-test). Significance levels for weeks 9, 12 and 16 were 0.002, 0.006, and 0.03, respectively. Gourmet field study: Beginning week 8 and continuing through week 14 the ant numbers in the treatment plot were significantly lower than in the controls. The greatest reduction was at week 11 (66%). The average reduction from week 1 to week 14 was 44%. These results are for the 200-ft grid pattern of bait stations, compared to the 100-ft patterns for the other treatments. Conclusions: We have shown significant reductions in ant numbers in citrus groves using liquid baits in bait stations. Because the bait is containerized, there is little ground contamination by the pesticide. This approach is therefore environmentally sound.
Publications
- No publications reported this period
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Progress 08/01/06 to 07/31/07
Outputs
We did our project in a 10 acre block at the State Historic Citrus Park, Riverside, CA. The 2 different materials were tested at plots on opposite ends of this block, with approximately 600 ft separating them. Each of these plots was 1.6 acres, and contained about 260 navel orange trees. Within each plot we randomly selected 25 trees for monitoring of ant numbers. Within each area KM AntPro bait stations were placed in a 100-ft grid pattern, resulting in 12 bait stations for each plot. Bait stations hold about 500 ml of liquid bait, and were re-filled as necessary every 2 weeks. The bait stations in one of the plots contained Gourmet Liquid Ant Bait, which is 1% disodium octaborate tetrahydrate. Bait stations in the other plot contained the Impetus liquid ant bait, 0.0051% imidacloprid. The control plot (0.8 acres and containing about 121 navel oranges) was in another block of oranges that was separated by a paved road and hundreds of feet from any of the treatments.
Twenty trees in this control plot were randomly selected for monitoring. Monitoring of ant numbers was done by taping 50 ml centrifuge tubes containing 25% sugar water onto the trunks of the monitored trees for 24 hrs. The tubes were weighed before and after they were put on the trees, so we knew how much the ants consumed. We also know that a single ant can consume 0.3 mg of liquid, so that 1 ml of consumption corresponds to about 3,300 ant visits to the tube. Consumption of sugar water is therefore an indirect measure of ant numbers. During the 24 hrs that the monitors were on trees, the bait stations were closed so that they would not compete with the monitors during the time they were on the trees. Post-treatment evaluation of the plots were done at 2, 4, 6, and 8 weeks. For the Gourmet bait over these time intervals the reductions in ants were 38, 30, 88 and 91 %, respectively. For the Impetus bait the respective reductions were 40, 42, 87, and 88%, respectively. Ant numbers in
the controls increased through week 8. There did not appear to be any significant difference in the performance of the 2 pesticides. After the first year of this project we have shown significant reductions in ant numbers in a citrus grove using liquid baits in bait stations. Because the bait is containerized, there is little ground contamination by the pesticide. This approach is therefore environmentally sound. In the second year of this project we are continuing to determine the optimal spacing of the bait stations as well as trying additional pesticides in the bait stations.
Impacts
We have demonstrated that ant numbers in citrus groves can be successfully reduced using liquid ant baits in EPA approved bait stations. By putting the pesticides in bait stations we greatly reduce the chance of environmental contamination and water runoff containing pesticides. These procedures can be applied to other urban and agricultural situations where pesticides are used.
Publications
- No publications reported this period
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