Progress 07/15/10 to 07/14/12
Outputs
OUTPUTS: Activities: Data for this project was collected from four different field-based persea mite research programs in Ventura, Orange, and Santa Barbara Counties in California. The resulting data set was composed of 301 sampled trees, from which a total of 30,416 leaves were examined, and 588,920 persea mites counted. These data were used to develop statistical relationships between the proportion of leaves infested with persea mites and the average densities of this pest on leaves. This result enables pest managers to keep a tally of the proportion or percentage of infested leaves as they sample. This proportion then translates to the average number of mites per leaf. This estimate is achieved without having to count any mites. This is a major time saving sampling method as counting tiny mites with a hand lens in the field is very time consuming and inaccurate method of estimating mite densities. The spatial distribution of persea mite infested trees was also determined. Analyses indicated that sampled trees needed to be separated by a minimum of four of trees (i.e., every fifth tree is sampled). The results of this work have shown that avocado orchards can be sampled in ~30 mins to determine the average mite densities per leaf. If average mite densities are estimated to be in the range of 50-100 mites per leaf, then treatments may be necessary. Events: Two field days were held to demonstrate this new sampling technique to avocado growers. Three workshops were held on these field days. The workshops were divided into three sections: (1) Overview of persea mite biology, ecology, damage, and biological control (lecture). (2) Pesticide and resistance management of persea mite (lecture). (3) Sampling for persea mite using the presence-absence sampling strategy (lecture and field demonstration). The field demonstration involved walking blocks of avocados with participants and having the participants use the sampling method to estimate persea mite densities in blocks of trees in demonstration orchards. The positive feedback on the new sampling technique was universal. Approximately 35 growers participated in these workshops which were held in June 2012 at the UC Thelma Hansen Trust in Ventura County, and the South Coast Field and Research Center in Orange County. Continuing Education credits were offered as part of this training. Presentations were given on this work at professional and grower meetings: Li, J.X., D. Jeske, D.J. Lara, and M.S. Hoddle. Sequential Hypothesis Testing for Pest Count Spatial GLMM Models. Mathematical Models of Random Phenomena at the Meeting of the American Mathematical Society in Los Angeles, California, October, 9-10 2010. Lara, J. and Hoddle,M.S. Nov. 10 2010. Progress on a simple "no counting needed" monitoring strategy for persea mite. UCR-CAPCA Annual Fall Meeting, Santa Paula Community Center, Santa Paula. Lara, J.R. and M.S. Hoddle. December 13 2010. Development of a sequential binomial sampling plan for Oligonychus persea (Acari: Tetranychidae) on avocado. Poster presentation at the 58th Annual ESA Meeting, Town and Country Convention Center, San Diego CA December 12-15, 2010. First place Student Competition. PARTICIPANTS: This project was a collaboration between faculty and students in the Departments of Entomology and Statistics at the University of California Riverside with local avocado growers in Orange, Ventura, and Santa Barbara Counties in southern California. TARGET AUDIENCES: Target audiences for this work are professional pest control advisors (PCA's), avocado growers, and avocado ranch/orchard managers in California. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This is very difficult to estimate at this stage. The outreach efforts for this sampling plan are only 6 months of age. More effort is being invested in promoting this sampling plan, for example, in the upcoming 2013 volume of the California Avocado Society Yearbook we are publishing an article directed at growers on how to use the sampling plan. The article is entitled: "Sampling Guidelines for Persea Mite in California Avocado Orchards." This Yearbook will reach several hundred avocado growers in California. Other grower-specific media will be used to promote the sampling plan in the upcoming year - including magazines (e.g., CAPCA [Calfiornia Association of Pest Control Advisors] Advisor) and grower meetings targeting avocado growers.
Publications
- DePalma, E. D.R. Jeske, J.R. Lara, and M.S. Hoddle. 2012. Sequential Hypothesis Testing With Spatially Correlated Presence-Absence Data. Journal of Economic Entomology 105: 1077-1087.
- Zhang, Z., D.R. Jeske, X. Cui, and M.S. Hoddle. 2012. Co-clustering spatial data using a generalized linear mixed model with application to integrated pest management. Journal of Agricultural, Biological, and Environmental Statistics 17: 265-282.
- Lara, J.R., and M.S. Hoddle. 2013. Sampling guidelines for persea mite in California avocado orchards. California Avocado Society Yearbook 95: (in press).
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Progress 07/15/11 to 07/14/12
Outputs
OUTPUTS: Presentations on the results of this work at professional and grower meetings have been given by Jesus Lara, a Ph.D. student working on this project: Lara, J. and M.S. Hoddle. Comparison of techniques for modeling mean-proportion relationships with implications for presence-absence sampling. Graduate Student Ten-Minute Paper Competition, Plant-Insect Ecosystem Section 10. The 59th Annual Meeting of the Entomological Society of America, Nov. 13-16, Reno-Sparks Convention Center, Reno, NV. Nov 14 2011. This presentation made Second Place in the Student Competition. Lara, J. and M.S. Hoddle. Monitoring and controlling persea mite on avocado. Annual UCR-CAPCA Ventura Entomology Meeting, Santa Paula Community Center, Santa Paula CA. November 9 2011. PARTICIPANTS: People who have worked on this project include: J. Li and E. DePalma Ph.D. Students in the Department of Statistics at UC Riverside(both graduated in 2011); Jesus Lara, Ph.D. student in Entomology at UC Riverside; and several summer student helpers who provide field assistance with the set up of experiments with cooperating avocado growers in Carpinteria. TARGET AUDIENCES: The target audience for this work are California's avocado growers who use pesticides to control persea mite, a pest that attacks avocado foliage. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This project in not yet complete and no impacts have resulted. However the potential impacts expected are as follows: Upon completion of this project and field demonstrations we are optimistic that this sampling plan for estimating persea mites in avocado orchards will be adopted by growers and pest control advisors who scout orchards and provide pest control recommendations. We anticipate that this no counting mite sampling program will improve the accuracy of pest control decision making, increase the speed at which reliable "spray" or "don't spray" decisions can be made, and growers will reduce the frequency of applying pesticides when they are not needed thus saving money, lowering the likelihood of resistance development to efficacious products, and reducing environmental contamination. The statistical methods developed for this project will be applicable to pests infesting other perennial cropping systems, especially tree crops planted in grids (e.g., citrus, walnuts, apples etc). Ultimately, we hope to be able to develop software for this sampling program that can be downloaded as an "App" onto a smart phone or tablet that will generate a real-time sampling report with a pest control decision that can emailed by the PCA or scout directly from the field to the orchard manager with GPS coordinates and photos of problem areas needing treatment.
Publications
- Li, J.X. D.R. Jeske, J.R. Lara, and M. Hoddle. (2012) Sequential hypothesis testing with spatially correlated count data. IMTA 2: (in press)
- DePalma, E. D.R. Jeske, J.R. Lara, and M.S. Hoddle 2012. Sequential hypothesis testing with spatially correlated presence-absence data. Journal of Economic Entomology (in press)
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Progress 07/15/10 to 07/14/11
Outputs
OUTPUTS: Activities: Considerable progress has been made on the development of a sampling plan for persea mite in avocados. This has involved statistical analyses of very large field-generated data sets for persea mite. This analytical work has involved two major steps: (1) determing the relationship between the proportion of infested leaves and the mean number of mites on leaves, and (2) evaluating tree selection rules to eliminate spatial correlation and subsequent non-independence between sampled avcoado trees. A total of 72 data sets from 9 avocado orchards in California were analyzed. This effort encompassed examination of 30,656 leaves and the counting of almost 600,000 mites. The relationship of the mean proportion of leaves infested with one or more mites with the average number of mites per leaf was determined using an empirical equation for mean-proportion relationships. This accomplishment is the first step in developing a presence-absence or binomial sampling method (i.e., no counting of mites on leaves is needed because the proportion of infested leaves provides an estimate of the mean number of mites on a leaf) for estimating the average number of mites per avocado leaf. The spatial distribution of mite infested avocado trees is affected by the densities of mites on neighboring trees. This spatial relationship means that population samples are not independent of one another if sampled avocado trees are too close together. Consequently, spatial analyses of trees sampled for persea mite indicated that a maxi-min tree selection approach eliminates this correlation problem. Maxi-min maximizes the minimum distance needed for sampling trees thereby ensuring that they are spaced far enough apart to eliminate spatial correlation. In addition to maxi-min tree selection several other tree sampling patterns were analyzed with computer simulations: (1) Orchard borders were sampled, (2) trees were selected along corner to corner diagonals, (3)zig-zag, (4) grid pattern, and (5) simple random sampling. Statistical analyses indicated that maxi-min tree selection was the superior tree selection method and that just 6 leaves per tree needed to be examined for the presence or absence of persea mite. In many instances a treat or no-treat decision for this pest was reached after examining just 5-10 trees. Preliminary findings from work completed so far have been disseminated via oral presentations or posters at professional meetings: Lara, J. and Hoddle, M.S. Nov. 10 2010. Progress on a simple "no counting needed" monitoring strategy for persea mite. UCR-CAPCA Annual Fall Meeting, Santa Paula Community Center, Santa Paula, California. Lara, J.R. and M.S. Hoddle. December 13 2010. Development of a sequential binomial sampling plan for Oligonychus persea (Acari: Tetranychidae) on avocado. Poster presentation at the 58th Annual ESA Meeting, Town and Country Convention Center, San Diego California December 12-15, 2010. First place Student Competition. PARTICIPANTS: Mr. Elijah DePalma, Department of Statistics, University of California, Riverside, Riverside, CA 92521 (Ph.D. student in Statistics) Dr. Daniel R. Jeske, Department of Statistics, University of California, Riverside, Riverside, CA 92521 Mr. Jesus R. Lara, Department of Entomology, University of California, Riverside, Riverside, CA 92521 (Ph.D. student in Entomology) Dr. Mark Hoddle, Department of Entomology, University of California, Riverside, Riverside, CA 92521 Cooperating avocado growers in Ventura and Santa Barbara Counties, California. TARGET AUDIENCES: Target audiences have been: Growers who are interested in learning about advanced methods for monitoring pests to make control decisions. An extension talk at a California Association of Pest Control Advisors (CAPCA) was given: Lara, J. and Hoddle, M.S. Nov. 10 2010. "Progress on a simple "no counting needed" monitoring strategy for persea mite." UCR-CAPCA Annual Fall Meeting, Santa Paula Community Center, Santa Paula. Additionally, academic colleagues were exposed to the research developments through a poster given at a professional meeting (Entomological Society of America): Lara, J.R. and M.S. Hoddle. December 13 2010. Development of a sequential binomial sampling plan for Oligonychus persea (Acari: Tetranychidae) on avocado. Poster presentation at the 58th Annual ESA Meeting, Town and Country Convention Center, San Diego CA December 12-15, 2010. First place Student Competition. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
This project has generated new fundamental knowledge for the sampling of pests in tree crops. The work completed for this project is the first statistical application of spatial analyses coupled with sequential sampling for the development of a sampling plan for pest management. Our proposed presence-absence sampling methodology for persea mite evaluates a sequential hypothesis test of pest population densities which, 1) accounts for aggregation of pest populations on individual trees, and 2) mitigates spatial correlation of pest populations on adjacent trees using a tree-selection rule which sequentially selects trees to be maximally spaced from all other previously selected trees (sequential, maximin tree-selection).
Publications
- No publications reported this period
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