Ecoinformatics updates for citrus IPM
The current Citrusformatics database contains records for 327 different citrus blocks in the San Joaquin Valley, each observed by pest control advisors and growers for 1-20 years, for a total of ca. 1,800 field-years of data. These data are from ten citrus industry collaborators, and most data are from the calendar years 2008 – 2012, with data entry ongoing for years 2013-present. Records for each field-year include agronomic information, field scouting reports of pest and beneficial arthropod densities, plant nutrient status, agrichemical use, natural enemy surveys and releases, “bin sampling” of damage at harvest, and yield records (not all data types are reported for each field-year). Field scouting reports include >35,000 quantitative (counts, presence/absence) and >30,000 qualitative (e.g. low-medium-high scale) individual in-field observations of pest and natural enemy densities. Bin sampling records include quantitative counts of harvested fruit with damage by the main direct insect pests (California red scale, citrus thrips, katydid, peel miner, and citrus cutworm), plus qualitative estimates of damage intensity by other damage types (e.g. wind, mold, splits, sunburn).
If you are interested in contributing citrus management records to have your data included in these analyses, please contact us:
Principal Investigator: Prof. Jay Rosenheim e-mail: jarosenheim [at] ucdavis.edu phone: (530) 752-4395
Postdoctoral Researcher: Dr. Bodil Cass e-mail: bncass [at] ucdavis.edu phone: (530) 752-4481
Direct pests on oranges vs. mandarins
The Citrusformatics database has allowed us to compare in-field pest densities during the growing season with damaged fruit frequencies at harvest in mandarins vs. oranges. For fruit-scarring pests, preliminary analyses of the dataset have uncovered two key differences:
1) Classical katydid fruit scarring, the quarter-sized circular scars, are regularly observed on oranges, but almost never on mandarins, despite equal katydid densities on both varieties.
2) Oranges and mandarins may be sensitive to thrips scarring for longer than previously recognized, with a late peak of damage occurring 7-8 weeks after petal fall, during the third thrips generation.
Katydids not a pest on mandarins?
We collected a complementary researcher-generated dataset from 21 citrus groves this year to double-check the result that : 125 of 9446 oranges had katydid scars at harvest (1.32%), compared with only 2 of 8537 mandarins (0.02%). Thus katydids may not be significant pests on mandarins.
(1) katydids may not prefer to feed on mandarin fruits;
(2) katydids may feed on mandarin fruits differently, creating different types of scars;
(3) katydid-scarred fruits may be preferentially dropped by the trees after petal fall or during the “June drop”
(4) mandarins may recover from katydid damage.
We are currently running field experiments at the Lindcove Research and Extension Center to distinguish among these hypotheses.
In surveying fruit at harvest for katydid scarring, we observed some putative katydid scars on oranges that were smaller than the typical nickel- or quarter- sized scars. The field experiments will help to determine the range of katydid scarring phenotypes.
Citrus thrips window of fruit susceptibility
Feeding by citrus thrips 7-8 weeks, but not 5-6 weeks after petal fall appears to be creating fruit scarring. Our project may result in updates to thrips management guidelines to suggest a sliding window of spray thresholds that more accurately corresponds to thrips risk.
Experiments are scheduled for the 2018 and 2019 growing seasons to test specific windows of fruit susceptibility to thrips scarring.