9/1/1 Bean Thrips Basic Biology and Post-harvest Treatments Australia Citrus Preseason Meeting 17 September 201, Tulare, CA Joseph Morse Department of Entomology University of California, Riverside Bean Thrips Basic Biology Egg laying ceases ca. early October and larvae disappear by ca. the middle of October Mid October to November, adults seek out overwintering sites, moving mainly to plants which are still green, on which they spend the winter in "hibernation, feeding a little whenever the weather warms up Exposed overwintering adults appear to suffer mortality as a result of heavy rains; thus, they have evolved to seek out well protected areas in which to overwinter (e.g., the navels of navel oranges) 1
9/1/1 Bean Thrips Host Plants Wide host range - Crop plants reported as hosts (those that carry egg, larval, and adult stages) include alfalfa, almond, apple, asparagus, avocado, bean, beet, cabbage, cantaloupe, carrot, cauliflower, clover, corn, cotton, fig, garlic, grape, hops, kale, leek, lettuce, melon, olive, onion, orange, peach, pear, pea, pepper, persimmon, plum, potato, prune, radish, Swiss chard, tangerine, tomato, turnip, and walnut Not generally considered a pest on any of the above crops Many native or uncultivated plants are also known to support bean thrips-- most common are buckeye, morning-glory, poppy, prickly lettuce, bur clover, white melilot, common sow thistle, tree tobacco, and wild vetch Bean Thrips - Fruit Cutting To maximize the likelihood of finding bean thrips if present: Select fruit from the outside of the block facing likely sources of bean thrips fly-ins (creek bed, weeds, nut crops, or other crops likely to harbor bean thrips in late summer) Select fruit with a small exterior navel opening Take thin slices across the navel and inspect for infestation; a head or hand lens is needed to confirm identification Some bean thrips can go very deep into the navel Differentiate live bean thrips from other insects or mites and from the blackened tip of a flower stigma often found in the navel (thin slices result in it often being the length of a bean thrips) 2
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9/1/1 Identifying Bean Thrips Thrips found in field samples -- mostly bean thrips (black when wet), citrus thrips (yellow), and flower thrips adults (usually yellow but can see darker morphs) Adult bean thrips are uniformly dark grayish-black and the front wings have transverse white bands with brown tips Western flower thrips can also be problematic in Australia and New Zealand mostly dead by January or so after sustained cold weather (but can be alive earlier) 5
9/1/1 Adult bean thrips Color morphs of adult female western flower thrips
9/1/1 When during the fall / early winter do bean thrips fly to citrus? Two main factors appear to be important in fall and early winter Winter rains keep alternate host plants succulent and delay flights to citrus (versus dry conditions) Bean thrips are more active during warmer weather - fly less in cooler weather (0 F and below) Note: during winter, bean thrips will come out of the navel to feed on fruit and leaves during warm days Citrus Other than Navel Oranges Going to AU Can Sometimes Harbor Bean Thrips (2009-2010 data from APHIS) 2009-10 was an unusual bean thrips year in CA (high levels) 1 BT shipment finds in CA 27 on navel oranges, on Clementines, 1 lemon (Edison) 2 Fresno Co., 17 Kern Co. (1 lemon, 2 Clem.), 12 Tulare Co. (1 Clem.) 7 BT shipment finds in AU on navel oranges, 1 on mandarins (Kern Co., late January) Kern Co., 4 Tulare Co. Remain vigilant regarding bean thrips on mandarins, especially before 1 January ( of 4 Dec. 8), in addition to navel oranges (mandarin crevice not deep) 7
9/1/1 0-5 scale for rang the size of the mandarin stylar end opening (0 = none, 1 = too small) 0 1 2 4 5 Bean thrips placed in a 5 size hole for perspective; Clemenules fruit from Kern County 8
9/1/1 Post-harvest Bean Thrips Treatments Warm the fruit to 5 degrees F for 8 hours prior to fruit immersion/washing Treatment with Cropfume (same as Turbocide Gold ) or Evergreen (June 2011 Citrograph article by Morse et al.) Other treatments not registered yet: Spencer Walse (USDA ARS, Parlier) phosphine, others Ethyl formate = Vapormate TM planned 8-1-1 workshop cancelled when US-EPA notified the Linde Group that additional studies were needed before registration new target date ca. Oct. 2014 Cropfume Sweat Room Studies Full trade name of the product = MGK AgriPest Cropfume P-H with Pyrethrins (= same as older Turbocide Gold ) With overhead Cropfume applications, the bottom bin yields the lowest mortality in our research trials Previous Turbocide Gold label allowed 1 gram/ 1,000 cu ft applied up to times; trials were at g / 1,000 cubic ft Current Cropfume label allows 5 g / 1,000 cubic ft Degreening room fill to no more than 75% capacity Room temperature should be brought to 5 F (18 C) and allowed to reach thermal equilibrium from ceiling to floor 4 trials run to date with the higher use rate 9
9/1/1 Bean thrips infested fruit transported to the sweat room in a cooler Bioassay Navels Placed in the Center of a Carton of Valencia Oranges 0 1 2 4 5 10
9/1/1 March 18-19, 2010 Turbocide Gold Trial Cooperators: Fruit Growers Supply; MGK; Tri- County Packinghouse, Orange Cove, CA Sweat room bin configuramon (normal = bins high, 4 stacks wide by 1 deep) * * * * * * 2 sets of 9 stacks on left - normal bin spacing here (4- between 4 rows, tight down the columns [normally 1 columns]) 2 sets of 9 stacks on right - equal distance between walls and stacks in both directions Numbers designate number of bins high in a stack all bioassays were done in the top center of the bottom bin in the experimental stack 20 infested fruit, mean of 10.4 total bean thrips per treatment 11
9/1/1 Mean % mortality= 95.9% (8 boxom bins) 87.5% of full room capacity (14/1 rows, high); 94.9% mortality 72.9% of full room capacity (14/1, 5 high); 9.9% mortality Turbocide Gold Jan. 18, 2011 Mean % corrected mortality = 50.8% Room filled to 8% of capacity Mean temperature in the room = 52.2 F (i.e. the room was too cold to achieve good control) 12
9/1/1 Turbocide fog delivered by the overhead nozzle systems (11-21- 11) Summary - Bean Thrips Research with Pyrethrins v v Turbocide Gold (same as Cropfume ) provided 90-97% bean thrips mortality with the g / 1,000 cubic ft use rate except when the fruit were too cold (label allows 5 g with repeat application) v 4 trials average mortality of 94% v With enough bean thrips in the navels, inspection could still find a live bean thrips or two, even with this levels of control v 1 of 5 trials, 50.8% mortality when room temperature was 52.2 F must warm up the load to 5 F before application Only a single application of Evergreen is allowed per load industry pressure could likely bring back 2 treatments v Should not expect more than 70-80% bean thrips mortality 1
9/1/1 Acknowledgments Research was supported in part by the Citrus Research Board and previously by the USDA Foreign Agricultural Service, Technical Assistance for Specialty Crops Program (FAS TASC) Jim Cranney and CCQC helped to obtain the Turbocide Gold SLN and helped to design current IR-4 trials to maintain registrations Thanks to Julie Doctor, Marty Coert, and David Sorenson (Fruit Growers Supply) and MGK Corp. for assistance with past Turbocide Gold trials These trials would not be possible without the assistance of cooperating citrus packinghouses (Visalia Citrus Packers, Orange Cove; Porterville Citrus, Terra Bella; Yokohl Valley Packing, Lindsay) 14