Flea Beetle Management in Brassica Greens Ruth Hazzard, Caryn Andersen, Roy Van Driesche, Francis Mangan University of Massachusetts Crucifer Flea Beetle • Predominant flea beetle species in this area • Solid black in color, with metallic sheen • Feeds only on brassicas • Introduced to America in the 1900’s • Scientific name: Phyllotreta cruciferae Striped Flea Beetle • Much less numerous in New England • Black with one yellow stripe down each wing cover • Emerges slightly earlier • Feeds only on brassicas • Scientific name: Photo courtesy of Manitoba Agriculture and Food Phyllotreta striolata Host Crops for Crucifer and Striped Flea Beetle Brassica oleracea Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Kale, Collards, White- flowering Chinese Broccoli, Gai Lan Brassica rapa Chinese cabbage, Turnip, Hon Tsai Tai, Yellow-flowering Chinese Broccoli, Broccoli Raab, Komatsuna, Pac Choi, Tat Soi Brassica juncea Mustard Greens, Bok Choy Brassica nigra Black Mustard Brassica napus Red Russian Kale, Rutabaga, Oilseed rape, Canola Brassica campestris Canola, Turnip Raphanus sativus Radish, Daikon Eruca vesicaria Arugula Host Crops for Crucifer and Striped Flea Beetle Brassica oleracea Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Kale, Collards, White-flowering Chinese Broccoli, Gai Lan Brassica rapa Chinese cabbage, Turnip, Hon Tsai Tai, Yellow-flowering Chinese Broccoli, Broccoli Raab, Komatsuna, Pac Choi, Tat Soi Brassica juncea Mustard Greens, Bok Choy Brassica nigra Black Mustard Brassica napus Red Russian Kale, Rutabaga, Oilseed rape, Canola Brassica campestris Canola, Turnip Raphanus sativus Radish, Daikon Eruca vesicaria Arugula Host Crops for Crucifer and Striped Flea Beetle Brassica oleracea Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Kale, Collards, White-flowering Chinese Broccoli, Gai Lan Brassica rapa Chinese cabbage, Turnip, Hon Tsai Tai, Yellow-flowering Chinese Broccoli, Broccoli Raab, Komatsuna, Pac Choi, Tat Soi Brassica juncea Mustard Greens, Bok Choy Brassica nigra Black Mustard Brassica napus Red Russian Kale, Rutabaga, Oilseed rape, Canola Brassica campestris Canola, Turnip Raphanus sativus Radish, Daikon Eruca vesicaria Arugula Host Crops for Crucifer and Striped Flea Beetle Brassica oleracea Broccoli, Brussels Sprouts, Cabbage, Cauliflower, Kale, Collards, White-flowering Chinese Broccoli, Gai Lan Brassica rapa Chinese cabbage, Turnip, Hon Tsai Tai, Yellow- flowering Chinese Broccoli, Broccoli Raab, Komatsuna, Pac Choi, Tat Soi Chinese broccoli Chinese cabbage Bok Choy Host Crops for Crucifer and Striped Flea Beetle, continued Brassica juncea Mustard Greens Brassica nigra Black Mustard Brassica napus Red Russian Kale, Rutabaga, Oilseed rape, Canola Brassica campestris Canola, Turnip Raphanus sativus Radish, Daikon Eruca vesicaria Arugula Mustards Daikon Cabbage root maggot damage is also a serious problem on daikon Flea Beetle Damage Shot-hole Damage • Tends to occur on non-waxy leaves • Examples: Brassica rapa, B. napa, B. juncea Flea Beetle Damage Marginal Damage • Tends to occur on waxy leaves • Examples: Brassica oleracea, B. napus Why are flea beetles getting worse in the Northeast US? 1. More production of preferred crops 2. Succession planting from May to October 3. Small farms with few rotation options 4. Low mortality from insecticides, esp. on organic farms Flea beetle life cycle Above ground, on foliage ADULT Underground, near plant roots PUPA EGGS LARVA How many flea beetle generations are there per year? Emerge → feed → head to overwintering sites 2nd Summer generation Some emerge → feed → reproduce → die 1st Summer generation Some feed → head to overwintering sites Emerge from overwintering→ feed → reproduce → die Overwintered generation eggs May June July August September October Above ground, on foliage ADULT Underground, near plant roots PUPA EGGS LARVA Where do flea beetles spend the winter? Fall crop Sampling Site- 2002 Average Number of Flea Beetles per sample Overwintering Study Winter 2001-2002 30 25 les 20 et e b f 15 e # o ag 10 aver 5 0 woods shrubby grassy location of sample Spring Movement into Fields • Flea beetles rapidly locate new crops • Heavy damage (or death) to young plants may result • Numbers are high from May - early July When and how much do Flea beetles feed? Feeding Experiment • 1 collard plant (3-4 leaf stage) per cage • 5 flea beetles • 24 hours in growth chamber at 25°C and 16L:8D • 10 reps per week • Recorded # of feeding holes per plant Average number of holes per plant after being caged for 24 hours with 5 flea beetles (2003 data) 120 a 100 July 14 Emergence of 1st ab generation 80 abc ant l p bcd / bcd s bcd e bcd l 60 o bcde bcdef bcdef defg 40 bcd bcdef August 26 avg # h defg defg cdef Emergence of 2nd generation 20 efg fg g 0 7 4 4 8 2 9 6 6 3 0 30 1 21 28 11 1 25 1 23 30 13 20 27 1 17 5/ / 6/ 7/ 7/ 8/ 9/ 4/ 5/ 5 5/ 6/ 6/ 6/ 7/ 7/ 7/ 8/ 8/ 8/ 9/ 9/ date Conclusions Feeding exp’t • Propensity to feed significantly higher in early August • Early August peak may reflect emergence of first new generation of adults • Increase in feeding in mid-September may reflect emergence of 2nd generation and their feeding before moving to overwintering sites Response to sticky cards Percentage of beetles captured by a yellow sticky card during 24 hour cage exp't 100 a 90 July 14 st 80 Emergence of 1 generation ab 70 ab ab ab ab ab d e 60 abc r u bcd t p 50 ab a bcd ab abc 40 % c bcd 30 August 26 bcd Emergence of 2nd 20 generation cd 10 d 0 4 4 8 2 6 6 3 3 0 30 /7 1 21 28 11 1 25 /9 1 23 30 1 20 27 1 5 6/ 7/ 7 8/ 9/ 4/ 5/ 5/ 5/ 6/ 6/ 6/ 7/ 7/ 7/ 8/ 8/ 8/ 9/ date Overlay of feeding graph and response to Feeding and response to sticky cards peak in late July/August sticky cards graph 4 / 3 0 5/ 7 5 / 14 5 / 2 1 5 / 2 8 6/ 4 6/ 11 6 / 18 6 / 2 5 7/ 2 7/ 9 da 7 / 16 te 7 / 2 3 7 / 3 0 8/ 6 8 / 13 8 / 2 0 8 / 2 7 9/ 3 9 / 10 Management Strategies for Flea Beetles… 1. Escape them (rotate to new fields) 2. Starve them (don’t till after overwintered adults die) 3. Kill them (use insecticides) 4. Shut them out (use row cover) 5. Combine as many of these as possible 1. Escape: Crop Rotation • Plant spring crops into fields that have NOT had brassica crops in the past 2-3 years • Avoid fields with brassica weeds, which also harbor flea beetles • Plant fall crops (seeded after late July) in fields that are isolated from early season crops. • How far? As far as possible. Rotate to new a field to escape the next flush of adult beetles 2nd Summer generation Brassicas in field 2 1st Summer generation Brassicas in field 1 Overwintered generation eggs May June July August September October 2. Starve Them: Delayed Planting • No brassica crops until late July, after overwintered adults are dead or departed >No food plants for overwintering adults >No place for eggs, no roots for larvae to feed >No new adults emerge in late summer >Reduces the population of adults NEXT year May require major changes in marketing plans eg. Mesclun without brassica greens 3.Kill them: Insecticides for flea beetles Organic Insecticides for Flea Beetle Control on Brassica Greens or Eggplant approved for organic production: Pyrethrin PyGanic EC 5.0 (no DH restriction; rate 4.5-18 oz/acre) Spinosad Entrust (Labeled for use on all Brassicas, but not for control of flea beetles; states differ in whether it can be recommended) Kaolin Surround WP (labeled for eggplant; 1/2lb/gal in backpack, 12.5 to 50 lb/acre) Eggplant and potato flea beetles Prevention: Row cover • Keeps all beetles out! • Use hoops Sprays you can use for flea beetle Surround WP on eggplant Kaolin clay Organic status uncertain: not currently approved Hot Pepper Wax Broad label – many pests and crops showed efficacy in one of Umass trials. would be very expensive. Effect of treatment on leaf damage in Komatsuna (# holes per plant) at harvest (2002 Trial) 350 a 300 t an l 250 p r b e 200 b es p 150l o c c 100 # h g c av 50 d 0 control kaolin htpepw rowcov carbaryl spinos thiameth Treatment Effect of treatment on leaf damage (holes per plant) in Komatsuna Weekly samples, cotyledon stage to harvest, 2003 180 control ab 160 row cover 140 Sevin abc Pyganic 120 abc t n spinosad (Entrust) la p 100 er spinosad (Spintor) p 80 es l thiamethoxam (furrow) o cd # h 60 cd 40 d 20 0 e 12345 Weekly Samples from June 9 to July 8, 2003 Entrust (spinosad, organic formulation) • Manufacturer: Dow AgroSciences • EPA Classification: Caution -- General Use – NOP approved. – “the ingredients in this product meet the requirements of the USDA national organic program” • Derived from soil micro-organism -- natural source • Toxicity – very low toxicity to mammals, birds, aquatic invertebrates. Slightly toxic to fish – easy on beneficial insects – rat LD50 oral and dermal > 5,000 mg/kg • Mode of action – nerve poison ( by contact with treated surfaces) – stomach poison (by ingestion of treated surfaces) Entrust (spinosad, organic formulation) • Insect groups controlled: Colorado potato beetle (adults and larvae), caterpillars, leafminers, thrips • Crops labeled: Brassicas, fruiting vegetables, leafy vegetables, potatoes & tuberous and corm vegetables, sweet corn, cucurbits • Rates: 0.5 – 3 oz per acre depending on the pest • REI: 4 hours • Pre-harvest interval: 1 day for brassicas, leafy and fruiting vegetables • Use limits for resistance management: no more than 3 times in 30 day period (brasssicas); no more than 9 oz per year (sweet corn, peppers) Pesticide Trial Summary: Rate and Cost of Tested Products (2002 & 2003) cost per treatment- treatment- rate per acre