Onion Thrips: Population Survey of Northern Utah Onion Fields 2008 Diane Alston USU Extension UtahOnion Association Meeting February 17, 2009 Egg
Onion Thrips Fact Sheet
www.utahpests.usu.edu
Western Region SARE Grant: 2008: Survey of commercial onion fields Describe onion thrips population dynamics in commercial onion fields 9 farms / 15 fields (2 transplanted, 13 seeded) Relationship of crop management practices to thrips densities (N, irrigation, insecticides) Relationship of thrips densities to Iris Yellow Spot Virus (ISYV) incidence
Why are onion thrips such a pest? Life history and ecology well adapted to onions Females reproduce asexually (parthenogenesis) Short generation time (2 3 wk) High mobility of adults Rapid development of resistance to insecticides Life stage survival strategies Later larval instars are non feeding & protected ( prepupae & pupae ) Eggs are protected females insert them into leaf tissue Thrips life stages
Sources of onion thrips Adults Eggs, Larvae, & Adults Prepupae & Pupae
Thrips sampling tools 1. Whole plant 2. Stain 3 rd wash leaf Larva Adult Egg
# of thrips life stage pe r plant 400 350 300 250 200 150 100 50 0 29 May Farm A (Davis/Weber Co.) Transplants East Transplants West Seeded Mod & High Thrips 5 Jun 12 Jun 19 Jun 26 Jun 3 Jul 10 Jul Date 17 Jul Trans: 350 # N/acre (100 100 150) Seed: 250 # N/acre (100 150) 5 or 6 thrips sprays (2 wk interval) 24 Jul 31 Jul 7 Aug 14 Aug Trans E: OT Ad Trans E: WFT Ad Trans E: Larvae Trans W: OT Ad Trans W: WFT Ad Trans W: Larvae Seed: OT Ad Seed: WFT Ad Seed: Larvae
# of thrips life stage pe er plant 400 350 300 250 200 150 100 50 0 Farm B (Davis/Weber Co.) 300 # N/A (100 150 50) 150 50) Seeded 5 thrips sprays (2 wk interval) Low Thrips OT Ad WFT Ad Larvae Date
400 350 300 250 200 150 100 50 0 Farm C (Davis/Weber Co.) Seeded Low/Mod dth Thrips OT Ad WFT Ad Larvae # of thrips life stage per plant 1 Jul 8 Jul 15 Jul 22 Jul 29 Jul 5 Aug 12 Aug 19 Aug 26 Aug Date
# of thrips life stage pe er plant 400 350 300 250 200 150 100 50 Farm D (Box Elder Co.) 300 # N/acre (100 100 100) 100) Seeded North 6 thrips sprays (2 wk interval) Seeded South High Thrips N: OT Ad N: WFT Ad N: Larvae S: OT Ad S: WFT Ad S: Larvae 0 Date
# of thrips life stage pe er plant 400 350 300 250 200 150 100 50 0 Farm E (Box Elder Co.) 260 # N/acre (100 100 30 30Irr) 30I Seeded North 4 thrips sprays (2 in Jul, 2 in Aug) Seeded South High Thrips N: OT Ad N: WFT Ad N: Larvae S: OT Ad S: WFT Ad S: Larvae Date
# of thrips life stage pe er plant 400 350 300 250 200 150 100 50 0 Farm F (Box Elder Co.) 90 # N/acre (10 80) Seeded North No thrips sprays Seeded South Mod d& High Thrips N: OT Ad N: WFT Ad N: Larvae S: OT Ad S: WFT Ad S: Larvae 3 Jul 10 Jul 17 Jul 24 Jul 31 Jul 7 Aug 14 Aug 21 Aug 28 Aug Date
# of thrips life stage pe er plant 400 350 300 250 200 150 100 50 0 Farm G (Box Elder Co.) Seeded West Seeded East 250 # N/acre (50 100 100) 100) 3 thrips sprays (2 in Jul, 1 in Aug) Low & Mod/High Thrips W: OT Ad W: WFT Ad W: Larvae E: OT Ad E: WFT Ad E: Larvae 3 Jul 10 Jul 17 Jul 24 Jul 31 Jul 7 Aug 14 Aug 21 Aug 28 Aug Date
400 350 300 250 200 150 100 50 0 Farm H (Box Elder Co.) Seeded Low/Mod dth Thrips OT Ad WFT Ad Larvae # of thrips life stage per plant 18 Jun 25 Jun 2 Jul 9 Jul 16 Jul 23 Jul 30 Jul 6 Aug 13 Aug Date
# of thrips life stage pe er plant 400 350 300 250 200 150 100 50 0 Farm I (Box Elder Co.) 110 # N/A (More Life, K Thiosulfate) Seeded No thrips sprays Low Thrips OT Ad WFT Ad Larvae 1 Jul 8 Jul 15 Jul 22 Jul 29 Jul 5 Aug 12 Aug 19 Aug 26 Aug Date
Summary of Thrips Populations in Onion Fields 5 Mean # thr rips per pla nt (across sa ample date es) 200 180 160 140 120 100 80 60 40 20 0 Adults Larvae Eggs Farm Field Field Farms F & I: Lo N, No sprays; Farms E & G: Mod N, Mod sprays; Farms A, B & D: Hi N, Hi sprays; Farms C & H: no data
Fa arm and fie eld location A D/W H* A D/W H E BE H D BE H C D/W B D/W H BE D BE A D/W E BE F BE G BE F BE I BE G BE LM LM LM H LM H Predatory Thrips Abundance LM H Black Hunter Thrips H LM LM 0 1 2 3 4 5 Cumulative # of predatory thrips per plant *H indicates fields with high onion thrips densities and LM indicates fields with low to moderate onion thrips densities.
Acknowledgements Utah onion grower cooperators Lincoln Andreasen, USU undergraduate student Jennifer Reeve Dan Drost C. Kent Evans USU onion research/extension team Funding: Western Region SARE
Insecticide efficacy Adult Onion Thrips (Thrips p tabaci) ) July, 2007 Untreated Movento 5 oz + MSO Movento 8 oz + MSO Movento 5 oz + Induce Radiant 8 oz + Oil Carzol 0.75 lb + Oil Vydate 4 pt + Oil Lannate 3 pt + Oil Warrior 3 oz + Oil s per plant Mean # of thrip 18 16 14 12 10 8 6 4 2 0 * Pre 1 wk 2 wk 3 wk In an August trial, NS differences among treatments
Insecticide efficacy Adult Western Flower Thrips (Frankliniella occidentalis) ) July, 2007 Untreated Movento 5 oz + MSO Movento 8 oz + MSO Movento 5 oz + Induce Radiant 8 oz + Oil Carzol 0.75 lb + Oil Vydate 4 pt + Oil Lannate 3 pt + Oil Warrior 3 oz + Oil s per plant Mean # of thrip 3 2.5 2 1.5 1 05 0.5 0 * * * Pre 1 wk 2 wk 3 wk Similar results in an August trial
Insecticide efficacy Thrips Larvae July, 2007 Untreated Movento 5 oz + MSO Movento 8 oz + MSO Movento 5 oz + Induce Radiant 8 oz + Oil Carzol 0.75 lb + Oil Vydate 4 pt + Oil Lannate 3 pt + Oil Warrior 3 oz + Oil Mea an # of thrip ps per plan t 25 20 15 10 5 0 * * * Pre 1 wk 2 wk 3 wk Similar results in an August trial
Egg hatch from leaves Egg hatching chamber Plastic bag Collect 3 rd onion leaf (8 reps per treatment) Wash leaves & place in hatching chamber with moist filter paper Place at 25 C for 2 wk Wash to collect thrips from leaf & inside of bag at 1 & 2 wk High tech thrips hatching chamber
Insecticide efficacy Thrips egg hatch (over 2 wk) July, 2007 Untreated Movento 5 oz + MSO Movento 8 oz + MSO Movento 5 oz + Induce Radiant 8 oz + Oil Carzol 0.75 lb + Oil Vydate 4 pt + Oil Lannate 3 pt + Oil Warrior 3 oz + Oil Mean # of hatched thr rips per lea af 35 30 25 20 15 10 5 0 * * * Pre 1 wk 2 wk 3 wk Results from an August trial were similar
Onion thrips life history Reduce/repel dispersing adults Reduce re infestation of plants Eggs, Larvae, & Adults Prepupae & Pupae Adults Egg laying Egg hatch
Many ways to skin a cat Multi pronged approach will be the most sustainable ti Mortality factor (insecticide): Short term quick knock down of adults & larvae Longer term egg reservoir in leaves (2 wk) Longer term immigration of adults Longer term survival of pre pupae & pupae
Multi pronged approach will be the most sustainable Sustained Mortality & Repellency of Thrips Cultural practices: Sprinkler irrigation Varietal tolerance Mulches Trap crops Nitrogen management Insecticides: Manage to prevent resistance Systemic activity Slow release (microencap) Ovicide, larvicide, adulticide Repellents Combinations
Thrips population suppression strategies Make onions as tolerant / unattractive to thrips as possible Start suppression early in the season Use long term suppressive controls Target egg reservoir in leaves Target multiple life stages Morgan Reeder field on 2006 Utah Onion Tour, Corinne, UT