WEED AND NON-ONION CROP HOSTS OF ONION THRIPS

Transcription

1 WEED AND NON-ONION CROP HOSTS OF ONION THRIPS Diane Alston & Bonnie Bunn (MS Student) Utah State University Utah Onion Association Meeting February 11, 2014 Brigham City, UT

2 How do onion thrips find onion plants? Flying onion thrips* Distance: Visual Color reflected light from leaves Close-up: Chemical Odor & taste Chemoreceptors *Not to scale

3 Utah Agricultural Landscapes: Corinne vs. Syracuse

4 Utah Onion Landscapes Onion Weeds Alfalfa Onion Wheat Flixweed Common Mallow

5 Utah Onion Landscapes Corn Weeds Onion Onion Weeds Field Bindweed Dandelion

6 Onion Thrips Vector Iris Yellow Spot Virus (IYSV) IYSV transmission: persistent, propagative IYSV acquired only by early larvae Virus must circulate & replicate in thrips midgut; moves to salivary glands Adults must lay eggs on IYSV-infected plants for larvae to acquire the virus Reducing thrips re-infestation will reduce IYSV spread Adults 3 weeks Eggs, Early Larvae, & Adults Late Larvae 1 week (non-feeding) Onion Thrips

7 Green-Bridge Between Growing Seasons & Host Plants Fall Spring Onion Alfalfa or Weeds Weeds to Onion

8 Host Range Iris Yellow Spot Virus Onion Thrips Very broad Grass & broadleaf plants Vegetables Monocots: onion, leek, garlic Dicots: cabbage, bean, tomato Forage & field crops alfalfa, wheat, corn Ornamentals Fruits Weeds First identified in iris (Netherlands, 1998) Grass & broadleaf plants Vegetables Monocots: onion, garlic, chives Weeds pigweed, saltbush, lambsquarter, green foxtail, purslane, sowthistle, others Legumes vetch, cowpea Flowers iris, lily, rose, others Onion (Allium) is a Monocot (grass)

9 Thrips Sampling on Weeds & Adjacent Crops Bonnie Bunn (MS Student Project): 2011 & : Sampled targeted weeds in May/early June Corn Common mallow Dandelion Field bindweed Alfalfa Onion Wheat Flixweed Foxtail barley Prickly lettuce Weeds Perennial Biennial Winter Annual Sampled weeds along onion field edges

10 Thrips Sampling Methods 1. Whole plant wash 2. Stain 3 rd youngest leaf Egg Adult 3. Hatch Larva 25 C/16 hr light 7 days

11 Data from 26 onion fields in 2013

12 Data from 10 sentinel onion fields in 2011 and 2012

13 Effect of distance from onion field edge on numbers of thrips and IYSV incidence 10 ft 85 ft 330 ft Data from 5 sentinel fields in 2012; data in 2011 was similar

14 No. thrips per g plant dry wt. Grams dry weight per plant Greenhouse Expt: Thrips on Weeds Onion Thrips Adults and Larvae on Onion & Weeds A b A a B c Adults Plant Dry Weight C B A 20 Larvae Onion Common Mallow Prickly Lettuce 0 Onion Common Mallow Prickly Lettuce

15 Square-cm per leaf No. thrips per sq-cm leaf area Greenhouse Expt: Thrips on Weeds Onion Thrips Eggs and Hatched Larvae on Onion & Weeds A a A a B b Plant Leaf Area 2 Eggs Hatched Larvae A B A Onion Common Mallow Prickly Lettuce 0 Onion Common Mallow Prickly Lettuce

16 Greenhouse Expt.: Proportion of Thrips Life Stages Onions Common Mallow Prickly Lettuce 1% 56% 43% 35% 20% 45% 56% 2% 42% Eggs Larvae Adults Healthiest & most robust populations

17 2013 Commercial Field Survey: Onion Thrips Samples 26 fields were sampled; 12 plots per field Three sample dates: Early season: May 17-Jun 12 Mid season: Jun 17-Jul 1 Late season: Jul 22-Aug 15 In situ (in place) counts were collected from 3 onion plants per plot In addition, on late-season sample dates, 3 onion plants were collected and processed with a washing technique to collect thrips Onion bulb diameter was measured for 3 in situ plants on late season sample date

18 Mean number onion thrips (adults + larvae) per plant Range of onion thrips densities per plant across the 26 fields for 3 sample dates: in situ and whole plant wash Field Early-In Situ Mid-In Situ Late-In Situ Late-Wash

19 Onion bulb diam (in) Onion bulb diam (in) Onion buld diam (in) Onion bulb diam (in) Weak relationship between bulb size on the late sample date and onion thrips densities on plants in early, mid, or late season (in situ or whole plant wash samples) Bulb Size in August vs Early Season In Situ Thrips Counts Mean no. thrips per plant Bulb Size in August vs. Mid Season In Situ Thrips Counts Mean no. thrips per plant Bulb Size in August vs. Late Season In Situ Thrips Counts Mean no. thrips per plant Bulb Size in August vs. Late Season Whole Plant Wash Thrips Counts Mean no. thrips per plant

20 Continue Commercial Field Surveys in 2014 Thank you to our 2013 cooperators!! Looking for more cooperators for 2014.

21 Acknowledge Students!! Megan O Laughlin, Jessica Larsen, Anne Leschen, Katelyn Clark, Tyler Shumway, Erika Rowley Grower Cooperators USU Onion Team Dan Drost, Claudia Nischwitz, Jennifer Reeve, Corey Ransom, Ruby Ward Funding Western Sustainable Agriculture Research and Education Utah State University Agricultural Experiment Station

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23 This Slideshow is Posted Landscape Ornamental Slideshows