Studies on Abamectin for Stem and Bulb Nematode Management in Garlic Michael Celetti Plant Pathologist Horticulture Crops Program Lead Ontario Ministry of Agriculture, Food and Rural Affairs

Stem and Bulb Nematode Didylenchus dipsaci one of the most serious nematode pests worldwide wide number of hosts (>450 plant species) >30 biological host races easily spread from farm to farm via infested seed and plant parts eg. bulbs and cloves up to 90% crop loss

Stem and Bulb Nematode Survey 2011

Current Management Options Plant clean (nematode free) cloves (seed) in nematode free fields Hot water seed treatment Crop rotation for 4-5 years Nematode Suppressing Cover Crops (needs further investigation) study showed infested garlic cloves soaked in a solution of abamectin produced higher yields with most harvested bulbs testing negative for the nematodes (Becker 1999)

2011 Abamectin Clove Soak cloves with High infestation (617 nematodes/g dry cloves) and with Low infestation (17 nematodes/g dry cloves) were soaked prior to planting in: abamectin solution (0.072 g.a.i./liter water) for 4 hours water alone for 4 hours untreated

Effect of soaking stem and bulb nematode infested garlic cloves in water and abamectin prior to planting compared to planting untreated infested cloves on the severity of damaged bulbs at harvest (0 = no damage, 1 = slight, 2 = moderate, 3 = severe, 4 = dead). a b c c c c (617 D. dipsaci/g dry clove) (17 D. dipsaci/g dry clove)

Effect of soaking stem and bulb nematode infested garlic cloves in water and abamectin prior to planting compared to planting untreated infested cloves on number of bulb and stem nematodes/g dry bulb at harvested. a a b b b b (617 D. dipsaci/g dry clove) (17 D. dipsaci/g dry clove)

Effect of soaking stem and bulb nematode infested garlic cloves in water and abamectin prior to planting compared to planting untreated infested cloves on yield of bulbs harvested. a a ab ab bc c (617 D. dipsaci/g dry clove) (17 D. dipsaci/g dry clove)

2013 Abamectin Drench at Planting Effect of drenching different rates of abamectin over nematode infested colves (432 nematodes/g dried clove) planted in open furrows compared to soaking infested cloves in a solution of abamectin for 4 huors prior to planting: Water Soak for 4 hours prior to planting Abamectin Soak (0.073 g.a.i./liter water) for 4 hours prior to planting Water Drench at planting 1/2x rate - 11.4 g.a.i./ha abamectin drench at planting 1x rate - 22.8 g.a.i./ha abamectin drench at planting 1 1/2x rate - 34.2 g.a.i./ha abamectin drench at planting 2x rate - 45.6 g.a.i./ha abamectin drench at planting 3x rate - 68.4 g.a.i./ha abamectin drench at planting

Stem and Bulb Nematode Damage Effect of soaking nematode infested garlic cloves cv. Music (432/g dried clove) in a solution of abamectin prior to planting compared to drenching abamectin over infested cloves in open furrows at planting on the severity of stem and bulb nematode damage (0 = no damage, 1= slight, 2= moderate, 3= severe and 4= dead) in bulbs at harvest. Stem and Bulb Nematode Damage

Nematodes/gram dried bulb Effect of soaking nematode infested garlic cloves cv. Music (432/g dried clove) in a solution of abamectin prior to planting compared to drenching abamectin over infested cloves in open furrows at planting on the number of stem and bulb nematodes in bulbs at harvest. Nematodes/gram dried bulb

Effect of soaking nematode infested garlic cloves cv Effect of soaking nematode infested garlic cloves cv. Music (432/g dried clove) in a solution of abamectin prior to planting compared to drenching abamectin over nematode infested cloves in open furrows at planting on the yield (g) harvested/plot.

Foliar application of abamectin in Season 2015 Effect of abamectin applied as 3 foliar applications in mid spring over garlic plants grown from stem and bulb infested cloves (950 nematodes/g dried clove): Water soak for 4 hours prior to planting Abamectin EC soak (0.072 g.a.i/liter water) 4 hours prior to planting Abamectin SC Soak (0.072 g.a.i/liter water) 4 hours prior to planting Water applied 3 times in spring 1x rate - 22.68 g.a.i./ha abamectin 3 times in spring 2x rate - 45.36 g.a.i./ha abamectin 3 times in spring 3x rate - 68.04 g.a.i./ha abamectin 3 times in spring 4x rate - 90.72 g.a.i./ha abamectin 3 times in spring 5x rate - 113.4 g.a.i./ha abamectin 3 times in spring Clean Seed (University of Guelph)

Effect of soaking nematode infested garlic cloves cv Effect of soaking nematode infested garlic cloves cv. Music in an EC or SC solution of abamectin prior to planting compared to three foliar applications in the spring of abamectin to plants grown from infested cloves on stem and bulb nematode damage (0= no damage, 1= slight, 2= moderate, 3= severe and 4= dead) in bulbs at harvest.

Effect of soaking nematode infested garlic cloves cv Effect of soaking nematode infested garlic cloves cv. Music in an EC or SC solution of abamectin prior to planting compared to three foliar applications in the spring of abamectin to plants grown from infested cloves on the number of stem and bulb nematodes in bulbs at harvest

Effect of soaking nematode infested garlic cloves cv Effect of soaking nematode infested garlic cloves cv. Music in an EC or SC solution of abamectin prior to planting compared to three foliar applications in the spring of abamectin to plants grown from infested cloves on garlic yield/plot at harvest.

Summary Planting clean nematode free seed from reputable seed grower in non infested fields is the best way to manage stem and bulb nematodes in garlic Nematode infested garlic cloves soaked in abamectin prior to planting significantly reduced nematode damage, nematodes in bulbs and increased yields at harvest Drenching abamectin at high rates over infested cloves planted in open furrows did not reduced nematode damage, nematodes in bulbs or increased yields at harvest 3 foliar application of abamectin up to 5x thrip rate in the spring did not reduced nematode damage, nematodes in bulbs or increased yields at harvest

Acknowledgements Marion Paibomesai, OMAFRA, Guelph Becky Hughes, University of Guelph, New Liskard Garlic Growers Association of Ontario Investment provided by Agriculture and Agri-Food Canada delivered through the Agricultural Adaptation Council California Garlic and Onion Research Advisory Board Horticulture Crop Ontario

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