The stem or bulb nematode, Ditylenchus dipsaci, can attack over 400 plant species including alfalfa, onion, dry bean, soybean, potato and many common weeds. It has generally been a minor problem on onion in western regions.
Nematodes survive on seeds, onion debris, weeds and in infected transplants. The pathogen is favored by free moisture and an optimum soil temperature of 70°F. Its life cycle is completed within 23 days at 60°F with four molts and four juvenile stages; and adults live up to 73 days. Damage occurs in many crops at infestation levels as low as 10 nematodes per 500 grams of soil.
Stem nematode-injured plants are dwarfed, twisted and abnormally white with swollen split areas of the bulbs. Plant stands may be erratic. In older onion bulbs, tissue softens near the top of the bulb and at the base of leaves of stunted plants. Older plants often crack or produce doubles. Secondary breakdown by bacteria and fungi is common. Nematode losses generally small, but precise yield loss estimates in the High Plains production regions are not available.
Incorporation of green manure crops such as sudangrass, sesame, rapeseed, white mustard, or perennial ryegrass the season before potatoes are planted can reduce some nematode populations.
Select high quality transplants produced in fields fumigated before planting. Practice a four-year or longer rotation. Avoid aggravating plant stresses such as soil compaction, root pruning during cultivation, and moisture extremes. Avoid reuse of irrigation water, as nematodes are readily moved in water. Thoroughly wash equipment to prevent moving contaminated soil into new fields.
Nematicides and soil fumigation are effective, but very expensive and probably not cost effective in most fields unless high populations of the Fusarium basal plate rot and pink root fungi are present.
Product List for Stem and Bulb Nematode (Bloat):
Pesticide |
Product per acre |
Remarks |
Nematicide |
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Vydate L |
0.75-2 gal |
Apply 0.75-1 gal as an in-furrow drench at planting and make 1 to 2 additional applications at 1-2 gal in a banded applications |
Fumigant |
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Restricted use; Preplant application, aerate 7-14 days. |
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Telone C-17 |
10-17 gal |
Restricted use; Preplant application, aerate 7-14 days. |
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Vapam |
40-100 gal |
Restricted use; Preplant application, aerate 7 days. |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Onion, Disease, Stem Bulb Nematode (Bloat)
Date: 04/01/2007