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Elements of IPM for Onions in NY State

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PESTS
Major Insects Major Diseases Weeds
onion maggot Botrytis leaf blight annual grasses
onion thrips smut annual broadleaves
bulb mite downy mildew perennial grasses
Minor Insects purple blotch perennial broadleaves
western flower thrips Aspergillus black mold nutsedge
cutworms Stemphylium leaf blight  
aster leafhopper pink root  
mites bacterial rots  
aphids Fusarium basal rot  
leaf miner Botrytis neck rot  
seed corn maggot damping off  
  white rot  
  Botrytis flower blight and scape girdling  
  Smudge (white onion only)  
  yellow dwarf  
  aster yellows  
  root knot nematode  
  lesion nematode  
A. Site Preparation/Selection Priority Points
1) Select varieties resistant or tolerant to bacterial rots, Fusarium basal rot, damping off, and pink root. High 10
2) Crop rotation to control (or improve control of) sour skin/bacterial canker, Fusarium basal rot (3 years), downy mildew (2 years), nematodes, smut, black mold, onion maggot (1 mile or more in distance), and weeds Medium 5
3) Remove cull piles, volunteer onions and field debris to improve control of Botrytis flower blight, Botrytis leaf blight, Botrytis neck rot, downy mildew,  purple blotch,  Stemphylium leaf blight, onion yellow dwarf, onion maggot, bulb mite, Medium 5
4) Cultivate and destroy weeds 10 days before planting to reduce cutworm larvae. Medium 5
5) Tillage at least 2-3 weeks before planting if there is a heavy cover crop to avoid seed maggot problems Low 3
B. Planting    
1) Use treated seed at planting to control damping off, and onion maggot and to help control smut. High 10
2) Plant seed free of Alternaria purple blotch,  smut, Stemphylium leaf blight,, black mold and Botrytis neck rot. High 10
3) Do not plant deeper than 1/4 inch to avoid smut unless soil is very dry. Low 3
4) If using transplants make sure they are free of pink root, damping off organisms and downy mildew or virus diseases. High 10
C. Nutrient and SOIL Management    
1) Soil test every 3 years. High 10
2) Fertilize according to the soil test for P, K and pH to amounts recommended by CU. High 10
3) Maximum of 125 pounds of N per year broadcast after plowing. Avoid excessive N applications to allow necks to dry down and avoid infection by Botryis neck rot, bacterial diseases and black mold. Medium 5
4) Plant a soil building rotational crop to reduce compaction. Medium 5
5) Use cover crops in the off season to protect soil from wind erosion and reduce compaction. High 10
D. Pest Monitoring and Forecasting    
1) Scout at least once per week for insects and foliar diseases (onion thrips,  BLB,  onion maggot, downy mildew, purple blotch). High 10
2) Use available CU thresholds for diseases, nematodes, and insects. High 10
3) Use an on farm disease forecasting instrument or join a disease forecasting network (e.g. NEWA or CCE updates) to predict Botrytis leaf blight, downy mildew, and Alternaria purple blotch risk. Medium 5
4) Apply fungicides according to disease forecasts High 10
5) Make a weed map/list 3 times annually and choose herbicide/tillage strategy according to weed species and populations. See the Weed Assessment List available for use in satisfying this element. Low 3
6) Remove and destroy any onions infected with yellow dwarf virus to avoid additional transmission by aphids. Medium 5
7) Chose effective labeled pesticides with the least environmental and beneficial organism impact (EIQ). Medium 5
8) Calibrate sprayer at least once per season High 10
9) Keep complete records of soil tests, fertilizer applications, cultural practices, weed maps, scouting results, and pesticide applications. Medium 5
10) Rotate insecticides differing in classes of chemistry for onion thrips management High 10
11) Do not spray an insecticide (for onion thrips) that did not work well earlier in the season. High 10
12) Monitor susceptibility of onion thrips populations to major classes of insecticides (as techniques become available - Shelton/Nault). High 10
13) Handweed prior to weed flowering to remove escapes from herbicide treatments. Medium 5
14) Assess or index soil for nematode populations (as techniques become available - Abawi). High 10
E. Harvesting    
1) Minimize damage to onions while harvesting to avoid attracting adult onion maggots; reduce drops on harvest equipment to no more than 6 inches. High 10
2) Remove all bulbs from the field at harvest in order to avoid overwintering sites for bulb mites, onion maggot, downy mildew. High 10
3) Harvest in dry weather, allow onions to air-dry, and sort damaged onions before storing at 32 to 33 F and below 70% relative humidity to reduce spread of purple blotch, Botrytis neck rot, Fusarium basal rot, and bacterial diseases in storage. High 10
4) Wait until onion necks are completely dry before harvesting windrowed onions to avoid Botrytis neck rot, black mold, neck rot, and bacterial diseases. High 10
5) Use artificial curing if necessary (forced heated air at recommended temperature and duration) to avoid Botrytis neck rot. Low 3
6) Clean up field to reduce overwintering weeds and onion residue prior to planting cover crop. High 10

REFERENCES...

Specific information about the use of these IPM elements can be found in the following publications:

Hoffmann, Michael P., Curtis Petzoldt, Anne Frodsham. 1996. Integrated Pest Management for Onions. New York IPM Publication No. 119.

Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production.

A Method to Measure the Environmental Impact of Pesticides. 1992.  New York Food and Life Sciences Bulletin Number 139.

T.L. Widmer, J.W. Ludwig, and G.S. Abawi. The Northern Root-Knot Nematode on Carrot, Lettuce, and Onion in New York.  New York Food and Life Science Bulletin No. 156. Department of Plant Pathology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY

Contact the Frank A. Lee Library to view these publications.

Last Revision June, 2004