Vegetables - Disease Management          Pat Donald, MU  (573) 882-2716 
                                         Om Sehgal, MU (573) 882-7060

                               KEY
                          1 = Symptoms
                           2 = Control

ONION (garlic, leeks, shallots)         

Downy mildew (fungus)   Bremia lactucae     
   1.  Usually, symptoms appear after leaves are six inches long
       with oldest leaves first. Lesions are pale green, oval to
       elongated. May have band of yellow and green. Purplish mold
       may form rapidly in wet, cool weather and may kill the tops. 
  2.   Use healthy sets. Use a three-year rotation. Apply foliar
       fungicides at 7 to 10- day intervals when weather is
       favorable for disease development. Use fixed or neutral
       copper, copper hydroxide (Kocide DF) or mancozeb--Dithane
       DF, Manzate 200 DF 3 lb./A (dry bulb only), Penncozeb DF 2-3
       lb./A (dry bulb only), Aliette DG Ridomil/Bravo 80W 1 1/2-2
       lb./A (dry bulb only), or Ridomil MZ58 1 1/2 lb./A.

Fusarium basal rot (fungus)   Fusarium spp.  
   1.  Plants wilt and die. Roots become dark brown, flattened,
       hollow and transparent. Kills roots and invades bulbs causing rot.
       Under moist weather conditions, white mold may develop between
       seals. Under dry conditions, roots may dry and shrivel.
   2.  Plant in well-drained soil. Use healthy sets and long crop
       rotations. Control insects and use resistant varieties.    
       Grower should consult seed catalogs for current information
       on resistant varieties. Cure and store bulbs in dry conditions.

Neck rot (fungus)   Botrytis spp.  
   1.  Essentially a post-harvest disease problem. Sunken, dry
       lesions around neck. Inside of bulb may be soft, light brown
       with gray fungal growth appearing between the scales. Brown
       to black sclerotis may form in crusty area around neck. Soft
       rots (bacteria) may follow.   
   2.  While harvesting, cut tops close and dry stubs before storing. 
       Dry with artificial heat whenever possible. Store in well-ventilated,
       cool and dry place. Yellow and red varieties are less susceptible
       than white. Same fungicide treatment as for Downy mildew.
       Rovral 1 1/2 lb./A dry bulb onions only.

Pink rot (fungus)   Pyrenochaeta terrestris  
   1.  Seedlings may die. Roots turn pink, shrivel and die, making
       very small bulbs. Fungus lives a long time in garden soil. 
   2.  Use a three- to six-year rotation. Use resistant or tolerant
       varieties.  Grower should consult seed catalogs for current
       information on resistant varieties.

Purple Blotch (fungus)   Alternaria porri    
   1.  Reddish or purple boat-shaped spots surrounded by a yellow
       zone. Begins as water-soaked spots. In moist weather, spots
       become covered with a brown dusty mold growth.
       Fungus over winters in diseased plants.   
   2.  Use healthy sets in well-drained soil. Use at least 3-year
       rotation. Apply fungicides program as for Downy mildew. Use
       chlorothalonil (Bravo 500 1 1/3-3 pt./A, or 90 DG 1 1/8-2
       1/4 lb./A), iprodione - Rovral (dry bulb only), mancozeb-
       Dithane DF 3 lb./A, Dithane F-45 2.4 qt./A, Dithane M-45 3
       lb./A, or Manzate 200 DF 3 lb./A, Penncozeb DF (dry bulb only).

Smut (fungus)   Urocystis capulae   
   1.  Appears as gray-colored streaks on leaves, leaf sheaths and
       bulbs. Mainly in young plant tissues. Leaves and bulbs of
       young plants filled with black powdery mass of spores.   
   2.  Use captan or thiram seed treatment.  Rotate crops. Start
       onions from clean, healthy and disease-free plants. Apply
       soil fungicide in furrow. Use mancozeb--Dithane DF 3 lb./A,
       Dithane F-45 2.4 qt./A, Dithane M-45 3 lb./A, Manzate 200 DF
       3 lb./A (dry bulb only). See labels for rates and time of application.