Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Garlic (Allium sativum) -- Neck Rot (Gray Mold)
 
Cause: Botrytis porri and B. aclada (formerly B. alliiaclada), fungi. Both fungi are found in western Oregon but only B. porri is found on garlic east of the Cascades. Organisms survive the winter on dead plant parts in soil, as sclerotia, and on infected bulbs. Infection is through neck tissue or through wounds in bulbs. Severe losses are most commonly from excessive irrigation and/or rain. Other factors such as excessive nitrogen, inadequate or improper curing, and improper storage have not been investigated.
Symptoms: The disease usually appears first on necks near the soil line at any time after spring greenup when weather conditions permit. The disease becomes worse when it starts early in the season. Extensive development of sclerotia is best seen on maturing bulbs just before and during harvest. The fungus moves rapidly into the succulent garlic bulb's neck region, producing a water-soaked appearance. A gray mold develops on the surface of or between garlic scales, later producing black bodies (sclerotia) which develop around the neck. Before bulbing, plants may die or recover if weather permits. Bulbs infected late break down to a soft mass, and secondary infections by other organisms follow.

Note the large, black sclerotia in the elephant garlic on the left.

Garlic with neck rot.

 
Cultural control: Difficult to control in extended wet weather.
  1. Allow the tops to mature well, then lift or undercut the garlic.
  2. If normal dry weather prevails, cure garlic on the ground for 6 to 10 days.
  3. When topping, minimize bruising and mechanical injury.
  4. Store garlic in well-ventilated houses at temperatures of 32°F, or just slightly higher.
  5. Avoid frequent and excessive irrigation.
  6. Visual inspection of seed garlic with a hand lens may help. Examine the basil plate or bottom of garlic for gray mold.
Chemical control: Treat seed (cloves) to reduced incidence of fungi in the seed. Foliar sprays may prove effective as well.

  1. Scala SC at 9 or 18 fl oz/A when tank mixed or used alone on 7- to 14-day intervals for great-headed garlic. When applying alone, do not make more than two (2) consecutive applications of Scala SC without alternating to an equal number of applications of a fungicide from a different resistance management group. Do not use Scala SC or another group 9 fungicide for more than 2 of 6 applications or 3 of 7 applications in any one season. Do not apply within 7 days of harvest. 12-hr reentry.
  2. Switch 62.5WG at 11 to 14 oz/A on 7-day intervals. No more than 2 sequential applications. 12-hr reentry.
Content edited by: Fred Crowe and Cynthia M. Ocamb on January 1, 2009
 
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