How to Manage Pests

UC Pest Management Guidelines


Crown and Spear Rot

Pathogens: Phytophthora megasperma var. sojae and other Phytophthora spp.

(Reviewed 6/09, updated 6/09)

In this Guideline:


Phytophthora spear rot is characterized by soft, water-soaked lesions on shoots at, slightly above, or below the soil level. The lesions elongate rapidly and become light brown. As the lesion collapses and shrivels, the affected side of the spear becomes flattened, and the shoot becomes extremely curved and may even collapse. This symptom is not diagnostic, however, as insect and mechanical injury can result in crooked spears. Infected young storage roots appear water soaked but firm.

Crowns infected with Phytophthora spp. have yellow-orange colored tissue. In severe infections the tissue appears waterlogged and fibrous.


Phytophthora is a soilborne fungus; it infects the shoot near or just below the soil line during very wet periods. Heavy spring rains can induce severe disease losses. Although crown and spear rot is erratic in California, the fungus is present in all production areas of the state. Desert areas, however, usually escape the disease unless conditions are unusually wet. Infected spears, if hydrocooled during packing for market, may contaminate the water and spread the pathogen to other spears, causing extensive rot during transit.


Whenever possible, plant in Phytophthora-free soil and use disease-free transplants. Provide good drainage and do not overwater. If symptoms occur, treatment may be necessary.

Organically Acceptable Methods

Avoid Phytophthora-infested soils and use disease free transplants when growing an organically certified crop.

Common name Amount per Acre R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
The following materials are listed in order of usefulness in an IPM Program. Also, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
  (Ridomil Gold) SL 1 pt 48 1
  COMMENTS: Cutting beds: Apply 30–60 days before the first cutting. For additional control, make another application just before the beginning of harvest. New plantings: Apply after planting seedlings or after covering 1-year-old crowns.
  (Aliette) 5 lb 12 110
  COMMENTS: Apply once over the top to fully expanded asparagus ferns. Control with fosetyl-al is erratic.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1,4,9,11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Asparagus
UC ANR Publication 3435


  • B. J. Aegerter, UC Cooperative Extension, San Joaquin County
  • R. M. Davis, Plant Pathology, UC Davis
Acknowledgment for contributions to Diseases:
  • R. J. Mullen, UC Cooperative Extension, San Joaquin County
  • F. F. Laemmlen, UC Cooperative Extension, Santa Barbara County

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