How to Manage Pests

UC Pest Management Guidelines

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/Acre	P.H.I.+
(trade name)			(days)
A.	MEFENOXAM
	(Ridomil Gold) EC	1 pt	1
	MODE OF ACTION: A phenylamide (Group 4)1 fungicide.
	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.
B.	FOSETYL-AL
	(Aliette)	5 lb	110
	MODE OF ACTION: A phosphonate (Group 33)1 fungicide.
	COMMENTS: Apply once over the top to fully expanded asparagus ferns. Control with fosetyl-al is erratic.
+ Preharvest interval. Do not apply within this many days of harvest. 1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different group number are suitable to alternate in a resistance management program. For more information, see www.frac.info/.

PUBLICATION

UC IPM Pest Management Guidelines: Asparagus
UC ANR Publication 3435
Diseases
R. M. Davis, Plant Pathology, UC Davis
F. F. Laemmlen, UC Cooperative Extension, Santa Barbara Co.
Acknowledgment for contributions to the diseases section:
R. J. Mullen, UC Cooperative Extension, San Joaquin Co.

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