UC IPM: UC Management Guidelines for Eutypa Dieback on Apricot

UC Pest Management Guidelines

Apricot

Eutypa Dieback

Pathogen: Eutypa lata

(Reviewed 11/07, updated 11/07)

In this Guideline:

Symptoms
Comments on the disease
Management

Eutypa dieback, also known as Cytosporina, gummosis, and limb dieback, causes limbs or twigs to wilt and die suddenly in late spring or summer with the leaves still attached. The bark has a dark discoloration with amber-colored gumming; infected areas in the interior of the wood are discolored brown.

This fungus infects fresh pruning wounds when rainfall occurs 2 to 6 weeks after pruning. While infections can occur at any time of the year during rainy periods, the greatest incidence is in fall and winter.

Remove infected limbs at least 1 foot below any internal symptom of the disease. The preferred control method is to prune during July and August after harvest. There is less regrowth from pruning cuts if pruning is done in August. Ideally, pruning should be completed at least 6 weeks before the first fall rains. Wound treatments with paints or sealants have not been satisfactory because of lack of efficacy or difficulty in treating all of the pruning wounds immediately after being made. If pruning wounds are made outside of the preferred pruning period of July/August, use a fungicide to treat the wounds.

Common name

Amount/Acre

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

When choosing a pesticide, consider the general properties of the fungicide as well as information relating to environmental impact.

THIOPHANATE-METHYL

(Topsin M) WSB

1 lb/5 gal water

MODE OF ACTION GROUP NAME (NUMBER¹): Methyl benzimidazole (1)

COMMENTS: Requires a Special Local Needs (section 24C) registration.

BORON

(B-Lock)

Label Rates

N.A.

COMMENTS: Use on fresh pruning cuts as well as older tissues to form a water resistant, elastic coating that will stretch as plant grows. Do not apply more than 15 gal product per acre.

+	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 http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. For fungicides with mode of action Group numbers 1, 4, 9, 11, or 17, make no more than one application 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.
N.A.	Not applicable.

UC IPM Pest Management Guidelines: Apricot
UC ANR Publication 3433
Diseases
J. E. Adaskaveg, Plant Pathology, UC Riverside
W. D. Gubler, Plant Pathology, UC Davis
W. W. Coates, UC Cooperative Extension, San Benito Co.
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
J. L. Caprile, UC Cooperative Extension, Contra Costa Co.
B. A. Holtz, UC Cooperative Extension, Madera Co.
Acknowledgment for contributions to the diseases section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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How to Manage Pests

UC Pest Management Guidelines

Apricot

Eutypa Dieback

Pathogen: Eutypa lata

SYMPTOMS

COMMENTS ON THE DISEASE

MANAGEMENT

PUBLICATION