UC IPM: UC Management Guidelines for Verticillium Wilt on Strawberry

UC Pest Management Guidelines

Strawberry

Verticillium Wilt

Pathogen: Verticillium dahliae

(Reviewed 6/08, updated 6/08)

In this Guideline:

Symptoms
Comments on the disease
Management

Initially infected plants may be stunted. Outer leaves exhibit marginal and interveinal browning, followed by eventual collapse. Inner leaves remain green but are stunted and exhibit brownish black streaks or blotches. This last symptom sometimes helps to distinguish this disease from Phytophthora crown rot.

The fungus is not host-specific and infects many weed species and crops worldwide. It is especially destructive in semi-arid areas where soils are irrigated. Inoculum densities may be high following planting of susceptible crops. Disease severity is greater when high levels of nitrogen are used.

Preplant fumigation is an important component of managing Verticillium wilt in strawberry fields. If fumigation is not desirable, select fields isolated from established growing areas, avoiding any fields with detectable levels of the pathogen or with a history of susceptible crops. Crop rotation with broccoli has been shown as an effective way to reduce Verticillium in the soil. Solarization of formed beds may be used to reduce pathogen levels in areas that get adequate amounts of sunshine and warm weather during summer months, although the usefulness of this technique for reducing Verticillium wilt in strawberries is unknown.

Cultural Control
If infested fields cannot be avoided and fumigation is not feasible, either solarize the soil or implement a crop rotation program. Cover crops of cereal rye or ryegrass can help to reduce soil levels of Verticillium. Use relatively tolerant strawberry cultivars when practical. Also, use drip irrigation and avoid excess amounts of nitrogen fertilizer.

Soil solarization. In warmer areas of the state, solarization has been shown to be effective for the control of soilborne pathogens and weeds. Solarization is carried out after the beds are formed and can be effective if weather conditions are ideal (30-45 days of hot weather that promotes soil temperatures of at least 122°F). The effectiveness of solarization can be increased by solarizing after incorporating the residue of a cruciferous crop, in particular broccoli or mustards, into the soil or following an application of metam sodium (40 gal/acre). For more details on how to effectively solarize soil, see Soil Solarization: A Nonpesticidal Method for Controlling Diseases, Nematodes, and Weeds, UC ANR Publication 21377.

Crop rotation. Rotating strawberries with broccoli can significantly reduce levels of the Verticillium pathogen in the soil and has been shown to be an economically viable option under moderate levels of Verticillium wilt disease pressure.

Organically Acceptable Methods
Select fields isolated from established growing areas. If fields have detectable levels of the pathogen or a history of susceptible crops, plan to solarize the soil, preferably after incorporating the crop residue from broccoli or mustards. Use drip irrigation and practice crop rotation with a nonsusceptible crop such as broccoli. Avoid high nitrogen fertilizers.

Treatment Decisions
If drip fumigation is planned, good results have been obtained with a sequential application of chloropicrin (200 lb/acre) or 1,3-dichloropropene/chloropicrin (300 lb/acre) followed 7 days later with metam sodium (45 gal/acre) or metam potassium (37 gal/acre).

Common name

Amount/Acre**

R.E.I.+

P.H.I.+

(trade name)

(hours)

(days)

The following materials are listed in order of usefulness in an IPM Program, taking into account efficacy. Also consider the general properties of the fungicide as well as information relating to environmental impact.

PREPLANT FUMIGATION

METHYL BROMIDE*/CHLOROPICRIN*

300–400 lb

COMMENTS: The current Critical Use List only allows use where 1,3-dichloropropene can't be used because of local township limits. Fumigants such as methyl bromide are a source of volatile organic compounds (VOCs) but are not reactive with other air contaminants that form ozone: methyl bromide depletes ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.

Sequential application of:

(Note: Fumigants such as 1,3-dichloropropene and metam products are a source of volatile organic compounds (VOCs) but minimally reactive with other air contaminants that form ozone. Fumigate only as a last resort when other management strategies have not been successful or are not available.)

1,3-DICHLOROPROPENE*/CHLOROPICRIN*

(Telone C35)

9–12 gal (shank)

5 days

COMMENTS: Effective for control of nematodes, soilborne fungal pathogens, and insects. One gallon of product weighs 11.1 lb.

. . . or . . .

1,3-DICHLOROPROPENE*/CHLOROPICRIN*

(InLine)

28–33 gal (drip)

5 days

COMMENTS: Effective for control of nematodes, soilborne fungal pathogens, and insects. Requires plastic mulch. Using higher rates or plastic mulch, especially virtually impermeable film (VIF), improves weed and nematode control. One gallon of product weighs 11.2 lb.

. . . or . . .

CHLOROPICRIN*

(MetaPicrin)

15–30 gal (shank)

(Tri-Clor)

15–21.85 gal (drip)

COMMENTS: A liquid that diffuses as a gas through soil. Very effective for control of soilborne fungal pathogens and insects. Drip irrigation requires an emulsifier. For shank fumigation, using higher rates or plastic mulch, especially virtually impermeable film (VIF), improves weed control. For drip fumigation the use of VIF will improve both nematode and weed control. One gallon of Tri-Clor weighs 13.7 lb; one gallon of MetaPicrin weighs 13.8 lb.

Followed 5-7 days later by:

METAM SODIUM*

(Vapam HL, Sectagon 42)

37.5–75 gal

COMMENTS: Water-soluble liquid that decomposes to a gaseous fumigant (methyl isothiocyanate). Efficacy affected by soil texture, moisture, temperature, and percent organic matter. One gallon of product contains 4.26 lb of metam sodium.

. . . or . . .

METAM POTASSIUM*

(K-Pam HL)

30–60 gal

Rates are per treated acre; for bed applications, the rate per acre may be lower.

Permit required from county agricultural commissioner for purchase or use.

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.

UC IPM Pest Management Guidelines: Strawberry
UC ANR Publication 3468
Diseases
S. T. Koike, UC Cooperative Extension, Monterey Co.
W. D. Gubler, Plant Pathology, UC Davis
G. T. Browne, USDA Crops Pathology and Genetics, UC Davis

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r734100811.html revised: June 9, 2008. Contact webmaster.

How to Manage Pests

UC Pest Management Guidelines

Strawberry

Verticillium Wilt

Pathogen: Verticillium dahliae

SYMPTOMS

COMMENTS ON THE DISEASE

MANAGEMENT

PUBLICATION