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How to Manage Pests

UC Pest Management Guidelines

Sweet pea, Lathyrus odoratus, blossoms.

Floriculture and Ornamental Nurseries

Sweet Pea (Lathyrus odoratus)

Disease Control Outlines

(Reviewed 3/09, updated 3/09)

In this Guideline:

Disease (causal agent) Symptoms Survival of pathogen and effect of environment Comments on control
Black root rot
(Thielaviopsis basicola)
Poor top growth. Black lesions on roots and root rot. Seedlings may be killed. Fungus is soilborne. Favored by cool, wet soils and any condition that weakens the plant. Avoid fields previously planted in legumes. Avoid overirrigation and overfertilization. Plant on raised beds.
Powdery mildew
(Erysiphe polygoni)
White powdery growth on surface of leaves and stems. Older infected leaves yellow and wither. Growth of heavily infected plants is diminished. Favored by moderate temperatures. Spores (conidia) are produced in great abundance and they are airborne. Moisture is not necessary for germination and infection and is actually detrimental to the fungus. Several powdery mildew fungicides are effective if applied in a regular preventative program commencing with the first signs of the fungus. Check product label for registration. more info *
Ramularia leaf spot
(Ramularia deusta)
Large, irregular or circular tan spots without definite margins. Lower leaves are first affected. Infected leaves often drop. Fungus is specific to sweet pea and survives in sweet pea refuse. Favored by wet conditions. Rotate with other crops for 2 years. A fungicide may be necessary in some severe cases. Avoid overhead irrigation.
Seed decay
(Pythium spp. and other fungi)
Seeds rot in soil. Seedlings do not emerge. Favored by wet soil and poor aeration. Provide better drainage. Grow on raised beds.
Virus or viruslike disease Symptoms Host range and natural spread Comments on control
Enation mosaic
(Pea enation mosaic virus)
Leaves contain scattered translucent areas ("windows"). Foliage may be crumbled and stunted. There may be "windows" in the flowers. Virus is spread by aphids. Host plants include many legumes. Control nearby weeds, especially legumes. Control aphids.
(Pea mosaic virus)
Mottling and chlorosis of the foliage. Dark green areas interspersed with yellow‑green portions of leaves. Flowers have "broken" colors. Virus is spread by aphids. Host plants include many legumes. Control nearby weeds, especially legumes. Control aphids.
Spotted wilt
(Tomato spotted wilt virus)
Reddish brown streaks on stems. Leaves with circular spots that are yellow at first and later turn brown. Plant may die. Spread by thrips. Virus has a wide host range, including many weeds. Juvenile thrips (nymphs) acquire the virus and transmit it as adults. Control nearby weeds including grasses. Control thrips.
Sweet peas are also susceptible to Ascochyta blight (Ascochyta lathyri), bacterial streak (Erwinia herbicola), fasciation (Rhodococcus fascians), Pythium root rot * (Pythium spp.), cottony rot * (Sclerotinia sclerotiorum), downy mildew * (Peronospora trifoliorum), and damping-off * (Rhizoctonia solani, Fusarium spp., and Pythium spp.)
* For additional information, see section on Key Diseases.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
S. T. Koike, UC Cooperative Extension Monterey County
C. A. Wilen, UC IPM Program, UC Cooperative Extension San Diego County
Acknowledgment for contributions to Diseases:
R. D. Raabe, (emeritus) Environmental Science, Policy, and Management (ESPM), UC Berkeley
A. H. McCain, (emeritus) Environmental Science, Policy, and Management (ESPM), UC Berkeley
M. E. Grebus, Plant Pathology, UC Riverside

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