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Phytophthora blight (herbaceous) - Phytophthora species (H)

Damage

Symptoms appear as dark brown to black leathery tissue on plant parts, but commonly the lower halves of young shoots, stems or the bases of blighted leaves. Shoots may wilt and collapse. Severe infection may affect the entire crown. If you cut into the stem, vascular tissues show brown, olive green, reddish or dark streaking. Phytophthora is a 'water mold' and it is favored by frequent irrigation and wet, slow draining soils. Saturated soils encourage spore production, causing more severe disease.

Cultural Controls

Phytophthora is favored by cool, wet conditions and remains in the soil for years. Once it appears in a growing area, rotate out of the susceptible crop or take other cultural measures to reduce future losses. Phytophthora is strongly influenced by drainage, so consider constructing raised beds or incorporating amendments to improve soil drainage. This disease is spread by rainsplash or contaminated tools, soil, or plant material. Remove and destroy all infected materials.

Chemical Controls

Azoxystrobin

Signal Word: Caution
Pesticide Class: Systemic-Upward only

Boscalid+Pyraclostrobin

Signal Word: Caution
Pesticide Class: Local Protectant

Chlorothalonil+Thiophanate methyl

Signal Word: Danger
Pesticide Class: Protectant, Systemic-Upward only

Cyazofamid

Signal Word: Caution
Pesticide Class: Protectant

Etridiazole

Signal Word: Warning
Pesticide Class: Protectant

Etridiazole+Thiophanate-methyl

Signal Word: Danger
Pesticide Class: Protectant, Systemic-upward only

Fenamidone

Signal Word: Warning
Pesticide Class: Protectant

Fludioxonil+Mefenoxam

Signal Word: Caution
Pesticide Class: Protectant, Systemic-upward only

Fosetyl-aluminum

Signal Word: Caution
Pesticide Class: Systemic

Phosphorous acid

Signal Word: Caution
Pesticide Class: Systemic

Propamocarb-hydrochloride

Signal Word: Caution
Pesticide Class: Systemic-upward only

Pyraclostrobin

Signal Word: Caution
Pesticide Class: Local protectant

Trifloxystrobin

Signal Word: Caution
Pesticide Class: Local protectant

Locations Affected

flowers, leaves, stem

Plant Environment

greenhouse, outdoors

Scouting Season:

January - Early , January - Mid , January - Late , February - Early , February - Mid , February - Late , March - Early , March - Mid , March - Late , April - Early , April - Mid , April - Late , May - Early , May - Mid , May - Late , June - Early , June - Mid , June - Late , July - Early , July - Mid , July - Late , August - Early , August - Mid , August - Late , September - Early , September - Mid , September - Late , October - Early , October - Mid , October - Late , November - Early , November - Mid , November - Late , December - Early , December - Mid , December - Late

Plants Affected

• Aconitum - Monkshood
• Capsicum - Ornamental pepper

Photos

Wilting and dying plants infected with Phytophthora.

Peony leaves showing symptoms of Phytophthora-similar to Botrytis, but doesn't get the fuzzy gray mold.

Flagging or wilting of Catharanthus due to Phytophthora.