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IPM Scouting in Herbaceous Perennials

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Phytophthora
IPM scouting in herbaceous perennials > phytophthora
Pathogen: Phytophthora spp. (P. cactorum, P. drechsleri, P. nicotianae, etc.)

Hosts include: Achillea, Clematis, Euphorbia, Fragaria, Heuchera, Leucanthemum, Lilium, Phlox, Platycodon, Sedum, Sempervivum, Scabiosa and Viola.

Symptoms: Stem and crown rot, root rot, stunting, wilting, yellowing. Infection of aboveground plant parts causes foliar dieback. Plants with low levels of infection may not have obvious symptoms.

Spread: Phytophthora is a soil-borne pathogen; spores can also be disseminated short distances through the air. Moving infested plant material can spread the disease. Phytophthora has several
different spore types, including chlamydospores, sporangia, zoospores and oospores. (Refer to Pythium root rot for a description of these spore types.)

Management: Management strategies for Pythium spp. also apply to Phytophthora. Symptomatic plants should be removed and destroyed. Fungicides are often used to prevent losses. It is important to get good coverage of the affected plant parts. Fungicides have limited scope and should not be expected to cure heavily infected plants. Systemic fungicides should be used in rotation with protectant fungicides to delay resistance development. Applications at the high end of the labeled rate are required for Phytophthora control.
Phytophthora infection Discolored roots
Aerial Phytophthora infection caused water-soaked lesions and stem collapse of lily. Discolored roots caused by Phytophthora infection.
This information was developed from A Pocket Guide for IPM Scouting in Herbaceous Perennials by Jan Byrne and Raymond A. Cloyd. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2981).
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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Updated 9/28/07