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A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

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Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

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Wednesday - November 09, 2005

From: Lexington, TX
Region: Southwest
Topic: Diseases and Disorders
Title: Cotton root rot in Purple Sage, Leucophyllus frutescens
Answered by: Joe Marcus

QUESTION:

We had three Purple Sage shrubs in our front yard. They did very well for about three years and then this past year they just died. From what I have read they are pretty hardy so we are really stumped as to what happened to them.

ANSWER:

 

Purple Sage, Leucophyllum frutescens is also known as Cenizo, Texas Ranger, Texas Sage, Barometer Bush and Silverleaf. It is a tough-as-nails shrub native to south Texas.

 

Purple Sage is highly resistant to most insect pests and diseases. However, it is susceptible to Cotton Root Rot (Phymatotrichopsis omnivora) in poorly drained soil, in over-watered landscapes or during wet seasons. Once Cotton Root Rot, also known as Texas Root Rot, has infected one plant in a landscape, the pathogen stays in the soil and will infect other susceptible plants that replace it. The much-used Red Tip Photinia, Photinia xfraseri is particularly susceptible to Cotton Root Rot and is responsible for many of the occurrences of the disease that we see.

 

To positively identify Cotton Root Rot, it is best to pull a dead plant out of the ground, shake off as much soil as possible away from your landscape, and take the plant -- roots and all -- to your county agriculture extension office. For more information on this particularly pernicious fungal disease, see this article on Diseases of Urban Landscapes.

 

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