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The P&PDL Picture of the Week
for 17 March 2003



Ringspots and Line Patterns on Impatien Leaves Spell Trouble

Gail Ruhl, Interim P&PL Director, Senior Plant Disease Diagnostician, Department of Botany and Plant Pathology, Purdue University

Impatiens Necrotic Spot Virus (INSV) is the cause of the spots, line patterns and rings on the leaves of these impatiens. INSV has a very wide host range and is spread from plant to plant by the western flower thrips. An adult thrips can infect a plant with virus after feeding for only 30 minutes. Some of the common flowering plants that may become infected by INSV are impatiens, New Guinea impatiens, begonias, petunias, snapdragons, cyclamen, cineraria and gloxinia. Although the symptoms caused by INSV on impatiens are quite diagnostic, INSV causes a wide variety of symptoms on other types of plants including wilting, stem death, stunting, yellowing, poor flowering; and sunken spots, etches, or ring spots on leaves. Symptoms on different kinds of plants may not be very specific or consistent, and merely indicate that there is something wrong with the plant. Many other diseases and plant problems may cause symptoms that resemble INSV. Virus symptoms may depend on time of year, type of plant, age of plant, plant physiological state, growing conditions at the time of infection, and strain of virus. Positive diagnosis of INSV requires either inoculation of special indicator plants or serological tests to determine if the virus is present. Purdue’s Plant and Pest Diagnostic Laboratory uses a rapid serological test (10 minutes) to verify the presence or absence of INSV in symptomatic plant tissue.

Prevention is worth a pound of cure! Do not buy impatiens with symptoms indicative of INSV infection. If INSV is diagnosed on your plants, discard the infected plants since infected plants cannot be cured. For information on insecticides to control western flower thrips in a greenhouse situation contact your local plant diagnostic lab.

Click on the small image to view a larger image.

Impatiens Necrotic Spot Virus -
Ring spots and line pattern
symptoms

Impatiens Necrotic Spot Virus -
Leaf spots and line pattern
symptoms
Impatiens Necrotic Spot Virus -
Ring spots

Impatiens Necrotic Spot Virus -
Ring spot symptom

Impatiens plant infected with INSV

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Last updated: 14 March 2003/amd
The Plant & Pest Diagnostic Laboratory at Purdue University