Scouting Notes - July 2007

Pathologists identify palm disease. University of Florida plant pathologist Nigel Harrison has identified Texas Phoenix Decline phytoplasma in several palm species in Ruskin, Apollo Beach and Balm-area nurseries and landscapes.

Harrison and fellow plant pathologist Monica Elliott are looking for additional Phoenix and queen palms infected with the disease. Elliott said the symptoms on Phoenix palms have been easier to distinguish than on queen palms. Based on information and samples collected, Elliott said the phytoplasma appears to be insect-vectored and not spread by pruning.

Symptoms include necrosis with fruit dropping all at once. Palms without flowers or fruit exhibit browning and necrosis of the lowest leaves, followed by death of the spear leaf, root necrosis and eventual browning of the rest of the leaf canopy.

For more: (954) 577-6300; http://flrec.ifas.ufl.edu/palm_prod/palm_production.shtml.

White mold appears on ornamentals. This spring, several cases of white mold (Sclerotinia spp.) were identified by the Michigan State University diagnostic lab. Plant pathologist Jan Byrne reported infected plants included lobelia (stem rot), gazania (blighting) and gerbera (crown rot).

Disease symptoms include pre- and postemergent damping off, crown rot and blighting of foliage and petioles. Small, hard, irregular, black structures called sclerotia may be present on or in plant tissue. White fluffy growth, which is most readily visible in high humidity, is produced on infected plant parts.

Apply fungicide drenches, including chlorothalonil, thiophanate-methyl and PCNB, to protect plants.

For more: (517) 355-3504; www.ipm.msu.edu.

Sweet potato virus detected in N.C. Sweet potato chlorotic stunt virus has been detected for the first time in the United States in North Carolina . The virus is vectored by whitefly. When this virus is found in association with sweet potato feathery mottle virus, they cause sweet potato virus disease. The mottle virus is transmitted by aphids.

Symptoms of sweet potato virus disease include stunting, leaf narrowing and distortion, vein clearing and chlorotic mosaic.

Control measures are limited to using clean plant material and resistant or tolerant cultivars. Disease spread is through movement of infected plant material and grafting.

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For more: www.pestalert.org.