BOTRYTIS BLIGHT OF TULIP Botrytis tulipae   F A C T S H E E T

Introduction

Botrytis blight or gray mold is a fungus disease which infects a wide array of herbaceous annual and perennial plants. There are several species of the fungus Botrytis which can cause blights; the most common is Botrytis cinerea. Botrytis infections are favored by cool (60^oF or 15^oC), rainy spring and summer weather. Gray mold can be particularly damaging when rainy, drizzly weather continues over several days. A Botrytis blight fungus with a strict host preference is Botrytis tulipae which infects tulip causing the disease known as tulip fire.

Symptoms

Tulip fire infects causing malformations and/or large, light tan patches on tulip leaves. These patches are most noticeable on light-colored varieties. On leaves these infections are somewhat sunken, yellow to light tan, and surrounded by a water-soaked area. On colored petals the spots appear white and on white petals they appear brown. These spots can coalesce to blight entire flowers or leaves. On stems the infections appear gray to brown and zonate or target-like; infected stems collapse. Outer bulb scales may also become infected and show yellow to brown, somewhat sunken, circular lesions. Small, shiny black sclerotia, resting structures of the fungus, may be found develop on rotting leaf, flower, stem, and bulb tissue.

Fig. 1 Tulips

Disease Cycle

Tulip fire infects tulip leaves as they emerge in the spring. Patches of infected tissue turn tan, and spores are produced in these infected areas that will cause additional infections on leaves, petals, and stems. The fungus overwinters as sclerotia in in infected plant debris.

Management Strategies

The best way to manage this disease is by inspection and sanitation. While inspecting plants carry a paper bag for sanitation. Remove faded or blighted flowers, blighted leaves, or entire plants infected at the base and place them in the paper bag so that they may be discarded with the trash or burned. It is best not to do any sanitation when plants are wet with dew or rain since this could spread fungal spores during conditions which favor infection. Likewise avoid overhead watering, syringing, or misting plants especially if Botrytis blight has been troublesome in the past. To promote rapid drying of plants space them to allow good air circulation.

Fungicide sprays may also help by protecting plants from infections. Apply these when spring weather is continuously cool and wet or if Botrytis blight has been a problem the previous year. Fungicides registered in New York State to treat tulip fire include copper, Serenade, Dexol Bordeaux, or Camelot. Similar fungicides may registered for use on different plant(s) or groups of plants so always make sure the plant which will be treated is also listed on the label of the product purchased. The label also contains information on how to apply the fungicide as well as any precautions. Additional products may be available for use in commercial plant production. Commercial applicators should refer to the appropriate pest management guidelines for more information.

When tulip fire is a problem, cut and remove fading flowers before petal fall, and cut and remove foliage at ground level when it yellows. Remove plant debris from the garden destroy or discard it. Apply the first fungicide spray when leaves are four inches high. With continuous inspection and careful sanitation gray mold can be effectively managed. Keep an eye out for the silvery-gray mold and/or tiny black sclerotia which are sure signs of this disease.

Updated, SLJ, 1/07