Diseases

April Pest Message

Low levels of thrips feeding damage (white scarring) were found on Gerbera daisies.  Other favorite plants include garden impatiens, dahlias, peppers and Ipomoea ‘Marguerite”.  Monitor for distorted new growth and white scarring.

Fuchsia - Botrytis Stem Canker

Botrytis can be managed by management of environmental conditions, sound cultural practices, and fungicide applications. Control weeds and remove plant debris. Space plants to allow good air circulation, reduce humidity within the canopy, and minimize leaf wetness. Improve horizontal air flow with fans. Reduce humidity by a combination of heating and venting in the evening, particularly when warm days are followed by cool nights Water in the morning if practical.

Thielaviopsis basicola

Thielaviopsis basicola has been seen on a number of crops this year including Calabrachoa, pansy, vinca (Catharanthus) and snapdragon. Plants in a tray will often be uneven in height and stunted plants tend to be lighter in color. Roots may be shriveled, brown to black and under-developed. The fungus thrives in cool weather and pH above 5.6. As temperatures warm up injury to the root system may slow down and plants may or may not recover. However, infected plants should be discarded.

Powdery Mildew

Powdery mildew has become more common in the past few week on susceptible crops including gerbera daisy, vegetative petunias, viola, phlox and other favored hosts. Some varieties of verbena including Babylon Blue, Babylon Carpet Blue, Babylon Purple, Babylon Red, Babylon White, Sparkler Red White, Tukana Scarlet and Tukana White were also very susceptible to powdery mildew in a recent Michigan State Horticultural Demonstration Garden cultivar trial.

Lupine Anthracnose

Some varieties of lupine are very susceptible to Lupine anthracnose, caused by the fungus Colletotrichum gloeosporioides. On young seedlings, tips begin to die back like a shepherd's crook. Leaf blights that start with a half-circular brown spot at the edge of the leaf then develop into stem cankers. Severe losses can occur on both seedlings and mature plants ready for sale. Fungal spores are spread by water splashed from overhead irrigation or rainfall.

Daylily Leaf Streak

Daylilies may become infected with a foliar disease known as yellows disease or daylily leaf streak caused by the fungus Aureobasidium microstictum. Small, reddish-brown flecks and brown spots develop on infected tissue. You may then see a central yellow streak along the midvein that begins at the leaf tip. If severe, entire leaves can turn yellow. However, daylily leaf streak does not affect daylily flowers. Different cultivars will vary in how susceptible they are to this fungal disease.

Daylily Rust

Daylily rust (Puccinia hemerocallidis) was found on the daylily cultivar "Twice as Nice" in Massachusetts. Daylily rust was first detected in four states in the southeastern United States in 2000. As of June 2005, it was reported in a total of 28 states. In 2003 several cases were reported in Massachusetts and in 2004 one case of daylily rust was reported. Due to the limited number of cases of daylily rust in Massachusetts it is possible to limit the spread this disease in the state.

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