August 11, 1993

Crown Gall

Crown gall was recently diagnosed on a euonymus samplesubmitted to the Plant Disease Clinic. Crown gall is a bacterialdisease caused by Agrobacterium tumefaciens. Crown gall can affectmany species including ornamental shrubs and vines, particularilyeuonymus, honeysuckle, and rose. Certain perennial flowers, suchas chrysanthemums, asters, and daisies, are also susceptible.Blackberry, raspberry, and tomato are hosts. The disease can alsooccur on young nursery stock including shade trees, nut-bearingtrees, pome fruits (apple and pear), and stone fruits (peach,cherry, etc.).

Conditioning Cut Flowers

Proper preparation and careful maintenance maximizes the vase life of any cut flower whether grownyourself or purchased at the local flower shop. Properconditioning or hardening of flowers is critical. Recut stemsunder water to prevent air bubbles from forming within the stems.Remove 2 inches from the bottom of each stem, cutting at an angle.Transfer the cut flowers into the container in which they will beconditioned. To condition flowers, immediately immerse flowers intepid water (110 F) containing floral preservative almost up to theflower heads.

Fabraea Leaf Blight on Hawthorn

A leaf blight on hawthorn was diagnosed recently in the PlantDisease Clinic. The disease is caused by the fungus Fabraeathuemenii. Symptoms of leaf blight begin in spring and earlysummer as small, angular, reddish-brown spots on the upper surfaceof leaves. The spots increase in size and run together, causingpremature defoliation during wet years. From a plant pathologist'sview point, the disease is very interesting because of thecharacteristic spores, which resemble minute, winged insects.