June 16, 1995

Hollyhock Rust

Hollyhock rust is caused by the fungus Puccinia malvacearum. The undersides of infected leaves show raised brown spots about the size of a pinhead. The upper leaf surfaces usually show a yellow to orange discoloration above the brown spots. Infected areas may run together and destroy large portions of the leaf. Stems may also be infected.

Leaf Cuttings

Successfully starting plants from leaf cuttings is an easy way to experience one of nature's miracles, totipotency. Totipotency is the ability of each and every plant cell to regenerate an entirely new plant. Leaf cuttings can be made from the leaf blade and petiole, leaf blade alone, or sections of the leaf. Many houseplants such as rex and rhizomatous begonias, African violets, streptocarpus, gloxinias and sansevierias are willing candidates.

Pesticide Exposures in 1993: Report from Poison Control Centers

The American Association of Poison Control Centers summarizes calls received about human exposures to poisons on an annual basis. The 1993 summary involves 1,751,476 exposures, reported to one of the 64 poison control centers nationwide. The 64 centers serve approximately 181 million people. Calls concerning a pesticide exposure represented about 4% of all 1993 contacts. Of these, 1,107 dealt with a fungicide, 7,059 with an herbicide, 49,378 with an insecticide, and 14,920 with a rodenticide.

Summer Pruning of Raspberries

To maximize yields, raspberries must be properly pruned in spring and summer. The pruning procedures for red, black, and purple raspberries are based on the fruiting characteristics of the plants.

Summer pruning of raspberries, though overlooked by many gardeners, is vital. After the last summer harvest, promptly remove the old fruiting canes of all raspberries at the soil surface and destroy them. Removal of the old fruiting canes helps control diseases. Their removal also permits more light to reach the new shoots, resulting in higher yields.

Slime Molds on Turf

Turf samples showing the presence of slime mold have been arriving in the Plant Disease Clinic. Slime molds are fungi that grow on decaying organic matter. During wet weather they "ooze" onto leaf blades. This growth at first may appear black, yellow, or other color, and slimy. Eventually it turns to a powdery substance (usually white or grayish). Slime molds are common on turf, strawberries, or in plant beds with high organic matter.