What's the Best Time to Spray Roses?

Attention of roses (Rosa spp.) Sometimes maintains even the most intrepid gardeners from enjoying the beauty of this popular flowering semi-evergreen or deciduous shrub. But there are strategies that make it possible to develop roses for enjoyment without the hassle of grueling spray schedules and upkeep. A vast selection of rose varieties grow in U.S. Department of Agriculture plant hardiness zones 5 through 9, and also certain species live colder climates. Low-maintenance shrub roses give dependable bloom with very little care. But hybrid teas, grandifloras, floribundas and polyanthas require more focus. Rose plant spray schedules can be intended for prevention or utilized for eradication of diseases or insects.

Rose Diseases

Roses are subject to bacterial, viral and bacterial diseases. Black area (Diplocarpan rosea) is a widespread disorder of rose bushes, manifesting as round black spots with yellow borders on leaves. Warm, humid weather and overhead irrigation supply conditions for development of this fungus. Cool, humid weather provides rise to infection with powdery mildew infestation (Sphaerotheca pannosa var. rosae). Symptoms include a grayish-white coating on leaves, stems and flower buds. Botrytis blight fungus (Botrytis cinerea) also attacks plants during periods of high humidity and cool temperatures. Stem canker and dieback happen when injury or pruning permit entry of Botryosphaeria, Leptosphaeria, Coniothyrium and Cryptosporella fungi. Cankers and dieback are common on roses already weakened by disease. Rose mosaic (Rose mosaic virus) and also rose rosette disease (Rose rosette virus) are both viral diseases that severely damage roses and require removal of their plants. Crown gall results in a soil-borne bacterium (Agrobacterium tumefaciens) that interferes with the plants vascular system and stunts plant growth.

Insect Pests

Sawflies (Endelomyia aethiops, Cladius difformis and Allantus cinctus), aphids (Macrosiphum rosae and Macrosiphum euphorbiae) and spider mites (Tetranychus urticae) attack leaves, stems and rose flowers. Aphids and sawflies frequently can be controlled by spraying roses in early morning with a strong spray of water. More severe infestations are treated using insecticidal soaps. Spider mites and sawflies can be controlled with insecticidal soaps or horticultural oils. Neem Oil, or azadiractin, is just a slow-acting remedy for youthful sawflies. Japanese beetles (Popillia japonica) attack rose bushes in midsummer, voraciously chewing all parts of the plant, skeletonizing leaves or defoliating the plant. Traps or sprays control this pest of roses.

Spray Formula

Rose spray products are available at garden and home supply shops. But an extensive spray formula to control both disease and insect pests can be produced at home. 1 recipe, called Witherspoon Spray Formula, is made using 1 gallon of water, 5 teaspoons captan, 2 1/2 teaspoons thiophanate methyl, 1 1/2 teaspoons acephate and 1/2 teaspoon surfactant or spreader sticker. Four teaspoons of fluid carbaryl can replace acephate during Japanese beetle infestations.

Spray Schedules

Winter maintenance involves spraying the ground around rose bushes having an insect-and-disease formulation or horticultural oil. The insect-and-disease formulation can be utilized again in late winter to spray the two bushes and the surrounding ground region. If insects are present in blossom buds, the formulation is used in early spring. The growing-season spray program for roses requires spray each seven to ten days, however when temperatures are over 86 degrees Fahrenheit. Spray is applied to all surfaces, including backsides of leaves, during morning hours to allow spray to dry before night.

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