It is further proper to insist, before separately treating the various insects and diseases in question, that the location of the rose beds has much to do with their health. Roses the roots of which are starved through proximity to some strong shrub or tree cannot be vigorous enough to sustain healthy life.
Roses placed where there is not a free air circulation, and where there is a settling of cold air currents or fog in the night and early morning, are favourably disposed toward mildew and black-spot, the chief disease troubles that beset roses in America.
While it is true that the rose, particularly in the Tea and Hybrid Tea classes, needs a certain shelter from harsh and heavy winds, and is advantaged by not exceeding 20 per cent. of shade, preferably during the afternoon, it is also true that an open sunshiny situation is of the utmost importance for rose health and rose protection. The shelter of a distant hedge or a slope away from the prevailing winds is sufficient for the rose.
Insects and roses
The Rose Aphid (Macrosiphum rosae Linnaeus) is probably the most widely distributed rose insect, and infests the queen of flowers both in the open and in the greenhouse. It is a small green or pinkish plant louse, found on the tender parts of the plant, particularly its terminal growths, in vast numbers, and there multiplying with great rapidity. It feeds by sucking out the plant juices, and thus stunts the tips of the branches and promotes the formation of imperfect and deformed flowers.
In the same class is the Small Green Rose Aphid (Myzus rosarum Walker) which particularly bothers roses in greenhouses and in California. It is about half as large as the first sinner above mentioned.
The Pink and Green Potato Aphid (Macrosiphum solanifoliae Ashmead) is a plant louse better known as a pest on potatoes, spinach, kale, etc. It has been found to be an important factor in the transmission of the mosaic disease of potatoes and spinach, and sometimes winters over on the rose in the egg stage, later doing its dangerous transmission work on the plants above mentioned.
Control—All of these aphides, or lice as they are, may usually be dislodged with a stiff stream of water from the garden hose, and that is a simple and practicable means of destroying them. In small gardens the thumb and finger of a hard-hearted friend of roses usually makes quick work of the beginning of the colonies of these lice.
They are very subject to any form of nicotine, and in greenhouses are destroyed by burning tobacco stems. In the open, control is easily accomplished by using commercial nicotine sulphate, known as "Black-leaf 40," at the rate of one part to eight hundred parts of water, to which is added a small amount of soap solution to make the liquid stick and spread better. For small gardens it is sufficient to use a teaspoonful of the " Black-leaf 40" in two gallons of water, adding about one ounce of soap. It has also been found that a strong soap solution itself will almost completely eradicate these aphides if the spraying is done with some thoroughness, care being taken to wet all of the lice. Tobacco dust, applied when the plants are moist, will kill all the aphides it touches.
There are three mean slugs that attack roses, the first being the American Rose Slug (Endelomyia rosae Harris), widely distributed throughout the eastern United States, and particularly abundant in the northern or more intensely rose-cultivated parts of this land. The parent is a four-winged fly which does its work unnoticed soon after the leaves open. The eggs deposited by the female hatch in ten days to two weeks, and the young slugs feeding at night skeletonize the upper surface of the leaves. They are unpleasant-looking little greenish animals, like miniature caterpillars.
The Bristly Rose Slug (Cladius pectinicornis Fourcroy) does its worst work in the southern part of the eastern United States. Produced in the same fashion as the one first named, the slugs quite soon follow the laying of the eggs, and not only feed on the upper surface of the leaves, but as they get stronger, eat out large irregular holes in the edges. The mature slug or larva is about three fifths of an inch long, yellowish or greenish in colour, and somewhat bristly. This slug is dangerous because it has three or four broods during the season.
The Coiled Rose Slug (Emphytus cinctus Linnaeus) is larger than either of the two above mentioned, and more voracious, for the larvae devour the entire surface of the leaf, feeding along the edge with the tip of the body coiled beneath it. When mature the larva is about three-fourths inch in length. There are two broods of this pest, and it lives over, if uncontrolled, by hibernation in the pith of a dead rose branch or some near-by plant.
Controlling rose slugs—A strong stream of water is efficacious also for these pests. Fresh hellebore powder is also effective on these slugs, either stirred into water at the rate of one ounce to three gallons of water, or dusted on the foliage dry, diluted preferably with double its weight of powdered plaster or cheap flour. The previously mentioned tobacco extract, " Black-leaf 40," will destroy these slugs. Powdered tobacco, now easily obtainable, likewise terminates their activities. Further, the control of mildew and black-spot later proposed usually takes care of all of the slugs.
The Rose Leaf-Hopper (Typhlocyba rosae Linnaeus) injures the leaves of rose bushes as it feeds on the under side of the leaves. It is small, nearly white, and very active. It frequently destroys the leaves through its feeding activities. If not controlled it hibernates through eggs inserted in the bark on rose bushes, ready for trouble the next season. The leaf-hopper can be disposed of in the same fashion as the aphides and slugs above mentioned.
The Rose Leaf-Roller (Archips rosaceana Harris) is more of a greenhouse pest than an outdoor pest. It produces blackheaded olive-green caterpillars which feed on the leaves and blossoms, rolling them together into a web with fine silken threads.
The Rose Bug, or June Bug, or Rose Chafer (Macrodactylus subs pinosus Fab ricius), is by all means the meanest, most persistent, and bothersome insect related to roses in America. It is a beetle about one half inch in length, grayish brown in colour, with long, ungainly legs. One brood emerges through a period of sometimes several weeks, just when the blossoms and leaves of rose bushes are beginning to be pleasant to the sight, and often destroys the bloom, preferring the lighter coloured roses.
Fortunately, the heavier soils are unfavourable for hibernation of this wretched bug, which prefers sandy regions, particularly near waste grass lands or weed-infested areas. The larva: become mature by November, descending then to about a foot in depth and spending the winter curled up in oval earthen cells. Their transformation into the nasty beetle which is their destructive form occurs the following spring, and the pest is serious to crops as well as to roses.
Control—The rose bug is a hard citizen to discourage. Where the garden is surrounded by other gardens intensively cultivated, it is hopeful to hand-pick them, using a tin pail of water on the surface of which a little kerosene has been poured, and into which they are dropped or shaken. The best time to get at them is early in the morning, when they are a little less active, but any time is an "open" time for killing a rose bug! A proprietary insecticide known as "Melrosine," if used often enough to catch the successive crops of the brood, has proved efficacious in some sections. Persistence, keeping in mind the fact that each female beetle destroyed shuts off between thirty and forty eggs for next year, is the best way eventually to destroy this pest.
The Rose Midge (Neocerata rhodophaga Coquillett) is a greenhouse rose pest, and needs, therefore, merely to be mentioned here. It has been successfully controlled in greenhouses through the free use of nicotine preparations, including a half-inch layer of green tobacco stems thoroughly covering the ground in which the roses grow.
The Rose Scale (Aulacaspis rosae Bouche) is a whitish unpleasant scale found on old stems, particularly of the stronger-growing roses. Badly infested rose bushes seem as if they had been whitewashed, and naturally the scale weakens the plants.
Control—Spraying the rose bushes with commercial lime-sulphur solution in the proportion of one to nine, in the winter or in the spring before any growth starts, will kill this scale, though in some cases it will be better to cut off and burn the worst infested stems.
The Rose Curculio (Rhynchites bicolor Fabricius) is a bright red snout-beetle having black legs and snout, and being about a quarter inch in length. It is widely distributed throughout the United States, and has the unpleasant habit of eating holes with its beak in the unopened buds of roses, while it also sometimes injures leaves. There is but one brood annually.
Control—Hand-picking into water covered with kerosene is the best control in small gardens.
The Rose Slug-Caterpillar (Euclea indetermina Boisduval) does harm particularly in the Southern States. It is of striking appearance because of its orange colour, and it is covered with tufts of spines which tend to irritate the bare hand used in picking them from the bushes.
Control—Hand-picking with gloves is the best control.
It should be generally noted that the control of all these insects is similar and simple, save only the hateful June bug. It should be noted further that the treatment for black-spot and mildew about to be proposed may readily be so conducted as to take care of all the rose insects (always excepting the rose bug) in one prescription, as repeatedly applied.