The entire life cycle from egg to adult occupies approximately 30 days. In the vicinity of Washington, D. C., there are six of these 30-day life cycles or generations each season. There is such a great overlapping of these generations, due to the irregularity of emergence of the overwintering adults and the variation in individual development, that shortly after the first brood all stages may be present at the same time. THE EUROPEAN ROSE SLUG. The European rose slug is probably the next most common rose sawfly and is reported as injurious in States as far west as the Rocky Mountains. The eggs of this species are laid in pockets in the leaf tissue quite near the edge of the leaflet, with the slit at the base of one of the leaflet's serrations and with the egg prominent on the underside of the leaflet and protected and held in place there by the thin under membrane of the leaf. The larva is yellowish green in color with food causing the alimentary tract to appear dark olive green. It feeds upon the upper surface of the leaf by a characteristic chafing method, eating only the soft tissue and leaving the veins and under tissues showing yellowish on the green leaflet. When full grown the larva leaves the bush and enters the ground where it constructs a cell, cementing together particles of sand and earth to form a capsule-shaped chamber. It is within this cavity that the quiescent period is spent. This stage occupies most of the year, carrying the species through the summer, fall, and winter until the following spring. Thus the life cycle is approximately a year in length and the species has only one generation a year. THE COILED ROSEWORM. The coiled roseworm is not especially abundant in any section of the country, but occasionally occurs in sufficient numbers to attract attention, either because it bores into the pruned ends of shoots or because it feeds on the leaves. It is the former habit that causes it to be most frequently the object of inquiry. This species occurs from Minnesota to Maine and as far south as northern Virginia. Its eggs are laid in the upper surface of the leaflet and not especially near the edge, as in the preceding species. The larva which hatches begins feeding by skeletonizing patches from the underside of the leaflet, leaving only the thin upper skin which appears whitish transparent. This method of feeding does not last long, as the larva soon begins devouring all of the leaf tissue, first eating holes through and then feeding on the entire leaflet, exclusive of the largest veins. When full grown this larva searches for a piece of soft wood or similar material, and when the pruned ends of rose shoots are avail able it will bore into the pith of these and construct a gallery and cell for its resting stage. In the southern range of the species there are two generations, one having a short life cycle of several days more than a month and the other occupying the remainder of the year. HOW TO CONTROL ROSE SLUGS AND PROTECT THE FOLIAGE. The control of these pests is easy. So simple a thing as a strong stream of water applied often and from different angles is a remedy in that it knocks the larvæ from the leaves and they perish before they are able to return.. In places where a strong stream of water is either unavailable or inconvenient to use, a stomach poison like lead arsenate and water sprayed upon the leaves gives good results. If the spraying is to be extensive and a large quantity of the mixture is to be used, 1 pound of powdered lead arsenate to 50 gallons of water is the proper proportion and a large compressed-air hand sprayer or barrel pump will be found suitable. If the spraying is to be limited to several bushes 3 rounded teaspoonfuls of powdered lead arsenate to a gallon of water is a good mixture and one of the small hand spray pumps will serve the purpose. Another spray which will be effective against young larvæ and which has the additional advantage of being a good aphid remedy is 40 per cent nicotine sulphate which should be diluted as recommended upon the container, usually 1 part to 800 parts of water in which some fish-oil or laundry soap has been dissolved. For small quantities use approximately 1 teaspoonful of the nicotine sulphate to 1 gallon of water in which 1 ounce of soap has been dissolved. The life cycles and the number of generations have been discussed in this paper in order that those whose plants are infested may be le to determine for themselves whether it will be necessary to splay once or a number of times during the year. Since the European rose slug spends most of the year in cells or resting chambers in the ground, thorough working of the soil will help to reduce its numbers, by breaking up the cells and exposing the soft, weak, unprotected pupa to the weather and various predatory enemies. The coiled roseworm may also be combated by painting the ends. of pruned twigs, removing all pithy stems and brashy wood, and leaving no suitable hibernating place available. The bristly rose slug can be destroyed in large numbers by burning the old leaves and other litter in which they have spun cocoons. Hence clean cultural methods are to be strongly recommended as a means of insect control in the growing of roses. It will further simplify the task of a grower if he will endeavor to interest his neighbors who have roses to cooperate with him in destroying pests, for if bushes belonging to them remain infested they will be a constant source of reinfestation for his. A STUDY of this bulletin should make it possible to identify the particular kind of sawfly attacking roses. This done, information on the number of generations to be expected may be had by consulting the life-cycle diagrams (fig. 7). If only one generation occurs, as in the European rose slug, one or two sprayings should effect control; but if there is more than one generation, as with the coiled roseworm and the bristly rose slag, the gardener will have to keep a closer ich upon his bushes and spray more often. Farmers' Bulletin 750, which deals with roses and their culture, contains a discussion of the remedies for various insect pests. This bulletin is of value to all rose growers and may be obtained from the Division of Publications, United States Department of Agriculture, Washington, D. C. О |