Strigoderma arboricola Fabricius Coleoptera Scarabaeidae

Natural History

Distribution. Spring rose beetle is a native species found in the northeastern United States from New

York to North Carolina, west to Colorado and Minnesota. In Canada it is known from southern Ontario.

Host Plants. The adults feed on the blossoms of many plants. Wild and cultivated rose are favored food plants, which is the basis for its common name. Blossoms, and sometimes fruits, of other economically important plants such as blackberry, cotton, clover, coreopsis, hairy vetch, hollyhock, honeysuckle, iris, lilies, perennial pea, timothy, and peony also are consumed. Vegetable crops attacked by adults include bean, cantaloupe, corn, cowpea, and cucumber. Among weeds fed upon by adults are dewberry, Rubus spp.; elderberry, Sambucus canadensis; hoary verbena, Verbena stricta; horsemint, Mondarda punctata; plantain, Plantago spp.; prickly pear cactus, Opuntia humifusa; water lily, Nymphaea sp.; water willow, Justicia americana; wild parsnip, Pastinaca sativa, and others. Larval feeding habits are not well-known, but spring rose beetle larvae are reported to damage roots of corn, cotton, peanut, potato, soybean, strawberry, sweet potato, and various grasses and grain crops.

Natural Enemies. Little is known about the natural enemies of this insect. An entomopathogenic nematode, Steinernema glaseri (Nematoda: Steinerne-matidae), is known to affect the larvae of this and other scarab beetles (Poinar, 1978).

Life Cycle and Description. There is a single generation per year, with overwintering occurring in the last larval instar. In Virginia, adults are abundant starting in May or June, while eggs are abundant in June. In Minnesota and Ontario, adults were reported to be common in June and July, while eggs were found in July and early August.

  1. The eggs are deposited singly in the soil at a depth of 5-10 cm. Grayson (1946) reported a fecundity of 30-40 eggs per female, but this seems to be an underestimate. The eggs are white and oval. Size varies because the eggs absorb water as they mature; the length increases from about 1.59 to 1.86 mm, the width from 1.07 to 1.63 mm. Duration of the egg stage is reported to average about 13.5 days (range 8-21 days).
  2. The larva is whitish, with a light brown head. There are three instars. Duration of the instars is about 16 days for each of the first two stages and 270 for the third, or overwintering, instar. The terminal portion of the last instar, or prepupal period, is relatively short, about 11 days. Larvae occur in the soil at a depth of 12-28 cm. Under warm conditions, larval development proceeds faster. Hoffmann (1936) reported larval development of about 160 days in the laboratory.
  3. Pupation occurs in the soil, normally during April or May. Larvae form an earthen cell measuring about 30 mm long and 10 mm wide, and pupate within. The pupa measures 9-12 mm long and gradually changes its color from light to dark brown as it matures. Duration of the pupal stage is usually 12-24 days.
  4. The beetles are moderate in size, measuring 8.5-12.5 mm long. They are somewhat variable in color, but the head and thorax are usually blackish green, and the elytra brownish yellow. The elytra are marked with distinct ridges. The underside of the beetles bears long hairs, and is brown or brownish gray. Adults appear to persist for about 30 days. Mating is relatively brief in duration, requiring only 2-15 minutes. Mating is often observed on flowers, a favorite food for adults. The pre-oviposition period is 7-16 days, followed by oviposition in the soil.

The biology of spring rose beetle was given by Hayes (1921), Hoffmann (1936), and Grayson (1946). The larvae were described by Ritcher (1966).

Damage

This insect is known principally as a pest of roses, as the adults feed greedily on the blossoms. However, the larvae feed on the below-ground parts of several plants, and they not infrequently are associated with sweet potato and peanuts.

Management

Historically, larvae are usually more abundant in low and heavy soil than in well-drained, sandy soil. Soils high in organic matter also are more prone to injury. Application of liquid or granular insecticide to the soil at planting-time or early in the growth of the crop has generally prevented injury. However, in Colorado injury has occurred in sandy soils, and it

Coleoptera Scarabaeidae Resimleri

has proven difficult to attain protection with planting-time treatments, because the insecticide dissipates before eggs hatch (Peairs, pers. comm.).

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