|Crop Knowledge Master|
Eurytoma orchidearum (Westwood)
Victoria L. Tenbrink, Research Associate
Arnold H. Hara , Entomologist
Beaumont Research Center
The cattleya fly attacks mainly Cattleya, but will also infest Laelia, Epidendrum, and Brassavola (Tanada, 1953). Some Cattleya are more resistant than others. Epidendrum were not a good host in Hawaii according to work done by Ikeda (1952).
Although damage from cattleya flies may have been noticed in Hawaii earlier, Swezey first recorded the pest in Honolulu in 1914. Cattleya fly is native to the tropical areas of the New World. Because of the movement of infested plants, it was in England by 1860, Massachusetts in the United States by 1889, and San Francisco by 1914 (the same year it was first discovered in Hawaii.) (Ikeda, 1952). Probably eradicated in Hawaii soon after it was discovered, it was re-introduced in 1948. Thought to be again eradicated, it returned as a major pest in 1951-52 (Bess, 1952; Tanada, 1953). Cattleya fly is now on Oahu, Hawaii, Maui, Kauai, and Lanai (Nishida, 1992).
The damage to orchid plants is extensive and is mainly done by the feeding larvae. Oviposition by the female wasp and subsequent early feeding of the larvae cause dormant bulbs to actively grow. Both dormant and growing infested bulbs become characteristically deformed. The base of the bulb swells abnormally, and the tip elongates. Continued feeding by the larvae destroys tissue necessary for proper nutrition and flowering of the plant. Secondary damage from introduced fungi and bacteria may further damage the plant. Infested plants usually fail flower. They do not thrive and may eventually die (Ikeda 1952).
The cattleya fly is not a fly; it is a wasp. Like other wasps, the cattleya fly has 4 wings, whereas flies have 2 wings. The life cycle of the cattleya fly moves through 4 stages: egg, larva, pupa, and adult. The larval stage is the familiar maggot or grub. Reports of the length of the life cycle vary from a few weeks to 4 months; several generations a year are possible (Ikeda, 1952; Tanada, 1953).
The wasps mate within a few hours of emerging from the orchid plant. The female then pierces plant tissue with her ovipositor and deposits eggs, making a separate puncture for each egg. Eggs are usually laid in the young shoot or eye at the base of the plant. Sometimes eggs are deposited in rhizomes, pseudobulbs, or rarely leaf blades or flower buds. Although females are not selective and lay eggs in old as well as young tissue, wasps develop only in the young tissue (Tanada 1953). A female may lay 50 eggs over her 5 day life span (Ikeda, 1952).
Once hatched, the larva feeds on surrounding plant tissue. This creates a cavity where the larva lives. The larva feeds as it grows, enlarging the cavity. Often the cavities of several larvae will join to form a single, larger cavity containing many larvae. After pupation, many adults will often emerge from the same hole.
Eggs are creamy white. They are rarely seen because they are tiny (1/32 in) and located inside plant tissue. The puncture made by the female as she oviposits is also tiny and barely visible (Tanada, 1952).
The legless body is creamy white. Mature larvae are 3/16 in long (Tanada, 1953).
Orchid flies pupate inside the cavity where the larvae develop. At first pupae are white, but they gradually darken to black (Tanada, 1952).
Adults are jet-black with two pairs of transparent wings. The legs are a lighter color than the body. The rear section of the body, the abdomen, is shiny, while the rest of the body and the head are dull. Females are about 3/16 in long and males are about 2/3 as long at 1/8 in (Tanada, 1953). The wasps are so small as to be easily overlooked. They are similar in size to beneficial parasitic wasps.
Adults are not strong fliers, appearing to hop from place to place. Adults are active only during daylight hours (Tanada, 1953).
Young shoots that are abnormally swollen at the base with long, pointed tips should be removed and destroyed by burning, crushing, immersion in oil, etc. Lightly infested shoots may be hard to distinguish from normal shoots (Tanada, 1952). ItŐs important not to introduce infested plants into the nursery.
Control has been achieved by piercing the larvae with a needle. It is more successful when the larvae are in a single cavity rather than in separate cavities (Tanada, 1952).
Life stages in the tissues, including eggs, larvae, and pupae, are difficult to control by chemical means. Adults are susceptible to contact insecticides. Consult the University of Hawaii Cooperative Extension Service for effective, currently registered chemicals.
Best, H. A. 1952. Stem wasp pest of cattleya orchids. Bulletin of the Pacific Orchid Society of Hawaii 10 (2): 56-58.
Ikeda, W. S. 1952. The Cattleya fly (Eurytoma orchidearum). Na Pua Okika o Hawaii Nei 2 (1): 5-9.
Nishida, G. M. ed. 1992. Hawaiian Terrestrial Arthropods. Bishop Museum Press: Honolulu. P. 171.
Tanada, Y. 1953. The Cattleyafly, Eurytoma orchidearum (Westwood), in Hawaii. Hawaii Orchid Society Bulletin. 5: 41-47.