|Crop Knowledge Master|
Arnold H. Hara, Extension Entomologist
Ruth Y. Niino-DuPonte, Research Associate
Department of Entomology
The blossom midge has a wide host range spanning at least six plant families, including the flower buds of orchid, plumeria, hibiscus, pikake (jasmine), white mustard cabbage or pak choi, tomato, eggplant, pepper, potato, bittermelon, and other vegetables and ornamentals.
Blossom midge, Contarinia maculipennis Felt (Diptera: Cecidomyiidae), has been present in Hawai`i since the early 1900s and is thought to have originated from Asia (the West Indies). Jensen (1946) presented compelling evidence that C. maculipennis had been misidentified in earlier reports as C. solani (Rübsaamen) or C. lycopersici Felt due to its diverse range of hosts. Currently, the blossom midge can be found on all of the major Hawaiian islands. Elsewhere in the USA, the blossom midge was reported on dendrobium orchids in Florida in 1992.
Blossom midge maggots feed inside unopened flower buds, causing deformed, discolored buds and blossoms, and in severe infestations, premature bud or blossom drop (Fig. 1). As many as 30 maggots may be found infesting a single dendrobium bud.
Figure 1. Feeding damage to flower buds by blossom midge: left, plumeria buds; center, dendrobium buds; right, dendrobium bud drop [Photos: A. Hara, R. Mau]
The blossom midge reproduces year-round in Hawaii. The duration of the blossom midges life cycle from egg to adult is approximately 21 to 28 days.
The eggs are deposited in masses by the adult female into the open tips of flower buds. They are white to cream colored, invisible to the naked eye, and hatch within 24 hours into maggots that move into the bud.
The maggots feed on fluids
drawn by their rasping mouthparts from the damaged flower bud tissue. The maggots are white
when newly hatched, becoming yellow, with a pink tinge as they age (Fig. 2). As they mature in 5-7 days to 1/12 inch (about the
thickness of a nickel in length), the maggots are capable of flipping themselves several
inches into the air to exit the buds and burrow into the soil to pupate, like other
ground-pupating fly larvae such as the melon fly and oriental fruit fly.
The maggots are white when newly hatched, becoming yellow, with a pink tinge as they age (Fig. 2). As they mature in 5-7 days to 1/12 inch (about the thickness of a nickel in length), the maggots are capable of flipping themselves several inches into the air to exit the buds and burrow into the soil to pupate, like other ground-pupating fly larvae such as the melon fly and oriental fruit fly.
Figure 2. Blossom midge larvae feeding in dendrobium bud (actual size=1-2 mm long). [Photo: Walter Nagamine, Hawaii Dept. of Agriculture]
Pupation is most successful in soil that is moist but not wet. The late-stage pupa turns from yellowish-white to brown (Fig. 3) and burrows back up to the soil surface in preparation for emergence as an adult in14-21 days after entering the soil. The pupa works itself partially free of the soil, and the adult emerges, leaving the pupal skin protruding from the soil.
Figure 3. Blossom midge pupae from hibiscus (actual size=1-2 mm long). [Photo: Walter Nagamine, Hawaii Dept. of Agriculture]
The adult blossom midge is very tiny (about the thickness of a nickel in length); males are slightly smaller than females. The adult is somewhat mosquito-like, with typical fly features, and survives for only 4 days. It has relatively large, multifaceted eyes and a single pair of spotted wings about one to two times as long as its body (Fig. 4).
Figure 4. Adult blossom midge (actual size=2 mm in length). [Photo: S. Chun]
Except for the adult, all stages of the blossom midge are secluded within the bud (as maggots) or in the soil (as pupae). Adult emergence from pupae in the soil usually occurs in the early evening.
When laying eggs, the adult female blossom midge is unable to penetrate plant tissues but rather inserts its ovipositor into the open end of a bud. The adult midge avoids late-stage buds and prefers to lay eggs in young buds to ensure an optimal food source and moist environment for the maggot until it matures.
If growing conditions become unsuitable for larval development (for example, if the flower or bud on which maggots are feeding begins to dry), immature maggots may leave the flowers or buds to pupate in the soil; however, their pupation may take a few weeks longer and the emerging adult midges are invariably smaller than adults from fully mature maggots.
In Florida, blossom midge populations maintained in greenhouses were observed to decrease rapidly during the winter, even though the temperature was maintained at 65o F and plants had sufficient numbers of buds.
To date, no parasites have been isolated or specifically introduced to Hawaii to control the blossom midge. The adult is vulnerable to general predators, such as web-spinning spiders and ants. Ants may also prey on pupae in the soil.
Sanitation is the most important management practice for the blossom midge. Remove and destroy all dropped buds and infested buds still on the plant. Place infested flower buds in a plastic bag or a sealed container to prevent escape of maggots.
Due to the blossom midges wide range of hosts, avoid planting possible alternate hosts around the crop area.
A certain variety of tomato was observed to be more susceptible to blossom midge infestation due to its flower structure which facilitates ovipositing. Host plant varieties in which petals remain tightly fitted until the bud is almost ready to open may reduce susceptibility.
Only the adult stage of the blossom midge is vulnerable to contact insecticides, because the maggots are protected within the bud and the pupae are burrowed in the soil.
Some insecticides can be applied as a foliar spray against larvae as well as a soil treatment to target the pupal stage. Translaminar insecticides (those that move from the sprayed leaf surface to the other surface) may be capable of penetrating the bud to affect the maggots. Trials of systemic insecticides (those that are spread from the site of application throughout the rest of the plant) on dendrobium have been disappointing, possibly because the chemicals are not able to reach the flower buds to affect the maggots.
Consult the Hawaii Department of Agriculture or the University of Hawaii Cooperative Extension Service for registered chemicals that are known to be effective against the blossom midge.
FOLLOW SAFETY PRECAUTIONS GIVEN ON MANUFACTURERS LABELS.)
Consult a chemical sales representative, the Hawaii Department of Agriculture, or the University of Hawaii Cooperative Extension Service for correct formulation of insecticides, more information, or updated recommendations. The user is responsible for the proper use, application, storage, and disposal of pesticides.
Reference to a product does not imply approval or recommendation by the College of Tropical Agriculture and Human Resources, Cooperative Extension Service, University of Hawaii, or the United States Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable. All materials should be used in accordance with label instructions.
This information is the culmination of a series of interviews with researchers, extension agents, chemical sales representatives, and growers in Hawaii and a worldwide literature search.
FOR QUESTIONS OR COMMENTS PLEASE CONTACT:
Arnold Hara: 461 West Lanikaula St. Hilo, HI 96720, Ph: (808) 974-4105 Fax: (808) 974-4110 E-mail: firstname.lastname@example.org
Felt, E.P. 1933. A hibiscus bud midge new to Hawaii. Proc. Haw. Ent. Soc. 8(2):247-248.
Gagné, Raymond J. 1995. Contarinia maculipennis (Diptera: Cecidomyiidae), a polyphagous pest newly reported for North America. Bulletin of Entomological Research 85: 209-214.
Jensen, D.D. 1946. The identity and host plants of blossom midge in Hawaii (Diptera: Cecidomyiidae: Contarinia). Proc. Haw. Ent. Soc. 12(3):525-534.
Jensen, D.D. 1950. Notes on the life history and ecology of blossom midge Contarinia lycopersici Felt (Diptera: Cecidomyiidae). Proc. Haw. Ent. Soc. 14(1):91-100.
Osborne, L.S., T.J. Weissling, J.E. Pena, and D.W. Armstrong. 2001. A serious pest is causing significant problems for dendrobiums and hibiscus growers. In: Proceedings for the 17th Conference on Insect and Disease Management on Ornamentals. February 25-27, 2001, Orlando, FL. Felter, L., T.Higgins, and N. Rechcigl (eds.). Society of American Florists, Alexandria, VA. p. 21.
Adapted from the authors' CTAHR publication, "Blossom Midge in Hawaii - a Pest on Ornamentals and Vegetables". Insect Pests IP-11, June 2002.