orchid problems Blossom midge

Insect Pests Blossom Midge - Orchid Problems

June 2002

IP-11

Blossom Midge in Hawaii—

a Pest on Ornamentals and Vegetables

Arnold H. Hara and Ruth Y. Niino-DuPonte

Department of Plant and Environmental Protection Sciences

Blossom midge, Contarinia maculipennis Felt (Diptera:

Cecidomyiidae), has been present in Hawaii

since the early 1900s and is thought to have originated

in Asia (the “West Indies”). Currently, the blossom midge

can be found on all of the major Hawaiian islands. 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. Elsewhere in the USA, the blossom

midge was reported on dendrobium orchids in

Florida in 1992.

Damage

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.

Hosts

The blossom midge has a wide host range spanning at

least six plant families, including the flower buds of orchids,

plumeria, hibiscus, pikake (jasmine), white mustard

cabbage or pak choi, tomato, eggplant, pepper, potato,

bittermelon, and other vegetables and ornamentals.

Biology

The blossom midge reproduces year-round in Hawaii.

The duration of its life cycle from egg to adult is approximately

21–28 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 and feed on fluids from the damaged

plant 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, growing to 1⁄12 inch long (about

the thickness of a nickel), 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.

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 14–21 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.

The adult blossom midge is 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).

Behavior

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.

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IP-11 Blossom Midge in Hawaii—a Pest on Ornamentals and Vegetables CTAHR — June 2002

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. To ensure an optimal

food source and moist environment, the adult midge

avoids late-stage buds and prefers to lay eggs in young

buds whose growth to maturity will approximately parallel

that of the maggot.

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 65°F and the plants had sufficient numbers of

buds.

Cultural control

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 midge’s 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.

Biological control

To date, no parasites have been isolated or specifically

introduced to Hawaii to control the blossom midge. The

adults are vulnerable to general predators, such as webspinning

spiders and ants. Ants may also prey on pupae

in the soil.

Chemical control

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 lower surface) may

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)

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IP-11 Blossom Midge in Hawaii—a Pest on Ornamentals and Vegetables CTAHR — June 2002

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 CTAHR Cooperative Extension Service for registered

chemicals that are known to be effective against

the blossom midge.

References

Felt, E.P. 1933. A hibiscus bud midge new to Hawaii.

Proceedings, Hawaiian Entomological Society 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).

Proceedings, Hawaiian Entomological Society

12(3):525–534.

Jensen, D.D. 1950. Notes on the life history and ecology

of blossom midge Contarinia lycopersici Felt

(Diptera: Cecidomyiidae). Proceedings, Hawaiian Entomological

Society 14(1):91–100.

Figure 4. Adult blossom midge.

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: Felter, L., T. Higgins, and N. Rechcigl (eds.),

Proceedings, 17th Conference on Insect and Disease

Management on Ornamentals. February 25–27, 2001,

Orlando, FL. Society of American Florists, Alexandria,

VA. p. 21.

The actual size of the larvae and pupae is 1–2 mm; the adult is about 2 mm long.

1 mm is just over 1⁄32 inch; the following lines are 1 and 2 mm long, respectively:

Figure 2. Blossom midge larvae in a dendrobium bud. Figure 3. Blossom midge pupae from hibiscus.

Photos in Figures 2 and 3 by Walter Nagamine, Hawaii Dept. of Agriculture;

Figure 4 photo by S. Chun.