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common name: predatory gall midge (unofficial common name)
scientific name: Feltiella acarisuga (Vallot) (Insecta: Diptera: Cecidomyiidae)

Introduction - Synonymy - Distribution - Description - Life Cycle - Effectiveness - Commercial Availability and Use - Selected References

Introduction (Back to Top)

The predatory gall midge, Feltiella acarisuga (Vallot), is one of the most effective and widespread natural enemies of spider mites (Tetranychidae) (Gagné 1995). It is a particularly important natural enemy of the twospotted spider mite, Tetranychus urticae Koch, in a number of cropping systems (Opit et al. 1997). Feltiella acarisuga could be particularly useful for integrated pest management of spider mites that attack greenhouse crops (Gillespie et al. 1998).

Synonymy (Back to Top)

Cecidomyia acarisuga
Mycodiplosis minuta
Therodiplosis persicae
T. beglarovi
Arthrocnodax rutherfordi
Feltiella tetranychi
Feltiella davisi
Feltiella americana
Feltiella ithacae
Feltiella quadrata (Gagné 1995)

Distribution (Back to Top)

The genus Feltiella is virtually cosmopolitan and contains eight species: Feltiella acarisuga (worldwide, except for the Neotropical Region), Feltiella pini (Felt) (North and Central America and West Indies), Feltiella curtistylus Gagné (Brazil), Feltiella occidentalis (Felt) (U.S.- California), Feltiella acarivora (Zehnter) (Indonesia- Java), Feltiella insularis (Felt) (eastern U.S., West Indies and Colombia), Feltiella reducta Felt (northeastern U.S. - New York), and Feltiella ligulata Gagné (Cape Verde Is.) (Gagné 1995). Feltiella acarisuga is the most widely distributed species in the genus and is listed from the U.S., Canada, Finland, Germany, U.K., Switzerland, Italy, Morocco, Greece, Israel, India, Sri Lanka, Taiwan, Japan and New Zealand. It is the only species of Feltiella found throughout most of Europe and Asia.

Description (Back to Top)

Egg: The shiny, translucent oblong eggs are deposited individually near prey mites on leaves. They are 0.1 x 0.25 mm in size (Koppert 1997). The eggs hatch within two days after oviposition and the larvae immediately begin to feed.

Eggs of the predatory gall-midge

Figure 1. Eggs of the predatory gall-midge, Feltiella acarisuga (Vallot). Photograph by David R. Gillespie, Agassiz.

Larva: The orange-brown larvae vary in length from 0.2 to 2 mm during their four developmental instars (Koppert 1997). They forage for mites on leaves and feed for four to six days, depending on temperature, relative humidity and the abundance of prey mites (Gillespie and Raworth 1999). They feed exclusively on all developmental stages of several species of spider mites. Feltiella acarisuga larvae occur in populations as large as 160 per cm2 of eggplant leaf.

Larva of the predatory gall-midge

Figure 2. Larva of the predatory gall-midge, Feltiella acarisuga (Vallot). Photograph by Lance S. Osborne, University of Florida.

Pupa: The fluffy white, 1 to 1.5 mm long pupa requires four to six days to complete development and produce an adult (Koppert 1997). Pupation occurs mainly on the underside of a leaf next to a vein.

Pupa of the predatory gall-midge

Figure 3. Pupa of the predatory gall-midge, Feltiella acarisuga (Vallot). Photograph by Lance S. Osborne, University of Florida.

Adult: The adult Feltiella acarisuga is a delicate pink-brown fly about 2 mm in length with long legs (Koppert 1997). Females have a five day life span and produce about 30 eggs. Males do not live as long as females. The sex ratio is about 1:1. Adult Feltiella acarisuga are not predaceous but drink water and nectar.

Adult of the predatory gall-midge

Figure 4. Adult of the predatory gall-midge, Feltiella acarisuga (Vallot). Photograph by David R. Gillespie, Agassiz.

 

Life Cycle (Back to Top)

In climates without extremely dry or cold seasons, every stage of Feltiella acarisuga is present year-round. Feltiella spp. apparently develop from egg to egg in 26 to 33 days, averaging around 29 days (Sharaf 1984); however, Feltiella acarisuga requires about 15 days (Gillespie et al. 1998). Reproduction and development occur at 15-25°C. Eggs and larvae do not survive above 30°C or below 30% relative humidity. At least 50% relative humidity is required for a normal rate of development. The optimum temperature and relative humidity combination is about 20°C and 90% relative humidity. However, with an abundance of prey, the level of predation remains constant over the developmental range of temperature and relative humidity (Gillespie et al. 1998). If prey populations are sub-optimal, larvae can survive by pupating at a smaller size. Larvae also can survive for several days without prey.

Effectiveness (Back to Top)

Feltiella acarisuga can be used to manage spider mite populations in a variety of greenhouse and field crops, especially when incorporated into a bio-intensive IPM program. In eggplant, for example, Feltiella acarisuga has appeared naturally and reduced spider mite numbers by more than 40% (Sharaf 1984). Each midge larva can consume an average of least 15 adult mites, 30 mixed developmental stages, or 80 eggs per day. Weekly releases of 1000 individuals per ha have been extremely effective for controlling spider mites on tomato, pepper and cucumber (Gillespie et al. 1998). In addition, Feltiella acarisuga (sold as Therodiplosis persicae) is being used to manage spider mites on strawberries and various ornamental crops. It is recommended that 200 to 1000 individuals per ha. be released weekly as a trial rate for growers. The weekly release rate is approximately doubled for heavy infestations, 2,500 adults per ha for six successive weeks (Biobest 1999).

It is highly advised that Feltiella acarisuga be released in combination with the predaceous mite, Phytoseulus persimilis, a well-established natural enemy used to control spider mites. Feltiella acarisuga is more mobile as an adult than is the predatory mite and, once established, eats at least five times as many spider mites (Biobest 1999). However, Phytoseulus persimilis should not be released where Feltiella acarisuga is becoming established because they are known to eat midge eggs if prey is limited (Gillespie 1998).

Commercial Availability and Use (Back to Top)

Feltiella acarisuga pupae are commercially available from several producers and suppliers of natural enemies (http://www.anbp.org/ and http://www.cdpr.ca.gov/docs/ipminov/ben_supp/contents.htm). Pupae are shipped on leaves or an inert substance in various containers, such as 1-liter pots. Pots are placed in the crop on the ground at the beginning of rows and their lids are pierced to release the adult midges. It is best if the midges are released near concentrations of spider mites. To establish, Feltiella acarisuga requires fairly large prey populations (Gillespie and Raworth 1999). The pots should be stored in the dark for no more than two days at 10 to 15°C (Koppert 1997). Adults should be released from containers every 24 hours, late at night or early in the morning because of the cooler and more humid conditions. The RH should be kept above 80%, if possible (Gillespie and Raworth 1999).

It is essential to avoid non-target side effects of chemical pesticides, such as Thiodan, Diazinon, and Kelthane; however, most fungicides are safe to use with Feltiella acarisuga (Gillespie and Raworth 1999). Sulfur products used as dusts or sprays do not cause mortality in larvae but females avoid laying eggs on treated plants. Another concern is parasitization of Feltiella acarisuga larvae by Aphanogmus floridanus, potentially a very abundant parasitoid during warmer months. However, if necessary, releases can be timed to avoid the parasitoid because unlike the parasitoid Feltiella acarisuga does not diapause during the cooler months. Feltiella acarisuga parasitized by Aphanogmus floridanus have pupal cases with characteristic round emergence holes.

Selected References (Back to Top)