Volume 12 Part 2 Article 86: Advances in Control of the Sciarid Fly, Lycoriella mali (Fitch)

Volume 12 Part 2 Article 86
Year 1989
Title: Advances in Control of the Sciarid Fly, Lycoriella mali (Fitch)
Author: W.W. Cantelo


Substantial progress has been made in the United States of America in controlling the sciand fly, Lyconella mali. An average yield loss of about 17% that occurred in Pennsylvania in 1978 (Cantelo, 1979) is unlikely to reoccur. This can be attributed to several factors. First, there is a better understanding of the biology and behaviour of the fly due to the efforts of R. Snetsinger and his students at Pennsylvania State University (MacDonald et al., 1977; Kielbasa and Snetsinger, 1978, 1980). Second, the better growers have made their growing rooms more difficult for the flies to invade by screening all openings to the exterior and by sealing the inside of the rooms with urethane insulation. Third, the availability of efficacious insecticides for treating the compost and casing has substantially improved. Diazinon was the first effective material registered for incorporation in the compost (Cantelo and McDamel, 1978). It is highly effective in controlling both L. mali and the phorid fly, Megaselia halterata, but many mushroom strains are sensitive to it and as a result major yield reductions could result from its use (Cantelo et al., 1982). The next effective material that came on the market was the insect growth regulator (IGR), methoprene (Cantelo et al., 1977; Cantelo, 1979, 1983). This is still widely used as a compost drench and as a casing treatment; however because of its short residual activity, timing of application is essential to obtaining good control. The next material registered for use was another IGR, diflubenzuron, which is presently widely used (Cantelo, 1979, 1983). At their registered dosages neither methoprene nor diflubenzuron are effective in controlling M. halterata. Chlorpynfos, the most recent insecticide registered for use in mushroom growing media, is effective in controlling both species of flies (Cantelo, 1979, 1985), but has been withdrawn from use by the manufacturer because it has, at times, been associated with mushroom yield reductions. One other IGR with a high degree of efficacy against L. mali is close to becoming available for mushroom growers use, i.e., cyromazine.

The fourth factor responsible for lessened fly problems was the development of the blacklight fly monitor ca. 1979 by W.H. Barber, who at the time was a grower with C.P. Yeatman and Sons of Avondale, Pennsylvania. Basically this is a 45 cm 15 watt blacklight lamp mounted vertically with removable paper on either side (Finley et al., 1984). An adhesive is applied to the surface of the paper to trap the flies attracted to the light. Use of the monitor has enabled growers to obtain an index of the fly population in each growing room and from this judge whether or not to apply control measures. Previously, growers often would not be aware of flies being present until after casing. The flies seen then were offspring of the initial invasion that occurred after cooldown. The invading population was usually not observed because of the relatively small number entering. When the flies were seen after casing, the large destructive second generation had begun and control was more difficult. The fly monitor enabled the grower to detect small numbers of the invading population and take appropriate action. Also, if no insects were trapped he would not treat, which would be a major benefit particularly to growers who had routinely treated as a defensive measure. The monitor also enabled him to know the type of fly present and act accordingly. Another cause of reduced fly damage may be the cessation of mushroom growing by less efficient growers as a result of reduced profit margins. It is a common belief in the mushroom industry that inefficient growers are often the source of flies that plague other growers. This has not been proven, however. Because of the high cost of some of the more efficacious insecticides and phytotoxicity problems that have occurred, additional materials were sought as control agents for L. mali by application to the compost or the casing. This paper describes the results of these investigations.

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