Steinernema carpocapsae(Rhabditida: Steinernematidae) as a biological control agent against the fungus GnatBradysia agrestis(Diptera: Sciaridae) in propagation houses

Abstract

A recently introduced fungus gnat, Bradysia agrestis, has caused serious problems in Korean propagation houses where vegetable seedlings are produced for transplant into the fields. Although chemical insecticides are available against this pest, alternate control measures are needed. A Korean isolate of the entomopathogenic nematode, Steinernema carpocapsae Pocheon strain, was tested against this insect in the laboratory and propagation house. In the laboratory, S. carpocapsae affected oviposition, with the untreated females laying an average of 1219/25 eggs, whereas the treated females averaged 79/2 eggs. The infectivity of S. carpocapsae to the fungus gnat was affected by the developmental stage and temperature, with highest mortality observed with the third and fourth instars and pupal stage. Nematode mortality in the second instar fungus gnat ranged between 23 and 35%, but showed no significant differences among the temperatures tested. The egg and first instar were not infected by the nematode. In nematode dispersal studies, adult female fungus gnats alone dispersed S. carpocapsae from the nematode-treated area to the control area at a higher rate than male and female gnats or male gnats alone. In the propagation house experiments with watermelon seedlings, no significant difference was observed in fungus gnat larval reduction at S. carpocapsae concentrations of 5, 10, or 20 infective juveniles (IJs)/g of soil at 7, 14, and 21 days after treatment. In comparison with the control, the S. carpocapsae treatments significantly reduced B. agrestis larval numbers. When the watermelon seed was treated with S. carpocapsae at sowing, the larval density of B. agrestis was significantly reduced, that is, the number of B. agrestis larvae ranged from four to eight and from five to eight in the nematodetreated plots compared with 26 and 30 in the control plots on the 17th and 34th day posttreatment, respectively. In the chemical insecticide treatments, diflubenzuron and chlorpyrifos were significantly more effective than S. carpocapsae and diazinon in reducing larval populations of the fungus gnat. Our data show that, although some of the chemical insecticides were more effective than S. carpocapsae Pocheon strain, the nematode was still an effective tool for management of the fungus gnat larvae and in protecting seedlings from damage in propagation houses.

Entomopathogenic nematodes for the control of phorid and sciarid flies in mushroom crops

“…Gouge & Hague (1995) established that S. carpocapsae was relatively ineffective against different sciarid species. The results obtained in the present work are in agreement with this, but contradict those of Kim et al (2004), who found that S. carpocapsae can be an effective tool for the management of the fungus gnat larvae. Both nematode species were applied together so that each could combat its own target pest.…”

“…For the control of sciarids with nematodes, many authors defend the use of S. feltiae, having observed effectiveness between 66 and 95%, depending on the fly population and the timing of nematode application (Scheepmaker et al, 1997;Shamshad et al, 2008). In the case of S. carpocapsae, Gouge & Hague (1995) reported the relative inefficacy of this species against sciarids, whereas other authors defend its efficacy, but with a lower infectivity than that of S. feltiae (Kim et al, 2004). Furthermore, some authors observed a detrimental effect of treatments involving entomophathogenic nematodes on mushroom mycelia, such as reduced yield in early flushes, depending on the nematode dosage rate (Grewal et al, 1992).…”

Laboratory efficacy against neonate larvae of the banana weevilCosmopolites sordidusof two indigenous entomopathogenic nematode species from the Canary Islands (Spain)

“…Differences in host size and immune response can affect the susceptibility of nematodes among the instars of an insect species (Kaya 1990). Kim et al (2004) noted that the first and second instars of Bradysia agretis (Diptera: Sciaridae) showed lower levels of susceptibility to the nematode compared to older instars. In our study, the small size of the neonate larvae of C. sordidus (1.5-2.0 mm) was not a limiting factor for the infestation of the EPNs.…”

The development of integrated pest management for the control of mushroom sciarid flies, Lycoriella ingenua (Dufour) and Bradysia ocellaris (Comstock), in cultivated mushrooms

“…Kim et al 83 tested Steinernema carpocapsae (Weiser) against Bradysia agrestis , a serious problem in Korean propagation houses, under laboratory conditions. Their results indicated that S. carpocapsae affected oviposition: treated females averaged 7 ± 2 eggs compared with an untreated average of 121 ± 25 eggs.…”