Seasonal abundance of hymenopteran parasitoids of the leafminer Chromatomyia horticola (Diptera: Agromyzidae) and the impact of insecticide applications on parasitoids in garden pea field

Abstract

The seasonal abundance of hymenopteran parasitoids reared from the agromyzid leafminer Chromatomyia horticola was monitored on garden pea in Shizuoka, central Japan, for 17 months between 2004 and 2005. The leafminer was abundant during the cool seasons (December to May) but parasitoid populations generally lagged behind the leafminer by approximately two months. Twenty-one parasitoid species were reared from C. horticola, and the most abundant parasitoid species were Diglyphus isaea, D. minoeus and Chrysocharis pentheus, comprising ca. 90% of the total number caught. Diglyphus isaea and D. minoeus were abundant during the cool season (December to May), while C. pentheus was abundant in the warm season (May to June). Other common parasitoid species were Dacnusa nipponica, Neochrysocharis formosa and Halticoptera circulus. The effects of two insecticides, malathion and tralomethrin, on parasitoid populations were investigated both in the cool and warm seasons. The insecticides caused a reduction in the density of most parasitoid species for at least one month and resulted in resurgence of the leafminer. However, the density of H. circulus increased after insecticide applications, suggesting that this parasitoid was tolerant to both insecticides but H. circulus could not reduce C. horticola populations when insecticide applications were made to the crop. These studies provide insight into the development of integrated control strategies of leafminer pests in field and glasshouse crops.

Seasonal Abundance and Spatial Distribution of the Leafminer,Liriomyza trifolii(Diptera: Agromyzidae), and its Parasitoid,Opius dissitus(Hymenoptera: Braconidae), on Bean in Southern Florida

“…Abou-fakhr-Hammad (2000) reported that the population density of pea leafminer, L. huidobrensis was reduced by high daily average temperatures. Saito et al (2008) found that the garden pea leafminer, Chromatomyia horticola (Goueau) (Diptera: Agromyzidae), was abundant during the cool season in Japan. Homestead is located within a subtropical area, and the leafminer L. trifolii was more abundant when the average monthly temperature was relatively low (< 20 °C).…”

“…Some of the reasons for the rapid increase in leafminer population densities include intensive insecticide applications leading to the development of resistance (Saito 2004) and reduction in natural enemy densities (Minckenberg & van Lenteren 1986). Other abiotic factors that may affect leaf miner population densities include temperature, light intensity and moisture (Shepard et al 1998;Saito et al 2008, Leibee 1986 Bordat et al (1995b) reported that 20 °C was optimal for both the adult male and female, and the optimum temperature for female reproduction was 25 °C. Light conditions could also affect leafminer density levels, and the pupariation of emergent L. trifolii larva can be delayed for a short time by continuous lighting condition (Leibee 1986).…”

The leafminerLiriomyza trifolii(Diptera: Agromyzidae) encapsulates its koinobiont parasitoidHalticoptera circulus(Hymenoptera: Pteromalidae): implications for biological control

“…In Japan, L. chinensis and C. horticola are indigenous species while L. trifolii is an invasive species that was first reported in Japan in 1990 (Saito, 1993; Sasakawa, 1993). The pest status of these leafminers is compounded by their lack of susceptibility to insecticides (Parrella & Keil, 1984; Saito et al ., 1992, 1996, 2008 a ; Saito, 2004; Tokumaru & Okadome, 2004). A koinobiont parasitoid of leafminers, Halticoptera circulus (Walker) (Hymenoptera: Pteromalidae), is also resistant to the broad-spectrum insecticides, malathion (organophosphate) and tralomethrin (pyrethroid), and is, therefore, considered to have great potential as a biological control agent of leafminers within integrated pest management systems that include the use of insecticides (Saito et al ., 2008 a ; Matsuda & Saito, 2014).…”

“…The pest status of these leafminers is compounded by their lack of susceptibility to insecticides (Parrella & Keil, 1984; Saito et al ., 1992, 1996, 2008 a ; Saito, 2004; Tokumaru & Okadome, 2004). A koinobiont parasitoid of leafminers, Halticoptera circulus (Walker) (Hymenoptera: Pteromalidae), is also resistant to the broad-spectrum insecticides, malathion (organophosphate) and tralomethrin (pyrethroid), and is, therefore, considered to have great potential as a biological control agent of leafminers within integrated pest management systems that include the use of insecticides (Saito et al ., 2008 a ; Matsuda & Saito, 2014). However, H. circulus is rarely reported from L. trifolii in Japan (Saito et al ., 1996, 2008 b ; Arakaki & Kinjo, 1998; Amano et al ., 2008) while it is relatively abundant in L. chinensis and C. horticola populations (Takada & Kamijo, 1979; Tokumaru, 2006; Saito et al ., 2008 a ).…”

“…A koinobiont parasitoid of leafminers, Halticoptera circulus (Walker) (Hymenoptera: Pteromalidae), is also resistant to the broad-spectrum insecticides, malathion (organophosphate) and tralomethrin (pyrethroid), and is, therefore, considered to have great potential as a biological control agent of leafminers within integrated pest management systems that include the use of insecticides (Saito et al ., 2008 a ; Matsuda & Saito, 2014). However, H. circulus is rarely reported from L. trifolii in Japan (Saito et al ., 1996, 2008 b ; Arakaki & Kinjo, 1998; Amano et al ., 2008) while it is relatively abundant in L. chinensis and C. horticola populations (Takada & Kamijo, 1979; Tokumaru, 2006; Saito et al ., 2008 a ). To develop successful biological control of leafminers using H. circulus , we need to understand the reasons why so few have been reported from L. trifolii .…”