A large-scale rearing method forPeristenus digoneutis(Hymenoptera: Braconidae), a biological control agent ofLygus lineolaris(Hemiptera: Miridae)

Abstract

Releases of Peristenus digoneutis against Lygus spp. in North America have been conducted for many years; however, no published procedures for mass production of the biological control agent were available. A laboratory rearing method was developed using Lygus lineolaris as the host to enhance establishment efforts and provide large numbers of wasps for inundative releases into high value fruit crops. Experiments were conducted to determine optimum host:parasitoid density and rearing temperature. The effects of nymph:wasp ratios and temperature on parasitism and wasp survival showed a 20:1 ratio at 208C provided high parasitism (256 parasitized nymphs/wasp over lifetime) and excellent wasp survival of 27 days. Experiments on diapause-inducing conditions for P. digoneutis demonstrated that fluctuating temperatures of 238C (day) and 168C (night) and corresponding photo phases of B16 h light, for rearing parasitized nymphs, produced 100% diapausing parasitoids whereas non-diapausing parasitoids were only produced at more than 16 h light. Furthermore, parasitized Lygus nymphs need to be transferred to short day conditions no later than 10 days after parasitism to produce diapausing parasitoids. Critical life stages for exposure to conditions inducing diapause, the egg, first and second instar parasitoid larva, occurred from 0 to 10 days at 248C constant temperature. Increased time in cold storage reduced the number of days to first emergence of parasitoids from diapausing cocoons when transferred to warm temperatures. The optimum storage time for diapausing P. digoneutis is between 25 and 44 weeks, depending upon the length of time that cocoons remain at warm conditions prior to chilling.

Spatial Density and Movement of theLygusspp. ParasitoidPeristenus relictus(Hymenoptera: Braconidae) in Organic Strawberries With Alfalfa Trap Crops

“…Parasitoid larval abundance was Ϸ13-and 5-fold greater in alfalfa than strawberries in 2008 and 2010, respectively. Peristenus digoneutis larval abundance increased 5-fold when nymphal densities were augmented (from 5 to 40) in a laboratory study by Whistlecraft et al (2010).…”

Bioclimatic analyses of distributions of a parasitoid Peristenus digoneutis and its host species Lygus spp. in Europe and North America

“…Climate requirements were inferred from known distributions of P. digoneutis in Europe. Initial model parameter values for P. digoneutis (Carignan et al , 1995, 2007; Day et al , 1998; Haye, 2004; Whistlecraft et al , 2010) and for L. rugulipennis and L. lineolaris (Ridgway & Gyrisco, 1960; Butler & Wardecker, 1971; Easterbrook et al , 2003) were derived from published data and from previous climex distribution models (Dosdall et al , 2002; Olfert et al , 2003) (Table 1). We then parameterized the models through an iterative process to represent the actual distributions in Europe.…”

“…The model, based on these values as inputs, suggests that P. digoneutis activity slows as mean weekly minimum temperatures decrease to 16 °C and ceases below a weekly mean temperature of 13 °C. Whistlecraft et al (2010) showed that parasitoid activity is clearly reduced at 15 °C. Conversely, adult activity slows at temperatures above 25 °C (Whistlecraft et al , 2010).…”

“…Whistlecraft et al (2010) showed that parasitoid activity is clearly reduced at 15 °C. Conversely, adult activity slows at temperatures above 25 °C (Whistlecraft et al , 2010). Values chosen for DV2 (upper optimal mean weekly maximum temperature) and DV3 (limiting high mean weekly maximum temperature) were 23 and 29 °C.…”

“…Termination of diapause will occur only after the species has been exposed to unfavourable conditions for a specified period of time. The overwintering stage requires that P. digoneutis goes through a period of diapause (minimum 2.5 months) followed by a lengthy period of quiescence (Bilewicz‐Pawinska, 1978; Haye, 2004; Whistlecraft et al , 2010). The climex model requires an input for DPD1 (dormancy termination temperature); however, technically, P. digoneutis terminates dormancy, not diapause, in the spring.…”