Factors Affecting Entomopathogenic Nematodes (Steinernematidae) for Control of Overwintering Codling Moth (Lepidoptera: Tortricidae) in Fruit Bins

Abstract

Fruit bins infested with diapausing codling moth larvae, Cydia pomonella (L.), are a potential source of reinfestation of orchards and may jeopardize the success of mating disruption programs and other control strategies. Entomopathogenic nematodes (EPNs) were tested as a potential means of control that could be applied at the time bins are submerged in dump tanks. Diapausing cocooned codling moth larvae in miniature fruit bins were highly susceptible to infective juveniles (IJs) of Steinernema carpocapsae (Weiser) and Steinernema feltiae (Filipjev) in a series of experiments. Cocooned larvae are significantly more susceptible to infection than are pupae. Experimental treatment of bins in suspensions of laboratory produced S. feltiae ranging from 10 to 100 IJs/ml of water with wetting agent (Silwet L77) resulted in 51-92% mortality. The use of adjuvants to increase penetration of hibernacula and retard desiccation of S. feltiae in fruit bins resulted in improved efficacy. The combination of a wetting agent (Silwet L77) and humectant (Stockosorb) with 10 S. feltiae IJs/ml in low and high humidity resulted in 92-95% mortality of cocooned codling moth larvae versus 46-57% mortality at the same IJ concentration without adjuvants. Immersion of infested bins in suspensions of commercially produced nematodes ranging from 10 to 50 IJs/ml water with wetting agent in an experimental packing line resulted in mortality in cocooned codling moth larvae of 45-87 and 56 - 85% for S. feltiae and S. carpocapsae, respectively. Our results indicate that EPNs provide an alternative nonchemical means of control that could be applied at the time bins are submerged in dump tanks at the packing house for flotation of fruit.

Potential of South African entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) for control of the citrus mealybug, Planococcus citri (Pseudococcidae)

“…Factors that increase desiccation include high temperatures, low levels of relative humidity, and wind. Although higher temperatures increase the rate of desiccation, nematode activity has proved to increase from 15°C to 32°C (Lacey et al, 2005), and nematodes should be able to reach hosts within a shorter time, when they are exposed to higher temperatures. The exposure time and temperature experiment demonstrated that nematodes were able to infect mealybugs in an exposure time as short as 30 min long at all three temperature levels tested (15°C, 20°C and 25°C), with no significant difference regarding such ability being shown among them.…”

Key elements in the successful control of diapausing codling moth,Cydiapomonella(Lepidoptera: Tortricidae) in wooden fruit bins with a South African isolate ofHeterorhabditis zealandica(Rhabditida: Heterorhabditidae)

“…Wooden fruit bins used during harvesting and to transport and store fruit have been reported to be infested with diapausing codling moth larvae (Higbee et al 2001). The control of codling moth, using the above-mentioned density-dependent and non-insecticidal practices, can therefore be compromised due to the invasion of orchards by moths emerging from wooden fruit bins which were previously infested and placed in or near orchards prior to harvesting (Cardé and Minks 1995;Higbee et al 2001;Lacey, Neven, Headrick, and Fritts 2005). Bin treatments will thus contribute to lowering the pest population levels and therefore indirectly benefit mating disruption and the sterile insect release programme (Lacey et al 2005).…”

“…Cossentine, Jensen, and Moyls (2002) investigated treatment of bins with Steinernema carpocapsae Weiser infective juveniles (IJs) by submersion or drenching, respectively (Weiser 1955). Lacey et al (2005) investigated drenching bins with S. carpocapsae in an industrial bin washer. The use of EPNs to successfully control oriental fruit moth, Grapholita molesta (Busck), in miniature wooden fruit bins has also been documented by Riga, Lacey, Guerra, and Headrick (2006).…”

Influence of humidity and a surfactant-polymer-formulation on the control potential of the entomopathogenic nematode Steinernema feltiae against diapausing codling moth larvae (Cydia pomonella L.) (Lepidoptera: Tortricidae)

“…To achieve optimum control of codling moth, EPNs have to be applied against the most Influence of humidity and a surfactant-polymer-formulation 783 susceptible stage. Lacey et al (2005) reported that pupae are less susceptible than cocooned last instars, when the insects were exposed to S. carpocapsae at 25°C in perforated cardboard strips fixed to tree trunks in the field. Our findings corroborate these data, however, they reported 63.1 ± 1.7% mortality of pupae with S. carpocapsae, whereas in this study obtained only 4.5% with S. feltiae.…”

“…Additives like humectants can help to reduce the negative impact of low RH or low water activity on nematode performance (Baur et al 1995;Lacey et al 2005). We tested the SPF formulation developed by , which not only prolonged survival of the DJs, but also produced favourable environmental conditions for invasion of P. xylostella.…”