Entomopathogenic nematodes for the control of the codling moth (Cydia pomonellaL.) in field and laboratory trials

Abstract

Three commercially available entomopathogenic nematode (EPN) strains (Steinernema feltiae and Heterorhabditis bacteriophora Hb1 and Hb2) and two local species (S. jeffreyense and S. yirgalemense) were evaluated for the control of the codling moth (Cydia pomonella). In field spray trials, the use of S. jeffreyense resulted in the most effective control (67%), followed by H. bacteriophora (Hb1) (42%) and S. yirgalemense (41%). Laboratory bioassays using spray application in simulated field conditions indicate S. feltiae to be the most virulent (67%), followed by S. yirgalemense (58%). A laboratory comparison of the infection and penetration rate of the different strains showed that, at 14°C, all EPN strains resulted in slower codling moth mortality than they did at 25°C. After 48 h, 98% mortality was recorded for all species involved. However, the washed codling moth larvae, cool-treated (at 14°C) with S. feltiae or S. yirgalemense, resulted in 100% mortality 24 h later at room temperature, whereas codling moth larvae treated with the two H. bacteriophora strains resulted in 68% and 54% control, respectively. At 14°C, S. feltiae had the highest average penetration rate of 20 IJs/larva, followed by S. yirgalemense, with 14 IJs/larva. At 25°C, S. yirgalemense had the highest penetration rate, with 39 IJs/larva, followed by S. feltiae, with 9 IJs/larva. This study highlights the biocontrol potential of S. jeffreyense, as well as confirming that S. feltiae is a cold-active nematode, whereas the other three EPN isolates tested prefer warmer temperatures.

Entomopathogenic nematodes in agricultural areas in Brazil

“…Infectivity, environmental tolerance and suitability for commercial formulations vary between EPN isolates and species2122 which can be used to control pests of various orders, such as Coleoptera232425, Hemiptera2627282930 and Lepidoptera313233.…”

Entomopathogenic nematodes as biocontrol agents of insect pests in orchards.

“…Their caterpillars are fruit-boring/feeding pests, but when they are fully grown, they leave the fruit in search of protected (cryptic) habitats in which they spin their cocoons and pupate. EPN applications (after harvest) directed at such potential (overwintering) cryptic habitats (bark cracks, leave litter) can have a significant impact on the population next spring [40,42]. Fruit bins that are in the orchard during the time when diapause-destined larvae are seeking cryptic habitats can also provide overwintering sites.…”

Transmission Success of Entomopathogenic Nematodes Used in Pest Control

“…Although some EPN species have been shown to be efficient against a large number of different pest species (e.g., H. bacteriophora or S. carpocapsae , see Table 1 ), several different species of nematodes are usually compared in order to identify the best species for the proposed purpose (e.g., [ 21 , 22 , 23 , 24 , 25 ]). Native species are often considered [ 23 , 25 , 26 ], as they are expected to be adapted to local conditions, ideally including the pest itself. Use of native species is also preferred for the purpose of limiting environmental risks.…”

“…As for desiccation tolerance, nematodes have different thermal limits and optima depending on their species [ 43 , 44 , 62 ]. Temperature is probably the most important factor impacting EPN efficacy [ 23 , 25 , 38 , 48 , 51 , 63 , 64 ]. Temperature can also be used as a tool to improve EPN efficacy.…”

“…Apart from some specialist species [ 20 ], most EPNs can infect a wide range of different host species, at various developmental stages, with substantial differences in susceptibility to nematodes both between species and between developmental stages of the same species. Insect larvae and pupae are often found to be more susceptible to EPN infection than adults [ 25 , 85 , 142 ]. Such differences in susceptibility can result from various mechanisms, such as differences in behavior (in particular higher activity levels and avoidance behaviors in adults), immune system or physical barriers to nematode penetration.…”