Infection of Anastrepha ludens following soil applications of Heterorhabditis bacteriophora in a mango orchard

Abstract

To determine the efficacy of Heterorhabditis bacteriophora Poinar (Nematoda: Heterorhabditidae) for control of Anastrepha ludens (Loew) (Diptera: Tephritidae), field experiments were performed in a mango orchard with soil temperatures of 24–29 °C. The density of third‐instar A. ludens (50–500 larvae per plot) released into 0.25 m2 wood‐framed experimental plots containing soil (16% wt/wt moisture) previously treated with 125 infective juveniles per square centimetre soil surface did not significantly influence the prevalence of infection by H. bacteriophora. In subsequent experiments, the percentages of infection of fly pupae were positively correlated with the concentration of infective stages applied to soil plots. The highest average percentage of infection (74% at 250 infective juveniles per square centimetre) was observed when fly larvae were released simultaneously onto soil, compared to larvae that emerged from laboratory‐infested mangoes over a period of 8 days (52% infection at 500 infective juveniles per square centimetre). Double applications of infective juveniles at an interval of 4 days did not greatly improve the prevalence of infection (∼10% higher) compared to single applications. Between 9 and 15% of larvae that remained within infested mangoes became infected by nematodes, irrespective of the concentration of nematodes applied to each experimental plot. We conclude that effective control of A. ludens requires very high densities of H. bacteriophora. The successful use of this nematode for biocontrol of A. ludens will depend on identifying ways of overcoming the fly's ability to avoid infection.

Efficacy of indigenous entomopathogenic nematodes (Rhabditida: Heterorhabditidae, Steinernematidae), from Rio Grande do Sul Brazil, against Anastrepha fraterculus (Wied.) (Diptera: Tephritidae) in peach orchards

“…Treatments with S. riobrave were lower (20% and 24.3%). In a field test, Toledo et al (2006a) observed 52.1% pupal mortality 8 days after application of H. bacteriophora Costa Rica on mango fruit infested with the third instar of A. ludens. In that study, pupae came from larvae that emerged from fruit, and 15% of remaining larvae were infected by the nematode.…”

“…No nematodes were found in these soil samples. Experimental units were open soil trenches (55 Â 29 Â 17 cm) under the tree canopy, according to methodology modified from Toledo et al (2006a). To prevent interference from natural enemies, especially ants, the soil from the trenches was contained in wooden boxes coated at the base and sides with black plastic canvas, and covered at the top with thin cloth (voile) attached with metal clips, allowing aeration, and preventing escape of emerged adults.…”

“…A reduction in the fruit fly population occurs due to parasitoids, predators and pathogens (Wharton, 1993). Among these, entomopathogenic nematodes (EPNs) show potential for controlling Diptera (Toledo et al, 2006a) and may help to control of A. fraterculus (Lindegren et al, 1990) have been performed with different species of the same genus: A. ludens Loew (Lezama-Gutierrez et al, 1996;Hernández, 2003), A. obliqua (Macquart) (Toledo et al, 2005a), A. serpentina Wied. (Toledo et al, 2006b), and A. suspensa (Loew) (Beaver and Calkins, 1984).…”

Microbial control of arthropod pests of tropical tree fruits

“…EPNs and fungi have been evaluated as alternatives to conventional insecticides for control of some important fruit A. ludens is susceptible to a variety of EPN species under laboratory conditions (LezamaGutiérrez et al 1996, Toledo et al 2001, 2005, extremely 2 IJs of H. bacteriophora/cm 2 ) (Toledo et al 2006). Similarly, of EPNs against C. capitata, revealed susceptibility of larvae to several nematode species (Lindegren & Vail 1986, Gazit et al 2000, Laborda et al 2003, but high application 2 IJs of S. carpocapsae/cm 2 (Lindegren et al 1990).…”

Entomopathogenic nematodes against the main guava insect pests

“…Lezama-Gutierrez et al (1996), evaluated the susceptibility of third instar A. ludens larvae to various EPN species in pots containing sterile sandy soil, and found higher larval and pupal mortality (90 %) when larvae were exposed to S. riobrave and S. carpocapsae All. However, Hernández (2003) Toledo et al (2006a) applied H. bacteriophora against larvae and pupae. Infection rates reached the highest levels ([70 %) only at the two highest tested concentrations (250 and 500 IJs cm -2 ) on the soil surface, equivalent to 2.5 and 5 9 10 10 IJs ha -1 , respectively.…”