The plant-parasitic nematode Nacobbus aberrans is an endoparasite that induces gall formation in the roots and causes severe losses to diverse crops. Some populations of this nematode show preference for certain hosts, revealing the existence of "races/groups" with different behaviour and making nematode management difficult. A possible biological control alternative to reduce the damage caused by this species may be the use of arbuscular mycorrhizal fungi (AMF). In the present work, the effect of Glomus intraradices on tomato plants inoculated with the nematode at transplanting and three weeks later was tested. At 60 days, the following parameters were estimated: percentage of AMF colonization, root and aerial dry weight, number of galls and egg masses, and reproduction factor (RF=final population/initial population) of N. aberrans. AMF colonization was higher in the presence of the nematode. The use of AMF favoured tomato biomass and reduced the number of galls and RF on the plants inoculated with the nematode at transplanting.

Spodoptera frugiperda Smith and Helicoverpa gelotopoeon (Dyar) are important agricultural pests of several crops. The aim of the present work was to evaluate the susceptibility of larvae of both insects to an isolate of Steinernema diaprepesi Nguyen & Duncan under laboratory conditions, as well as the capacity of the nematode to multiply on these lepidoterans. Larvae (n = 15) were exposed to 0 (control), 50, and 100 infective juveniles (IJs) per Petri dish. Mortality was evaluated every 24 h during 6 d, and emerging IJs were counted. Mortality of S. frugiperda was 93% and 100% with 50 and 100 IJs dosage, and 87% and 93% in H. gelotopoeon, respectively. The production of IJs was significantly different between doses (P ≤ 005) for S. frugiperda (11 329 with 50 IJs vs. 27 155 with 100 IJs) but not for H. gelotopoeon (19 830 vs. 26 361, respectively). This is the first study evaluating the susceptibility of these lepidopterans to S. diaprepesi. These results encourage the possibility of using this nematode for biological control of both pests.

The effects of insect cadavers infected with three isolates of Heterorhabditis bacteriophora and one isolate of Steinernema diaprepesi on a population of Meloidogyne incognita in pepper (Capsicum annuum) and summer squash (Cucurbita maxima) were evaluated in greenhouse experiments carried out in Santa Fe (Argentina). Insect cadavers were obtained for the experiments from last instar larvae of Galleria mellonella and Tenebrio molitor that had been infected with entomopathogenic nematodes. Two six-day-old insect cadavers per pot were placed below the soil surface, and the soil was inoculated with 100 second-stage juveniles ofM incognita. Sixty days after inoculation, the following parameters were recorded for each plant: number of leaves; dry weight of aerial parts; numbers of galls, egg masses and eggs; and numbers of galls, egg masses and eggs g-1 of root fresh matter. In pepper, the only variable affected by the infected cadavers with respect to control was the number of eggs in the treatment involving T. molitor cadavers infected with the H. bacteriophora isolate Rama Caída. In summer squash, several treatments using infected cadavers resulted in a decrease in the numbers of galls and egg masses. Only the treatment involving G. mellonella cadavers infected with the H. bacteriophora isolate Rama Caída proved to be efficient in reducing the number of M. incognita eggs. Our results indicated that the application of insect cadavers infected with the entomopathogenic nematodes studied might reduce M. incognita damage in pepper and summer squash plants.

El efecto de cadáveres de insectos infectados con tres aislados de Heterorhabditis bacteriophora y un aislado de Steinernema diaprepesi sobre una población de Meloidogyne incognita en plantas de pimiento (Capsicum annuum) y zapallito redondo de tronco (Cucurbita maxima) fue evaluado en experiencias de invernadero conducidas en Santa Fe (Argentina). Los cadáveres de insectos necesarios para la experiencia se obtuvieron infectando larvas de último estadio de Galleria mellonella y Tenebrio monitor con nematodos entomopatógenos. Dos cadáveres de seis días de infección se colocaron debajo de la superficie del suelo de macetas que fueron inoculadas con 100 juveniles de segundo estadio de M. incognita. A los sesenta días se registraron los siguientes parámetros en cada planta: número de hojas, peso seco de la parte aérea, número de agallas, masas de huevos y huevos, y número de agallas, masas de huevos y huevos g-1 de materia fresca radical. En pimiento, la única variable afectada por los cadáveres en relación al testigo fue el número de huevos de M. incognita en el tratamiento de cadáveres de T. molitor infectados con H. bacteriophora aislado Rama Caída. En zapallito redondo de tronco, varios tratamientos provocaron una disminución en el número de agallas y masas de huevos. Sólo la aplicación de cadáveres de G. mellonella infectados con H. bacteriophora aislado Rama Caída demostró ser eficiente en reducir el número de huevos de M. incognita. Nuestros resultados indicaron que la aplicación de cadáveres de insectos infectados con los nematodos entomopatógenos estudiados podría reducir los daños causados por M. incognita en plantas de pimiento y zapallito redondo de tronco.