Helena Rojht

Nontarget effect of entomopathogenic nematodes on larvae of twospotted lady beetle (Coleoptera: Coccinellidae) and green lacewing (Neuroptera: Chrysopidae) under laboratory conditions.

ABSTRACT The nontarget effect of Steinernema feltiae, Steinernema carpocapsae, Heterorhabditis bacteriophora, and three mixed suspensions of two species of entomopathogenic nematodes on the larvae of the twospotted lady beetle, Adalia bipunctata (L.) (Coleoptera: Coccinellidae), and on the larvae of the lacewing Chrysoperla cornea (Stephens) (Neuroptera: Chrysopidae), were studied in a laboratory bioassay. The assay was performed at three temperature (15, 20, and 25°C) and at three different concentrations of the suspension (500, 2,500, and 5,000 infective juveniles [IJs]/ml). The larvae of A. bipunctata were more susceptible to nematode attack than the larvae of C.. cornea. Four days after treatment, significantly the lowest mortality of A.. bipunctata and C.. cornea larvae was recorded at 15°C, whereas no significant differences were noted between 20 and 25°C. At 500 IJs/ml, the nematodes had significantly the lowest nontarget effect on the larvae of both aphid predators, whereas no significant differences in this regard were established between 2,500 and 5,000 IJs/ml. We conclude that the entomopathogenic nematodes under investigation exhibit a pronounced nontarget effect on the larvae of both predators mentioned.

Chemical analysis of three herbal extracts and observation of their activity against adults of Acanthoscelides obtectus and Leptinotarsa decemlineata using a video tracking system

Ethanol extracts of Rosmarinus officinalis, Lavandula angus-tifolia and Ruta graveolens were tested against adults of Acanthoscelides obtectus and Leptinotarsa decemlineata. Using a newly developed computer tracking system, a choice test revealed that all of the extracts have a repellent action. The highest repellent activity against the bean weevils adults was the ethanol extract of rue, whereas the highest repellent activity against the Colorado potato beetle adults was the lavender extract. We suggest that a cocktail of volatile components in the ethanol extracts was responsible for the observed repellent action. All three of the extracts have insecticidal effects on bean weevils, reducing F1 adult emergence, with no side effects on the germination of the bean plants. In contrast, the extracts did not demonstrate an insecticidal effect on Colorado potato beetles.