Mortality of Metopolophium dirhodum (Homoptera: Aphididae) caused by strains of Erynia neoaphidis (Entomophthorales: Entomophthoraceae) from Slovakia and Greece

The aim of the study was to test isolates of <I>Erynia neoaphidis</I> originating from Slovakia and Greece for infectivity to <I>Metopolophium dirhodum</I>, and evaluate selected strains for their infectivity at different temperatures. For alatae, an LC<SUB>50</SUB> (number of spores/mm<SUP>2</SUP>) from 109.97 to 230.90 was calculated for the Slovakian strain and of 218.9 for the Greek strain. For apterae, the LC<SUB>50</SUB> was 82.2–194.5 for the Slovakian strain and 367.2 for the Greek strain. The temperature during the incubation period influenced mortality and length of life cycle of the fungus. Lower temperature decreased the mortality and extended the incubation time. With the Slovakian strain and at 22°C, the highest proportion of individuals killed by the fungus was recorded on the third day of incubation (47.8% of the alatae and 49.9% of the apterae), while at 11°C most individuals died on the seventh day (55% and 37.5% of alatae or apterae, respectively). With the Greek strain and at 22°C, the highest proportion of individuals killed was recorded on the fourth day of incubation (40.6% of alatae and 57.9% of apterae). A lower incubation temperature (11°C) prolonged the life cycle and most apterae killed by this strain were recorded on the ninth day (35%), while the highest proportion of killed alatae was recorded on the tenth day (42.8%).

Seasonal dynamics and entomophthoralean infection of the pea aphid, Acyrthosiphon pisum Harris

The seasonal dynamics of the pea aphid, Acyrthosiphon pisum Harris, and entomopathogenic fungi from the order Entomophthorales attacking the aphid were analysed in alfalfa and field pea crops during the growing seasons of 1998 and 1999 at Nitra-Malanta. In both years, pea aphid populations on pea showed a pattern with one peak, culminated at flowering and pod formation. The infestation level on alfalfa was low in both years. Entomopathogenic fungi attacking the pea aphid were identified as Erynia neoaphidis Remaudičre and Hennebert and Conidiobolus obscurus (Hall and Dunn) Remaudičre and Keller. Both pathogens infected the aphid on pea, but only E. neoaphidis was found in the alfalfa plots. Infected aphids were not found on alfalfa during 1999. The maximum levels of infected aphids on pea were 10.30% and 48.39% in 1998 and 1999, respectively. During both years alate aphids were more frequently attacked than apteral ones. Correlation coefficients indicated a positive relationship between the number of infected aphids and precipitation, but this relationship was weak or moderately strong. A strong correlation was found between the number of dead aphids and number of alate aphids counted 5 to 10 days earlier.