Thirty-three washing solutions with various molar concentrations were visually tested as potentially washing solutions for separation of the Western corn rootworm (WCR) eggs from the soil. The results showed that 1.5 or 2.0 molar solution of MgSO4.7H2O, 1.0 and 1.5 molar solution of ZnSO4.7H2O, 3.0, 4.0 and 5.0 molar solution of NaNO3, MgCl2.6H2Owith molarity of 2.0, NaCl with molarity of 4.0 or 5.0, Ca(NO3)2.4H2O with molarity of 1.5 and 2.0, solution of sucrose with molarity of 1.5 or 2.0, KCl with molarity of 4.0, and NaH2PO4.2H2O with molarity of 2.0, 3.0 or 4.0 were considered as suitable for the separation of WCR eggs from soil and they would be useful tool in integrated pest management for monitoring the density of WCR eggs in maize fields. After separation of the eggs from soil, the eggs were tested for their viability. Percentages of hatched eggs after separation of eggs from soil by washing solutions were not significantly different to control variant. Marginal density of washing solution was determined by beaker and tube test. Marginal density of washing solution, in which the eggs started to move up towards the surface of solution was calculated at the level of 1.086929 g/cm3. As a safe solution density for the separation of the WCR eggs from soil (the density, in which all eggs completely flew to the surface), was considered the level of 1.125 g/cm3.
During the autumn of 1999, an outbreak of Rhopalosiphum maidis (Fitch) was observed on barley volunteers at locality Nitra-Malanta (48° 19´ N, 18° 09´ E) in Slovakia. Barley plantation arose from dropped grain of spring barley harvested on July 20, 1999. The soil was not cultivated after the harvest. During the observation, in October, nearly 80% of tillers were in growth stage of heading and nearly 20% of tillers were in growth stage of booting. The abundance of R. maidis reached 61.13 and 67.37 individuals per main and lateral tiller respectively. R. maidis was not observed on maize fields in the vicinity of the infested barley plantation. The highest percentage of populations constituted larvae and nymphs. Alate females formed 6.7% of the R. maidis population. From 2116 aphids observed on 30 main tillers 97 (4.58%) and from 2283 aphids observed on 30 lateral tillers 153 (6.70%) were infected by entomophthoralean fungi Entomophthora planchoniana Cornu or Erynia neoaphidis Remaudičre et Hennebert.
Seasonal development of entomophthoralean unfection in colonies of
was evalauted on summer barley under conditions of south-western Slovakia in 2001 and 2002.
was infesting summer barley during both years, while
was only recorded in 2002. Further three cereal aphids,
, were also observed on summer barley. Complex of entomophthoralean fungi identified in cereal aphid colonies included four species,
as the most prevalent fungus during both years. Two parasitic fungi,
, were identified from
was predominant. Infection rate in
colonies was low, not exceeding 15% and 10% in 2001 and 2002, respectively. Only nine
individuals were killed with entomophthoralean fungi. The fungi were identified as
. No epizootics were observed in the aphid colonies. The fungi could not control development of the aphid populations since they did not appear until high host densities had been established in the crops.