The Occurrence and Sex Ratio of Diabrotica virgifera Le Conte Beetles on Sweet Maize (Zea mays var. Saccharata) In South-Eastern Poland Near Rzeszów in 2007-2009

Studies were conducted in 2007-2009 on sweet maize (Zea mays var. saccharata), Candle variety, in Terliczka near Rzeszów. The observations were carried out based on an permission from the Main Inspectorate of Plant Health and Seed Inspection, No. WF-411d/5/2008.

The objective of the conducted study was to specify the occurrence dynamics of Western corn rootworm (WCR) (Diabrotica virgifera) beetles on sweet maize in order to establish the optimal period for their control. In addition their sexual structure between July and September were specified.

In south-eastern Poland D. virgifera beetles began their flights onto sweet maize plants from the second decade of July. Male occurred first, and the flights of females began several days later. Moreover, it was found that the maximum number of males on plants is recorded earlier than that of females.

During the feeding of beetles on maize the period of their most abundant occurrence was from the end of July to the third decade of August. During the flight of adult one population peak was usually recorded: in the third decade of July and the first decade of August, and only in 2007 was it in the second decade of July. In 2007-2009, D. virgifera ended their feeding in late September.

Females dominated among the captured insects during the study years. Their percentage share in the total number of captured beetles was from 59.7 to 84.1%. The population of males in individual years varied, and their percentage share was between 15.9 and 40.3%.