Erdal SERTKAYA and Serpil KORNOSOR
University of Cukurova, Faculty of Agriculture, Department of Plant Protection 01330 Adana TURKEY

The corn stalk borer, Sesamia nonagrioides is a most important pest on maize in the Mediterranean countries. The population densities of this pest increase starting from August and causes economic damage in September and October on the second crop maize in the Southeast Mediterranean region of Turkey. The egg parasitoid, Platytelenomus busseolae, is the most effective natural enemy of S. nonagrioides in this region. The population changes and natural parasitization rate of P. busseolae on S. nonagrioides eggs were determined on the second crop maize in Adana during 1994-1995.

Maize plants were sampled once a week and 50 samples were investigated for egg parasitoid in each sampling. Egg masses of S. nonagrioides collected were brought to laboratory and each egg mass was counted and put into glass vials separately that were kept at 25±1ºC, 65±10 % relative humidity, 16 hours photoperiod. Those egg masses were checked daily and parasitized or non parasitized eggs were recorded. Emerged parasitoids were then distinguished according the their sexes.

In 1994, the first parasitized eggs were seen on 15 July and parasitism continued till the beginning of November. The highest parasitism rate (92.8 %) was recorded on 13 September. In 1995, first parasitized eggs were seen on 18 July and continued till the mid October and highest parasitism rate (79.1 %) was recorded on 14 September. 63.3 and 58.01 % all eggs collected throughout the seasons were found parasitized with P. busseolae in 1994 and 1995, respectively. The sex ratio (male : female) of P. busseolea observed in this study were 1:1.2 and 1:1.3 in 1994 and 1995, respectively.

The population densities of P. busseolea increased at the end of season with the increase of its host S. nonagrioides and gave high rates of natural egg parasitism, indicating a very promising biological control agent for the control of S. nonagrioides.

Key words: Sesamia nonagrioides, Platytelenomus busseolae, natural parasitism