ROSCA, Ioan
University of Agriculture and Veterinary Medicine-Bucharest, Romania, Department of plant protection; Bucharest, Bdl. Marasti nr.59, ROMANIA

A new pest to Romania, the western corn rootworm (Diabrotica virgifera virgifera LeConte) was found in 1996 in one district, after 4 years from the first registration in Europe Yugoslavia, near Beograd, 1992). This invasion of southwestern districts of Romania is a continuation of a 4-year eastern and northern migration from Yugoslavia and Hungary.

The emergence of key developmental stages of D. virgifera virgifera calculated for main corn growing areas in Romania by means of minimum temperature sums basses on the lower development threshold for eggs has shown that there is no limiting factor for pest spreading all over the corn cultivated area in Romania.

The rotation on maize and other cultures seems to be the primary management strategy advocated for control of western corn rootworm, but an area of 3 M hectares was planted by maize in Romania during the period 1990-2000, this crop is grown on more than 50% of the total plough-field area very often in continuous cropping and this remains a popular option in Romania. The recent western corn rootworm adaptation to crop rotation in USA, will limit this method of control of pest in Romania too.

Seed treatment of corn which is usual done in Romania on over 500,000 ha annually, for controlling of corn weevil (Tanymecus dilaticollis) and wire worms (Agriotes spp.) is inefficient for control of western corn rootworm due to the fact that usually products, based of carbofuran, are inactive in the middle of June when WCR eggs are hatching and larvae are feeding (sowing time for corn is generally at the beginning of April).

In Romania applying of granular pesticides during cultivation seems to be the future strategy for control of WCR. Based on long-term data from USA and Canada, potential rate of use rootworm granular insecticide is about 32% from area with continuous corn in which WCR is adapted. That means that in the next future, we have to aspect that in southwestern part of the county where more than 700,000 ha are cultivated with corn, it will be necessary to apply rootworm insecticides on more than 100,000 ha. Until now Counter 5G (based on terbufos), seems to be the most suitable for this purposes, but the cost of treatment, 8.38 million USD, will limit applying of treatment

It was done a comparison between WCR and the most important corn pest, till now in Romania, Tanymecus dilaticollis Gyl.. The actual IPM strategies, which should be adopted in Romania for, attempt to control WCR pest is presented.