FURLAN Lorenzo¹; VETTORAZZO Marco² ; MONTAGNER Moreno³; DONANTONI Lanfranco⁴; FUNES Vanna^4
1 Department of Agronomy, Entomology, University of Padova, Agripolis, via Romea 16, EGNARO PD, Italy
² Phytosanitary Service of Veneto, Venice Office, via Poerio 34, 30173 MESTRE VE, Italy
³ Department of Agronomy, Entomology, University of Padova
⁴ Phytosanitary Service of Veneto, Venice Office

Due to the discovery of the first specimens of Diabrotica virgifera virgifera Le Conte near the International Airport of Venice in 1998, an attempt to eradicate or at least to contain the newly arrived population was implemented by using different strategies in 1999 and 2000. The methods chosen and the results obtained in 2000 are reported.

In 1995, following the first organized workshop by IWGO, Italy began preparing for the possible introduction of the western corn rootworm (WCR), Diabrotica virgifera virgifera Le Conte.  In 1996, systematic monitoring was started in north eastern Italy using chromotropic traps.  Unfortunately this trap design is not suitable for monitoring newly introduced populations because the insect density is too low and no reliable information was obtained.  As soon as they became available, sex pheromone traps were used to monitor for WCR populations.  Fields near potential introduction areas (airports, customs areas, etc.) where maize had been grown continuously (monoculture) were selected to be monitored.  The first 7 WCR specimens were trapped between 21 July and 13 August of 1998 in Tessera, a site near the Marco Polo International Airport of Venice.  Immediately strategies were implemented to avoid or to delay as long as possible the:
a) establishment of a conspicuous population in the area where the first specimens were captured, as well as the spread of this pest into surrounding areas;
b) further accidental introduction by vehicles from regions where high populations were already present;
c) progressive, natural expansion of WCR populations into Italy from eastern Europe.

METHODS AND RESULTS IN 2000
An eradication program was implemented in and just around a focus area near the Venice Airport. The program was based on:

• monitoring the WCR population in the focus area (1200 ha) and in a safe area (22-25 km around the focus area) using sex pheromone traps;
• imposing restrictions on the planting of maize in fields where corn was grown the previous year;
• the application of insecticide treatments to control WCR adults to all maize fields in the focus area; the insecticide used was Dursban WG, the only insecticide registered for Diabrotica in Italy, at the rate of 1,1 kg/ha; each maize field was sprayed twice between the first days of July and the end of August;
• prohibiting the moving of fresh corn or soil in which corn was grown the previous year outside of the focus area;
• not allowing corn to be harvested before October 1^st.

Farmers were required to comply with these measures by Ministerial Decree and by specific ordinances of the Veneto Region.  The region also made money available to support the eradication program. In 2000 four hundred sex-pheromone traps (PAL and PALS produced by the Plant Protection Institute of Budapest) were placed in maize fields within the focus area (part of them according to a grid of about 400 X 400 meters, the rest concentrated in areas where WCR specimens had been captured the previous years).  Two hundred and fifty PAL traps were deployed in the safe area according to a 1 km X 1km grid. For research purposes, several more traps of different types were added in focus area.  The traps of the grid captured no specimens.

Field checks.  After the farmers had been informed of the eradication program by their organizations, all the fields in the focus area that had been planted to maize in 1999 were checked to determine what crop was planted in 2000.  The field checks were completed in late June and 9 fields totaling  6.7 hectares of monoculture corn were found. These fields were immediately sprayed and, after the legal procedures had been completed, mechanically destroyed.  In July new maps were used to conduct a second field check.  Four very small fields of monoculture corn (140-1050 sq. m each, totaling 0,3 hectares) were discovered hidden between houses and vegetables crops planted for home consumption.  70 PALs traps were immediately placed in and around these fields (a circle of traps was deployed around).

Seventy three WCR males were captured by 4 PAL and 4 PALS traps over a 4 day period (26-29 July) just before the insecticide treatment (29 July).  No beetles were caught on the day of the treatment, one specimen was captured the day after the insecticide application, and another one 2 days after the treatment.  Two days after the treatment a specimen was also found on a trap of the circle  placed 50 meters away from the continuous maize fields.  The insecticide application was repeated after 7 days and another WCR male was captured two days after the second treatment.  After that, no other specimens were captured.

• The most important conclusions from this year’s work can be summarized as follows:
• from 1998 when WCR was first captured over a wide area by using only 10 traps, the area where specimens can be captured was greatly reduced (from 1200 to 350 hectares); in 1999 and 2000 all the specimens were captured in a restricted area between the airport and the national road n° 14 using a very high numbers of traps.
• the key factor to eradication of the species appears to be the interruption of monoculture on all the fields of the focus area; also very small continuous maize fields can allow high WCR reproduction and spread; insecticide treatments directed against the adults are very effective in dramatically reducing the populations and stopping their spread.