The damn Canadians are holding out on us.
The following info is from the Ontario Ministry of Agriculture Food and Rural Affairs http://www.gov.on.ca/OMAFRA/english/crops/facts/98-023.htm#groundhogs
Control
Winter is a poor time for groundhog control, as these pests hibernate in a sealed off chamber in the burrow.
The following are commonly used methods of control: Phostoxin, a fumigant, contains aluminum phosphide. In the presence of moisture, phosphide gas (phosphine) is released, which is claimed to be effective against groundhogs. When handling Phostoxin, a full face mask repirator with an acid gas canister should be worn and the use of cotton gloves is recommended. A second person with personal protective equipment should be assisting during the fumigation. Always consult the product label. This product is manufactured in tablet form. Rate of application is one tablet per hole. All entrances must be sealed to prevent the gas from escaping.
A Grower Pesticide Safety Certificate is required before Phostoxin can be purchased by a farmer. The policy with this pesticide also requires the user to take instruction on using the product before it can be purchased. (A Factsheet, Aluminum Phosphide for Groundhog Control, is available from the Ontario Ministry of Environment.)
Gas Cartridges are cardboard cylinders containing a mixture that burns slowly and asphyxiates the groundhog. The cartridge is placed in the burrow of the groundhog and all entrances must be sealed. Follow manufacturer’s instructions on the preparation and use of cartridges.
Trapping can be effective for groundhog control, however, it is time-consuming. The use of No. 2 steel traps (muskrat traps) are most practical. Traps should be checked at least twice a day and should be cleaned after each catch.
Shooting can be an excellent means of keeping groundhogs under control. However, it must be done regularly from spring to fall.
The Phostoxin sounds just nasty enough to work. You’ll have to check with your state regulatory agency about requirements because it is restricted use in the USA too. Maybe check with the county extension guys again. They might be a little more helpful if they find out you are going to begin conducting chemical warfare.
Information on obtaining Phostoxin can be found at the following site.
1999 Fumigation Service & Supply Catalog http://www.surf-ici.com/insectslimited,inc/FSScatol.htm
“You know, by god, I actually pity those poor bastards we’re goin’ up against. By god, I do. We’re not just gonna shoot the bastard, we’re going to cut out their living guts and use them to grease the treads of our tanks. We’re going to murder those lousy Hun bastards by the bushel…The Nazis are the enemy. Wade into them, spill their blood, shoot them in the belly.”
George C. Scott from the movie PATTON
Good luck Scylla…We want you on that wall! We need you on that wall!!