Zinc Phosphide 2.0%
In the picture above it is very difficult to see the zinc phosphide bait, especially because it is dyed black. However, squirrels are excellend foragers and will have no trouble finding it.
HOW THEY WORK:
- Zinc phosphide (ZnP) is the only acute toxicant that is registered for control of California ground squirrels.
- Zinc phosphide is adhered with oil to grain and dyed black to deter birds and for identification purposes.
- When ingested, the zinc phosphide reacts with the moisture and stomach acids inside the body of the animal, which produces a lethal phosphine gas causing death by asphyxia (lack of oxygen).
- The animals should die within 24 hours of consumption, or they will have developed a bait shyness and will not likley consume anymore bait material, rendering additional ZnP applications useless.
- Zinc phosphide does not accumulate in the tissue of poisoned squirrels.
HOW TO USE IT:
There are two different methods for distributing zinc phosphide bait:
Be sure to do a bait acceptance test. Do not apply in areas if the ground or vegetation is moist because the zinc phosphide will deteriorate. Squirrels are also less likely to forage for wet grain. Whichever method you choose, keep in mind that the bait should not come in contact with crops used for food or feed.
Mechanical and Aerial Broadcast Baiting (ZnP 2.0%)
- This method has been shown to be effective and should be considered for when dealing with larger areas.
- Green forage may hinder bait consumption to the point where the onset of symptoms and subsequent bait shyness occurs before a lethal dose is consumed.
This method is used for: 
- Rangeland during the dormant season only
- Orchards, Groves, and Vineyards during non-bearing season only
Squirrel territory 5 - Non-bearing fruit tree plantings
- Non-crop borders and uncultivated agricultural areas
- Rights-of-ways such as highways, levees, utilities and railroads
- Forest trees, recreational areas, campgrounds, and nurseries
Also approved for:
- Norway and Roof Rats
- Voles (Meadow Mice)
Spot (Hand) Baiting (hand) (ZnP 2.0%) 
- Spot-baiting is a good method for this bait due to its rapid onset of symptoms. If the squirrels do not consume a lethal dose quickly (54 grain kernels) they may become bait shy.
- Never pile the bait. Ground squirrels can easily find it when it is spread out. A pile of bait would create an unacceptable hazard to non-target species.
This method is used for:
Almond branch: BEFORE
- In and around agricultural buildings and facilities for domestic animals
- Agricultural crops (orchards, vineyards, forage crops, grain and edible seed crops, oil crops, fiber crops, fruits and vegetables)
- Rangeland
- Non-crop borders and uncultivated agricultural areas
- Rights-of-ways such as highways, levees, utilities and railroads
- Forest trees, campgrounds, recreational areas, and nurseries
Also approved for:
- Norway and Roof Rats
- Voles (Meadow Mice)
SAFETY:
- Zinc phosphide is acutely toxic to birds, fish and other wildlife and should be handled with great care.
- Scavengers and dogs can be affected by the toxicity that remains in the dead carcasses of animals that have consumed this bait. Immediately dispose of any carcasses you may find.
WHERE TO GET IT:
- Zinc phosphide is available from your local agricultural commissioner offices and from some agriculture supply outlets.
- Zinc phosphide requires a restricted use permit.
OTHER CONSIDERATIONS:
- NA