Q. My new year’s resolution is to clean out my garage and get rid of any pesticides that are expired, not needed, or harmful to wildlife. How do I find out what I should get rid of? Do fertilizers have an expiration date?
ANSWER: This is an excellent new year’s resolution! If you have any pesticides that are expired or not needed anymore, make sure they are labelled (hopefully with the original) and place them in a sturdy box so you can take them to your nearest hazardous materials disposal site. Fertilizers don’t really expire, but they may become clumpy and unusable, so these can be disposed of in a similar way.
The laws concerning pesticides change frequently, so it’s always a good idea to take inventory and get rid of any chemicals that are no longer considered safe to use. Take note of the active ingredient(s), which should be listed on the front of the container, and look them up on the UC IPM website. There you can find an active ingredient index that will give you information on precautions, how it works, and possible adverse effects, including effects on wildlife. There is also a list of less toxic alternatives that is quite useful.
When you are ready to dispose of your old pesticides, fertilizers, and other household chemicals, you can find a drop off site by searching “Household Hazardous Waste + (your county)”. Alternatively, your waste management company’s website should also have this information.
Q. What rodenticides are least likely to harm wildlife? We have a terrible rat problem, but I don’t want to hurt the local predators.
Realistically, there are no rodenticides that are completely safe for non-target species like owls, bobcats and coyotes. Poisons such as brodifacoum, bromadiolone, and difethialone are single-dose rodenticides. These poisons kill quickly, usually within a day of ingestion. Once eaten, the drug is stored in the liver and prevents blood clotting. Since these drugs are not excreted before the rodent dies, predators and scavengers can be poisoned. If you have any of these rodenticides, please dispose of them properly and do not use them.
Older poisons such as warfarin, chlorophacinone, and diphacinone are multiple-dose rodenticides. These are generally considered to be less harmful to wildlife but can cause problems if a predator or scavenger consumes multiple rodents that have been poisoned.
To minimize the risk of secondary poisoning to wildlife or pets, follow the instructions on the label closely. Promptly remove and dispose of any dead rodents by sealing in a plastic bag and disposing in a secure trash container. Don’t handle dead rodents with bare hands. Buried rodents can be exhumed by dogs or coyotes.
If possible, find other ways to kill rodents. I prefer the electrocution-type traps since they are humane and easy to use. Never use sticky traps outdoors since they are more likely to catch non-target animals and are inhumane.
For more information on rat control, see ipm.ucanr.edu/home-and-landscape/rats/pest-notes/#gsc.tab=0