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PAL Questions: 2 - Garden Tools: 1
Is there any scientific reason to not use the iron phosphate based slug baits (Sluggo etc.) near bodies of water (streams, ponds, lakes)? I did some preliminary (not exhaustive) Google research and did not find anything to suggest they cause increased algae growth. Please let me know what you can find on this subject. Are other water-borne organisms harmed?
The Material Safety Data Sheet for Sluggo indicates that one should avoid disposal of this product near bodies of water (see Section 13), though there is not definitive information in Section 12 on the ecological impacts of the product on algae and other life forms. Here is a link to the PDF document.
See also "Grow Smart" from King County Hazardous Waste Management on dealing with slugs in gardens.
It does not list Sluggo, Escar-go, or any of the other iron phosphate products as water pollution hazards, but the MSDS sheet makes me think there is a potential problem with dumping large quantities. It seems not enough information is out there, perhaps because the research has not been done. Here is the page from the Pesticide Action Network database, where you can see that iron phosphate's eco-toxicity has not been established.
Here is what the Environmental Protection Agency has to say about iron phosphate slug baits:
Ecological Effects Hazard Assessment
"A number of ecological effects toxicology data requirements were waived based on the known lack of toxicity of iron phosphate to birds, fish and non-target insects, its low solubility in water, conversion to less soluble form in the environment (soil), and its use pattern (soil application). An acute oral toxicity study in Bobwhite quail (NOEL & LD50 greater than 2000 mg/kg) indicated that iron phosphate was practically nontoxic to avian species. Based on these factors, the data requirements for the toxicity studies in Mallard duck, rainbow trout, freshwater invertebrates, and non-target insect/honeybees are waived. It is likely that there will be exposure to ground-feeding non-target insects and earthworms. Submitted studies involving ground beetles, rove beetles and earthworms demonstrated that the product will not affect these organisms at up to two times the maximum application rate.
Environmental Fate and Ground Water Data
Exposure assessments on this type of product (biochemical pesticide) are not performed unless human health or ecological effects issues arise in the toxicity studies for either of these disciplines. Since no endpoints of concern were identified, there is no requirement for environmental fate data.
Ecological Exposure and Risk Characterization
Exposure to daphnids and other aquatic invertebrates would not occur based on current label use directions. Exposure to honeybees is also not expected to occur, due to the composition and particle size of the end-use product and its use pattern (soil application). Non-target insects, such as ground beetles and earthworms, could encounter the end-use product; however, in tests of rove beetles, ground beetles and earthworms, no effects were observed at up to twice the maximum application rate. Thus, the acute risk to aquatic invertebrates, non-target insects, and earthworms is considered minimal to nonexistent."
United Nations Environment Programme has information on the impact of Phosphorus on aquatic life, a process called eutrophication. However, the iron phosphate in Sluggo and similar products binds with Phosphorus, which may mitigate the effects in water.
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I have a big snail population in my yard. I don't use pesticides and I want to avoid Sluggo or other iron phosphate type baits.
I have read online that decollate snails (Rumina decollata) eat brown garden snails (Helix aspersa). I'm thinking about ordering some of these as they say the decollate snails don't eat your plants. Also I've read that garter snakes will eat the slugs and snails.
Decollate snails may not be imported into the Pacific Northwest. See this information from Oregon State University on nursery pests, excerpted here:
"Decollate snails, Rumina decollata, have been reared and released as biological control agents to control brown garden and other snails. They are native to the Mediterranean and have been in the US since the 1820s and in southern California since the 1950s. They are commercially available and have been used rather commonly in citrus orchards in California. They can harm native snails and are also plant feeders themselves. Decollate snails are prohibited from shipment to the Pacific Northwest but have managed to slip in at times."
Oregon also lists Rumina decollata on its 2003 Invasive Species Report Card, and states that it is polyphagous, eating both plants and other snails:
"decollate snail, Rumina decollata (a polyphagous species that consumes both plant material and other snails, promoted as a biological control agent in areas heavily infested with European brown garden snail in California, reported for sale in a Eugene garden center in 2003)"
The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) also states that decollate snails cannot be permitted across state lines:
"Decollate snails (Rumina decollata) and aquatic snails in the family Ampullaridae (e.g., Pomacea canaliculata, channeled apple snail), with one exception, may not be imported or moved interstate except for research purposes into an APHIS inspected containment facility."
I'm not sure I'd recommend importing garter snakes, though there may be natives already in your garden or surrounding areas. See the Washington Department of Fish and Wildlife's information about our native species, which includes tips for attracting snakes.
There are much easier methods than the above for controlling destructive snails. The same traps that work for slugs--beer in saucers, upturned melon rinds, or copper barriers around plants--should help. A vigilant eye will catch lots of them, too, and they can be squished if you aren't squeamish. More information from University of California, Davis Integrated Pest Management is here.
I understand your reluctance to use iron phosphate products like Sluggo. Although it is certified as acceptable for organic use by the Organic Materials Review Institute (OMRI), information published on the website of Oregon State University in May 2013 quotes recent research suggesting that even "less toxic" iron phosphate slug bait can cause iron toxicosis, and should be kept away from animals and children. Here is a fact sheet from the National Pesticide Information Center which explains the risks. Stormwater runoff may also be a concern, although one typically doesn't use much of the stuff at a time. You might borrow a duck or two to come in and do some serious snail-eating!
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Garden Tool: What unites gardeners from all walks of life? A passionate loathing of slugs and snails. Perhaps if we understood these little slimy mollusks better - their lifecycle, their tastes - we'd learn to appreciate them for the successful creatures they are. Or at least we could learn how to drive them out of our gardens with the latest science has to offer.
The BBC's Science and Nature web site has an in-depth article on snails and slugs that makes fascinating reading. http://www.bbc.co.uk/nature/animals/features/291feature1.shtml
- Slugs have memory and will return another night to finish off tasty seedlings until they are all gone.
- A few plants slugs find distasteful: foxgloves, many species in the daisy family, Lavateras, hollyhocks, azaleas, Euphorbia, hardy Geraniums.
A long list of "Slug Resistant Plants" is given in a Seattle Times article by local writer Valerie Easton
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March 22 2017 13:26:25