We are really excited about a new development in the control of these disgusting and destructive pests. Not all gardeners have slugs, but most do, including both of us. The old standard slug bait was is based on metaldehyde but it is not worth the problems it presents. For one thing, it is poisonous to too many things - like pets. We have never recommended it because we consider it one of the "big guns" we avoid.
Secondly, experiments have shown that many slugs were sickened by their first taste, slid off to recuperate, and when they felt better went forth into the world determined never to touch that bait again.
We have, however, recommended slug traps. The slimy, shell-less mollusks love the taste of beer or yeasty, fermented sugar solutions. The traps, homemade or store-bought, work by attracting the slugs into a container from which they cannot escape and they drown. They do die happy, we presume. There is some debate about which beer brand slugs prefer, but we have found there was no difference.
Now there is a new bait on the market that is based on iron phosphate. This is supposed to cause slugs to stop eating and then die and it is harmless to everything else. We don't know yet just how it achieves its effect on the slugs. As a bonus, once it breaks down it becomes fertilizer. It is marketed under two trade names, Slug and Escar-Go.
We can offer some information based on personal experience this spring.
We knew that our cold frame had been a real slug pocket last year. At the beginning of this season, as soon as the seedlings began to come up, we killed a couple of hundred slugs that arrived to devour the tender young things. We applied the iron phosphate bait and went away for 10 days. We returned to find all plants intact. There also were some slugs in our traps in the same general area of the garden, so we know creatures were around. We are impressed with this method not only because of its efficiency, but also because of its staying power.
Results were just reported on an experiment done last year in England where they have industrial-size slugs. The tests don't translate directly to this country because iron phosphate bait is not yet available in England and they used bait that is not available to us, but the results of their research on baits in general is encouraging.
They found that on plots treated with bait seedling was mortality was decreased by 30 percent over that in the control plots where no treatment was used. In other words, don't expect miracles, but 30 percent more seedling survival is significant. In addition, among the plants that did survive in the unbaited plots, half had been damaged. In the baited plots, only three percent had been harmed.
The English bait was supposed to last for two weeks, but in this experiment it proved to be effective for much longer. Researchers divided the baited plots into two areas. In one they put out fresh bait every two weeks during the growing season. In the other they applied it as soon as the slugs started to show up and not again all season. There was only one percent less damage in the plot that was baited every fortnight.
We feel we can safely say that if you have slug problems, you could put the new bait out as soon as you see slugs and not again all summer. Of course, you would want to assess your results to determine whether or not to use it again.
We still think the traps work well, but they have some inconveniences. They have to be covered so rain or sprinkler water doesn't dilute the liquid, but not so closely as to impede the slugs' progress into the container. You must space them about five feet apart because that is as large an area as one trap will serve. Probably worst of all, you have to empty the traps of the juice and corpses and put in fresh liquid twice a week.
This is our nomination for brilliant idea of the year. We are happy to pass along, although we can't claim credit for originating it.
A couple of the problems of container gardening are that they get too heavy and they take a lot of potting soil. So you look for things to put on the bottom to take up room. Rocks only make matters worse. Styrofoam works okay if you have it, but somebody came up with the idea of using empty aluminum soda or beer cans.
The recommendation is to stack the cans upside down in layers, leaving room for about six inches of dirt on top. Fill it up, plant it full and it will be easier to take that pot wherever you want it whenever want to move it.
Master Gardeners Molly Hackett and Georgianna Taylor, whose motto is "Never trust a gardener with clean fingernails," welcome your questions. Send them to: 191 Eastside Highway, Hamilton, MT 59840; or call 961-4614.