Biological way of getting rid of snails?

Hi, I'm a qualified horticulturalist. It really is annoying when you put so much time and hard work into something, only to have it eaten by pests. Do you have these tomato plants in a greenhouse?

You say you want a biological control for these pests. Bio controls are a lot more expensive than buying a pesticide from the garden centres and can cause a lot more inadvertant damage if used outside and not in a greenhouse. If we take each pest one by one:

Thrips: there are mites which crawl around the plant feeding on thrips larvae (Amblyseius cucumeris), there are a range of soil-based mites that eat the thrips pupae (Hypoaspis miles). There are nematodes that live in the soil and eat the thrips pupae (Steinernema feltiae).

Spidermites: Phytosieulus persimilis are tiny predatory beneficial mites, shiny orange and relatively fast moving. It eats both adult and eggs of the Two Spotted mite giving excellent control. These predator mites need a minimum temperature of 15C but work best when temperatures are regularly 18C to 22C. This generally means application from the end of April until September indoors, or June and July outdoors.

Snails: Phasmarhabditis hermaphrodita are nematodes will kill snails if they come into contact with the soft part of their body. However snails feed on the surface, and the nematodes usually work underground within the soil so they are not a foolproof way of controlling snail populations.

However there are more effective and far less expensive controls for these pests. A general all purpose chemical spray from your garden centre (BugClear) will kill off spider mites and thrips. Slug pellets will kill off the snails too.

Hope this helps

A shallow dish of beer (or a bit of yeast dissolved in some warm water will do just as well, snails are attracted to the yeast not the alcohol) will take care of the snails.

The spider mites and thrips can be eradicated using a product put out by "Garden Safe" called "Fungicide 3". The product is OMRI certified (Organic Materials Review Institute is a nonprofit organization started in 1997 by organic certification agencies) and can be safely used to control Fungi (black spot, rust, powdery mildew, etc); Insects (aphids, thrips, whitefly, etc) and Mites in organic gardens.

Good housekeeping methods will help prevent such damage from predators, and you don't necessarily need to invest large sums of money to do this.

Snails won't cross copper barriers, which can be applied as adhesive tapes to pots that plants are grown in, sometimes as manufactured barrier stands too. They get a small electrical charge when their moist bodies tries to pass over the copper and they don't continue. This will mean that your tomato plants will need to be raised, such that no foliage is left in contact with the ground, for example.

Spider mites, as others point out, will be eaten by Phytocelius persimilis, which can be applied to affected plants, and these eat them voraciously, and breed faster than they do. Spider mites also need dry conditions and heat in order to thrive, so if you mist with water regularly you will deter them - you can also wash them off with water sprays, though beware of them climbing their way back. A more effective solution to kill them is to use fatty acids, a component of soaps, that you can spray onto the plants. As this is a water based solution you raise the humidity levels, and soap will kill the mites, as it also does insects. You can buy fatty acid based sprays in many nurseries or online, and they're usually fairly cheap. A similar home remedy is to use diluted liquid hand soaps, though these can dry out the leaves of plants, and so is not as recommendable.

Keep areas around your plants clear of debris, and wash down regularly too. A dish of water near to your plant will raise the ambient humidity around it, which the spider mites won't like either. You can stand a pot on top of pebbles, with water below it, as a way of getting the humidity to rise up from below plants, for example - just beware, as snails and slugs like moist conditions.

Hope this helps. Good luck! Rob

Diatomaceous earth is a good product, and all natural (crushed diatomes/seashells). You need to reapply after rain though.

I've also heard ringing a pot with copper wire works too, since it carries a small electric charge and slugs and snails don't like it.

For the other 2, I hear Pyrethrins is good. It's made from chrysanthemums and is natural. Never used it myself, but heard decent reviews.

Shallow dish of beer. They're attracted to it, fall in and drown. Works great