8.9.10

Something Ate My Plants !

Cuban Land Snail
This is one of the most frequent comments I hear, especially in the warm months. The comment can apply to any plant, and invariably is something that happens really fast. One grower I know calls it "the weekend syndrome", meaning that on Friday everything looks good, but on Monday the plants look like they were hit with a shotgun at close range. What happened, and why did the critters do so much damage so fast ? There are several answers, but some common threads in what caused the damage. First and foremost, you are unlikely to see the offending beast in the daylight. To find out what ate your plants, look under the leaves near dawn or at night. You will likely see the snail or slug or caterpillar, and then take appropriate action once you have identified the offender. Snail, slugs, and caterpillars all leave holes in the leaves. Caterpillars leave small black droppings, whereas snails and slugs leave a slime trail but no other evidence. Look for empty snail shells near the plant, where a predator may have done some dining last night.  In some cases, whole leaves or flowers are missing, which could be something larger, like an iguana or rabbit or even a rodent. I'll address them in a separate posting. 

snail damage
   

Controlling such pest problems is a chore. There are excellent synthetic pesticides to control most every pest problem, but many of them are non selective, and some are  risky to use around pets, children, vegetable gardens or near water supplies. Organic pest controls can be effective, but are often very short-lived and require a lot of labor to get good pest control. For instance, horticultural oil / soap sprays are very effective, but last only a few days, the same for cinnamon or sulfur sprays. You will have to determine the risk-reward ratio that works for you. If you have no pets or children to protect, and you want rapid and protracted control, then modern chemistry may be a good solution. Many organic farmers simply plant extra plants to allow the pests some food, which become food for predators like lizards and birds. The University Extension Service has great information about organic or low-impact pest control. 

Brown Slug- a 'shell-free' snail
Sphinx Moth Caterpillar- large and devastating
Bush Snail and edge-damage
One of the problems with "pest eradication" on a larger scale is that not all caterpillars or snails are doing the damage. Some of the organisms are beneficial or desirable, such as Monarch caterpillars or Liguus Tree Snails, which have gorgeous art-deco stripes on the shells. Using snail bait will kill all the snails, not just the plant eaters, likewise for using an insecticide for caterpillar control.  I have heard some unusual remedies for controlling pests, including using ground cinnamon as a dust, pool filter powder on the ground in snail territory every week, Neem Oil sprays, and dozens of others controls. I believe they all work to some degree, but trial and error will give you the best solution for your conditions. Once again, the local plant societies have run into these problems and can lend some spot-on advice on how to control the problems. Identify the pest, assess how much plant damage you will tolerate, and calculate the risk-reward ratio. One thing is clear: if the damage is severe and sudden, you have not been paying close enough attention to your plants. Pest populations don't explode without notice. A careful eye on your plants every day or two will help keep damage under control. In South Florida, you should be vigilant during the warm months, which means year-round. 

Craig Morell
Pinecrest Gardens       
Monarch Caterpillar on Milkweed

1 comment:

  1. Nice post mate, keep up the great work, just shared this with my friendz
    הרחקת יונים

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