The case against using poisonous insecticides.

The case against using poisonous insecticides BY JEFF WASIELEWSKI
Fairchild Tropical Botanic Garden

Insecticides have labels that list their toxicity: Caution, Warning and Danger. These are not words to be taken lightly. Insecticides are by their very nature dangerous and extremely toxic. The full effects of insecticides on humans and the environment are not entirely known; therefore, insecticides must be treated with extreme care and used only when absolutely necessary by trained professionals.

There are over one million named species of insects but fewer than 1 percent of those cause damage to plants. Nature was taking care of plants long before insecticides were invented; therefore, you can maintain a healthy, lush garden without ever spraying a drop of chemicals on your plants. You will have the ``bad'' bugs in your garden. If you grow it, they will come, but the damage they will cause is minimal and will rarely threaten the life of your plant.

The good news is that natural predators will also come. Natural predators are insects like the lacewing, the ladybug and parasitic wasps that feed on pests. Natural predators are part of the equilibrium that nature has in place to keep plants alive. It is often when we disturb nature's system that the pest populations swell out of control.

When a group of aphids is spotted feeding on a plant, your first impulse may be to spray the pest with insecticides. What you probably missed was the larval stage ladybug feeding on the aphids. The ladybug in the larval stage looks nothing like the adult ladybug and may be mistaken for just another bad insect. These young ladybugs are voracious feeders and a single insect can wipe out droves of aphids.

Aphids reproduce at a fantastic rate with a single female aphid putting out 50 to 100 offspring in a matter of weeks. Each female is ready to reproduce within five days. In contrast, ladybugs lay about 12-15 eggs and take more than a month to repopulate. If you spray the plant that is full of aphids and a very hungry ladybug, the population that is going to rebound the quickest is the aphids, not the natural predator that would have done an amazing job of cleaning up your plant.

Insecticides can also create super pests. If you repeatedly spray the same chemical to treat a pest, the pest will develop a resistance to that chemical until it is no longer affected by it. These now-resistant pests will breed, and a percentage of their offspring will also be resistant to that particular chemical. If another spray is made, it will wipe out all the pests except the growing population of resistant ``super bugs.''

Letting nature take its course doesn't mean that you will always have pest-free plants. There may be times when insect populations get very high before the predators can keep them in check. You must wait these times out and trust in nature's system.

There are times when natural predators cannot keep a pest in check because we have disrupted nature's system. This happens when a pest is accidentally transported (usually on plant material) to a new location far away from its natural predators. This has occurred throughout the United States in the past and especially in South Florida.

Insects have left indelible marks on our landscapes: the Thai scale of the 1990s attacked king and queen sago palms, virtually eliminating them. Recently the ficus whitefly has attacked species of ficus, and the redbay ambrosia beetle is threatening avocados and the native red bay trees. The newest gumbo limbo spiraling whitefly has a huge host range. These pests were removed from the predators that kept them in check and their populations exploded. Now, natural predators are being sought for them.

So before you spray insecticides, consider the risks and the dangers. Think about how you will not only kill the target pest, but also the natural predator. Don't feel badly if a few leaves or even a few plants are covered with insects; they will survive in almost every case.

Let nature do as it has done for millions of years. Let the delicate system of control that is in place take care of your plants.

Jeff Wasielewski is the multimedia specialist at Fairchild, an expert in South Florida horticulture and a professor of horticulture at Miami Dade College.



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