Answer: You are wise to seek an alternative to pesticides, which kill good and bad insects indiscriminately. In reality, only a very small percentage of insects are true pests. If we tolerate a little damage, beneficial insects will soon arrive to consume them. Birds and lizards also eat insect pests. A hummingbird can eat 1000 aphids in one day!
In most gardens there's a balance of beneficial insects and destructive insects. Once a population of bad guys gets established, a crew of good guys usually shows up. You can encourage beneficials by having something in bloom at all times, and by avoiding the use of pesticides. Even organic (botanically derived) pesticides can harm beneficial insects and should be used only as a last resort. Most pesticides are pest specific, so if you choose to use one, it's important to positively identify the destructive insects and use a product that targets them and them alone. At this point I'd try to identify the damaging insects. If you don't spot anything during the day, go out after dark with a flashlight and see if you can determine what's causing the damage. Also, many insects survive in particular temperatures, so as weather changes their populations disappear. For example, last week my brittlebush was full of aphids; today I hardly saw any! On cabbage-type vegetables, it could be a cabbageworm or cabbage looper, small green caterpillars that eat leaves. If you catch them early, handpicking them is an easy and effective control. Look under leaves and all around the plant. You can often spot their dark, pellet-shaped droppings which can help you locate them. If they are out of control, you can use Bacillus thurengiensis or Bt. It is a biological control--a bacteria that kills only caterpillars and is safe to other insects, humans and animals. However, butterfly caterpillars, which most people like in their garden, are just as susceptible to Bt, so weigh the pros and cons. I hope these approaches help you control the pests in your garden! If you are able to find a particular culprit, feel free to send another email describing it in detail.
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