Whiteflies are attacking our green beans and tomatoes and squash. In a perfect gardening world, our soil would be so rich that the plants would be so healthy that the whiteflies wouldn't be interested. Just like lions attack the weak and the young buffaloes, pests attack weak plants. We would also have a thriving perennial flower garden around and amongst our vegetable crops which would provide habitat, shelter, and nectar for beneficial predators like wasps and ladybugs. Alas, our garden is a work in progress and outside inputs are necessary.
Spraying insecticides, even organic ones, can be counterproductive. Think about the ratio between predators and prey. Usually one habitat supports many prey animals for just a few predators. The rate of reproduction is also much faster among the prey animals. So you spray and knock out half of the pests and also half of the predators. The problem is that the pests will now reproduce faster than the predators. In a week, your garden may now have the same amount of pests as before with only half of the beneficial predators.
Just because something is natural or organic doesn't mean you can use it indiscriminately. There are always unwanted side effects! Neem oil is much-touted but is definitely my least favorite. It stays in the body of the pest and if a predator eats the pest it will kill the predator as well! Yikes!
Insecticidal soap is a popular method for dealing with whiteflys and aphids. It has to come into contact with the insect in the moment and works by dissolving the insect's exoskeleton. We use soap everyday without thinking, but it turns out it is very dangerous for insects. You can use any real soap, not detergent, but most experts recommend using Safer's Insecticidal soap, or some other commercial brand, because it is specially formulated at the right concentration to not burn or damage your plants. Many home gardeners recommend using Dr. Bronner's Peppermint soap, diluted at 1 tsp to a liter. The peppermint oil will also act as a repellent when you're done spraying, whereas most soap is only effective in the moment! A soap spray that drys on the leaf and is eaten by an insect later is no longer effective; it has to be sprayed on the insect's body.
So, with a heavy heart I sprayed my beans and my tomatoes and my squash with Dr. Bronner's lavender soap (because that's what I happen to have). A moment too late I saw a ladybug; she will certainly not make it. I checked under the leaves, hoping to spray the eggs, and saw a spider. My good hard-working friend! I left her unsprayed. I also found many aphid lions which, you guessed it, eat aphids, and managed to shoo them away before spraying my death ray.
We will see how the struggle plays out in the days to come!