Managing insects in vegetables, without chemicals, is all about choosing the right varieties to grow and creating the right environment. Some vegetable varieties are more tolerant to insects than others, or show less visible insect damage than others. For example, I used to plant both white and purple mini-eggplants. Then I discovered that I ended up throwing away many of the white fruit because they had little brown lesions on them that came from insect feeding. The purple either didn’t have the lesions or else they weren’t visible. I learned quickly to only grow purple! Another example is stink bug damage on tomatoes. I can’t grow full size tomatoes very well without pesticides because stink bugs feed on the fruit and cause visible spots. So, instead I grow a variety of colorful cherry and grape tomatoes, and make beautiful colorful mixes that I am able to sell for more than the big tomatoes anyway! Sometimes, simply shifting what you are growing is a better idea than fighting a fight you can’t win without chemicals.
Not only is choosing the right varieties to grow very important, but equally important is creating an environment that is welcoming to beneficial insects and less friendly to pests. There are several components to this. First, don’t plant large blocks of a single crop. Instead, plant smaller plots of multiple crops. This looks a bit like a patchwork quilt. This seems to keep insect pest pressure lower. This may be due to simply confusing the insects a bit with all the different crops, or possibly making it a little more difficult for them to infest everything because they have to travel farther to get to the next plot of a host crop. It is also a great idea to keep habitat all around the fields and even in the fields, where predatory and parasitoid insects can live and breed. Add a row of wild flowers through the field. Plant plots of marigolds, cosmos, fennel, basil, dill, cilantro or other blooming crops at the ends of your rows. These areas make it much more likely that your fields will be filled with beneficial insects that keep the other pests in check.
If you plant varieties that are more tolerant to insects, as well as create habitat for the insects you DO want in your garden, you want to be careful to preserve this delicate ecosystem. A single broad spectrum insecticide can easily destroy all your hard work by killing not only the target pest, but also an entire spectrum of beneficial insects. If you find you have a pest that is getting out of hand and is threatening to ruin your crop, use the softest deterrent possible and use it when the beneficials are not present. This means that you may need to spray a soap or oil for aphids and do it in the evening or at night when the lady bugs are not working. Some other botanical extracts such as neem or rosemary oil also do a great job of deterring pests and not disrupting beneficials, assuming you don’t directly spray the beneficial. Remember that once you start spraying, you stand a high chance of disrupting your ecosystem, no matter how careful you are. If you have a problem that is going to require bug “nuclear war” it might be best to reconsider how important it is to be growing that variety. All in all, it is best to plant crops that have some tolerance to a low level of insect pressure, intercrop by making a patchwork of different fruits and vegetables in your fields, and create plenty of habitat for beneficial insects.