Early in the growing season, it's critical to establish some sort of spraying program to control insects and fungal infestations. Cultural methods for protection - rotation, removal of debris, pruning - are also critical and something that is done year 'round, but that is for another post. Here are the chemicals that I use that I consider safe when used properly and get the job done.
Thuricide, or Bt, is a bacterium that targets caterpillars only. I've found it to be the best control of the cabbage worm. I also spray it on the stems of squash plants to prevent the vine borer, which is a moth. Once a caterpillar comes into contact with Bt it stops feeding and dies within a day or two. The cabbage worms had already done some damage to the cole crops by the time I sprayed them with Bt, but I haven't seen any further damage. I just try to avoid using it on a brassica shortly before harvest.
The first sets of brassicas that I planted were mowed down by the cutworms. That's another control that I will have to develop next year. I've read that Bt sprayed on corn flakes around the base of the plants will stop them but haven't tried that yet.
Last year my two apple trees were beset by some sort of scale and aphids at the same time. I found that a combination of insecticidal soap and Neem extract was very effective in killing them, or any small soft-bodied insect such as thrips. I use 2.5 oz of soap and 1 oz of Neem per gallon of water, first adding the soap since it helps disperse the oil. The soap kills by dessicating, or sucking the water out of the insect, while the Neem disrupts cell membranes. It may not kill a full grown squash bug but it will make them come to the top of the leaf where they can be picked off. As an added bonus, I've found that Neem is effective in controlling powdery mildew on squash.
I noticed that a commercial maker of pesticides is using the same combination, with added pyrethrins, as an organic insecticide. I tried adding some pyrethrins to the first mix that I prepared and can say that it is deadly to flea beetles, but the pyrethrins may not have been necessary. It's important to avoid pyrethrins in the morning when bees are about. I also used this combination on the cucumber vines which were under attack by a bug that looks like a squash bug but has a harder shell (bugs are actually an insect family that has mouthparts that penetrate a leaf and suck the juices from the plant). It killed the bugs but I'm concerned that they may have already transferred a fungus or bacterium into the plants. The growing tips look bad.
The newest addition for fungal control is Liqui-Cop, for liquid copper. This is basically copper in a chemical form that is soluble in water, specifically copper diammonia diacetate complex, which sounds more exotic than it is. An alternative soluble copper is copper octanoate, or copper soap, which is found at Lowe's. I went with the Liqui-Cop, which I bought online, because it appears to be more effective. It's easy to mix and use. At a copper equivalent of 8%, the amount of copper in a gallon of mix at 4 teaspoons per gallon is actually very small.
The Liqui-Cop is mainly for the tomatoes, where it is supposed to be effective against bacterial spot, bacterial speck, early blight and late blight. As a preventive I have been spraying the tomatoes weekly, as well as the cucumbers, raspberries, and potatoes. So far the tomatoes look good, about 4 feet tall, but it's really too early to tell if it works.
One pesticide not shown is a deer and rabbit repellent. The bunnies have been a real problem this year. They ate most of the bean seedlings, some of the carrots, then got into the Earthbox and ate the lettuce. I reseeded the beans and once up, applied the repellent. The first ingredient is putrefied egg whites, and it smells kind of bad. It seems to work though and may keep them off the beans until they are big enough to be unpalatable.