While peppers are very sensitive to frost, and even cool weather, they are much less bothered by pests and disease than their close cousins, eggplants and tomatoes. Peppers belong in the second part of our rotation, so the soil will be fertile but not overly rich. High levels of nitrogen cause them to produce luxuriant foliage but little fruit.
Seed eight to ten weeks before the frost-free date in trays. Germination temperature should be above the normal 72F/22C that is our compromise temperature for most plants. Each time the leaves of adjacent seedlings touch they should be transplanted to a larger container, finishing in a four- to six-inch pot.
Two weeks before transplanting to the garden, prepare the bed, and in cool climates cover with black plastic to help raise soil temperatures; if you have drip irrigation tubing, lay it along the center of the bed first and dump a shovelful of compost every 18-24 inches. That way, once the plastic is in place you can look for lumps in the mulch, and then set a plant right in the compost. The plants should be hardened-off gradually, because they are quite sensitive to transplant shock, especially from temperature. Once the plants are in, we cover them immediately with a floating row cover to moderate the normal spring temperature fluctuations, and to keep flea beetles at bay.
Unfortunately, flea beetles are not the only pest that might go after your pepper plants. They are sometimes affected by leaf miners. The best control is to remove any damaged leaves and burn them, so that the reproductive cycle of the pest is broken. Row covers will keep out the fly whose maggot offspring does the damage, at least for as long as they are left over the plant.
The other occasional pest that bothers our pepper plants is a burrowing maggot that hatches from eggs laid within the ridges of the immature fruit by a small yellow fly with three brown bands across each wing. You may be able to discourage it by dusting the fruit with talc or kaolin clay dusts like Surround (developed by Dr. Michael Glenn) during the midsummer active season of the fly. The burrowing of this pest will eventually lead to rotting of the fruit.
I have heard of tomato hornworms bothering peppers, but have never seen one in our gardens; they, like other caterpillars, can be easily controlled with a Bacillus thuringiensis spray applied every seven to ten days during the egg-laying period of the adult moth.
Peppers share a number of disease and physiological problems with tomatoes. Many of these problems are made more severe by cool, wet weather, and it makes sense, as with beans, to stay out of the pepper patch when the plants are wet. There is very little work you can do at that time, anyway, and you can cause a lot of damage.
The most frequent problem we have with peppers is a lack of fruit set. This can be caused by three different situations, all of which you should try to avoid. Over fertilization is discussed above, but cool temperatures and hot temperatures can also lead to poor fruit set. Temperatures above 85F/29C or below 60F/16C can cause a failure of pollination and subsequent fruit drop. There is nothing you can do about it except wait, but don’t despair: the plants will continue to flower and set fruit as soon as the weather turns right. Remember, peppers are perennials; they are used to waiting around, and are in no real hurry to set fruit.
Pepper plants may also set a few fruit during the good weather in early summer, then apparently forget what they are supposed to be doing. This is not a problem south of USDA Zone 5, but in short season areas, if you wait for those first few to ripen fully, it may be too late for a second set to ripen in areas where seasons are short. Your can solve this problem by sacrificing those first few fruit. To be practical about it, I’d recommend taking half your plants and pinching out the first setting of fruit once they are the size of a marble; the plants will flower with renewed vigor and give you a bumper crop late in the season. The other half of the plants can be allowed to set a few fruit early and mature them for the first harvest.
As days shorten and the end of the season approaches, the same trick will have a different effect. To hasten the ripening of what fruit is on the plants in short season areas, give the plants a little yank to loosen the roots just a bit, or cultivate deeper and closer than usual about three weeks before anticipated frost. Then pinch off the remaining flowers and fruits smaller than the size of a marble. This will focus the plant clearly on your aim, which is to mature the remaining fruits you’ve got!