After all the lovely rain comes the hot weather, and with it, the bugs.

Bugs are at a slightly different stage from where they were at the beginning of the garden, and so are the plants on which they feed. Earlier, you had to worry about getting young seedlings established well enough to survive attack. Problems that arise among tender young shoots often don't occur with older, more established plants.

Companion planting often helps, but doesn't necessarily eliminate the problem. It's easy to say that a healthy plant will not be as susceptible to pests as a sickly plant, but even the healthiest broccoli and cabbage display large holes in their leaves when cabbage loopers attack, and even the sturdiest potato plants can be decimated by potato beetles. A garden with well-balanced soil and strong plants will suffer less than a sickly one, but pests pester both.

If Japanese beetles have been a problem in the past, now is the time to put out traps. These are widely available at garden centers and hardware stores.

The bait is a sticky, sweet-smelling concoction that comes in cans. You put a spoonful in the top of the trap and the beetles, drawn by the "mating" smell of the bait, land on the metal trap and fall in. I am particularly enamored of Japanese beetle traps because they're extremely effective and harmless to the environment. Several years ago Japanese beetles were a major threat, and I installed five metal traps in the vegetable garden, which is about a hundred feet long and forty feet wide. I also put out three in my small orchard (three fruit trees and one large grapevine). I found that I had to empty the traps daily, they were catching so many beetles. I emptied the beetles into a bucket of water to which I had added a half- cup of kerosene, which did an excellent job of killing the bugs. There was some damage to leaves and vegetables, but nothing was wiped out that year by the beetles, and, more important, I haven't had a heavy outbreak since. If left unchecked, the beetles will lay eggs and young grubs will develop in turf over the winter, producing new voracious adults in the summer.

Another control of Japanese beetles is milky spore disease, available at many garden centers. This is spread on lawns and attacks only Japanese beetle larvae. The disease has a life of its own, and spreads over the years, so that if you put just a small amount down on your property, after a while it will affect the lawn next door, and the one next door to that, and so on. But for immediate relief, nothing beats traps for nonchemical control.

Cabbage loopers are back in full force. During our recent rains they weren't too active, but they're thriving now, and conditions are excellent for the last big push to reproduce before they begin to disappear in early July. I've already recommended the use of Bacillus Thuringiensis (BT), available commercially as Thuricide or Dipel. These are bacteria whose active life (during which they effect pests in their larval, or soft-bodied stage) last only about a day. Environmentally benign, BT comes in a highly concentrated form, so it is not terribly expensive. I bought a pint two years ago for about $9 and still have about half left. I apply BT two days in a row every other week or as often as I see the loopers. I've found that I need to spray about eight times a season.

BT is also effective against tomato hornworms, but I haven't had to use it because I prefer to pick these off individually. If you don't like to handle hornworms, which are pretty ugly and very large, wear gloves or simply snip them with scissors. If you see a hornworm covered with small, oval white eggs, leave it alone! These are the eggs of the brachonid wasps, which are parasitic and very effective against tomato and tobacco hornworm. The former has a green horn and the latter a red one, but I have seen both varieties on tomato plants and on dill.

The flea beetle thrives in hot weather that immediately follows lots of rain. This pest tends to be less of a threat to eggplants (its best-loved food) once they are well established, but still can be a problem. It looks a lot like its name, being very small, with a hard black shell, and jumps when spooked. Flea beetles congregate in groups on a leaf and nibble away at it until it turns brownish and spidery. They are particularly fond of new growth.

I have used very light dustings of Sevin, but this year will try a garlic spray recommended by organic gardeners.

Another big problem that I face each year is wilt on cucumbers. Spread by the striped cucumber beetle when the plant is very young, it doesn't actually affect the plant until it's bearing fruit; this is frustrating, because by then there's nothing you can do about it. To keep the cucumber beetle off the young plant, I apply a light dusting of Sevin twice, about two weeks apart. Once the plants have begun to flower, I desist. Minimal handling of cucumber vines helps prevent the spread of wilt, because the plant is particularly prone to the disease if damaged. Growing cucumbers on hills helps avoid the need to handle the plants; grown on a trellis, they must be trained.

I know that use of Sevin offends many gardeners, especially those who, like me, are trying to stick to organic methods. Having said that, I hasten to add that I use the chemical very sparingly, and only when I have reached the point of despair. I don't know what else to do, for example, to ensure that my cucumbers don't succumb to wilt when heavy with fruit.

Even though the Mexican bean beetle does a lot of damage to my bean plants, I have found that with judicious hand-picking of the squishy larvae, the plants still bear well, even though they may look a little sad. The decision to apply Sevin, the only chemical pesticide I have used, is based on whether or not the plant will survive. If it produces well despite the pest, I don't worry too much as to how it looks.

And finally, be aware that organic vegetable gardening takes a little extra time, thought and planning, and quite a bit of extra reading. The best book I've found is Organic Plant Protection, Rodale Press Inc., Emmaus, Pennsylvania 18049. 688 pp. $12.95. ROSE CARE COUNSELING Jump right into the sticky wicket of rose care when the Potomac Rose Society demonstrates the summer care of its favorite flower. The pruning, fertilizing, mulching and pest control tips are in the rose garden at Brookside Gardens, free, Sunday at 2 at 1500 Glenallan Avenue in Wheaton. Call 949-8230. And the National Arboretum continues its shows featuring the native plants of Maryland. Free, Saturday and Sunday 10 to 5 and daily through July 16 at 24th and R streets NE. Call 472-9279.