Since I have 23 acres of which 20 are considered to be 'fields' up the sides of small mountains on my property, I have found that colorado potato beetles winter out there and come back to the potato plants. As I find the adults, very few now, I crush them or put them into a small tomato paste can with a few tablespoons of gasoline. Then I look under the leaves for the yellow eggs the adult lays..crush them where they are. A few might escape but you can spot them easily once they hatch because they go to the top of the leaf and are very bright red. Crush or pick off what you can, use tweezers to get the rest and crush or toss them into the can. When I started out nearly 20 years ago and had 350+ potato plants, I found thousands of these nasty critters...I found two adults last year and about 20 red babies...evidently I didn't get to the eggs fast enough but never found any of those...everything went to pest he..
Last year, I did find that there was a strange occurrance with pests...what I would normally find in corn silk, I was finding on tomato plants, along with two hornworms which I had only seen one of in 20 years here. Derek was horribly infested with hornworms two years in a row, illing off hundreds every day. He had over 70 tomato plants (I have had as many as 280 plants at a time and only saw one in all those years so they must have wintered near his house unchecked before he bought it).
Slugs...I get quite a few of those because of my low-lying cabbage plants...I tried the 'beer in a saucer' trick with no success...but found an instant wonderful cure. It's such a pleasure to watch them die immediately that I feel like the Wicked Witch curling my hands in glee...take a salt shaker with you and sprinkle a few crystals on them. They immediately turn yellow and actually MELT.
Never use Roundup in a garden, even on a very close up and personal touch, to get rid of weeds or grass. On a windy day, it carries to your plants...on a very still day, the mist lingers in the air and gets to your plants anyhow. Gather your grass clippings and lay down about six inches (right now I have three and need to add more in the next day or so) completely around your plants and in the walkways. They collect and store moisture when you water or it rains, stays moist enough that when it is scalding hot outside it smothers all weeds and grass, puts nutrients back into the ground, and it prevents the dirt from splashing back up onto the stems of your plants (especially tomatoes) which is the ultimate cause of spotted wilt and other diseases. Never use the FIRST mowing of the season clippings...they are full of seeds and will sprout in your garden. Hold off until the second cutting and add to it the rest of the season as needed.
Green cabbage worms...they love anything in that family, such as broccholi, brussel sprouts, etc. Get yards of really cheap cheese cloth and cover your plants...light, rain, etc. gets in, the plants will keep growing under it, and it will prevent the white with black spots on its wings moth from getting to it to lay its eggs.
Corn...put a few drops of mineral oil into the opening when the silk first appears...or use cheese cloth again to cover the stalk. This prevents the brownish corn moth from laying its eggs inside the bottom entry port of the silk.
If you have an abundance of tomato cages like I do, use extras to stake your pepper plants with. When they have a chance to stand upright and if they are planted rather close together, the peppers have a better chance at being shaded enough to grow well without getting sun scalded.
Cukes...build a wooden frame (have the outside pieces long enough so you can pound it into the ground near where your plants will be, staple small square metal fencing to it and try to get the metal fencing close to the ground. Plant your cukes nearby and they will gravitate to it and climb...the leaves are large enough to shade them and they won't get white on one side from laying on the ground and possibly attract slugs.
Watermelon/lopes....never touch the vines during the early morning when nighttime dew is still around. Once the dew dries off, you can move the vines around to where they are all over each other. The fruit needs shade to develop, and once they get about softball size, get a bucket, turn it upside down, and lay the fruit on top of it so it now gets the sunshine it needs. Turn the fruit a couple of times a week so it doesn't get a 'white' side, and when the curlycue tendril that grows next to the attached stem turns brown, the fruit is ready to pick.
Brussel sprouts...start your plants either in the house around end of May or beginning of June (zone 6 for me) or outside about that time. The plants are normally a cold weather plant and will actually do well in the summer heat, but by the time the plants are ready to start producing the sprouts, the darn cabbage worms will pretty much be gone and less of a problem. Do not pick any of the sprouts as they grow larger...but do break off the bottom leaves as the begin to show. That forces the growth into the sprout instead of the leaves...break off the whole top of the plant (main stem) when you get as many as you think you want on each plant and that will also force sprout growth. The most important thing....DO NOT PICK ANY SPROUTS UNTIL AFTER YOUR FIRST FROST. This is what gives sprouts the sweet taste you want instead of them being bitter. This is another reason why I suggest not even starting your plants until well into late spring early summer because they will be the last things you get from the garden and you don't want the sprouts to begin to get 'old' waiting for that first frost.
Field mice were my biggest problem...they love my corn and very carefully pull out each kernel without any evidence that they had been around. Haven't figured out that one yet as I have a cat and a dog who love to kill critters and if I put out regular mouse traps, one of them is bound to get nailed.
As I think of more stuff, I'll let you know. lol