What you think of as a daisy flower is made up of many tiny flowers grouped together in a single head. Small, tubular disc flowers occupy the central disc, and the outside petallike structures are individual flowers, called ray flowers. Any flower that has this structure can be called a daisy. One example is "Becky" Shasta daisy (Chrysanthemum x superbum "Becky"), which grows in U.S. Department of Agriculture plant hardiness zones 5 through 9. It has white petals and a golden central disc. Daisies are generally pest-free, but sometimes insects eat daisy petals.
If you live in the eastern U.S., your daisy flowers could be visited by Japanese beetles. They seem to be spreading westward, with populations now in Colorado's Front Range. About 1/2 inch long, the beetles are metallic green with coppery wing covers. The adults eat petals on daisies and other flowers, as well as the leaves of many different plants. The larvae are white, C-shaped grubs that feed on grass roots. Hand-pick the beetles or knock them off the daisies into a container of soapy water for disposal. Collect them in the early morning when they're easiest to find.
You won't see European earwigs eat your daisies unless you go out at night with a flashlight. Living in most parts of North America, earwigs are reddish-brown with short, somewhat rectangular, leathery forewings and a long abdomen that has a pair of pincers at the end. Earwigs aren't venomous but can release an unpleasant smell. You can trap them by putting pieces of hollow bamboo or rolls of corrugated cardboard in areas where you notice earwig activity. In the morning, empty earwigs out of the traps into a pail of soapy water. Several species of native earwigs, which resemble European earwigs, live in various areas of the U.S.
Grasshoppers of many kinds abound everywhere. They eat daisy petals and leaves, and large grasshoppers can make serious inroads in a daisy patch. Adult grasshoppers have wings and can fly long distances, so they are difficult to control. Young grasshoppers look like miniature adults except they have wing pads instead of fully formed wings. Grasshoppers are more common in hot, dry weather. Cold, wet weather kills many of the young. To prevent grasshopper damage on daisy flowers, cover the plants with nonwoven row cover fabric, held away from the plants on wooden or pipe frameworks. Hold the fabric edges down with rocks or bury the edges under soil to prevent grasshoppers from crawling under the fabric.
Snout Beetles or Weevils
Weevils are beetles with downward-projecting mouth parts enclosed in a short snout. Small mandibles at the end of the beak or snout chew half moon-shaped holes on the sides of the petals. These small beetles are about 3/8 to 3/16 inches long and there are several kinds, all blackish to brown or tan. They feed at night and often hide in or near the blossoms during the day. Hand-pick and destroy the adult weevils as soon as you see them to keep numbers low.
Different kinds of adult rootworm beetles feed on daisies. The northern corn rootworm beetle is green, the southern rootworm beetle, also known as the spotted cucumber beetle, is yellow-green with black spots, and the western corn rootworm, also called the striped cucumber beetle, has black stripes on a yellow ground. Cucumber beetle traps use a pheromone, which is a naturally occurring compound produced by the insects to attract mates, to lure the beetles, and can effectively reduce your yard's beetle populations. Generally, you place one trap for each 400 square feet of garden space to trap the beetles and replace them once a month. Follow all instructions and precautions on the label because they vary by brand.