Grasshoppers don't limit themselves to eating grass; they enjoy a tasty snack of your flowers as well. When you notice nibbled flowers in your yard, grasshoppers aren't the only culprits to point fingers at, but they can decimate your garden in a short amount of time. Grasshopper control is difficult but not impossible in many cases.
What They Eat
Most grasshopper species are herbivores. They're rather nonselective when it comes to what they eat. Grasshoppers enjoy a variety of grasses and grains, as well as many parts of other plants such as stems, leaves and flowers. The sweet nectar of some flowers gives grasshoppers energy they need to grow. According to the University of California Statewide Integrated Pest Management Program, grasshoppers prefer annual flowers to perennial ones. They also enjoy tree leaves and the greens and fruits of vegetables.
When They're a Problem
Spotting a couple of grasshoppers in your yard doesn't mean you have a problem. They might take a few bites out of your flowers, but it's unlikely a few grasshoppers can kill your flowers or destroy their beauty. As migratory insects, most grasshoppers pass through your yard briefly, enjoying a few meals and moving on. When grasshoppers descend on your yard en masse, however, they can quickly decimate your plants by eating the flowers, leaves and stems. Large groups tend to stay in a food-filled area until it can no longer support their appetites.
Why Control Is Difficult
Grasshoppers' migratory nature, which helps your flowers when just a few are passing through your yard, also makes it difficult to control the insects. When you treat your yard chemically for grasshoppers when they are eggs or nymphs, you kill the ones in your yard at that moment, but you don't kill the adults that pass through later in the season. There's no way for you to control the population outside your yard -- the ones that find your yard after maturing. Even when the adults find their way to your tasty flowerbed, they don't fall to many insecticides because of their size and an inherent resistance to pesticides.
Some chemicals, such as carbaryl and acephate, work against adult grasshoppers, but they also kill helpful insects such as bees and can be dangerous to fish if spread near a garden pond. These aren't chemicals you want near children, especially if used in bait form that they could pick it up and ingest. Organic alternatives exist that can help rid your yard of grasshoppers. For example, introducing insects or animals that naturally hunt grasshoppers, such as robber flies, blister beetle larvae or guinea fowl, helps reduce the number of grasshoppers in your yard. Covering your flowers with floating row covers allows light and moisture to enter but keeps bugs out, especially if you use an aluminum mesh screen, which the grasshoppers can't chew through. Also, planting flowers that grasshoppers don't normally eat, such as biennial sweet William (Dianthus barbatus) in U.S. Department of Agriculture plant hardiness zones 3 through 9, can encourage them to migrate past your yard without stopping to snack.