I have been plagued with grasshoppers this year. They seem to be chewing up everything in sight. Large grasshopper populations are common during years when the spring is dry and the summer is long and hot.
The best time to get a handle on a grasshopper problem is in early summer when the insects are still in a juvenile stage. Check areas of tall grass or weeds where they like to breed and lay eggs. This is where you are most likely to find young grasshoppers.
Your direct treatment strategy should be two-fold. For immediate results spray them with an insecticidal soap. Next, sprinkle the area with bait called Nosema locustae, which is a microscopic organism that infects grasshoppers with a disease. It's usually mixed with bran meal. The grasshoppers eat the bran meal, become infected and eventually die. The disease is passed on to new generations as well. While this treatment may take a while, it has a long-term impact. Both the insecticidal soap and Nosema locustae are safe for you and your pets. Nosema locustae is available commercially under the brand name of Semaspore and I use Garden Safe Insecticidal Soap.
There are some indirect solutions you can try as well. If you have the space, allow the grass to grow in one area of your garden. The grasshoppers will congregate there and thus be easier to treat.
In late summer and early fall, turn the soil in spots where you think grasshoppers might be breeding. This will expose and destroy eggs that will hatch next spring. Again, look for those weedy or grassy areas.
Chicken, guineas, praying mantis and cats are all grasshopper predators.
Sprinkle the ground around your roses with diatomaceous earth. This dust is actually tiny algae fossils that cut into the grasshoppers' exoskeleton causing them to dehydrate.
There are also ways you can repel grasshoppers. Try planting calendula and cilantro to drive them away or spray your roses with a garlic spray or a hot pepper spray.