Grasshoppers can be devastating to gardens as well as landscape. The number of grasshoppers depends on weather and biological conditions. Grasshopper females lay eggs in late summer. They deposit these elongated masses of eggs in the soil. Early spring grasshopper nymphs which resemble the adults but are smaller emerge. The nymphs frequently molt and take 40-60 days to develop into adults.
Utah has three major groups of grasshoppers: the slant-faced grasshoppers, the band-winged grasshoppers, and the spur-throated grasshoppers. (USU Vegetable Pest Advisory)
The slant-faces, as their name implies, generally have angled faces and long, thin bodies that enable them to blend into the grassy vegetation. (USU Vegetable Pest Advisory)
The banded-wings are the conspicuous hoppers with often brightly colored hindwings that snap and crackle as they fly short distances. The banded-wings are especially common in open desert and scrub; they blend in well with their brown surroundings. (USU Vegetable Pest Advisory)
The spur-throats include the most injurious species. Their name derives from the tubercle projecting between their front legs. (USU Vegetable Pest Advisory)
Damage from Grasshoppers
Grasshoppers with their chewing mouth parts can devour a whole plant or leave ragged holes in plants. Grasshoppers love young green plants of corn, lettuce, bean, carrot, onion, some annual flowers, and melons. Damage occurs in the early summer after rangeland weeds dry up and usually lasts for a few weeks. (USU Vegetable Pest Advisory)
Management:
Grasshoppers are difficult to manage because different species hatch a different times and they can travel long distances. It's best to go after the young nymphs in spring.
- Row Covers: Row covers are a plant fabric used to protect crops from cold and insects. They need to be removed; however, for pollination. If this is done in early morning grasshoppers are less active. The crops can be covered again in the afternoon.
- Use baits. The insecticide, carbaryl, is mixed with wheat bran to create a bait. Spread it evenly throughout the habitat and reapply weekly. The bait can also be placed inside a container, such as PVC pipe segments, to protect it from getting wet (wet bait is no longer attractive to grasshoppers). Carbaryl is toxic to beneficials but safer for bees if used as a bait. It is not an organic spray. USU Vegetable Pest Advisory
- Nosema locustae is a biological insecticide bait that must be applied to early nymph stages and is specific to grasshoppers. It is a fungi that affects the digestion of grasshoppers. It contains azadirachtin, a natural biological agent that is found in neem oil; and organic pyrethrins. If organic control is your goal, avoid compounds labeled as pyrethroids. These pesticides add synthetic chemical compounds to natural pyrethrins, and thus cannot be considered organic pesticides. After feeding on the bait, grasshoppers stop feeding, become lethargic, and die. The disease is contagious and will infect other grasshoppers that cannibalize diseased grasshoppers in the area. (USU Vegetable Pest Advisory)
- Kaolin Clay is a white clay sprayed on plants to discourage feeding insects. The clay is irritating to insects. It can discourage young grasshoppers nymphs. This is only a deterrent.
- Encourage predators that eat grasshoppers. Birds, praying mantis, toads, chickens, and some snakes. While chickens eat grasshoppers they will also eat and damage your garden but you could make a chicken run around your garden. Toads and praying mantis are easier to encourage in the garden but their impact will be small on large grasshopper populations. Personally not too excited about snakes in my garden. They may keep me away.
- Tilling, weeding, and mowing. If your garden is in a meadow mow a 6ft strip around the garden this makes it easier for predators to find grasshoppers and the low grass offers no food for nymphs. Grasshoppers lay eggs in the soil and the eggs overwinter and hatch in spring. Tilling the garden, turning raised beds with a shovel, or tilling ground around the garden in late fall and early spring will destroy eggs that were laid the previous summer.
- Aerial sprays can be coordinated with the Utah Department of Agriculture and Food. The USDA threshold for rangelands is 9 nymphs per yd2; agricultural thresholds would likely be lower. (USU Vegetable Pest Advisory)
Having given all these options grasshoppers are a difficult pest to control. Large infestations caused by migratory grasshoppers seem to be cyclic and are very difficult to manage. They cause extensive crop damage. They have multi-year cycles but will decline with each year.
The average grasshopper population will also be more challenging to handle if your garden is in a meadow. Hot dry conditions mean more grasshoppers.
On an average year you should have some success using multiple methods mentioned above. - For example tilling or turning beds in fall and early spring.
- Mowing a 6 ft wide strip around your garden.
- Using the bait Nosema lucustae in early spring when nymphs appear, remember it is only effective on the young nymphs.
- Covering crops the grasshoppers like such as corn, beans, carrots, and lettuce.
- Using kaolin clay as a deterrent
I'm linking to USU Grasshopper Pest Advisory that is more specific on products labeled for use on grasshoppers in Utah and how to use them. These products are not organic but you do have these options if your garden is only feeding the grasshopper population and not your family.
Comment if you have had good results with any of these products.
