Grasshoppers Invade Nevada County
What can Nevada County Gardeners Do About the pests?
A Meyer Lemon tree decimated by grasshoppers plaguing Nevada County gardens. Photo credit: Leilani Vevang (2024).
Grasshoppers are plaguing Nevada County crops and gardeners. The insects are also causing problems in Tehama, Yuba, and Colusa counties.
Which species are here?
According to the Nevada County Agricultural Commission, the grasshoppers we are seeing are the Adult Gray Bird and the Adult Devastating species.
“Devastating” is perhaps the operative word to Leilani Vevang, who saw her almond, fruit, and lemon trees eaten down to the stems from grasshoppers on her Penn Valley property.
“At about 2 o’clock everyday it looks like the earth is moving, there are so many crawling on the ground.” Leilani reflects.
According to a University of Wyoming Entomology report, the Devastating species of grasshopper is common to the Sierra Foothills and “destroys rangeland forage, orchards, grains, vegetable crops, and gardens.” It consumes a variety of grasses, shrubs, and trees. This species will avoid high soil temperatures in the hottest parts of the day by taking refuge in plants.
The insects may damage the epidermis of stems and the edges of leaves that they find less palatable. In my garden I have seen the edges chewed on the leaves of my redbud tree and the petunias, but the grasshoppers don’t seem to like the aromatic plants like mint and lavender.
Leaf from a redbud in Grass Valley this year, which has been picked only at the edges because the grasshoppers find this plant less palatable. Photo by Toni Mann Borelli.
Understanding the life cycle of the grasshopper will help you mitigate their damage.
The Nevada County Agricultural Commission informed me that grasshoppers usually come in an 8-10 year cycle, and flourish due to moist warm springs, which are advantageous to their life cycle and development. According to a report by the UC Statewide Integrated Pest Management Program, the insects lay their eggs in the top two inches of soil. Once they hatch, the young nymphs begin to feed on nearby plants.
Nymphs will exhaust nearby food supplies and then move on to new food sources.
A grasshopper will molt 5 to 6 times as it enters adulthood. By the time you see them devastating your plants, the insects are probably well into their final molts. At this point in their life cycle, the grasshoppers are also the most difficult to control.
According to the County Agricultural Commission, abatement has to be done early at the nymph stage, but even if one gardener succeeds at killing off eggs or nymphs on their soil, that won’t stop adults from flying on to your property from other areas.
Some Control Options
It may sound counterintuitive, but give the grasshoppers a home! According to the UC report, “an attractive green border of tall grass or lush green plants around the perimeter of the garden to trap insects and divert them from vegetables or flowers.” If the grasshoppers are comfortable, let them stay there. If you clear out the vegetation, they are likely to seek refuge - and food - elsewhere in your garden.
Hungry grasshoppers will chew through shade cloth and plastic covers. Metal screening is the only barrier that will stop them. For your most precious plants like fruit trees, consider wrapping the crowns with metal mesh window screening.
Pesticides are not very effective against adult grasshoppers once they have invaded your garden. The UC report cautions, “Carbaryl and other insecticides such as cyfluthrin or other pyrethroids commonly used as sprays for grasshopper control are very toxic to bees, natural enemies of grasshoppers, and aquatic life” and recommends that gardeners reserve the use of insecticides for serious outbreaks.
Chickens and guinea hens are excellent predators of grasshoppers and will help destroy the grasshoppers at all stages of their life cycle. Now may be the time to introduce them to your property or add some more to your flock.
Care for Devastated Trees and Plants
If you have a tree or shrub that has been stripped of foliage, the Nevada County Agricultural Commission recommends nursing it with special care.
As the foliage is compromised or gone, hot sun could do unforeseen damage. Protect the trunks and stems of younger trees and shrubs with a shade cloth or other plant-friendly wrapping.
Treat the soil around the plants with a compost or compost tea to nourish the roots, but do not fertilize, as there is not enough foliage to take up the increased nutrients. Keep the soil moist but avoid overwatering.
What about next year?
Unfortunately, the pests are likely to return next year, so you may want to plan ahead for some of the early soil-based mitigation and a hedge that can serve as the refuge for the adult grasshoppers.