Grasshoppers in Hemp

Order: Orthoptera
Family: Acrididae

Description

The redlegged grasshopper (Melanoplus femurrubrum) can be shades of red, brown, yellow, green, and olive green. These grasshoppers have a pointed spur located between the base of the forelegs and can fly up to 40 feet when disturbed and tend to fly fast and evenly about a yard above vegetation.

The migratory grasshopper (Melanoplus sanguinipes) is a medium-sized, dark gray grasshopper with red and yellow tinges near the back and bottom of the abdomen, respectively. Hindlegs of these grasshoppers have blue-green or red tibia, and wings that extend beyond the tip of the abdomen.

The clearwinged grasshopper (Camnula pellucida) is small or medium-sized with gray brown to yellow coloration. The hindwings are clear and can be used to easily distinguish this species from other grasshoppers found in hemp.

Melanoplus lakinus, commonly referred to as the Lakin grasshopper, is medium sized with brown and yellow markings. Often, the hindwings are short, however some individuals have longer wings that extend to the tip of the femur on the hindlegs.

The differential grasshopper (Melanoplus differentialis) and twostriped grasshopper (Melanoplus bivittatus) are the two largest species of grasshoppers that feed on hemp. Differential grasshoppers can be yellow, green to brown, or olive green. The hindleg femurs have a black chevron pattern. Twostriped grasshoppers are green or tan with black spines on the hind tibia. There are also two distinct yellow lines running along the length of the grasshopper’s back.

Quick Facts

  • There are over 100 species of grasshoppers in the western United States, but only six species have been observed to feed on cultivated hemp so far. They are the differential grasshopper, twostriped grasshopper, redlegged grasshopper, migratory grasshopper, clearwinged grasshopper and Melanoplus lakinus, commonly referred to as the Lakin grasshopper. The twostriped and differential grasshoppers cause the most severe injury to hemp.
  • Grasshoppers feed on hemp leaves and stems. Hemp can tolerate low to moderate levels of defoliation caused by grasshoppers with little to no yield reductions.
  • One species of grasshopper, Aeoloplides turnbulli, is sometimes found in hemp fields but does not feed on hemp.
  • There are several cultural control practices that can help limit grasshopper densities in hemp.
Twostriped grasshopper

Twostriped grasshopper. Note the two conspicuous stripes running down the back.
Whitney Cranshaw, Colorado State University, Bugwood.org

Redlegged grasshopper

Redlegged grasshopper. Note the red tibia on the hindleg.
Russ Ottens, University of Georgia, Bugwood.org

Migratory grasshopper

Migratory grasshopper. These grasshoppers are usually gray.
Joseph Berger, Bugwood.org

Clearwinged grasshopper

Clearwinged grasshopper. Note the clear wings.
Sangmi Lee, Grasshoppers of the Western U.S., USDA APHIS PPQ, Bugwood.org

Adult of Lakin grasshopper

Adult of Melanoplus lakinus, commonly referred to as the Lakin grasshopper. The short hindwings of adults are a key feature of this species.
Sangmi Lee, Grasshoppers of the Western U.S., USDA APHIS PPQ, Bugwood.org

hemp stem injured by grasshopper feeding

Hemp stem injured by feeding of twostriped grasshopper
Whitney Cranshaw, Colorado State University, Bugwood.org

Grasshopper frass on hemp

Grasshopper frass on hemp leaf
Frank Peairs, Colorado State University, Bugwood.org

Hemp stem injured by grasshopper

Hemp stem injured by grasshopper feeding
Whitney Cranshaw, Colorado State University, Bugwood.org

partial defoliation and stem injury

Partial defoliation and stem injury of potted hemp plants caused by feeding of twostriped grasshopper
Whitney Cranshaw, Colorado State University, Bugwood.org

Life Cycle

Grasshoppers have three life stages: egg, nymph, and adult. Nymphs have undeveloped wings, and all six species of grasshopper have a one-year life cycle. In late summer, eggs are laid in soil as pods that contain around two dozen eggs each. Eggs are the overwintering stage and do not hatch until the following spring. Removal of eggs is an important practice for cultural control.

Injury

Grasshoppers injure plants by chewing on leaves and stems. Young hemp plants are more susceptible to feeding injury, which can cause retarded growth or plant death when infestations are severe. Sometimes feeding can destroy the plant’s growing site, leading to increased branching and distorted growth. It is important to note that the increases in branching negatively impact yields of fiber varieties more than CBD varieties, which can benefit from the increase in flower bud production.

When grasshoppers feed on stems, breaking and girdling wounds can lead to wilting of plant tissues above the injury site. Flower buds can be destroyed or their size reduced when grasshopper feeding occurs late into the season. The twostriped and differential grasshoppers cause the most severe injury to hemp.

Cultural Control

The occurrence of weeds near hemp can increase the density of grasshoppers in fields. Tilling fields will expose overwintered eggs to natural enemies and environmental conditions, which will lower egg survival and help limit densities later in the season. In tilled fields, the infestations originate from eggs laid at the edge of fields. In fields that are not tilled, expect grasshopper densities to be more extensive throughout the growing season.

Chemical Control

Managing grasshoppers is challenging in any system. Further, since hemp cultivation was only recently legalized in the United States, there are limited insecticides available for pest management. Be sure to read all labels and confirm that insecticides are registered for use in hemp before purchasing.

References

Colorado State University. (n.d.). Grasshoppers. Available https://webdoc.agsci.colostate.edu/hempinsects/PDFs/Grasshoppers%20January%202020.pdf

Missouri State Governemtn. (n.d.). Differential Grasshopper. Missouri Department of Conservation. Available https://mdc.mo.gov/discover-nature/field-guide/differential-grasshopper

Missouri State Governemtn. (n.d.). Red-Legged Grasshopper. Available https://mdc.mo.gov/discover-nature/field-guide/red-legged-grasshopper#:~:text=Field%20Guide,-Aquatic%20Invertebrates&text=The%20red%2Dlegged%20grasshopper%20is,have%20a%20black%20herringbone%20pattern.

Montana State Government (n.d.). Clear-Winged Grasshopper – Camnula pellucida. Montana Field Guide. Available https://fieldguide.mt.gov/speciesDetail.aspx?elcode=IIORT61010

Montana State Government (n.d.). Migratory Grasshopper – Melanoplus sanguinipes. Montana Field Guide. Available https://fieldguide.mt.gov/speciesDetail.aspx?elcode=IIORT01210

University of Wyoming. (n.d.). Grasshoppers of Wyoming and the West – Twostriped Grasshopper (Melanoplus bivittatus). University of Wyoming: Entomology Department. Available http://www.uwyo.edu/entomology/grasshoppers/field-guide/mebi.html

University of Wyoming. (n.d.). Grasshoppers of Wyoming and the West – Lakin Grasshopper (Melanoplus lakinus). University of Wyoming: Entomology Department. Available http://www.uwyo.edu/entomology/grasshoppers/field-guide/mela.html