Agriculture: Citrus Pest Management Guidelines

Grasshoppers

  • Devastating grasshopper: Melanoplus devastator
  • Valley grasshopper: Oedaleonotus enigma
  • Description of the Pest

    Grasshoppers are robust, elongate insects with winged adults that are good flyers. Commonly they are brown, gray, green, or yellowish insects with greatly enlarged hind-leg femurs adapted for jumping. Grasshoppers have relatively short antennae, which distinguishes them from crickets, katydids, and other Orthoptera, which have long antennae.

    Most species of grasshopper overwinter as eggs and have only one generation a year. Adults live and feed for 2 to 3 months, during which females typically deposit elongate pods of about 20 to 100 eggs in the topsoil of undisturbed areas. Eggs hatch when soil warms in spring, usually in late April, and may extend to late July. The nymphs feed on most any species of nearby green plant, molting five or six times before becoming adults.

    Nymphs and adults readily move. Each individual typically feeds on several different plants. As vegetation is consumed or dries when the rainy season ends, grasshoppers migrate to succulent plants. Adults, sometimes in a large swarm, can fly several miles a day. Nymphs readily jump, walk, or are carried by wind.

    Grasshopper numbers vary from year to year. Grasshoppers become more numerous after warm, moist springs produce abundant vegetation in uncultivated areas, favoring grasshopper survival. Conversely, parasites and bacterial, fungal, and protozoan diseases can cause grasshopper numbers to crash. Many grasshoppers are eaten by arboreal predators such as birds, robber flies, and soil-dwelling egg predators such as blister beetles.

    Damage

    Grasshoppers become economic pests when young tree foliage is extensively chewed by large numbers of insects migrating from unmanaged vegetation. Grasshopper feeding does not harm mature trees.

    Management

    Do not take control action based solely on damage. Caterpillars, earwigs, Fuller rose beetle, June beetles, and snails also chew leaves. Some management methods vary depending on the cause. Where abundant, grasshoppers can be observed during the day feeding openly and flying or jumping among plants.

    Grasshoppers can be difficult to manage once large numbers move onto young trees. If you believe grasshoppers may become a problem, monitor for them in uncultivated areas near young trees. Before adjacent vegetation dries or is cut, consider applying insecticide combined with bait or spraying border areas to kill grasshoppers before they migrate and start to damage crops.

    Common name Amount to use REI‡ PHI‡
    (Example trade name) (type of coverage)** (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
    A. MALATHION
    (Malathion 8) 7.5 pt/acre (OC) 72 (3 days) 7
    RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
    PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
    MODE-OF-ACTION GROUP NUMBER1: 1B
    COMMENTS: Only spray infested trees to avoid destroying natural enemies of mites, loopers, scales, and other potential secondary pests.
    ** OC - Outside coverage uses 100 to 250 gal water/acre.
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment until harvest. In some cases the REI exceeds the PHI. The longer of these two intervals is the minimum time that must elapse before harvest.
    1 Modes of action are important in preventing the development of resistance to pesticides. Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode of action is assigned by IRAC (Insecticide Resistance Action Committee).

    Important Links

    Text Updated: 02/17
    Treatment Table Updated: 02/17