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Aquaculture Division Home
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Insect Management
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Adult |
Larva
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Distribution
Eastern US from Maine to Florida, west to southern Wisconsin, eastern Iowa and Kansas, south through Texas and from Oklahoma westward to southern California.
Life Cycle as Related to Rice
Legumes such as lespediza and soybeans are primary hosts of the grape colaspis adults. Multiple generations are common in legumes and the last generation of larvae overwinters deep in the soil. In the spring larvae move upwards in the soil seeking plants. Because soybeans and lespedeza are rotated with rice in the midsouth, grape colaspis larvae often have only rice on which to feed. Some larvae complete development on rice. However, rice is not a host plant that adults use for oviposition.
Damage and Symptoms
Larvae feed on roots and the portion of the plant stem between the germinated seed and the soil surface. Larvae eat away parts of the stem (girdle the stem) until only a thread-like portion remains. Damaged plants become yellowed, stunted, and wilted. Under water-stress many damaged plants will die. Plants with two or less above ground leaves are very susceptible to damage by colaspis larvae. With very high densities of larvae rice growers can lose 80 to 1 00% of plants - this level of damage often is when rice follows lespedza. None to moderate densities are often found in rice following soybeans. Areas of damage are randomly distributed and characterized by 6 to 1 0 inch portions of rows with plants showing damage symptoms.
Scouting and Treatment Thresholds
No formal sampling plan is available for scouting grape colaspis. Often the damage is completed before the above ground symptoms become obvious to growers or is altogether ignored or not seen. If the colaspis is suspected, the soil around plants about 2 to 4 inches deep must be removed and examined. Confirmation of grape colaspis presence or underground damage symptoms is needed to separate seedling diseases and problem soils as the cause of damage.
Grape colaspis has been a problem in rice for many years, especially in silt loam soils that tend to be a little sandy. Recent trends towards conservation tillage in rice are coincident with a higher frequency of problems with grape colaspis.
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University of Arkansas • Division of Agriculture |
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