Test of the Float Method of Assessing Northern Red Oak Acorn Condition

The float method of assessing the condition of acorns and other tree seeds is widely used, yet its efficacy has not been rigorously studied. In this study, 18,334 northern red oak (Quercus rubra L.) acorns collected from 2 sites in West Virginia were tested using the float method and then dissected to assess true condition. Immersion in water was found to be a reliable means of identifying insect-infested, diseased, and otherwise damaged northern red oak acorns. It was most effective in identifying undeveloped or aborted acorns and those infested by the stony cell gall wasp (Callirhytis fructosa Weld.), fly larvae (Drosophilidae, Psychodidae, and/or Anthomyiidae), and lepidopterous larvae-the filbertworm (Melissopus latiferreanus Walsingham) and acorn moth (Valentinia glandulella Riley). Use of the float method was also found to result in the unnecessary rejection of variable numbers of apparently sound acorns. On average, half of the 4,257 sound acorns used in this study failed the test. Based on these results, it is recommended that large collections of acorns from many sources be made to compensate for genetic differences and desiccation due to microsite conditions. Alternately, acorns may be soaked in water to raise moisture content before testing. Tree Planters' Notes 46(4):143-147; 1995.

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Author(s): Linda S. Gribko, William E. Jones

Publication: Tree Planters' Notes - Volume 46, Number 4 (1995)

Section: Research Reports

Volume: 46

Number: 4