Root Dip Treatments Affect Fungal Growth in vitro and Survival of Loblolly Pine (Pinus taeda)

Hydrogels and clay slurries are the materials most commonly applied to roots of pines in the Southern United States. Most nursery managers believe such applications offer a form of “insurance” against excessive exposure during planting. The objective of this study was to examine the ability of root dip treatments to (1) support fungal growth and (2) protect roots from injury during exposure for 1, 2, or 4 h. Four treatments were tested: kaolin clay, two grades of polyacrylamide hydrogels, and a cornstarchbased hydrogel. In petri dish tests, kaolin clay was the only treatment that inhibited the growth of three soil-borne fungi (Pythium, Fusarium, Rhizoctonia). When applied to roots, however, the clay slurry did not effectively prevent permanent root damage during exposure and subsequent mortality. Gel treatment provided some protection when roots were exposed to air for 2 or 4 h. If a gel treatment reduces the need for replanting only 1 ha in 3,333, the benefit/cost ratio might equal 2 (assuming a cost of $500 ha-1 for replanting and a gel treatment cost of $250 per 3.3 million seedlings).

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Author(s): Tom E. Starkey, David B. South

Publication: Tree Planters' Notes - Volumes 53, Number 1 (2008)

Section: 6

Volume: 53

Number: 1