|Skinner, Robert - Howard|
Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/28/2002
Publication Date: 11/20/2003
Citation: Sanderson, M.A., Byers, R.A., Skinner, R.H., Elwinger, G.F. 2003. Growth and complexity of white clover stolons in response to biotic and abiotic stress. Crop Science. 43:2197-2205. Interpretive Summary: White clover is a critical component of pastures in temperate humid grazing lands and persists by growth of stolons and establishment of new seedlings. Persistence of white clover in pastures depends on many factors such as soil type, slope aspect, water, frequency and extent of grazing and cutting, soil fertility, and insect and pathogen infestation. In this research we studied the effects of drought and two insect pests (the blue weevil, which feeds on above ground plant parts; and the clover root curculio, which feeds on clover roots) on white clover stolon growth and complexity. Our data show that the blue weevil can infest most of the stolons of white clover in pastures. The injury from the clover root curculio was greater in a dry year than in a wet year. Despite severe drought stress and chronic insect damage to white clover stolons, the white clover recovered dramatically when rainfall returned. Results from our study suggest that climate and insect pests are major factors controlling the variations in white clover abundance in northeast pastures. Management to maintain longer and heavier stolons will aid the persistence and competitiveness of white clover in pastures.
Technical Abstract: White clover (Trifolium repens L.) persists in mixed-species swards mainly by clonal growth of stolons. Morphologically complex (i.e., highly branched stolons) plants of white clover generally persist longer. We hypothesized that biotic and abiotic stresses limit white clover production on grazing lands by fragmenting plants into smaller, less competitive individuals. We measured changes in the size and structure of plants in a mixed white clover-orchardgrass (Dactylis glomerata L.) sward during an extreme drought (1999) and a favorable growing season (2000) in grazed pastures on a farm in southeastern Pennsylvania. A natural infestation of clover root curculio (Sitona hispidulus L.) and blue clover weevil [Ischnopterapion virens (Herbst)] provided an opportunity to examine the interaction of abiotic and biotic stress on stolon structure. White clover plants were dug from two orchardgrass- (cv. Pennlate) white clover (cv. Will) pastures during April to November 1999 and 2000. Stolon structure and damage from the blue weevil and curculio were determined each month. Drought in 1999 reduced stolon production, branching, and rooting in white clover. Stolon length (cm m-2) in 1999 was 50% of that in 2000. Clover root curculio damaged up to 25% of clover roots and 20 to 40% of stolons were damaged by weevils. Insect damage was greatest on primary stolons. With favorable rainfall during late 1999 and in 2000, white clover recovered quickly from fragmentation and produced nearly twice the stolon length, mass, and density in the next grazing season despite insect damage levels of 10 to 30%. Climate and biotic stresses are the major factors controlling the oscillations of white clover abundance in pastures of the northeastern USA.