CYANOGENESIS EFFECT ON INSECT DAMAGE TO SEEDLING WHITE CLOVER IN A BERMUDAGRASS SOD

Cyanogenesis in white clover (Trifolium repens L.) has been shown to c onfer resistance to a number of leaf-feeding insects and molluscs in l aboratory and field studies. Most cultivars grown in tie USA, however, are acyanogenic. White clover seedlings may be damaged or killed by i nsect feeding during establishment into a pass sad, The objective of t in's study was to determine if white clover stand establishment in a g rass sad is influenced by cyanogenesis. Two cyanogenic white clover po pulations, HCNpi and BLHplus, and two acyanogenic populations, 'Regal' and BLHminus, were sad-seeded into common bermudagrass [Cynodon dacty lon (L.) Pers.] at two Locations in 1994 and one location in 1995. The 1994 test in Forage Unit A was Planted on an Oktibbeha silty clay (ve ry-fine, smectitic, thermic Chromic Dystrudert), The 1994 and 1995 tes ts in Forage Unit B mere planted on a Savannah fine sandy loam (fine-l oamy, siliceous, semiactive, thermic Typic Fragiudult). The studies me re conducted in a randomized complete block design with four replicate s at Mississippi State, MS. Cotyledons, unifoliate leaves, and trifoli ate leaves mere rated for insect damage and leaf area loss due to inse ct feeding at 2, 4, and 6 wk after seeding. No differences were noted among the Populations for seedling survival at 2 wk after seeding. At 4 and 6 wk after seeding, the highly cyanogenic population, HCNpi, had fewer plants with trifoliate leaves damaged and lost less leaf area d ue to insect feeding than either acyanogenic population. Seedling surv ival at 6 mk was 88% for HCNpi, compared with 66% for acyanogenic Rega l. Cyanogenesis in white clover reduced insect feeding damage and impr oved seedling survival in bermudagrass sod, The incorporation of limit ed levels of cyanogenesis into acyanogenic U.S. cultivars could improv e seedling establishment without the animal toxicity concerns of highl y cyanogenic types.