Cyanogenesis Effect on Insect Damage to Seedling White Clover in a Bermudagrass Sod

Cyanogenesis in white clover ( Trifolium repens L.) has been shown to confer resistance to a number of leaf‐feeding insects and molluscs in laboratory and field studies. Most cultivars grown in the USA, however, are acyanogenic. White clover seedlings may be damaged or killed by insect feeding during establishment into a grass sod. The objective of this study was to determine if white clover stand establishment in a grass sod is influenced by cyanogenesis. Two cyanogenic white clover populations, HCNpi and BLHplus, and two acyanogenic populations, ‘Regal’ and BLHminus, were sod‐seeded into common bermudagrass [ Cynodon dactylon (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 (very‐fine, smectitic, thermic Chromic Dystrudert). The 1994 and 1995 tests in Forage Unit B were planted on a Savannah fine sandy loam (fine‐loamy, siliceous, semiactive, thermic Typic Fragiudult). The studies were conducted in a randomized complete block design with four replicates at Mississippi State, MS. Cotyledons, unifoliate leaves, and trifoliate leaves were rated for insect damage and leaf area loss due to insect 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 due to insect feeding than either acyanogenic population. Seedling survival at 6 wk was 88% for HCNpi, compared with 66% for acyanogenic Regal. Cyanogenesis in white clover reduced insect feeding damage and improved seedling survival in bermudagrass sod. The incorporation of limited levels of cyanogenesis into acyanogenic U.S. cultivars could improve seedling establishment without the animal toxicity concerns of highly cyanogenic types.