Damage potential of fourth- to sixth-instar larvae ofAgrotis ipsilon(Hufnagel) on one- to five-node cotton planted no-till into crimson clover was studied in barrier-enclosed plots. The percentage of cut plants decreased progressively with plant age as in a previous greenhouse study. However, depending on infestation category, only 17–42% as many plants as expected were cut from damage by individual larvae observed in the greenhouse. Duration of cutting activity expressed in cumulative degree-days was very similar to that in the greenhouse, but only half that expected from developmental rates at constant temperature in the laboratory.