COMPARATIVE DAMAGE POTENTIAL AND FEEDING DYNAMICS OF THE EUROPEAN CORN-BORER (LEPIDOPTERA, PYRALIDAE) AND COTTON BOLLWORM (LEPIDOPTERA, NOCTUIDAE) ON COTTON BOLLS

European corn borer, Ostrinia nubilalis (Hubner), larvae are more like ly to bore into 7-, 14-, 21-, and 28-d-old cotton bolls, Gossypium hir sutum L., when offered a no-choice situation than are cotton bollworm, Helicoverpa zea (Boddie) larvae. None of these four boll ages was saf e from European corn borer entry for any instar tested. Cotton bollwor m larvae were less able to penetrate larger bolls (21 and 28 d old) an d did so appreciably only in the fourth and fifth instars. Early insta r cotton bollworms did not appreciably penetrate younger bolls (i.e., first instars in 7- and 14-d-old bolls and second instars in 14-d-old bolls). Given adult and larval behaviors, bolls greater-than-or-equal- to 21 d old probably escape cotton bollworm entry; however, European c orn borers can enter cotton bolls of any age. The character of the fee ding damage is less severe and less cryptic in the cotton bollworm com pared with the European corn borer. Bollworm entry holes were larger i n surface area, which allowed drying of the wound. European corn borer s removed only enough boll wall tissue to gain entry into the carpels and left the wound watery and ideal for growth of boll rot organisms. The relatively few times that the cotton bollworm gained entry into th e boll, it entered from the top two-thirds of the boll. However, Europ ean corn borers usually entered the boll in the bottom third, often th rough or from within the axial surface of the calyx. The ramifications of the feeding dynamics of these two species for pest scouting and ma nagement are discussed, and a model for predicting the probability tha t these larvae will enter boll tissue is presented.