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P. C. Ellsworth, J. R. Bradley, Comparative Damage Potential and Feeding Dynamics of the European Corn Borer (Lepidoptera: Pyralidae) and Cotton Bollworm (Lepidoptera: Noctuidae) on Cotton Bolls, Journal of Economic Entomology, Volume 85, Issue 2, 1 April 1992, Pages 402–410, https://doi.org/10.1093/jee/85.2.402
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Abstract
European corn borer, Ostrinia nubilalis (Hübner), larvae are more likely to bore into 7-, 14-, 21-, and 28-d-old cotton bolls, Gossypium hirsutum L., when offered a no-choice situation than are cotton bollworm, Helicoverpa zea (Boddie) larvae. None of these four boll ages was safe from European corn borer entry for any instar tested. Cotton bollworm larvae were less able to penetrate larger bolls (21 and 28 d old) and did so appreciably only in the fourth and fifth instars. Early instar cotton bollwonns did not appreciably penetrate younger bolls (i.e., first ins tars in 7- and 14-d-old bolls and second instars in 14-d-old bolls). Given adult and larval behaviors, bolls ≥21 d old probably escape cotton bollworm entry; however, European corn borers can enter cotton bolls of any age. The character of the feeding damage is less severe and Jess cryptic in the cotton bollworm compared with the European corn borer. Bollworm entry holes were larger in surface area, which allowed drying of the wound. European corn borers 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 bollwonn gained entry into the boll, it entered from the top two-thirds of the boll. However, European corn borers usually entered the boll in the bottom third, often through or from within the axial surface of the calyx. The ramifications of the feeding dynamics of these two species for pest scouting and management are discussed, and a model for predicting the probability that these larvae will enter boll tissue is presented.
