Area Statistician USDA-ARS Raleigh, North Carolina
Prior herbivore damage accrued by a plant can alter the future herbivory potential of the same plant by changing plant quantity or quality. Such induced plant changes may either benefit herbivores nutritionally or upregulate plant defenses that may change plant attractiveness to future herbivores. In Louisiana sugarcane, the sugarcane borer (Diatraea saccharalis) or SCB is the primary herbivore of concern. SCB damage can be assessed at the end of a growing season, with the approximate time of damage indicated by location on the stalk. Using data from 1993-2021, we assessed whether the probability of SCB damage increased with prior damage lower on the same stalk and whether damage probability varied with sugarcane variety. We found that within a growing season, the probability of damage increased with prior damage. The overall risk of SCB damage differed across varieties, and generally followed previously established patterns of SCB resistance. However, the strength of the previous damage effect did not match known resistance patterns even though it varied with variety. The probability of damage changed from the first to the second year of growth. Again, this varied with the variety and did not match known patterns of resistance. These data indicate that like plants in natural systems, crop herbivore risk is impacted by prior damage. Protection of the plant early within a growing season is critical to preventing later herbivore damage, but the importance of early prevention differs with plant variety, the underlying mechanisms of which need to be assessed further.
