Phenology and Field Biology of Black Cutworm (Lepidoptera: Noctuidae) in Ontario No-Till Corn

Abstract

Black cutworm, Agrotis ipsilon (Hufnagel), is an occasional corn, Zea mays L., pest that is attracted to no-till fields. Understanding the phenology of black cutworm in Ontario no-till corn, particularly the time of arrival of adults in relation to the onset of crop damage and the stages of larvae that coincide with vulnerable corn seedling leaf stages, is important for their effective control. Pheromone and blacklight trap captures of moths first occurred in early April, whereas significant influxes did not occur until mid- to late April. Males and females were often captured simultaneously, in contrast to findings in Iowa and Illinois where males were captured in pheromone traps on average 3 wk ahead of females or males in blacklight traps. This may be a reflection of a more mature source population for the influxes into Ontario because first captures also were later than in the United States. Females arrived mated and corn seedling cutting occurred within 137 degree-days (DD) (base 10.4 degrees C) of first capture in Ontario corn. Cutworms were present in cornfields before planting, and the mean age of larvae increased along with corn leaf stage, suggesting that no new recruitment took place after planting. The apparent synchrony between corn and cutworm phenology in the northern areas of corn production seems more related to the availability and quality of food for young larvae relative to the development of the crop then the time of arrival of moths.

Sublethal Effects of Cry 1F Bt Corn and Clothianidin on Black Cutworm (Lepidoptera: Noctuidae) Larval Development

“…Fecundity is also frequently increased by sublethal pesticide exposure (Sota et al 1998, James andPrice 2002) but other Þtness parameters such as offspring survival may be reduced (Forbes 2000). Hormesis induced pest resurgence (Morse 1998) is not likely to be a problem in the system studied because corn plants are only vulnerable to black cutworm during the early leaf stages and a second generation does not occur in corn in the Great Lakes region (Kullik et al 2005). To determine the ecological signiÞcance of hormesis in response to a clothianidin challenge for black cutworm, several additional life-history traits not examined in the current study should be investigated.…”

“…Bioassays with leaf tissue grown as described above were repeated on three separate dates with 200 freshly molted third instar black cutworms per replicate to assess larval mortality and weight gain over time. Cutworms are present in cornÞelds before planting, and the mean age of larvae increases along with corn leaf stage (Kullik et al 2005). Under optimal conditions, black cutworm larvae have only six instars (Beck 1988), but larvae reared on corn may require seven or more instars as well as signiÞ-cantly more food intake to complete development (Schmidt and Reese 1988;Santos and Shields 1998).…”

“…4 Whatman Þlter paper (1004 125, Whatman International Ltd., Maidstone, England) with a four-leaf corn seedling. The number of larvae found in cornÞelds peaks at the four-leaf stage (Kullik et al 2005) and the size of four-leaf seedlings provided sufÞcient food for the growing larvae between leaf changes. Corn seedlings were inserted into an Aqua Pick (Westbrook Greenhouse Systems, Grimsby, ON, Canada) Þlled with deionized water to maintain plant turgor.…”

“…Early season cutworm control is an important component of corn pest management programs in the Great Lakes region (Kullik et al 2005); however, cutworm infestations are difÞcult to predict, scouting is time-consuming and expensive, and damage is often extensive before it is detected (Showers 1997). Plants are most often cut in the early leaf stages, at or below the growing point (Showers 1997).…”