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Pest Status
Background
Chapter 11
Euxoa messoria (Harris), Darksided
Cutworm (Lepidoptera: Noctuidae)
H.H. CHENG
The darksided cutwonn, Euxoa messoria (Harris), is the most destructive insect pest
of tobacco in Ontario and indeed throughout most tobacco-growing areas of Canada.
It is a northern species which has also done great damage to a variety of crops. The
principal injury is caused by larvae which attack the newly transplanted tobacco
seedlings and damage the leaves or growing points and sometimes notch or sever the
plants. If left uncontrolled, a low to moderate population level of this pest has resulted
in 20-48% damaged plants and 14-25% loss of yield (Cheng 1971a, 1971b, 1973c,
1975, 1980a). In the tobacco-growing areas, large populations of this pest are
produced in the rye rotation crop, but invasion by migrating larvae is always a problem
(Bucher & Cheng 1970).
The bionomics of the darksided cutworm in Ontario has been published (Cheng
1973a). It has one generation a year and overwinters as an egg in the soil from 6 to 12 mm
below the surface. Depending upon the weather, overwintered eggs begin to hatch
from the end of March to early April. Larvae in the early instars feed on the rye
rotation crop, later they attack newly transplanted tobacco seedlings. The duration of
the larval stage is about 3 months. The mature larvae cease feeding and transform to
pupae in the soil from late July to mid-August. The pupal stage lasts from 18 to 28 days.
The adults emerge from mid-August to October and lay their eggs in the soil during the
same period. These eggs are completely developed before winter and hatch in the
following spring.
Research on darksided cutwonn control in Canada in the past 10 years has centered
in two areas: (1) selection and evaluation of the more effective and safe chemical
insecticides (Cheng 1979, 1980a, 1980b), and (2) search and evaluation of effective
biological control agents (Bucher 1970, 1971; Cheng 1973b, 1977). These approaches
are reviewed in this chapter.
As more information becomes available on the hazards involved in the agricultural use
of insecticides, there is a greater demand for alternative methods for controlling
insect pests. Consequently, laboratory and field tests with virus pathogens and
Bacillus rhuringiensis preparations were conducted from 1968 to 1972 at the Research
Station, Delhi, Ontario (Bucher 1970, 1971, Cheng 1973b). The results indicated that
these pathogens were significantly less effective than chemical insecticides against E.
messoria larvae in the field (Cheng 1973b).
Studies on the biology and collection of parasitoids, predators, and diseases of E.
messoria have also been conducted by Agriculture Canada at the Delhi Research
Station. The degree of the influence of various biotic factors on E. messoria
populations and the importance and possible roles of the natural enemies in the
tobacco crop and pest relationship have been discussed (Bucher & Cheng 1971,
Cheng 1973a, 1977). In general. larval mortality in E. messoria from natural enemies
was low.
Tobacco is the number one cash crop in Ontario. Because of the high value of the
crop and the insufficient pressure of the various biotic factors on the dark sided
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