Mamestra brassicae (cabbage moth)

Cultural Control and Sanitary Methods

Damage to early cabbage can be reduced by early planting of the seedlings, so the development of marketable heads occurs before the mass emergence of larvae (Filippov, 1982).

Autumn ploughing has been found to increase winter mortality of M. brassicae pupae in Japan (Tsutsui et al., 1988); this is probably the result of factors such as increased predation, mechanical damage and exposure to low temperature. Filippov (1982) found that summer harrowing, ploughing after harvesting, and early autumn ploughing destroyed about 70-90% of the pupae.

Nets and fleeces prevent damage from M. brassicae provided there are no pupae in the soil when the crop covers are applied (Steene et al., 1992).

Intercropping has been found to decrease populations of M. brassicae in cabbage and Brussels sprouts (Theunissen and Ouden, 1980; Theunissen et al., 1992; 1995; Wiech, 1996; Finch and Kienegger, 1997; Brandsæter et al., 1998).

Host Plant Resistance

An Australian cauliflower line has been found to be resistant to infestation of M. brassicae in the Netherlands (Finch and Thompson, 1992). Different varieties of white and red cabbage and Savoy cabbage differ in susceptibility to M. brassicae; red cabbage has been found to be less infested with larvae than white cabbage and Savoy cabbage (Hommes, 1983). A red-foliaged variety of Brussels sprouts has also been found to show some resistance against M. brassicae (Dunn and Kempton, 1976). Some varieties of cabbage and kale have been identified as showing some resistance to M. brassicae (Cartea et al., 2009b; 2010). High glucosinolate content is a resistance factor that slows down the feeding and development of M. brassicae larvae (Badenes-Pérez and Cartea, 2021).

Biological Control

Mamestra brassicae has a wide range of natural enemies, but their effectiveness in suppressing this insect is variable. However, natural enemies may play an important role in population regulation, and measures that preserve and help the build-up of natural enemies should be integrated into pest management programmes and production practices. For instance, intercropping cabbage with different flowering crops has been found to increase the number of natural enemies (Theunissen et al., 1992). Only a few of the natural enemies of M. brassicae have been used commercially, such as the egg parasitoid Trichogramma. Different species of Trichogramma (e.g. Trichogramma evanescens, Trichogramma chilonis and Trichogramma dendrolimi) have been tested to control M. brassicae; a relatively high summer temperature and dense host population is required to achieve a high parasitization rate by these parasitoids (Finch and Thompson, 1992). The parasitization rates that can be achieved are variable, but rates of parasitism of up to almost 100% have been reported (see, for example, Filippov, 1982; Kahrer, 1984; Finch and Thompson, 1992). Other parasitoids that have been studied for biocontrol of M. brassicae include Eulophus pennicornis (Veire, 1993; Butaye and Degheele, 1995), Meteorus gyrator [Meteorus pendulus] (Smethurst et al., 2004), Microplitis mediator (Belz et al., 2014) and Telenomus laeviceps (Barloggio et al., 2019).

Mamestra brassicae larvae can be controlled by baculoviruses (Poitout and Bues, 1982; Geissler et al., 1991; Finch and Thompson, 1992) and Bacillus thuringiensis (Filippov, 1982; Ter-Simonjan et al., 1982; Terytze and Terytze, 1987; Collier et al., 1996). The bacterial or viral preparations should be applied when the larvae are small. Commercial products of B. thuringiensis and baculoviruses are available in some countries. Laboratory studies in France have indicated that the entomopathogenic fungi Paecilomyces fumosoroseus [Cordyceps fumosorosea] and Nomuraea rileyi are potentially valuable biological control agents (Maniania and Fargues, 1992). The entomopathogenic nematode Steinernema carpocapsae can also lower damage by M. brassicae larvae (Beck et al., 2012).

Chemical Control

In areas where two generations of M. brassicae occur during the growing season, several treatments with insecticides are often needed to control M. brassicae larvae (see, for example, Steene, 1994). In northern countries, where M. brassicae is univoltine, a single properly timed insecticide treatment may be sufficient (Finch and Thompson, 1992; Johansen, 1996a). In Belgium, insecticides are often applied to Brussels sprouts every 2-3 weeks to control M. brassicae larvae (Steene, 1994).

To be effective, insecticides must be applied when the larvae are small (less than 12-20 mm, first- to fourth-instar larvae) (Rygg and Kjos, 1975; Kahrer, 1984; Finch and Thompson, 1992). Older larvae bore into the heart of the plants and are protected from the treatment. Older larvae may also be more resistant to insecticides than younger larvae (Rygg and Kjos, 1975; Kahrer, 1984; Steene, 1994). Insecticides should be applied about 10 days after peak egg deposition (Kahrer, 1984). Thus, it is necessary to monitor the occurrence of M. brassicae (see Field Monitoring section below).

Insecticides currently in use are within the groups of organophosphates, pyrethroids, carbamates, organochlorines and insect growth regulators. Formulations of natural plant extracts have been tested and great attention has been paid to seed extracts from the neem tree (Azadirachta indica), which have shown promising results for the control of M. brassicae larvae (Schmutterer, 1985; Karelina et al., 1992; Mordue et al., 1993; Meadow and Seljåsen, 1996; Seljåsen and Meadow, 2006). Narrow-spectrum insecticides should be chosen when possible to preserve and encourage the build-up of natural enemies.

Timing of chemical and biological control tactics is essential to achieve a good control of M. brassicae, because insecticides and biological agents must be applied at the vulnerable stage. Temperature-dependent development and the lack of synchrony of the different life stages make precise timing difficult.

Pheromone traps can be used to detect and monitor the populations of the insect (see, for example, Terytze and Adam, 1981; Poitout and Bues, 1982; Hommes, 1983; Veire and Dirinck, 1986; Terytze et al., 1987; Bues et al., 1988; Injac and Krnjajic, 1989; Johansen, 1996a). Light traps can be used to monitor the flight of M. brassicae (Hommes, 1983; Injac and Krnjajic, 1989). The adults are also attracted to sugar (Skou, 1991). Sex pheromone traps have been found to be more effective than light traps in catching the first adults of the first generation (Injac and Krnjajic, 1989). Sex pheromone dispensers and traps are commercially available.

A degree-day model for the prediction of field occurrence of adults, eggs and small larvae, and favourable spraying time has been developed (Johansen, 1996a). The prediction model is implemented as a voice board response system for prognosis and advice for growers in Norway.

Hommes (1983) developed preliminary action thresholds for the different developmental stages of M. brassicae. Damage thresholds for injurious lepidopterous larvae on cabbage have been used in several European countries (Hommes et al., 1988).