Lacanobia subjuncta, commonly known as the speckled cutworm, is another member of the Noctuidae moths which has become a significant pest of Washington and Northern Oregon apple orchards since the 1990s. Research on organic management of this pest is scant, but Spinosad has been shown to be an effective insecticide. In a laboratory study, apple leaves were dipped in different concentrations of the insecticide and then fed to larval L. subjuncta. At 1.6 mg/L, Spinosad caused 50% mortality in the larvae.

Photo of an adult speckled cutworm moth. Image from Flickr.

Helicoverpa zea, commonly called the corn earworm, tomato fruitworm, or cotton bollworm, is a major pest that causes extensive damage to crops. The adult moth feeds on nectar from flowering plants and is capable of traveling more than 400 kilometers. When the moths are ready to deposit their eggs, they seek corn silks to lay their eggs on. The larvae hatch and begin to feed on the tissues of the plant. This pest is polyphagous, meaning it can infest and eat many crops, including soybeans, cotton, tomatoes, hemp, and some wild plants, but sweetcorn is the preferred dietary source due to its high sugar content. H. zea preferentially feeds on the reproductive and fruiting structures of crops. Spinosad, an organic insecticide, has been shown to be somewhat effective at controlling H. zea. A 2014 study showed that spraying crops in a 10% sucrose solution with 0.5 mg/L Spinosad baits the emerging moths. They consume the sucrose and Spinosad, which kills 50% of H. zea at a dose of 0.5 mg/L. Precisely applying insecticides in this way can be a great way to prevent outbreaks from occurring. Bacillus thuringiensis (BT) products are effective against H. zea as well. This bacterium produces protein crystals, which are fatal to the moths when consumed.

Spodoptera frugiperda (the fall armyworm) is a noctuid moth native to the Americas, although it is now globally invasive. The larvae of this moth can feed on over 300 different host plant species, and the adults are capable of flying upwards of 400 kilometers per night, making them able to colonize and infest new areas quickly.

Photo of a larval fall armyworm. Image from Flickr.

Spodoptera spp. are polyphagous, meaning the larvae can grow on many different species of host plants. In Florida, the fall armyworm can be a pest year-round, because it is able to grow on the cover crop species as well as the main crop. Corn and sorghum-sudangrass, common cover crops in Florida, both act as great host plants for S. frugiperda. Managing crop rotations and planting species which act as poor hosts to the fall armyworm can take the pressure off the main cash crop by preventing the moth population from expanding. Sunn hemp and cowpea have both been shown to be poor hosts for the fall armyworm, and replacing good host cover crop species with species like sunn hemp could help drastically reduce future numbers.

Spodoptera litura, commonly known as the tobacco cutworm, is polyphagous, migrates long distances, and the larvae can feed on over 300 host plants. Also like the fall armyworm, this species can thrive on certain cover crops and migrate to nearby crop fields, wreaking havoc. Sesbania, sunn hemp, and rapeseed are all viable hosts for larval S. litura. It is important to plow under any green manure at least 30 days before planting crops, so as to prevent an infestation in the cover crop from spreading to the next crop. BT treatments have been shown to be effective against S. litura, especially when combined with certain soil amendments. In a two-year study using 12-square-meter plots, an application of 2 g BT/L sprayed on okra reduced larval populations by 77% in the control, vs. 89% when the soil was also treated with 1.2 kg neem cake and 1.75 kg poultry manure.

Spodoptera exigua, commonly known as the beet armyworm, is another noctuid which attacks upwards of 90 plant species in North America, many of which are cultivated crops. A 2002 study showed that adult female S. exigua prefer to deposit their eggs on cotton, bell pepper, pigweed, compared to cabbage and sunflower. Like other noctuids, Spinosad is an effective control agent and has been shown to be less toxic to the natural predators of the moth than to the moth itself.

Agrotis ipsilon, commonly known as the black cutworm, feeds on grasses, weeds, and a wide variety of crop hosts, including wheat, corn, potatoes, and beans. Cutworms get their name from their feeding behavior. Larvae often chew through the base of seedlings, essentially “cutting” the plant down. Black cutworms are controlled quite easily with neem oil, spinosad, pyrethrins, and BT treatments.

Photo of a larval black cutworm. Image from Flickr.

Mamestra brassicae, the cabbage moth, is a major pest of cabbage. This species may be difficult to control with biological control alone. It has been demonstrated that creating wildflower strips does not increase egg parasitism rates, and may fail to increase predation rates as well. Even the introduction of parasitoid wasps is not very effective and is too costly to be worthwhile, whereas BT treatments of 1.12 kg/ha proved to reduce M. brassicae populations below an actionable threshold in a cost-effective manner.