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Owlet Moths


Owlet Moths, Miller Moths, Armyworms, Cutworms

Brithys crini Noctuidae Lily borer larva 8750s

by JonRichfield. CC BY-SA 3.0

A close up of a Brithys crini Lily borer larva in family Noctuidae
The Owlet Moths (Noctuidae) comprise roughly 20,000 species, making them the largest moth family. Some Owlet Moths are renowned pests. This is particularly true for species found in the genus Agrotis. Caterpillars will mine leaves and bore into the stems and fruits of plants. Sometimes they're called cutworms because they'll cut the stems of young plants at the base as a result of feeding. On the other hand, some can be beneficial, performing several services to the wider ecosystem. These eat nectar, lichen, dead leaves and fungi.
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Some species are important pollinators.
Some species are severe pests, mining leaves and boring into stems.


Adults: The species in this family tend to demonstrate wing patterning, including colours grey, brown, red, black and orange. Some possess spots, or lined patterning, whereas others show more of a marbled finish. Wingspans typically measure between 2-5cm. When at rest, the two wings come together forming a point, similar to the roof of a house. Larvae: They possess 'greasy' or shiny looking skin. The heads are generally dark brown or black. The body colour can also be variable, usually comprising tones of brown, yellow, green and black. The main colour morphs are green or black-brown. Younger larvae start feeding on the leaves, whereas the older larvae feed on and within the stalks, roots, fruits and tubers. Pupae: Normally between 1-3cm, are smooth and shiny and brownish-red in colour.


Masses of pearly cream eggs can sometimes be seen beneath leaves or in areas of new growth. Sometimes eggs can be green or brown, too. Young larvae feed only on the side which they were laid as eggs. Here, they graze the surface leaving behind distinctive silvery-white blisters and a skeleton of wing veins. Larvae will use silk to disperse from the original plant they were laid on. As larvae grow larger, the holes they leave behind become larger too. Caterpillar droppings are described as sawdust when dried. During the day, adult moths hide within plant debris and on the ground. Older larvae are the most damaging. These will tunnel into the fruits, pods and tubers that plants produce, feeding on the inner contents. Feeding can result in premature leaf fall. Small holes located on the roots, or leaves that have been partly pulled into the soil, indicates medium-sized larvae are present. In worse case scenarios, a whole plant can fall over onto its side.










Biological treatment

Unfortunately, some species of owlet moth give rise to caterpillars that can be highly destructive. Collectively known as Cutworms, these larvae can severely damage plants, particularly in agriculture. By regularly monitoring the high-risk plants in your garden (see below) you might be able to catch these pests before damage is made irreversible. If damage has already been done, not to worry, we've put together some tips and tricks that will help prevent another infestation in the following years. Always try to scarify and plough the soil before doing any planting. This will hopefully reveal any pupae or larvae hiding in the soil. Weeds and plant debris should be cleared two weeks to ten days before planting. Plant checks should be undertaken during the nighttime using a torch, or at dawn, this is when caterpillars will be most active. A range of insects and animals eat cutworms. Sometimes it's worth waiting for other insects to take care of your pests if the infestation is considered average. Parasitic wasps and flies use these caterpillars to feed their larvae. Likewise, ground beetles, lacewings, praying mantis, ants, and birds will all eat these insects. Before you sow your seeds, let your chickens loose on your veg patch. They will clear the area of grubs, caterpillars or any overwintering pupae. If available, you can purchase beneficial predatory nematodes from some commercial retailers. Watering these into the soil should eliminate the caterpillars hiding beneath the topsoil. Soil temperatures need to be between 12-20ºC for the treatment to be effective. Diluted neem seed and leaf sprayed onto potato in regular intervals is proposed an effective treatment. Baits are most effective when other resources are limited. These can be purchased online or from garden retailers. If available, pheromone traps are a brilliant way to catch male moths in search of females. Not only do you reduce the reproductive success of the males in the area, but you can also use traps to monitor the infestation level of your garden. Installing protective collars, made from plastic cups, bottles, or paper tubes, etc., can help protect the stems of young plants. Sticky substances are another barrier that can be effective at preventing caterpillars from reaching stems. Diatomite earth, sawdust, or crushed eggshells are substances disliked by caterpillars.

Chemical treatment

Lastly, there is a whole range of chemical products varying in persistence and toxicity, that can be purchased from a local garden centre. It's always best to check the products active components before using them. They're frequently undergoing restrictions and bans. Follow label instructions carefully and always double-check if you are feeling unsure. Be sure you're using the correct volumes of product to water ratio, using the proper nozzle. It's essential to assess whether the crop is worth saving or not because treatments can result in some resistance build-up in the pest population. Likewise, if you intend to eat your crop, be sure it's listed on the bottle label. Contact insecticides containing natural plant oils can be more environmentally benign than synthetic pesticides. Look out for products containing natural pyrethrums, fatty acids and plant oils. Synthetic pyrethroids that are available for home use include ingredients: Deltamethrin, lambda-cyhalothrin and cypermethrin.
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