Heliothis virescens, or Tobacco Budworm, is a moth belonging to the Owlet Moth Family (Noctuidae). It's the caterpillars which are most problematic in agriculture, horticulture, and, in the garden! The insect is native to North America, and it's range spreads as far as South America. In colder states, H. virescens is less successful because they struggle to survive the colder months. Damage done by caterpillars is aesthetic, impacting flowering specifically. Although vegetable damage is rare, it's still possible. There are rising concerns because the larvae are becoming more resistant to pesticides. Current research focuses on finding alternative treatments for plants within industries.
Caterpillars bore into flower buds, leaving the petals ragged.
Moths and larvae possess a range of natural enemies.
Adults: Looks like your typical cutworm moth. They reach 3.5cm (1.1 to 1.4 inches) in length. They possess a fluffy light brown thorax, white creamy pale green wings. The forewings possess 4 faint and slightly wavy diagonal streaks. Larvae: Max length of caterpillars will equal 3.5cm (approx 1 and a half inches). The colour highly depends on what that caterpillar has been feeding on. Sometimes they can appear bright green whereas other times they show purple hues. Some can also be brown. They comprise longitudinal bands which run the length of the body. Visibility of these bands also depends on the larval colouring. Pupae: These moths will overwinter as pupa (cocoons) in the soil. They begin red-brown and shiny, darkening with time. Eggs: Females deposit the eggs onto the flowers, fruits or areas of new growth. They're pearly white, turning pale grey with age, laid singly.
Holes in closed buds. Petals are chewed. Small larvae may tunnel into leaf buds. Ragged petal margins. Can result in reduced flower production. Irregular holes left in leaves.
Southern US; some parts of South America.
By regularly monitoring the high-risk plants in your garden (see below) you might be able to catch these pests before the damage becomes 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. 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.
Lastly, there is a whole range of chemical products varying in persistence and toxicity, that can be purchased from a local garden centre. 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. If it's late in the season, it might be best to act early next year! 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.
It's rarely a pest of vegetables.
Parasitic wasps, flies, ground beetles, lacewings, praying mantis, ants, and birds will all eat these insects.