These insects, some pests, some beneficial, were noted from scouting efforts in central Ohio from mid-May to early June 2018.
One of the most common predators of the brassicacea family of vegetables is the larval form of the cabbage white butterfly, called the imported cabbageworm. The butterfly is a constant presence in Ohio as our most common butterfly species. It lays eggs on cabbage family plants and the larval forms feed on the foliage. They can be difficult to spot due to coloration but feeding damage and frass (fecal material) can be observed via scouting.
Control is by scouting for eggs, which can be difficult, or for by early recognition of larvae and damage. Hand removal is very effective for small plantings. Organic control (check the label carefully) is possible with spinosad products.
Cucumber beetles are a serious pest of cucurbit family plants due to feeding on foliage, flowers and fruit. Control can be difficult. They also vector a devastating bacterial wilt disease that can quickly kill plants and has no treatment.
A good habit to use when scouting for insect pests on plantings is to look at the underside of the leaves for eggs. Many of the insect pests lay eggs singly or in clusters on the underside of leaves, where if undetected, will hatch into larvae that will feed on the foliage. This egg cluster was noted on oregano. I suspect these eggs to be from Box Elder bugs, which do not normally feed on oregano. Both a Box Elder and related Sugar Maple are in the vicinity of the oregano planting.
Control of slugs can be achieved with organic products containing iron phosphate. Slug Factsheet from PSU
This is the larval form of a night moth. It curls up around the stem of a plant and feeds until the stem is cut in half and the plant has been killed. They feed at night commonly so a grower would notice a dead plant that looks cut in half. Digging around the base of the plant can sometimes find the causative agent.
Ground Beetle – Beneficial
Not all insects are pests, some are beneficial and are feeding on pest and assisting the grower. Proper identification will allow the backyard grower, community gardener and urban farmer to know what to keep and what to treat.
If you have questions or concerns about an insect pest located via scouting, contact your Extension office for assistance with identification.