Iris borer damage can effectively kill off an old established iris plot in one season.This website occasionally uses cookies to ensure you get the best experience on our website.

July or August is the best time to dig, divide and transplant bearded irises. Iris borer damage escalates to include mushy, foul-smelling rhizomes and stems, and affects the entire vigor of the plant.Rose Of Sharon Care: How To Grow A Rose Of SharonThe moth responsible for these juvenile insects is rarely seen as it is a nocturnal creature. When dividing plants in late summer (August), dig up the entire clump, cut back the foliage to 6 to 8 inches and divide the clump into sections with each division containing several fans of leaves and a good root system.

The leaves will also leak a fluid. Tomato Sunscald: What To Do About Sunscald On TomatoesThe bacteria the iris borer introduces will cause the rhizomes to rot from the inside out and produce a smelly fluid. Irises are planted in fall and produce flowers from late spring to summer.

All rights reserved.Bearded irises perform best in fertile, well-drained soils and full sun.

They are low-maintenance and have beautiful foliage.

The leaves become ragged and dark streaked. Follow these tips from horticulturists with Iowa State University Extension and Outreach to maintain a colorful, attractive iris planting. Keep up to date with all that's happening in and around the garden. Each division should have a fan of leaves, a healthy rhizome and several large roots. Place the rhizome on top of the mound and spread the roots on both sides. To have additional questions answered, contact Hortline at Siberian irises don’t have to be divided as often as bearded irises. Siberian irises can be divided in early spring or late summer. Similar to Siberian iris, and also becoming increasingly popular, are Spuria iris. When dividing Siberian irises in early spring, dig up the entire clump when new growth has just begun to appear. A repeat iris borer treatment in ten to fourteen days will help ensure that the pests have been eradicated. In clay soils, incorporate compost or sphagnum peat moss into the soil prior to planting. These symptoms also mimic bacterial soft rot, leaf spot and iris scorch, all common iris diseases. Forming an attractive circle of 4-foot-tall foliage, they create a nice accent at the rear of perennial beds. The leaves will also leak a fluid. Siberian irises perform best in moist, well-drained soils in full sun.

Fill the hole with soil and firmly tamp around the rhizome but only partially cover the rhizome.

Find more gardening information on Gardening Know How:Houseplant Obsession: How My Indoor Plant Growing Got Started

Finally, water each plant thoroughly. Cut back the leaves to one-third their original height. Replant immediately. When dividing plants in late summer (August), dig up the entire clump, cut back the foliage to 6 to 8 inches and divide the clump into sections with each division containing several fans of leaves and a good root system.

In July or August, carefully dig up the iris clumps with a spade. Iris borers symptoms are first noticed in April or May as they tunnel into the leaves. Wash the soil from the rhizomes and roots with a steady stream of water. Each section should have several growing points and a good root system. Instead, cover the rhizomes of bare-root plants with one to two inches of soil.

When the rhizomes are destroyed there are no storage structures to promote leaf and flower growth and the plant dies out.Beneficial Iris Nematodes: Using Nematodes For Iris Borer InfestationsBy: Bonnie L. Grant, Certified Urban Agriculturist Iris borer symptoms may mimic those of common iris diseases. Japanese Irises Japanese irises are a beautiful group of beardless irises which are the latest to bloom, about a month after the tall bearded and Siberian irises. Promptly replant the divisions. Iowa State University of Science and Technology. Another effective way of killing iris borers is with nematodes. Iris borers symptoms are first noticed in April or May as they tunnel into the leaves. When planted, the rhizome should be just below the soil surface. Space the rhizomes 12 to 24 inches apart. Siberian irises perform best in moist, well-drained soils in full sun. Cascadia Iris Gardens boasts a fine collection of newer hybrids mixed with some of our favorite oldies.

With the largest flowers of all irises, some reaching 12" in diameter with lovely forms, colors, and patterns, they require an acid soil and may require extra water or mulch. They make holes in them and the tunneling and feeding opens the structures up to other bacteria and fungus. The rhizome is destroyed and should be dug out to prevent the spread of the bacteria. The leaves become ragged and dark streaked. When planting bearded irises, dig a hole large enough to accommodate the rhizome and roots. Japanese and Siberian iris do not require fre-quent division. Irises (Iris spp.) Irises are perennials which rise from their rhizomes every year.