Why are there notches all over the leaves of my rhododendron?

The answer is most likely the root weevil. Root weevils are little beetles about ½ inches long that appear in the late spring and early summer.

In the Northwest, they prefer to feed on the tender new growth of rhododendron plants. They also enjoy eating several other plants that are favorites of gardeners. You can find them on yews, hemlocks, strawberries, salal, huckleberry, and several others.

 

root-weevil-closeup

 

Adult root weevils are night feeders spending their days just under the soil surface staying cool and hiding from predators. The best way to know if you have a root weevil problem is the distinctive notching on the edges of leaves.

The Root Weevil Life Cycle

An adult root weevil will lay its eggs in the soil under your favorite rhododendron in mid-summer. Those eggs will hatch into larvae in late summer to early fall where they will over-winter in the top layer of soil, feeding on the fine root mass of the plant. As they grow, they will become more destructive, feeding on larger and larger roots and even the base of the plant. As the soil starts to warm in the spring, pupation takes place and the larvae will become an adult. The adult will forage on leaves for 20-45 days before it is able to start producing it’s own eggs. One adult can lay around 200 eggs in its life span of 90-120 days.

How to Get Rid of Weevils

There are many chemical insecticides on the market that can control root weevil, but they are tricky to use and can be harmful to beneficial insects. Timing is key when using chemical insecticides. You will need to know what stage of life the root weevil is currently in for maximum effectiveness. A granular grub control on the soil can wipe out the root weevil in its larvae stage if they are actively feeding at the time. A foliar insecticide can kill the adults if they are feeding as well. If they are not actively feeding you will just be wasting time, chemicals, and money. Root weevils are only actively feeding about 40% of their life.

 

image courtesy of Rhododendron.org

 

Biological Control

As an alternative to chemical treatment, use beneficial nematodes. Nematodes are small round worms that don’t get any bigger than 1 cm. They can be safely applied to the shrub and surrounding soil without use of masks, gloves, or protective equipment. They are harmless to pets, wildlife, beneficial insects, and humans, but they do quite a number on the root weevil. They actively and selectively seek out both the larval and adult root weevil.

Nematodes can be applied from early spring through fall and be completely effective. Looking for a place to buy? Give us a call!

A lifelong Oregon resident, Drake has been passionate about plants since childhood, beginning with propagating and growing flowers at his grandfather’s nursery. He opened Drake’s 7 Dees in 1974, while earning degrees in Business and Horticulture from Oregon State University. He later expanded into the design/build side of the industry, allowing him to combine his passion for plants with his love of family by maximizing the quality of family time spent outdoors.

Drake is co-founder of the Oregon Landscape Contractors Association and is a Landscape Industry Certified Manager (LICM)—a designation that less than two percent of landscapers have attained. Additionally, Drake serves on the Board of Directors for the Portland Japanese Gardens, widely regarded as one of the seven best Japanese gardens outside of Japan.

Drake is married to former Oregon Speaker of the House, Lynn Snodgrass. Together, he and Lynn received the Farm Bureau President’s award in 1999 for their service and dedication to agriculture in the state of Oregon. Drake and Lynn have two wonderful daughters, two talented son-in-laws, and seven grandchildren. In his spare time, Drake enjoys camping, water and snow skiing, reading, and of course, gardening.

Born and raised in the Portland Metro Area… Tim has had an appreciation for the outdoors from a young age.  Inspired by our local beauty ranging: the Mt Hood National Forest to salty, sea spray of Cannon Beach, the arid high-desert of Central Oregon to the rugged terrain of Steens Mountain – Tim sought higher education at the University of Idaho in their Landscape Architecture department.  Graduating with honors in 2004, he returned home to establish his professional career.

Now making his home in Sandy, Oregon – Tim and his wife [Nicole] are raising two happy and healthy kiddos and 4 fur-babies.  Between soccer, football, cheerleading, girl scouts and other extra-curricular activities… the Sellin family are heavily involved in their community and church family.  Since college, Tim has spent 13 of his 17 years with Drake’s 7 Dees and has ‘set roots’ in anticipation of long-term growth at the family-focused company.  Having spent his time away from Drake’s in a ‘boots on the ground’ capacity, Tim has fostered a love for the operational/production side of landscape business, as well as the design/sales.

His goal in life as well as business is to put others first.

Bachelor of Science Landscape Architecture, BSLA… 2009
California Polytechnic University, Pomona… Cum Laude
American Society of Landscape Architects – Honor Award

Steven has 15 years of experience in the residential landscape design/build and garden center industry, including 9 years with Drake’s 7 Dees. Steven also has experience working with the National Park Service in Yosemite on sub-alpine restoration projects, as well as volunteer experience as a Peace Corps Volunteer serving the community of Zaouiat d’Ifrane in Morocco.

Together, Steven and his wife Anna have four lovely children, all 5 years old and under! In his (very limited) spare time, Steven enjoys camping, hiking, archery hunting, and cooking. Steven’s passion for his work lies in helping others, through design to envision a more beautiful space that, once built, becomes a reality that improves their quality of life.