By RACHAL PINKERTON
KENNEWICK — Research has been done in the Western United States over the last few years into the life cycle of the Clover Root Curculio, an insect that damages hay.
While research has been done in the Eastern U.S., the field and weather conditions are vastly different in the West.
Steve Price, of Utah State Extension, in Price, Utah, has been working with a team to investigate the life cycle of the Clover Root Curculio. His research has looked at fields in Utah, Idaho and California.
As an adult, the Clover Root Curculio looks similar to the Alfalfa Weevil. The larvae are a whitish color with an orangish-brown head, have no legs and are usually smaller than a quarter inch. Adults feed on the leaves of alfalfa, while their larvae feed on the roots.
The insects are hard to study because they cause damage that is similar to other hay problems. Because the larvae eat the roots, they can have a huge effect on the overall establishment and density of a hay stand. The larvae interrupt the nutrient and water uptake into the plant. An infected root looks like a peeled carrot. Their roots have no fine root mass and have lesions on them.
“Beyond the normal direct damage they are doing to the plants, they cause indirect damage,” Price said during one of the sessions of the Washington State Hay Growers Association annual conference in January. “You can have stunting and yellow alfalfa. Hay tends to be patchy when coming in and has a hard time breaking dormancy. The yield is cut the first or second cutting, and there are losses in quality as well.”
The open wounds created by the larvae become the home to bacteria and fungus that further invade the hay plant and decrease the stand.
“It is the first storm of effects in fields that have the insect,” Price said.
All the research previously done on the insects was done on the East Coast, 20 to 30 years ago. Because research hadn’t been done in Western regions, it was hard for management tools to be recommended.
In 2015, Price and his team started studying the insects. The adults were caught in nets. To find the larvae, samples of alfalfa plants, including the dirt around them, were dug. Price said that the roots can’t be pulled out of the ground alone, as the larvae tend to stay in the ground. Once a sample of ground is dug, it is put into water, and the larvae float to the top.
Between research conducted in 2015 and 2016, it was discovered that larvae begin to pupate in June and July, becoming adults in late July. When the new adults come out of the soil, they begin to actively feed. They then have a period of inactive feeding, followed by another period of active eating and mating. During the summer, they can be found in the alfalfa crowns, instead of on the leaves. Eggs begin to be laid in the fall. While the exact timing varied between the Utah, Idaho and California samples, the approximate dates for the life cycles stayed the same. One thing Price noted is that the adults were able to live under the snow.
Price said that the data he collected indicated that young hay stands were affected by the Clover Root Curculio more than older stands.
“Where you would expect the old stands to have more of a population, it was not found,” Price said. “We found stands were infected early on, decreasing the density of the stand prematurely.”
The researchers also found that fields with the insects seem to be affected evenly across the entire field.
When looking at the roots, both old and new damage can be seen. The damage can also be overlapped.
Controlling the pests is challenging. Currently, the only sprays available work exclusively on the adults. There aren’t any registered chemicals for killing larvae. The best way to control the insect is to rotate to a non-legume crop, such as potatoes or small grains, for a year.
A fact sheet about Clover Root Curculio is available online on Utah State University’s website.