More beetles damaging leaves, harming plants
COLUMBIA – A non-native insect is eating and destroying leaves all throughout mid-Missouri more than ever before.
The culprit is the Japanese beetle, which is originally from Japan. The first beetle found in the United States was located in New Jersey during the early 1900s. The insects feed on the leaves of various trees and flowering shrubs.
Ben Puttler is an assistant professor in MU’s Division of Plant Sciences. He said there are more Japanese beetles in Missouri today than ever before.
“It’s all over the state,” Puttler said. “In many areas, it’s doing quite a bit of damage.”
Puttler said that current time of the year is the most abundant period for Japanese beetles.
“It has one generation a year,” Puttler said. “They’ll come out the first week of June and the adults will be around until the end of August. The major portion if it is from June until July.”
Puttler said while Japanese beetles are spread throughout mid-Missouri, they prefer warmer environments and specific plants.
“There are preferred hosts like as roses,” Puttler said. “Linden trees too. Also apples and a lot of weeds, but where it affects the human population the most is in the trees and roses.”
He said a beetle first inhabits a plant, and then starts to feed on the plant’s highest leaves (where the temperature is warmest due to the sun) and work its way down to the lowest leaves.
“They skeletonize the leaves and then they reach a a point where they’ll just drop off,” Puttler said. “You’ll see all the leaves with holes in them, all over the ground.”
Puttler said that most plants should be fine, but also said harm done to a plant’s leaves over time could result in damaging the plant.
“If you get enough of the foliation over years, it can hurt the plant, but some of these will regrow leaves afterwards,” Puttler said. “But a plant can only tolerate so much damage, especially if it’s a combination of insult to injury. If you have a drought, that weakens the plant. This is sort of the insult to injury – it’s sort of a double dose of harm to the plant.”
Puttler said that many garden centers and hardware stores have over-the-counter insecticides to protect plants from Japanese beetles. He also said that most commercial products should be labeled to specifically protect against adult and larval Japanese beetles.