Now is the time to be on the lookout for insects and diseases than can destroy your garden
Just like people, plants get sick, too. Diseases cripple leaves and branches, and insects eat away at their bark and wood. Unchecked, these pests and infections can dispatch an otherwise healthy plant or tree the same way cancer or heart disease can kill a human.
While all pests and diseases worry the staff at the Delaware Department of Agriculture’s Division of Plant Industries it’s the invasive species -- those not native to Delaware -- that cause the most concern.
“An invasive species could be any sort of plant, animal or disease, but we’re primarily focused on those that are not native to a specific location,” noted Stephen Hauss, pest survey coordinator with the state’s agricultural department. “They tend to spread more aggressively than a native species would.”
Generally speaking, things are best when an area is a balanced ecosystem, which results when everything within the area exists in harmony with each other. This equilibrium can be set out of whack when a non-native plant, insect or animal comes onto the scene and pushes out other species.
The native flora and fauna have little defense against these invaders, Hauss said.
Some examples include an aggressive honeybee imported from Africa and now found in Texas, and the European starling, which was imported in 1890 and has spread throughout the United States. Both tend to wipe out native bees or birds, not only causing environmental harm but economic damage by affecting local plants and crops.
The Department of Agriculture is looking for Delawareans to help identify invasive plants, insects and animals, Hauss said.
“We think people have a role to play,” he said. “There are only so many of us working on this.”
They need the help, Hauss said, because there are only two pest control specialists to cover the state: himself and an assistant.
“Between us, we have only four eyes,” he said. “But if there are thousands of other people, it’s more likely these harmful pests will be found.”
‘They starve the tree’
One threat to Delaware trees is the emerald ash borer, a beetle found primarily in the Midwest and Northeast.
“It’s probably the most destructive tree pest we’ve found in the United States,” Hauss said. “We found it in New Castle County last year and we’re looking to see if it spreads to Kent County.”
Actually, it’s not the beetles themselves that cause the problem: it’s their young.
Adult ash borers lay eggs in the bark and the hatched larvae bore their way inside, feeding on the tissue directly under the bark. They grow fat and mature on the tree’s nutrients while the tree itself suffers.
“They basically starve the tree,” Hauss said.
Patient observers may be able to spot the insects, but a more telling sign is developing new buds, or epicormic sprouts, on the lower part of the tree. This takes place because the feeding larvae keep vital nutrients from getting to the higher parts, he said.
A 2010 study estimated the cost of potential damage caused by the ash borer would exceed $10.7 billion in 25 states over the next decade.
Another invasive pest, the Asian longhorn beetle, which is native to China and Korea, poses a threat to Delaware maple trees. Like the ash borer, their larvae cause most of the problem, leaving large holes in trees as they emerge. These holes weaken the tree, leaving it open to infection. Many infested maples die within a few years.
Getting rid of these pests also can prove expensive; trees must be sprayed with a chemical insecticide, or if the damage is severe, they have to be replaced.
A plant disease that’s becoming a concern is ramorum blight, or sudden oak death. This is a fungus-like growth that affects oaks and other trees, shrubs and ornamental plants. Depending on the species affected, the blight causes cankers that appear to be bleeding. The disease can be stopped from spreading if infected plants in nurseries are destroyed, or if mature trees in forests are cut down and burned.
Don’t let it go
In addition to Hauss and his assistant, the state also fields a two-person nursery inspection unit that looks mostly at commercial venues where plants are grown and sold. In 2015 these inspectors found a species of fire ant imported in a stock of tropical plants. This potential problem was fixed by eradicating the ants.
“We find them mostly in tropical plants that come into Delaware from the southern United States,” Hauss said. “We always check for them in garden centers and other businesses.”
Hauss and his team are asking Delawareans to help with spotting invasive insects and diseases.
“The number one thing is to learn about the most important invasive species, look for signs and symptoms while out in their gardens our walking their dogs,” he said.
Detailed information can be found on the hungrypests.com website, Hauss said.
“The biggest thing is to learn about these pests, be on the lookout for any signs or symptoms and take action,” he said. “There are things everyone can do to help.”
If in doubt, call a certified arborist or the Department of Agriculture, Hauss said. They’ll come out and see if there’s a problem.
“Don’t just let it go because the longer it goes, the bigger a problem it will be.”