Garden pests, diseases expected on Long Island in 2018
A semi-closeup of impatiens plants just starting to yellow and curl their leaves downwards. There is sporulation of downy mildew on the undersurface of the leaves but it doesn't show in the picture. Credit: M. Daughtrey/Cornell University
Insects and diseases have plagued plants (and their growers) since the beginning of time, and this year there are a few new miscreants in town. As always, it’s important to keep a close eye out for the new ones, along with the usual suspects, and take steps to protect yourself and your family, pets and garden.
Threats to humans
Illnesses transmitted to humans from mosquitoes, ticks and fleas have tripled in the United States over the past 13 years, and nine new mosquito- and tick-borne pathogens have been discovered or introduced here over the same period, according to the Centers for Disease Control and Prevention. In addition to Lyme disease, infected insects can transmit pathogens that cause Zika, West Nile, chikungunya and other diseases.
Take cultural measures
Instead of spraying your yard against mosquitoes, discourage them from setting up residence in the first place. Old tires, children’s play sets, toys, wading pools, flowerpot saucers and even inverted trash can lids collect rainwater where mosquitoes (and bacteria) like to breed. Keep ahead of them by emptying these items regularly and storing them where they won’t collect water.
Before heading indoors from gardening, hiking or camping in tick-infested areas — even if you’ve applied a pesticide such as DEET — run a sticky lint roller over your clothing (and pets!). You might be surprised to find it’s picked up ticks that weren’t visible. Full-body searches (for humans and furry friends) still should be performed, but this step may reduce the number of ticks that hitchhike into your home on your clothing or pets.
Ticks are drawn to dark moist areas, so the CDC advises inspecting underarms, between toes, in and around ears, inside the belly button, in and around hair, the back of the knees, around the waist and between the legs. When checking pets, the American Kennel Club recommends paying close attention to the areas between toes, inside ears, under the collar, around eyelids, under the tail and in the genital region.
Clean out birdbaths
Providing fresh water is good for birds — and bad for mosquitoes. But simply changing water isn’t enough. Birdbaths should be cleaned and disinfected at least twice a week because algae also thrives in stagnant water, and fallen leaves, feces and debris introduce harmful germs. Here’s how:
Drain the basin completely and rinse it with as strong a stream of hose water as the birdbath’s construction will tolerate. Next, fill the basin with nine parts water and one part chlorine bleach to a level above the highest stain. Let it sit for 15 minutes, but remain nearby to prevent birds from visiting while the bath contains bleach. If you must leave it unattended as it soaks, cover the bath with a wooden board or secured plastic trash bag.
Drain, taking care to keep the water away from plants, grass and birdseed. If that’s not possible, pour water into a bucket and dispose of it elsewhere. Rinse for a minute or two, until you no longer detect the scent of bleach. Allow to dry in the sun for two hours, then refill the bath basin nearly to the top. Consider adding a natural enzyme and beneficial bacteria product to help keep water clean and clear longer. Note: Bleach is no more harmful to birds than it is to humans; just be sure to rinse well and allow the bath to air dry in the sunlight for two full hours to allow any residue to dissipate.
Some impatiens still off-limits
A semi-closeup of impatiens plants just starting to yellow and curl their leaves downwards. There is sporulation of downy mildew on the undersurface of the leaves but it doesn't show in the picture. Credit: M. Daughtrey/Cornell University
It’s important gardeners continue to avoid planting Impatiens walleriana. Once the local darling of shady summer gardens and containers, the plants have fallen victim in recent years to the devastating downy mildew disease.
“Last summer, I saw this disease all over the North Fork,” said Margery Daughtrey, a plant pathologist and senior extension associate at Cornell University’s Long Island Horticultural Research & Extension Center in Riverhead. “People must have thought it was safe [to plant impatiens] again, but it appeared that the oospores left in the soil from earlier outbreaks came back to haunt the plants in what was a wetter and cooler-than-usual summer.”
New Guinea impatiens are not affected by the disease and are “perfectly safe to plant and will do well, even in light shade,” she said. “And begonias are great alternatives in your most shady spots.”
Late blight of tomatoes, downy mildew loom
Keep an eye out for late blight of tomatoes, which was discovered in Riverhead late last August after a two-year absence. Credit: Meg McGrath
After a two-year absence, late blight of tomatoes was discovered in the Riverhead area last August, according to plant pathologist Margaret McGrath, so she’s asking residents to keep an eye out for it this season.
“It’s easy for everyone to get complacent and forget about it, but [it’s] really important for gardeners to report if they see it, as this is a ‘community disease,’ ” McGrath said.
The first sign of downy mildew of basil may be yellowing that appears on the upper side of a leaf. Credit: Cornell University
Tracing the source of outbreaks is key to reducing future outbreaks, said McGrath, who also is tracking occurrences of downy mildew of basil and downy mildew of cucumber and other cucurbits. If you suspect your plants are affected by one of the downy mildews or late blight, compare its symptoms to those pictured at blogs.cornell.edu/livegpath/gallery. If you see a match, check one of the following web pages to see whether the disease has been reported in your area: usablight.org for late blight, cdm.ipmpipe.org for cucurbit downy mildew, and bit.ly/2L94hgw for basil downy mildew. If not, McGrath asks that you send an email reporting your findings, including photos if possible, to mtm3@cornell.edu.
Monitor your trees
A spotted lanternfly adult at rest with its colorful wings folded up. Credit: Pennsylvania Department of Agriculture
The spotted lanternfly, first discovered in the United States in Pennsylvania in 2014, is posing a serious threat to New York’s agricultural crops and forest trees this year, and the state Department of Environmental Conservation is asking residents to report any sightings.
Emerging as black wingless nymphs with white dots and developing into 1-inch-by-half-inch multicolored adults with large wings, the bug’s preferred host is primarily the invasive tree Ailanthus altissima, which goes by the common name of tree of heaven. Adults also lay their eggs on black walnut and hops plants, as well as on play sets, vehicles, lawnmowers, yard waste and firewood.
Nymphs feed on several varieties of trees, including tree of heaven, apple, almond, cherry, oak, pine, poplar and sycamore, sucking sap from leaves to weaken trees and excreting a sticky substance called honeydew, which attracts harmful insects and upon which sooty mold grows.
If you have tree of heaven growing on your property, officials are asking that you place a sticky survey band around its trunk and inspect for evidence of lanternflies every two weeks. Report your findings to the New York Division of Plant Industry by emailing plants@agriculture.ny.gov or calling 800-554-4501.
In addition, the May rains encouraged the spread of spores that cause colorful rust infections, so be on the lookout for pear trellis rust on pear, Japanese apple rust on crabapple, quince rust on amelanchier, crabapple and hawthorne, and cedar-apple rust, Daughtrey warns.
Dan Gilrein, a Cornell University entomologist based in Riverhead, cautions that gypsy moth infestations, “although much diminished from last year,” are still evident, as is the presence of eastern tent caterpillars, southern pine beetles (“serious in some areas, like east of Sag Harbor”) emerald ash borer (“now found in western Long Island, in addition to Queens, Prospect Park and also on Staten Island”), oak wilt (“a disease with an insect vector”) and twolined chestnut borer (“populations probably will be high this year due to oaks weakened by various issues, especially gypsy moth”).
Gilrein also warns we could see outbreaks of spruce spider mite and boxwood leafminer.
Start small to control pests
Integrated pest management, or IPM, is the practice of using the most-benign control possible as a first defense against weeds and harmful insects — and escalating only when necessary. The premise is that there is a certain pest presence that can and should be considered tolerable. But because common sense should prevail, it’s up to the individual to determine a risk-benefit balance, consider what an acceptable threshold should be and act accordingly.
For example, if there are a few ants in your house, set out traps. If there is a literal ant invasion, and traps aren’t proving effective, you might have a case to escalate to pesticide spray.
The only exception I would make is for roaches. There isn’t any level that’s considered tolerable: Where there is one, there are many, and they do not respond to gentle measures, unfortunately.
Similarly, we should pull up weeds by their roots instead of dousing them with herbicides, even organic ones, which are not completely without risk. Consider buying a box of ladybird beetles and set them free in the garden to keep aphids in check. And if you notice Japanese beetles on your plants, pick them off by hand and drop them in a bucketful of soapy water.
Chemical controls cost money and expose people, birds, wildlife and plants to potentially harmful ingredients, and they often kill beneficial insects, such as bees, butterflies and ladybugs, that pollinate our plants or prey upon harmful insects. Pesticides should be used only as a last resort or in the case of severe infestation. When it is absolutely necessary, start with the least-toxic product available.
