by Bruce Bennett \u2022 As the days lengthen and the weather warms, newspapers and magazines are filled with articles and pictures of the newest plants coming into the retail marketplace and designs for sun and shade.\u00a0 By contrast, whenever my group of professional gardening colleagues get together for an alfresco cup of morning coffee and we discuss warming weather, we\u2019re usually discussing the latest warm weather waves of invasive insects that may begin chewing on those newest plants in the very near future.<\/p>\n
In North America, more than 3,400 non-native insect species are established (including, of course, the beneficial European honeybee). Fortunately, only about 10 percent of these non-natives are considered \u2018invasive\u2019, meaning they cause significant damage to native ecosystems and agricultural crops.\u00a0 Naturally, the Pacific Northwest is not immune to the winged beasties and we do our best to combat the culprits who already call the Pacific Northwest home as well as prepare for the hitch-hiking interlopers that are on their way here to chow-down on our juicy plants.\u00a0 \u00a0As many of these insect infestations are initially found by homeowners and gardeners during the summertime, let\u2019s use this month\u2019s column to update you about which terrors to watch for during the early summer weather.<\/p>\n
One of the newest invaders to Washington State is the Japanese Beetle<\/strong> (Popillia japonica<\/em>). They were first noticed in New Jersey around 1916.\u00a0 They have since become established in just about every state east of the Mississippi River and have been making their way to some of the western states.\u00a0 Their first Washington appearance was in Sunnyside in 2021 and, this year, reached Yakima.\u00a0 The Cascade Mountains will pose a barrier to them, but, as with the other insects mentioned on this list, it\u2019s only a matter of time until they hitchhike a ride on a commercial vehicle or RV and reach the western part of the state.\u00a0 They are most noticeable in their adult forms as fingernail-sized beetles with glistening green and copper colors to their wing shields.\u00a0 They look like bronze scarabs which could easily serve as jewelry for an Egyptian costume. But ours will leave skeletonized leaves in their wakes; LOTS of skeletonized leaves.\u00a0 Why is it always the pretty ones that do the most damage?<\/p>\n In winter and spring, the beetle larvae attack the roots of plants, particularly the roots of grasses.\u00a0 Roses are a particular delicacy for them.\u00a0 These insects were, and still are, the scourge of my Connecticut garden.\u00a0 Plants already stressed by our hotter summers may not survive with the added pressure of infestations from these guys.\u00a0 They have been a problem on the east coast and in the mid-west for decades.\u00a0 We haven\u2019t seen them in Washington before, but, with our new warmer temperatures, they have recently been found in Idaho, at a few sites south of Portland and near Yakima. So, it\u2019s only a matter of time, I fear.<\/p>\n Depending on their life stage, Japanese Beetles can be controlled in a few ways.\u00a0 With small populations of adult insects, hand-picking, pheromone traps, insecticidal soaps and Neem Oil can be effective in June \u2013 September.\u00a0 The beetles lay their eggs in early summer, so, in July \u2013 September, using HB (Heterorhabditis bacteriophora) beneficial nematodes, the root-feeding grubs can be located and killed.\u00a0\u00a0 Other options for grubs are BT (Bacillus thuringiensis) which is, to a grub, a stomach poison,and Milky Spoor (Bacillus papillae), a bacterium that interrupts the insects\u2019 blood system.<\/p>\n The Spongy <\/strong>M<\/strong>oth<\/strong>, AKA, Gypsy Moth, (Lymantria dispar) have<\/em> been in-country for many years.\u00a0 Originally native to Eurasia, and unlike most invasive insect pests, this fuzzy beastie did not stow away on some cargo ship and escape to fertile New England forests.\u00a0 It was actually imported to Boston in 1868 by several entrepreneurs who were interested in developing a silk industry in North America.\u00a0 Instead of serving as the foundation of a new business venture, the Spongy Moth has become one of the worst American forest pest insects. It devours the leaves of more than 500 different species of trees and shrubs and causes enormous damage to the environment and the economy.\u00a0 Following the banning of DDT, the Spongy Moth reached some of\u00a0its greatest population numbers,\u00a0culminating in my home state of Connecticut with the\u00a0extensive outbreaks of 1971 and 1981.\u00a0Those\u00a0outbreaks are legendary in both forestry and arboricultural circles.\u00a0A wide range of tree species were stripped\u00a0clean and the woods were turned\u00a0bare due to the\u00a0extensive feeding of these insects.\u00a0 The caterpillars covered houses, roads, and sidewalks.\u00a0They were\u00a0even blamed for traffic accidents, as people would skid on their massed numbers in the roadways.<\/p>\n The Spongy Moth appears in Washington every now and then after hitching a ride on some unsuspecting vehicle, RV or ship.\u00a0 The Department of Natural Resources is currently spraying newly found infestations in different parts of the State.\u00a0 While municipalities continually check for infestations, gardeners and homeowners can also do their part.\u00a0 Spongy moth caterpillars can be controlled with applications of the biological insecticide, Bacillus thuringiensis kurstaki (Btk). It must be applied to the foliage of the plants the caterpillars are feeding upon and will control them while they are still small and becoming less effective as they grow larger.\u00a0 This bacterial insecticide kills caterpillars that eat it within a week of its application by damaging the insect\u2019s digestive tract. Like Btk, certain foliar spray products can pose fewer risks to other insects. This group includes insecticidal soaps, horticultural oils, pyrethrins, and spinosad. The soaps, oils, and pyrethrins only kill when sprayed directly onto spongy moth caterpillars and are very short-lived. While they can be a good option for smaller plants, these ingredients are not a good option for larger trees.<\/p>\n While more commonly known as the Giant Asian Hornet<\/strong> (Vespa mandarinia), this publicized \u2018Murder Hornet\u2019 (cue the music from \u2018Jaws\u2019) ranks as the world\u2019s largest hornet and can grow to two inches long, with a wingspan of some three inches.\u00a0 These hornets need meat to feed their young and they are direct about getting it.\u00a0 Among protein sources, they prefer honeybees.\u00a0 A single Murder Hornets can decimate a honeybee hive in a day. They do so by biting the heads off the much smaller honeybees.\u00a0 Unlike honeybees, Murder Hornets can sting multiple times and have venom several times more potent than local bees and wasps.\u00a0 Fortunately, they are not terribly aggressive around humans unless their nest seems threatened.\u00a0 They arrived in Washington in 2020 and, thus far, they have only been sited and exterminated north of us in Bellingham, Blaine and British Columbia.\u00a0 This insect, with its half-inch stinger, is not something gardeners should fool around with.\u00a0 The best eradication advice is to contact the Washington State Department of Agriculture or the Washington Invasive Species Council and let the pros handle the problem.<\/p>\n The Brown Marmorated Stink Bug<\/strong> (<\/em>Halyomorpha halys)<\/em> is another native of East Asia and was first introduced in Allentown, PA in 1998, possibly having arrived in a shipping crate. It arrived in Washington in 2010.\u00a0 These half-inch long suckers will attack a large variety of plants, including many fruits and vegetables. It leaves small necrotic patches on any plant it eats, rendering produce inedible. As a homeowner, you will likely notice an invasion before anyone else, because this stink bug initially will attack vegetable gardens and landscape plants. The damage they do to crops and landscapes, as well as the efforts to control them are costly.\u00a0 These beasties will then spend the winter in homes and other structures.\u00a0 Look for them on the south side of your homes as the weather cools.\u00a0 Presently, there are no viable strategies for control of the Brown Marmorated Stink Bug, although insecticidal soaps and neem oil seem to be effective against stink bugs, especially early in the season.\u00a0 Remember to read and follow the directions and safety precautions on the labels<\/strong>.<\/strong><\/p>\n It is homeowners, campers and hikers who are usually the first to notice these new invasive insects.\u00a0 Trees, lights and standing water are great places to look for insects.\u00a0 Checking yards regularly plays a critical role in protecting Washington\u2019s unique environment from the pests.\u00a0 Citizens can help spot infestations when they are easy to handle. This not only saves time and money, but limits the damage these beasties can cause to our gardens, local and national parks and farms and forests.\u00a0 Residents who find a suspected invasive insect are encouraged to take a picture and report it via the Washington Invasive Species Council<\/u> or the Washington Department of Agriculture<\/u>.\u00a0 Be aware of what organisms, beyond the plants, are living in your little pieces of verdant heaven.<\/p>\n Further Reading<\/strong>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0<\/em><\/p>\n Washington Invasive Species Council Web Page, https:\/\/invasivespecies.wa.gov\/<\/em><\/a><\/p>\n