As Spring merges into summer, our gaze turns to our lawns, and we are tempted to envision green carpets and lawnmowers… and poisons. Craneflies, those delicate beauties we call “mosquito hawks,” because they look like giant mosquitoes, even though their only purpose and desire, not unlike other unnamed creatures, is to mate and lay eggs, have arrived. Craneflies neither bite us nor eat mosquitoes. So why do we reach for Raid® or the swatter, instead of marvel at the gossamer wings and the delicate body lightly dancing around?
Aside from their fly-ness, the other reason people kill Craneflies is because their eggs hatch into voracious maggots whose thick skins have earned them the nickname leatherjacket. Leatherjackets eat the roots of grasses and other plants, and so are blamed, wrongly, for lawn scourges. However, extensive surveys demonstrate that even unhealthy lawns tolerate leatherjacket infestations of up to 10-25 maggots per square foot, a concentration rarely found in the Pacific Northwest.
The lawns get help
Those bald-faced yellow jackets that build those magnificent paper nests in trees, under eaves, on cliffs and in shrubs (not the inground yellow jackets) seek out craneflies hiding in the grass, decapitate and dismember them, and transport their bodies back to their nests. Think of it as Yellow Jackets vs Leather Jackets. Birds like starlings, beetles, and beneficial roundworms like Steinerema, dine on the fat, juicy leatherjackets.
Insecticide ads scream flies! and attack them with prohibition-era cartoon G-insects (see refs), but never talk about the benefits to the soil from burrowing critters that feed not just on your grasses and plants, but on a variety of floral roots, aerating and fertilizing the soil.
In those Washington State EPA surveys of leatherjackets and lawns, analysts concluded that the real cost to consumers was the millions spent on insecticides, not only pointlessly with respect to their lawn problems, but also with respect to… chemical trespass!
Sadly, homeowners are tempted by advertisers to kill craneflies with various insecticides like Raid®. RAID® and similar products, contain pyrethrins, advertised as safe derivatives of Chrysanthemum flowers. However, pyrethrins are in fact neurotoxins that can also affect the endocrine and reproductive system of animals including humans, may cause cancer, and are highly toxic to fish, aquatic invertebrates and bees. Because they bind to soil they can migrate into our river, and if not exposed to sunlight or moisture, can persist from 60-150 days.
Healthy lawns and gardens rarely require any chemical pesticides or insecticides, which poison non-target organisms that normally nourish our pollinators, like bees, butterflies, ladybugs, and a host of other critters which feed on insect pests,and some of whose larvae feed on leatherjackets and other root-eating grubs.
For example, green lacewing (Chrysoperla carnea) larvae are generalist predators, and attack eggs and soft-bodied insects such as aphids, spider mites, whiteflies and thrips among others. Adults feed on nectar, pollen and honeydew. When provided with these, the lacewing adults will live longer and lay more eggs (Rincon-Vitova Insectaries 2005).
Regrettably, adult lacewings exposed to a familiar poison, imidacloprid®, a neo-nicitinoid (see Ortho Tree & Shrub Insect Control® below), were poisoned when ingesting plant nectar and pollen from dosed plants. Here’s why.
The neo-nicotinoids comprise another class of poisons that should never be used. These chemicals, derived from nicotine, disrupt the nervous system of all living things. They are systemic poisons, meaning they “…spread through a plant’s vascular system and remain active for extended periods of time, accumulate from year to year, especially in perennial plants.”
A review of the neo-nicotinoids by The Xerces Society cited extremely high non-agricultural imidacloprid levels in rhododendron blossoms six months and in cherry trees more than one year after dosing. Similar levels have been found in maples, apple and eucalyptus trees.
The American Bird Conservancy released the following warning: “The environmental persistence of the neo-nicotinoids, their propensity for runoff and for groundwater infiltration, and their cumulative and largely irreversible mode of action in invertebrates (e.g., leatherbacks, earthworms) raise environmental concerns that go well beyond bees…”
These chemicals are so dangerous that the European Union has just banned them because of their effects on pollinators, over the threats of the chemical-ag industry, which claimed, without irony, that banning these pollinator-killers will reduce crop yields. (They meant profits).
“For homeowner use products, for backyard plants, the amount of neo-nicotinoids used is like 40 times greater than anything allowable in agricultural systems,” said entomologist James Frazier of Penn State University, prompting one expert to caution: “I don't think anybody should be using these things in their backyards.”
Check the label and pass up anything with imidacloprid, acetamiprid, dinotedfuran, clothianidin, thiacloprid, or thiamethoxam in the ingredients. Flea poisons in Advantage® and Frontline® are also neo-nicotinoids (fleas have become resistant to these — they are better at beating the nicotine addiction than we are). Knowing all of this, it is irrational and dangerous to spray trees and shrubs with commonly marketed products like Ortho Tree & Shrub Insect Control®, which contains 2.5% imidacloprid, and “inert ingredients” which can also be toxic.
Store-bought insecticides like Orange Guard®, which are advertised as safe and natural, are mostly “inert ingredients” and expensive, so here is a truly safe and cheap home-made recipe that is effective against many garden pests, including aphids:
Mash a head of garlic with one teaspoon of cayenne pepper and dissolve in a quart of water with one tablespoon of Dr. Bonner’s liquid soap. Refrigerated, it lasts for three weeks and costs little. Safer® brand products are also generally safe and reliable.