As if contributing to the magnitude of bee and butterfly losses wasn’t reason enough to greatly curb or cease use of neonicotinoid pesticides, recent news piles on added concerns.
Bees & Pollinators
Let’s start with the bees. Some may assume getting overly concerned about bee losses is silly, because their numbers inflate significantly each spring once the queens lay new eggs. Yes, like most insects, bees are highly prolific. A queen can lay up to 2,000 eggs a day. However, continuance of each colony depends on the availability of healthy, viable sperm. However, it’s not a renewable resource like it is with so many other kinds of creatures. A queen bee collects all the sperm she will use throughout her life in a single mating spree upon reaching maturity.
Queen cells are specially capped in the hive. (Shawn Caza, CC by 3.0)
A Swiss study released this summer found that contact with neonicotinoid pesticides greatly reduces the virility of male bees. Published in The Royal Society Biological Sciences, the scientists report that the drones produced an average of 39% nonviable sperm, and an additional 8-10% of their sperm were dead.
Unfertilized bee eggs are always drones. The queen only fertilizes eggs laid in queen cells. If up to half of the sperm a virgin queen collects to supply her reproductive efforts for 2-7 years are blanks, the odds on egg fertilization are a crap shoot. If no new queens are born, the result is colony extinction. An all male culture is the end of the line.
To make matters worse, the University of Bern team involved in this study sees clear correlations to other Northern Hemisphere pollinator losses. Yes, butterflies, and they state that this discovery calls for study of neonictotinoid effects on butterfly sperm.
Skyrocketing Use
One of the biggest problems/perks of neonicotinoid pesticides is that they’re non-selective. But it’s made them super profitable, and the most widely used insecticides on the market. A handful of chemicals are capable of eradicating a wide variety of insects we humans determine as pests. They kill fleas on pets, termites under your house, whatever’s eating your daisies, and all manner of food crop pests.
These pesticides are similar to nicotine in chemical structure. They’ve been around since the 1990s, but use of this class of insecticides abruptly skyrocketed in about 2003, steadily soaring through today. This increase is mostly due to coating crop seed, namely corn and soy. It’s almost impossible to find non-organic corn seed without this pesticide coating, for the home garden and your farm. With soybeans, it’s on about 40% of seed sold. And the amount in use on lawns and in home gardens or other ornamental plant settings is minimal compared neonic crop applications.
This comes from a paper published by Pennsylvania State University last year in the journal, Environmental Science & Technology. Naturally, it’s pay per view, but the summary reports poor U.S. documentation on the use of neonicotinoids. And relates the discovery that the seed coatings aren’t included in the national tallies of pesticides used on crops. The graph showing real use escalation is sure to make eyebrows rise.
“Adoption of neonicotinoid insecticides by seed companies and farmers has been very rapid and does not appear to relate well to a corresponding risk from insect pests,” said John Tooker, associate professor of entomology. “This pattern suggests that neonicotinoids are often being used as an ‘insurance policy’ against uncertain insect attack, rather than in response to a documented pest threat.” — Science Daily
Plant Pest Predators
Slug control in crops already a problem. Neonics decrease their natural enemies (Virgina Cooperative Extension)
In 2014, Tooker’s entomology team revealed that neonic seed coatings have affected the balance in soil-dwelling creatures. Lab and field research discovered that the treated seeds were killing ground beetles that feed on slugs. The pesticide allowed crop-damaging slugs to survive while rendering the beetles’ food source toxic. This university study found the pesticide impaired or killed 60% of the beetles through secondary poisoning.
The journal PeerJ published the latest Penn State entomology research paper on neonicotinoids this week. Once again, Tooker and his team focused on the enemies of crop pests. They analyzed field studies done in North America and Europe testing effects of neonic seed coatings on predatory insects. The results? This pesticide is no less damaging to non-target species than the broadcast application of pyrethroids. They found the seed coatings are causing 10-20% predatory insect losses.
The solution? Tooker recommends controlling crop pests with IPM. Integrated pest management already has substantial research supporting its value in agriculture.
The Mite Explosion
Imidacloprid pesticides reduce plant pest resistance allowing pests like spider mites to skyrocket in population.(GrowGreenGuru screen capture)
Thousands of trees in New York City were sprayed with neonicotinoid pesticides to eradicate Asian long-horned beetles and emerald ash borer in 2005. They did succeed in saving the trees in Central Park from certain death. However, a population explosion of red spider mites erupted causing lots of leaf loss. This led to years of research for Ada Szczepaniec, an agricultural entomologist at Texas A&M University.
By 2011 she found that the reason behind the sudden spider mite multiplication stemmed from feeding on neonic treated elm leaves. The chemical coated leaves produced a 40% offspring increase over mites that fed on untreated leaves. Next she investigated if similar results were showing up in crops. Yes, the same thing was happening in corn, tomatoes, and cotton. But why?
Canceling Pest Resistance
Solving that puzzle took years, but Ada presented her findings at the entomology congress in Orlando this fall. The culprit? Alteration of more than 600 genes in soybeans treated with the neonicotinoid pesticide, imidacloprid. It changes the production of cells walls, reducing the pest resistance hormones. She’s not alone connecting the extreme population spike to the pesticide. There are other studies reporting neonics causing spider mite outbreaks in apples, roses, and other plants or crops.
This mite explosion info comes from a recent Newsweek article, but the reporter goes on in covering further problems with neonics. Including how they’re known to be harmful to aquatic life. Purdue University finds that over 90% of the neonic seed coatings join crop runoff. It’s highly soluble stuff too. So, its no surprise that many rivers test positive for contamination in excess of safe limits. In 2014, the EPA found little to no benefit from soy seed coatings. So, then why cover 40% of soy seeds with the stuff? Maybe it’s sales quota insurance.
Imidacloprid, by the way, is the most widely used insecticide in the world. But it does have many more uses than plant protection in farming, gardening, and landscaping. Still, is it worth using to get rid of whatever pest you’ve currently got only to have highly destructive spider mites move in? They’re one of the hardest of all common plant pests to eradicate.