Colony collapse disorder (CCD) is something I’ve been monitoring since it was first identified by entomologists over two decades ago. CCD occurs when the vast majority of bees in any given colony – generally worker bees – die unexpectedly. Because the queen bee needs the nectar provided by these workers to nurse new bees, ultimately the entire colony collapses.

Crop Comments: How an Insecticide Class Harms Soil BiologySince its emergence and identification, CCD has remained a major threat to most of agriculture – no exaggeration. Entomologists say that honeybees and wild bees are the most important pollinators of many of our fruits and vegetables. Of 100 crop species that provide 90% of our global food supply, 71 are bee pollinated.

The dollar value of bee pollination of food crops in the U.S. is estimated at over $20 billion; insect pollinators contribute over $30 billion to U.S. farm income. The two most important factors triggering CCD are Varroa mites and pesticide poisonings.

Regarding the latter, I was involved (as a field crops Extension agent) with the pesticide applicator certification pilot program in 1975 in Otsego County. I learned that the ULV (ultra-low volume) concentrations of the insecticide carbaryl (Sevin) were determined, by the newly formed EPA, to be toxic to honeybees.

Honeybees mistook carbaryl crystals from these ULV doses for pollen granules, taking them back to the hive to feed their larvae what ended up being their last meal. ULV formulations are sprayed by crop-dusting aircraft to minimize cargo weight. CCD mishaps are very visible. Less visible, but equally devastating – ecologically as well as economically – are biological trauma taking place under our feet, or just at foot level. To help me investigate such trauma, a former fellow county ag agent forwarded me a scientific paper titled “Neonicotinoid Seed Treatments Have Significant Non-Target Effects on Phyllosphere and Soil Bacterial Communities” by Mona Parizadeh et al.

Neonicotinoids (neonics) are “a family of systemic and neuro-active insecticides, chemically similar to nicotine, introduced in the late 1980s. Like nicotine, they interrupt neural transmission in the nervous system by binding to the nicotinic acetylcholine receptors (nAChRs). Because of fundamental distinctions between the nAChRs of invertebrates and vertebrates, neonicotinoids are selectively more toxic to invertebrates, like insects – particularly honeybees.”

As for the phyllosphere: “In microbiology, the phyllosphere is the total above-ground surface of a plant when viewed as a habitat for microorganisms. The phyllosphere includes … the surface of the stem, flowers and fruit, but most particularly the leaf surfaces.”

The rhizosphere is the underground environment directly contacting the plant’s root system. The phyllosphere and soil are colonized by microbial communities (microbiota), which are of great importance in regulating host and ecosystem functions. These microbiotas, including beneficial bacteria, play a crucial role in plant growth promotion, decomposition and health control, as well as in soil fertility, nitrogen fixation and organic matter production.

Quoting Parizadeh: “Environmental disturbances – such as cultivation methods, drought, climate change and pesticide treatments – can also alter the bacterial community structure and composition. If a disturbance is persistent, it can cause long-term changes in bacterial community structure, affecting bacterial succession. During the last decades, the widespread application of chemical pesticides in agro-ecosystems has influenced many non-target species and their succession patterns. Pesticides can change the interaction between plants and some bacteria, such as nitrogen-fixing rhizobacteria, which may lead to the inhibition of nitrogen fixation. They can also (adversely) affect soil fertility and quality by impacting soil bacterial diversity and function and altering their nitrification, denitrification and mineralization of organic matter.”

According to Daniel Rath, Ph.D., representing the National Resources Defense Council, “Neonics’ negative impacts are particularly pronounced on soil invertebrates, especially soil predators – this includes insects, nematodes and protists – higher up in the food web as well as decomposers such as springtails and earthworms.” He said organisms lower on the food chain can also be affected.

After neonic application, scientists observe declines in soil bacteria critical for plant growth and improving soil fertility. They also observe increases in other bacterial populations, as these microbes worked to break down neonics. Neonicotinoid application can impair microbial functioning – including breakdown of plant residues and provision of nitrogen for crop growth.

In this study, workers combined efforts to assess the effects of pesticides on the phyllosphere and soil bacterial community, focusing on a class of the most widely used insecticide pesticides – neonics, which are tiny molecules, highly soluble in water. In North America, neonics have mostly been used as seed treatments to control a variety of foliar and soil early-season insect pests in corn, soybean, wheat and others. Such treatments are most widely applied preventively, with no information on the actual presence of targeted pests. Thus, according to Cornell researchers William J. Cox and Jerome H. Cherney, multiple peer-reviewed studies indicate that neonics often have no significant beneficial impact on crop yield.

At the same time these two Cornell scientists were conducting their research, Quebec scientists (G. Labrie et al.)  evaluated yield variations in response to neonic seed treatment with regards to the abundance and incidence of pest populations. That Canadian study reported that there is no significant difference in crop yield when pest pressure is low, which was the case in most of the sites being studied.

Given neonics’ systemic nature, plants take them up from the seed coating, translocating them to different tissues and products, including nectar, guttation and pollen. (Guttation is a process in which water seeps out at the tips or edges of a plant’s leaves instead of the stomates. The water comes from the plant’s moisture transport tissue.)

Neonics may remain active for 20 to 30 days in soybean and corn and up to 200 days in winter wheat. Plants only absorb about 20% of the neonic seed coating. The rest of the pesticide persists in soil for up to three years, depending on its active ingredient and soil properties.