I have monitored colony collapse disorder (CCD) since it was first identified by entomologists over a quarter-century ago. CCD occurs when vast majorities of bees in any given colony – generally worker bees – die unexpectedly. Because queen bees need the nectar these workers provide to nurse new bees, ultimately the entire colony collapses.
Since its emergence and identification, CCD has remained a major threat to agriculture – no exaggeration. According to CNN science reporters, honeybees and wild bees are the most important pollinators 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 pollination of U.S. food crops by bees is estimated at $16 billion. Insect pollinators in general contribute $29 billion to U.S. farm income.
At least seven factors trigger CCD events, the two most major ones being Varroa mites and pesticide poisoning. Regarding the latter, I recall my involvement, as a field crops Extension agent, with the 1975 pesticide applicator certification pilot program in Otsego County – one of two New York counties chosen for that program. There I learned that the ULV (ultra-low volume) concentrations of the insecticide carbaryl (Sevin) were toxic to honeybees, according to the newly formed EPA. Evidently, honeybees mistook carbaryl crystals for pollen granules, taking them back to the hive to feed larvae what turned out to be their last meal. ULV formulations are sprayed by crop-dusting aircraft to minimize cargo weight.
CCD events are very visible, even to untrained observers. Less visible, but equally devastating – ecologically and economically – is the biological trauma taking place under our feet, or just at foot level.
Helping 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. This paper was published on Jan. 13, 2021.
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 the fundamental distinctions between the nAChRs of invertebrates and vertebrates, neonicotinoids are selectively more toxic to invertebrates, like insects (particularly honeybees).”
Note: “In microbiology, the phyllosphere is the total above-ground surface of a plant when viewed as habitat for microorganisms. A phyllosphere includes the total aerial (above-ground) surface of a plant, thus including 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.
Scientists state that the phyllosphere and soil are colonized by microbial communities (microbiota) which are of great importance in regulating the host’s and ecosystem’s functions. These microbial communities, including beneficial bacteria, are crucial in plant growth promotion, decomposition and health control, as well as in soil fertility, nitrogen fixation and organic matter production.
Quoting these researchers, “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 and affect bacterial succession. During the last decades, widespread application of chemical pesticides in agro-ecosystems has impacted many non-target species and their succession patterns. Pesticides can change interactions between plants and some bacteria, such as nitrogen-fixing rhizobacteria, which may lead to 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.”
In this study, workers combined efforts to assess effects of pesticides on the phyllosphere and soil bacterial community, specifically focusing on neonicotinoids. Neonic compounds are tiny molecules, highly soluble in water. In North America, neonics are extensively used as seed treatments to control a variety of foliar and soil early-season insect pests in corn, soybean, wheat and other important crops.
These treatments are typically applied preventively, without any information on the actual presence of targeted pests. As a result – according to Cornell researchers William J. Cox and Jerome H. Cherney – multiple studies indicate that neonics often have no significant beneficial impact on crop yield. Their evaluation was in 2011. A more recent study, published in 2020 by Quebec scientists G. Labrie et al., extensively evaluated yield variations in response to neonic seed treatment, with regards to the abundance and incidence of pest populations. Labrie reported that there is no significant difference in crop yield when pest pressure is low, which was the case in most of the sites 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 stomates. Water comes from xylem – plants’ main water 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 remaining pesticide persists in soil up to three years, depending on its active ingredient and soil properties.
In closing, let’s leave soil microbes and six-legged neonic victims behind, stressing these insecticides’ impacts on humans. A 2022 Chinese paper titled “Human exposure to neonicotinoids and the associated health risks: A review,” by Duo Zhang et al., emphasized that neonics have attracted growing concerns due to massive production, almost universal distributions and potential toxicity to non-targeted organisms. Thus, assessing human neonic exposure and the associated health risks is an urgent need.
Current assessments may underestimate human exposure to neonics. Zhang closed with “More evidences with larger sample and additional populations are needed to further demonstrate the relationship between NEOs’ (neonics’) internal exposure and health outcomes.”
This subject merits additional exposure.
Leave A Comment