The amount of food that farmers produced is very important as the human population increases. Unfortunately, other organisms want to consume these crops, resulting in a high loss in food production. This is why pesticides are used in agriculture not only to control weeds but manage insect infestation and diseases as well. However, traditional pesticides degrade quickly and don’t work to certain pests. This results in harmful effects on other insects, environmental contamination, and substantial wastage of pest control products.
The metal-organic frameworks (MOFs)
So, a team of chemists and chemical engineers from the University of Bath in England have developed a molecular sponge called metal-organic frameworks (MOFs) that soaks up the ant pheromones and releases them gradually to attract pests to an insecticide trap.
Their study, which appeared in American research platform Science Daily, shows that baits can be placed in certain areas of farms rather than spraying the whole crop with pesticides. According to the World Health Organization, pesticides are chemicals so they may induce adverse health effects on humans, including effects on immune, nervous, or reproduction systems. This is why pesticides have to be tested for all possible health effects before they can be authorized for use. The results of said tests should also be analyzed by experts to determine any risks to humans.
Our World in Data shows the countries with the highest total pesticide use measured in tonnes per year. This includes China (1.77 million tonnes in 2017), Brazil (377,176t), United States (407,779t), Argentina (196,009), Ukraine (78,201t), and Canada (90,839t). Meanwhile, the countries that used pesticides the least include Comoros, Congo, and Pakistan (all <1t). Tanzania (1t), Saint Kitts and Nevis (2t), Timor (2t), and Iceland (3t) are also on the list.
Simulating the movement of the pheromone molecule
Aside from designing the MOFs, scientists at the Universities of Bath and Sussex also utilize computational modeling to simulate the movement of the ant pheromone molecule inside the MOFs pores to determine which structures would give the optimum speed and capacity of release. By changing the chemical groups within the basic framework structure, the team found that it is possible to adjust the speed of the release of ant pheromones. This way, the chemicals can be released not just in days but a period of several months.
The team even conducted field trials in a eucalyptus plantation in Brazil and it shows that the pheromone-loaded MOFs can attract the ants into the trap. Trail pheromones are found in many social insects that forage on the ground, including ants and termites. Few non-social insects likewise use them. Trail pheromones are used by insects for marking their pathways to resources.
Lead author Professor Andrew Burrows, who is also the Head of the Department of Chemistry at the University of bath and a Professor of Inorganic Chemistry, explained that insect pheromones have been previously used for attracting pests. However, the trouble is that they are quite volatile, meaning their effects don’t last long. With their MOFs molecular sponge, though, the ant pheromones can be stored in the pores and then released slowly for a longer period.
“The insects respond normally to it,” he said, referring to the pheromones released from the metal-organic frameworks. The authors believe that their work can be used in plantations of high-value crops in small areas. It could likewise lessen the number of pesticides being sprayed on a crop. Currently, their team is also looking at other insect messenger chemicals. An example of this would be those used to control the fruit-piercing moths.
In the UK, the amount of agricultural production harvested per unit of the land area varies, depending on the types of crops. Our World in Data shows that the country’s crop yields for potatoes in 2018 amounted to 35.91 tons per hectare, for wheat 7.75t, barley 5.72t, and peas 2.80t. According to Crop Science UK, pea moths are widely distributed throughout the United Kingdom and the damage they create has a greater impact on the quality of crop rather than yield. This is especially true when peas are being grown for seed and human consumption.
Reducing human and environmental health risks when using pesticides
A study that appeared in the February 2020 issue of The Lancet Planetary Health classified 659 pesticides by chronic and acute risks to human health, such as carcinogenic and respiratory effects, and environmental risks, including atmospheric ozone depletion, the risk to marine life, the risk to pollinators and wildlife, and biomagnification.
Authors Paul C. Jepson Ph.D. from the Integrated Plant Protection Center of the Oregon State University and the team have created a stand-alone guideline for the selection of lower-risk pesticides. They also suggest the use of integrated pest management or IPM, which offers a framework for managing environmental, health, and economic risks while reducing undue outcomes for crop production.
Over the past years, there has also been an increase in the development of pesticides that target only a certain spectrum of pests. As a result, the targeted pests either disperse to a new environment or adapt to the novel conditions. This is why the US Environmental Protection Agency suggests that farmers should follow all requirements on pesticide product labels. They should also keep their pesticides out of storm gutters and drains for safety. Pesticides with groundwater contamination potential will include a statement on its label, which reads “This chemical has properties and characteristics associated with chemicals detected in groundwater.”
Another problem in using pesticides is resistance or the heritable change in the sensitivity of the pest population reflected in the repeated failure of the pesticide to achieve the expected level of control. Although resistant pests are rare in the normal population, the indiscriminate use of chemicals could offer resistant individuals a selective advantage and they can continue to multiply in the absence of their competition. Eventually, they end up as the dominant portion of their population for over generations.
Despite a clear increase in pesticide use globally, crop losses have not yet significantly decreased in the last years. The team’s metal-organic frameworks are a potential crop protection measure that may enable farmers in the future to increase their crop productivity without relying too much on chemical pesticides that may be doing more damage than we think.