HonorChemistry 2017: Bio- Pesticide

Pesticide are toxic substances that are intentionally released into the environment to kill or control the population of a certain animals or plants that are classified as a pest. Some of the common pesticide types include herbicides which is use to kill weed, insecticides which is use to kill insect, fungicides which is use to kill fungus, rodenticides which is use to kill rodent etc. As a result, pesticide is not limited to agricultural use because it is also use at homes, parks, school, forest, roads and building to get rid of the pest that disturb human activities.

A recent article that is posted on April 26, 2017 stated that there a high rate of bees colony collapsing in the world. The main reason that cause the collapse and decrease in honeybee population is because there an increase in the number of farmer that use neonicotinoids, which is a type of pesticide that is under the branch of insecticides. This toxic chemical is more harmful toward invertebrate and insect than toward mammals such as birds and other bigger organism. The active ingredient that are use to produce neonicotinoids are acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid and thiamethoxam. According to UC San Diego, neonicotinoids chemical are commonly use on corn, soybeans and cotton. The problem of using this insecticide is that it not only kill pest but also kill honeybee (Apis mellifera) that helps to pollinate crops. When honeybees come in contact with neonicotinoids it will fly faster and longer than normal but after several day of being exposed to this chemical their flying speed and flying distance will be reduced by half. Beside this factor, it also impact the honeybees ability to look for nectar, find their way home, to reproduce and locate flowers. As a result, it is harder for honeybees to find food to support its colony because the negative impact decrease their foraging area by nearly 80 percent. Due to this reason, 28 percent of the 2.6 million honeybee colonies in America died last winter. The decrease in the number of honeybees have a huge affect on agriculture because according to U.S. Department of Agriculture each year honey bee pollinate about $15 billion worth of crops.
The reason why this pesticide is commonly used by farmer is because it is soluble in water, it metabolized overtime and it is a systemic insecticide, which means the plant can absorb the chemical. The way that the plant absorb the neonicotinoids into the body is through the metabolic process because the metabolism is responsible for breaking down the molecule that enter the plant body to keep the plant alive. But instead the resulting particles that breakdown from the Neonictinoid are toxic chemical. Due to this reason, the plant will become toxic for pest and honeybee because the toxic chemical will spread and enter the cell of the plant. The reason why this pesticide is soluble in water is because water and the ingredients use are all polar and this follow the theory "like dissolve like". Polar is when the charge on the molecule are unevenly distributed, which will cause one side of the molecule to be more negative. The toxic chemical that is absorb by the plant will enter all the tissue and cell in the plant so when pests come in contact with the plant, they will die from being poison. Out of all the chemicals in the table below clothianidin, dinotefuran, imidacloprid and thiamethoxam are most toxic for bees, while acetamiprid and thiacloprid have a moderate toxic level. Table 3.1 also show the half-life of each main active ingredient in Neonicotinoids. Half-life is the time required for half of the radioactive nuclide to decay. This show that the active ingredient that take the longest time to decay is Clothianjdin because it have a half-life of 148-1,155 days in the soil, while the active ingredient that decay in the shortest amount of time is acetamiprid because it have a half-life of 1-8 days in the soil.

The way that this toxic chemical kill pest and honeybee is by sending the toxic to their central nervous system. This will disrupt the function of there immune and nervous system and cause them to die. The only different between honeybee and pest is that honeybees doesn’t die straight away because it depend on the concentration of the toxic chemical inside there body. Due to this reason, they need to consume sufficient amount of toxic into their body in order to die. If they expose to 220ppm they will instantly but if they expose to 2-20ppm they will die within several weeks. Neonicotinoids can enter honeybee body through ingesting or when they come in contact with pollen and nectar of plant that obtain this chemical.
In conclusion, Neonicotinoids play a very important role in the agriculture industry because it is use by farmer to kill pest that disturb the growth of plant and sometime even kill them. Moreover, the use of insecticide also help prosper the amount of healthy crops being harvest. Even though Neonicotinoids is a very important insecticide it should not be use any longer because it not only decrease the population of honeybee but it also affect other valuable animals that live in agriculture land.

If you want to learn more about the affect of Neonicotinoids on honeybee or other animals please watch the video below.