Aphis gossypii (aphid) is one of the important economic pests of cotton in the world, they feed on phloem sap of host plant with their stylets. Aphids seem to find their way into every garden. They are small, soft-bodied insects that can survive in almost any zone. They harm host plant by depriving them of nutrient, spreading plant pathogenic virus, and secreting honeydew, thus make serious impact on the yield and quality of cotton. Aphids, Because of the small size, strong fertility and short lifespan, is hard to control. In addition, Aphis gossypii prevention relies mainly on the use of chemical pesticides as for now, the misuse of pesticides has led to the stronger resistance of aphids to pesticides, as a result of which, the prevention and treatment of aphids is more difficult. While aphids in general feed on a wide variety of plants, different species of aphids can be specific to certain plants. For example, some species include bean aphids, cabbage aphids, potato aphids, green peach aphids, melon aphids, and woolly apple aphids.

Most of the method that treat aphid infection is by using pesticides, which are poisonous and may cause pollution. The impact of pesticides consists of the effects of pesticides on non-target species. Pesticides are chemical preparations used to kill fungal or animal pests. Over 98% of sprayed insecticides and 95% of herbicides reach a destination other than their target species, because they are sprayed or spread across entire agricultural fields. Runoff can carry pesticides into aquatic environments while wind can carry them to other fields, grazing areas, human settlements and undeveloped areas, potentially affecting other species. Other problems emerge from poor production, transport and storage practices. Over time, repeated application increases pest resistance, while its effects on other species can facilitate the pest's resurgence.

AIR POLLUTION:

Pesticides can contribute to air pollution. Pesticide drift occurs when pesticides suspended in the air as particles are carried by wind to other areas, potentially contaminating them. Pesticides that are applied to crops can volatilize and may be blown by winds into nearby areas, potentially posing a threat to wildlife. Weather conditions at the time of application as well as temperature and relative humidity change the spread of the pesticide in the air. As wind velocity increases so does the spray drift and exposure. Low relative humidity and high temperature result in more spray evaporating. The amount of inhalable pesticides in the outdoor environment is therefore often dependent on the season. Also, droplets of sprayed pesticides or particles from pesticides applied as dusts may travel on the wind to other areas, or pesticides may adhere to particles that blow in the wind, such as dust particles.

WATER POLLUTION:

In the United States, pesticides were found to pollute every stream and over 90% of wells sampled in a study by the US Geological Survey. Pesticide residues have also been found in rain and groundwater. Studies by the UK government showed that pesticide concentrations exceeded those allowable for drinking water in some samples of river water and groundwater.

SOIL POLLUTION:

The extensive use of pesticides in agricultural production can degrade and damage the community of microorganisms living in the soil, particularly when these chemicals are overused or misused. The full impact of pesticides on soil microorganisms is still not entirely understood; many studies have found deleterious effects of pesticides on soil microorganisms and biochemical processes, while others have found that the residue of some pesticides can be degraded and assimilated by microorganisms. The effect of pesticides on soil microorganisms is impacted by the persistence, concentration, and toxicity of the applied pesticide, in addition to various environmental factors. This complex interaction of factors makes it difficult to draw definitive conclusions about the interaction of pesticides with the soil ecosystem. In general, long-term pesticide application can disturb the biochemical processes of nutrient cycling.

PLANT HARM:

Nitrogen fixation, which is required for the growth of higher plants, is hindered by pesticides in soil. The insecticides DDT, methyl parathion, and especially pentachlorophenol have been shown to interfere with legume-rhizobium chemical signalling. Reduction of this symbiotic chemical signalling results in reduced nitrogen fixation and thus reduced crop yields. Root nodule-formation in these plants saves the world economy $10 billion in synthetic nitrogen fertilizer every year. Application of pesticides to crops that are in bloom can kill honeybees, which act as pollinators. The USDA and USFWS estimate that US farmers lose at least $200 million a year from reduced crop pollination because pesticides applied to fields eliminate about a fifth of honeybee colonies in the US and harm an additional 15%. On the other side, pesticides have some direct harmful effect on plant including poor root hair development, shoot yellowing and reduced plant growth

HUMAN HARM:

Children are more susceptible and sensitive to pesticides, because they are still developing and have a weaker immune system than adults. Children may be more exposed due to their closer proximity to the ground and tendency to put unfamiliar objects in their mouth. Hand to mouth contact depends on the child's age, much like lead exposure. Children under the age of six months are more apt to experience exposure from breast milk and inhalation of small particles. Pesticides tracked into the home from family members increase the risk of exposure. Toxic residue in food may contribute to a child’s exposure. The chemicals can bioaccumulate in the body over time. Exposure effects can range from mild skin irritation to birth defects, tumors, genetic changes, blood and nerve disorders, endocrine disruption, coma or death. Developmental effects have been associated with pesticides. Recent increases in childhood cancers in throughout North America, such as leukemia, may be a result of somatic cell mutations. Insecticides targeted to disrupt insects can have harmful effects on mammalian nervous systems. Both chronic and acute alterations have been observed in exposes. DDT and its breakdown product DDE disturb estrogenic activity and possibly lead to breast cancer. Fetal DDT exposure reduces male penissize in animals and can produce undescended testicles. Pesticide can affect fetuses in early stages of development, in utero and even if a parent was exposed before conception. Reproductive disruption has the potential to occur by chemical reactivity and through structural changes.

HOW WE TRIED TO SOLVE:

By using genetic engineering on plants, it can target on pest more effectively and more focused. Only insects that consume the leaves will be damaged by chitinase contained in plants. Thus, can save more beneficial animals, such as bees. Moreover, human body don’t contain chitin, which means consuming chitinase won’t negatively affect human health. Our research can go far beyond just on tobacco leaves. It can be applied to other crops, including rice, potatoes, and corns —— all are vital food source across the world. by increasing the production, this can help reduce feminine while contribute to sustainable development.

We contacted with Dr. WANG in Nanjing Agricultural University. He explained how the pesticides are causing impacts on crops and soil, which are not suitable for sustainable development. He helped us with final protocols, contributing to the choice of GOI in the process. He reminded us that we must choose the chitinase that will affect aphids after digestion, not simply by touching on the leaf which is kind of impossible. He supported us with our experiment.

If the our own result proved that we are successful, we will try to lower the price of the new plant and harvest seeds accordingly. Also, we will find ways to boost the expression of chitinase in plants while the gene is partly inhibited by insects during consumption.

Team:Nanjing/Human Practices

Human Practices