Agricultural practices can have effects on crops worldwide. The increased number of non-native and invasive pests in countries around the world has resulted in the widespread use of synthetic pesticides for crop maintenance due to their economic dependence upon successful growing seasons. Synthetic pesticides have been under much scrutiny in recent years as studies have revealed correlations between their use and the decline of biodiversity within agricultural operations.

What pests make farmers so concerned?

When a pest is introduced into a non-native environment, it has the potential to spread and damage large numbers of single species crop fields. These include the known occurrences of the wheat stem rust fungus, necrosis viral syndrome in maize, the Asian citrus psyllid, and Fusarium oxysporum f. sp. cubense1. With China being a top exporter of agricultural products, data on pest occurrences is vital to import countries. The top 10 pests found in China are also common worldwide. These are:

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Pest risk analysis methods

Pest risk analysis (PRA) is comprised of different methods that allow countries to prioritize protective methods against pest invasions¹. These methods have been adopted worldwide and allow countries to determine which pests are more likely to cause economic damage. PRA’s assess the likelihood of pest arrival, establishment, economic impact and the ease of control or eradication success¹.

Another analysis method that is used was designed to determine whether pesticide use is beneficial or harmful for pest management. The integrated pest management system (IPM) was developed after the second world war to help decision-makers determine the economic injury level (EIL) of certain pesticides⁴. The IPM’s mission is to find the lowest pest density capable of causing economic damage to determine at what point pesticides can be used for control and eradication to protect the economic value of each crop.

An additional method for determining pest risk analysis is the use of the action threshold (AT) which is the correlation between pest numbers and pest damage. The AT is then the point at which pesticides should be applied to prevent crop loss from pest pressure⁴. Field trials are conducted to determine at what point specific pesticides are necessary for specific crops resulting in a standardized application process. With this information known to be consistent, ATs are able to be adjusted for variations in planting dates and environmental conditions.

What have researchers uncovered while studying agricultural pests?

China produces the greatest tonnage of crops on a global scale and has the greatest diversity of crop production¹. This lends China to harbor the greatest number of pests. Although scientific data hypothesizes that China should have a large number of recorded pests, the actual recorded data has been found to be much smaller than anticipated¹. The distance between communities has resulted in the lack of education on pest identification and a complicated means of communication for reporting. If these hypotheses are correct, other countries with heavy agriculture production may also underreport pest data. In less developed countries with agriculture supported economies, lack of pesticide education has resulted in the reliance on synthetic chemicals due to their ease of availability⁴.

As with most insects, excessive use of pesticides disrupts a moth’s ability to mate. Research has indicated that residual pesticides have the ability to interrupt sex pheromones and disrupt a moth’s flight path³.

Pollinators, such as moths, are responsible for the reproduction of the majority of wildflowers worldwide as well as approximately 75% of the worlds crops³. Their population numbers are being affected by synthetic pesticides and modern agricultural practices. When fields contain a single crop variety, little plant diversity can lead to periods of low food availability for pollinators. To compensate, the UK implemented the Environmental Stewardship Schemes for farmers and land managers to alter management practices⁵. Government subsidies would allow farmers to maintain an average yearly income while transitioning fields to support pollinators during known stress periods.

These stress times have been determined to be:

• April – Late May
• Late June – Late July
• Mid-August – Late-October

Several flower varieties are capable of filling pollinator hunger gaps and include commonly known weed varieties.

Flowers best for the April to Late May hunger gap include:

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Pollinators can fill the Late-June through Late-July hunger gap with the following flower varieties:

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One of the most important hunger gaps occurs between Mid-August and Late-October when pollinators are preparing for migration or hibernation. Flower varieties that can fill this gap include:

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How have agricultural practices been modified to protect biodiversity?

Agronomy research has begun to determine non-chemical pest and disease management practices such as irrigation, pruning, and thinning which can manipulate a crop’s growing environment to control an epidemic².

Beyond land management practices, the use of botanical pest management has seen increased popularity worldwide. These pesticides have been developed to meet the demand for environmentally friendly and low toxicity products that are also effective against pest infestations⁴.

Are modified agricultural practices actually safer?

It has been determined that biopesticides have the ability to alter the behavioral and psychological process of non-target organisms⁴. For instance, the use of neem oil has been an effective agent against pest infestations. Although considered a biopesticide, the active agent in neem oil, azadirachtin, was found to be just as toxic to bees as the popular neonicotinoid imidacloprid⁴. More research is needed to determine how much biopesticide exposure pollinators are receiving after coming into contact with residues contained in pollen, nectar, and honey to make a determination as to whether biopesticides may be the answer to successful pest management⁴.

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References

1. Bebber, D., Field, E., Gui, H., Mortimer, P., Holmes, T., & Gurr, S. (2019, June 24). Many unreported crop pests and pathogens are probably already present – Global Change Biology. Retrieved from https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14698

2. Bevacqua, D., Genard, M., Lescourret, F., Martinetti, D., Vercambre, G., Valsesia, P., & Mirás-Avalos, J. (2019, June 11). Coupling epidemiological and tree growth models to control fungal diseases spread in fruit orchards. Retrieved from https://www.nature.com/articles/s41598-019-44898-6Bebber, D., Field, E., Gui, H., Mortimer, P., Holmes, T., & Gurr, S. (2019, June 24). Many unreported crop pests and pathogens are probably already present – Global Change Biology. Retrieved from https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14698

3. Navarro-Roldán, M., Amat, C., Bau, J., & Gemeno, C. (2019, May 31). Extremely low neonicotinoid doses alter navigation of pest insects along pheromone plumes. Retrieved from https://www.nature.com/articles/s41598-019-44581-w

4. Shah, F., Razaq, M., Ali, Q., Shad, S., Aslam, M., & Hardy, I. (2019, May 22). Field evaluation of synthetic and neem-derived alternative insecticides in developing action thresholds against cauliflower pests. Retrieved from https://www.nature.com/articles/s41598-019-44080-yBebber, D., Field, E., Gui, H., Mortimer, P., Holmes, T., & Gurr, S. (2019, June 24). Many unreported crop pests and pathogens are probably already present – Global Change Biology. Retrieved from https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.14698

5. Timberlake, T., Vaughan, I., & Memmott, J. (2019, April 19). Phenology of farmland floral resources reveals seasonal gaps in nectar availability for bumblebees – Timberlake – – Journal of Applied Ecology – Wiley Online Library. Retrieved from https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2664.13403