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Disease caused by whitefly-transmitted begomoviruses are problematic in many tropical and subtropical world regions and cause heavy losses in food and fiber crops grown there. The whitefly, Bemisia tabaci, shows a life-cycle that includes eggs, nymphs and adults. It has several biotypes, but the B biotype is the one responsible for spreading plant diseases, since it has many plants species as natural hosts, including weeds.

The begomoviruses includes the Tomato Severe Rugose Virus (TSRV), which is manifested in the infected plant as yellow mosaic or mottling leaf distortions, as well as crinkling and stunting.

The transmission occurs after the whitefly reaches the phloem of an infected plant and later reaches the phloem of a healthy plant. To control the disease, it is recommended to keep a plant-free period to diminish the whitefly population, and/or clear the field between plants to eliminate other host plants that may act as reservoirs.

Develop a mathematical model combining epidemiological and ecological dynamics that describes the interaction between whiteflies, tomatoes and the disease. Use it to understand the ecological and epidemiological consequences of TSRV.

• Whiteflies' life-cycle has three stages: egg, nymph and adult; modelling them may be important to get the dynamics right.
• Both the whitefly and the plant present latency periods between acquiring the virus and becoming infectious, This can be neglected for a first analysis.
• Is it really necessary to clear fields before new plantings?
• Or is it better to increase the time between plantings?
• What is the best procedure to decrease the whitefly population: attack the eggs, nymphs or adults?
• This whitefly species is also a disease vector for other plants, like potatoes. How can your model give us insights into other, similar agricultural problems?

Barbosa, J.C., Rezende, J.A. and Amorim, L., 2016. Temporal dynamics of Tomato severe rugose virus and Bemisia tabaci in tomato fields in São Paulo, Brazil. Journal of Phytopathology, 164(1), pp.1-10.

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