Shoo (White)fly – Predicting the Rise of Pests in India using Weather Data

06/21/16
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In 2015, Punjab, India saw the worst outbreak of the whitefly pest in its known history, and pest conditions in 2016 are expected to be just as bad.  Whitefly is a type of sucking insect that can decimate not only cotton plants but many other crops as well, both agricultural (cucurbits, citrus, most vegetables, etc) and woody ornamental.  Many estimate the economic damage these pests cause per year to be between $10 and $100 million dollars.  Last year in some parts of the Punjab region, over two-thirds of the crops were destroyed by the whitefly, causing great financial hardship among affected farmers.[1]  While the majority of Punjabi cotton farmers planted Bt Cotton and used pesticides extensively, the plants still proved susceptible to the onslaught of this pest.  In an effort to explain the loss, some of the impacted farmers have blamed the lower efficacy of Bt Cotton as a deterrent to pests for the outbreak.   However, both government officials and industry insiders believe there are other contributing factors to the outbreak.[2]  Farmers were spooked by the incident, and, as a result, are expected to cumulatively plant and, subsequently, harvest fewer hectares of cotton this year than last, due to hesitance to grow the crop again.

Cotton-India2016CurrentAvgMaxT0505to0603_Map.png  

 

Cotton-India2016CurrentAvgMaxT0505to0603_Map.png

Figure 1

Cotton-India2016DiffAvgMaxTFromLastYear0505to0603_Map.png  

Figure 2

Cotton-India2016DiffSumGDD5095FromLastYear0505to0603_Map.png

Figure 3

Like other cold-blooded creatures, the growth rate and activity of the whitefly is temperature dependent.  Because insects are cold-blooded, they rely on the ambient temperature of the environment to provide them with energy for growth.  In hotter temperatures, one would expect insects to grow and mature more quickly, and the whitefly is no different.  Using aWhere’s spatially precise and accurate weather data, we observe that this year has been much hotter than usual across India, providing ideal conditions for whitefly growth (see Figure 1).  Figure 2 shows the average maximum temperature across India over the past month compared to the previous year.  In the Punjab region – the area marked “A” in the figure – the hottest days have been hotter this year than last, implying pests such as the whitefly will grow more quickly than they did last year and will likely be more prevalent.  In addition, Figure 3 shows the number of Growing Degree Days over the past month, providing a more nuanced way of understanding the growth rate of the pest.  Growing Degree Days incorporates information about the range of temperatures throughout the day, and can be used to model how quickly the pest will mature.   Figure 2 shows the number of Growing Degree Days over the past month is different from last year.  Consistent with Figure 1, Figures 2 and 3 both suggest that this year will be more conducive to the growth of whitefly than last year, given weather conditions in the last month.

                Our predictions, based on aWhere’s weather and agronomic data, are consistent with on the ground observations – there have already been sightings of whitefly in the southern areas of Punjab, in the districts of Bhatinda and Mansa.[3]  These pest sightings are several weeks earlier than usual, perhaps due to the high temperature over the last month.  These districts are right on the boundary of the areas identified by aWhere’s weather data as being hotter this year than last.  Understandably, these early pest sightings have India’s remaining cotton growers concerned as to whether this coming season might be a repeat of last.  Whitefly is far easier to control when still at juvenile stages, and as such, tools such as those provided by aWhere have the potential help farmers protect their fields by alerting them as to when they need to be ready for the pest’s arrival. 

Punjab.png

[1] http://timesofindia.indiatimes.com/india/Whitefly-destroys-2/3rd-of-Punjabs-cotton-crop-15-farmers-commit-suicide/articleshow/49265083.cms

[2] http://indianexpress.com/article/india/india-news-india/white-epidemic-bt-not-to-blame-for-whitefly-infestation/

[3] http://timesofindia.indiatimes.com/city/chandigarh/Punjab-forms-panel-to-check-whitefly-spread/articleshow/52595927.cms

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