Horticulturists investigated two different methods for managing populations of whiteflies (Trialeurodes vaporariorum\textit{Trialeurodes vaporariorum}Trialeurodes vaporariorum) on tomato plants in a commercial glasshouse.
In the first method, they applied a synthetic pyrethroid spray to the tomato crop.
In the second method, they released the parasitic wasp, Encarsia formosa\textit{Encarsia formosa}Encarsia formosa, as a biological control agent.
The scientists recorded the relative density of the whitefly population (expressed as a percentage of the starting population) every 3 days over a 15-day period. The results are shown in the table below:
Time after treatment (days)Synthetic pyrethroid spray (%)Parasitic wasp treatment (%)0100100386061438935181270915925\begin{array}{c|c|c} \text{Time after treatment (days)} & \text{Synthetic pyrethroid spray (\%)} & \text{Parasitic wasp treatment (\%)} \\ \hline 0 & 100 & 100 \\ 3 & 8 & 60 \\ 6 & 14 & 38 \\ 9 & 35 & 18 \\ 12 & 70 & 9 \\ 15 & 92 & 5 \end{array}Time after treatment (days)03691215Synthetic pyrethroid spray (%)100814357092Parasitic wasp treatment (%)10060381895Explain the changes in the relative density of the whitefly population over the 15-day period when treated with the synthetic pyrethroid spray.
Give two advantages of using biological control (parasitic wasps) rather than chemical control (synthetic pyrethroid) to manage the whitefly population.
Describe a sampling method that could be used to estimate the population of whiteflies on the tomato plants in the commercial glasshouse.
74 exam-style questions on Edexcel IGCSE Biology Food production. Each one has a worked solution and a mark scheme showing where the marks go.