Figure 1 shows the percentage of poinsettias with whitefly in each greenhouse during Weeks 31-43. I know the graph looks a bit complex with 12 greenhouses represented by a mass of lines, but it can be simplified (in the mind anyway) by just looking at the red circle which indicates the final counts of the 9 greenhouses that were successful without using pesticides. The 20 % infestation level under which they all fell, seems to represent a level of whitefly that growers can tolerate and although this may seem like a high number of infested plants, in reality it was difficult to find whitefly in these crops. This result supports some work done at Cornell University back in the mid-1990s that found that a 10% infestation level was essentially non-detectable (they looked at just 6 leaves per plant whereas we looked at the whole plant).

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