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New Zealand: Takeaways from whitefly IPM workshop

Growers gathered online and in person at this popular workshop on managing whitefly in greenhouse tomatoes using an integrated pest management (IPM) approach. Ahead of the prime season for whitefly infestation, Seth Laarakkers described the fundamentals of an IPM approach and finished by sharing the progress of the TomatoesNZ and A Lighter Touch trials on new native predators, which, in theory, should help keep whitefly under control while they hunt for Psyllid.

The key points were:

  • Scout well, preferably with a hand lens
  • Introduce predators early and regularly
  • Pay attention and help the predators if you need to.

If scouting occurs regularly and with sufficient resolution, and this is coupled with an understanding of what you are seeing, the effects of regularly introduced Encarsia controlling a whitefly population are obvious. At this stage, we can apply physical mode of action sprays to help the encarsia keep up if required. Understanding the different temperatures that Encarsia survives at (the greenhouse should be at a minimum 24-hour average of 16 degrees) is important in determining your strategy. The average naked eye won’t be able to see whitefly eggs. However, mature larvae, pupae, and adults are easily recognized. That is why a scout with a hand lens is so important. We explored a decision-making tree (available on the TomatoesNZ website), which described the course of action to take for 3 levels of infestation. This was followed by a discussion around the 3 levels of spray (physical, soft, and hard) and why repeat applications are critical to success. There is no point in applying chemicals that impede your predators, short-term control often leads to long-term problems. For a better understanding of the hour-long presentation, please see the resources from the workshop, the slideshow, an educational video, and a decision tree matrix that will help you to get a better understanding. (add website link) Please note that these have been developed specifically for tomato growers but might transfer to other greenhouse crops.

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