Well planned spray programs are more effective than unplanned, random chemical applications. Have you ever considered spraying when there is no pests or diseases? Poorly planned spray programs or not following a spray program has the same effect. It costs a lot of money with no advantage other than the chemical supplier. Even nature loses, especially when useful insects are killed. All chemicals that control pests and disease are toxic—the less applied, the better, especially for the end-user and environment.

Important principles before starting

Before planning and identifying anything, follow these basic guides.

  • Identify and know the pest you want to spray or control. Good scouting will give all the information you need about the intensity and severity of the pest. Is the pest at the end of its cycle or just the beginning. Monitor the pest(s) with pheromone traps, sticky tape and water traps.
  • Select the right active ingredient for each pest you want to control
  • You need to know where the pest or target is. Are they in the ground, under leaves, in flowers etc.
  • Select the application method. That will determine the spray volume: high volume or low volume. In greenhouses most growers use low volume under high pressure.
  • Make sure that the pH and EC of the water is within the manufacturers specifications.
  • Add penetrators and stickers to the water as advised by the manufacturer.
  • Never spray in the heat of the day. The stomata of the plants are closed so less of the active ingredient is absorbed. Insects are active early in the morning.
  • Time your spray schedule with your irrigation. In greenhouses it is not that important but if you use spray misters it can dilute the concentration of the active ingredient on the leaves making the spray program less effective.
  • Never use cocktails of different chemicals. You never know what chemical reaction takes place. These cocktails can damage your crop and equipment. Worst case is that it might harm your crop and change the chemical composition which can affect the person eating the produce.
  • The plant growth stage is important. A good rule of thumb is spray systemics when plants are young and contact/stomacs on older plants.
  • Always rotate the active ingredient to reduce the chance of resistance.
  • Turn you greenhouse fans of during spraying.
  • Never let chemical mixtures stand overnight. Mix in the morning before spraying and use everything. If you use everything it is a sign of good planning.
  • Maintenance of equipment is crucial. Poorly maintained equipment will reduce the effectiveness and accuracy of the application and reduce the control of your target.

Never spray in a hot greenhouse or in the middle of the day. As said before, insects are active in the morning, so you will miss 80-90% of your target, making it a very expensive activity.

Know your target and target area. Compare it to a dart board, The dart board is the target area, the bull is the target. A chemical can only be effective if it hits the target. The target area is usually part of the plant such as the underside of a leaf, the fruit or the ground (seldom). The target is determined by the disease factor present and by the action of the chemical used.