Pest and Disease Control

Every greenhouse hydroponic system will be affected at some stage by insect pests or crop diseases.

No grower enjoys having to use agrichemicals but often these are a necessary requirement in order to bring a pest or disease problem under control or you can risk losing a crop.

Pure Hydroponics prefers to see hydroponic growers minimise the use of agrichemicals as much as possible.

A range of preventative measures are possible and modern IPM (Integrated Pest Management) techniques allow known parasites to be introduced into the growing area which feed on insects pests and their larvae.

Many modern hydroponic growers have eliminated the use of agrichemcials altogether and market themselves as providing “Spray Free” produce.

Hydroponic produce is already very healthy and nutritious. If a grower can achieve a spray free status for their crop and guarantee year round supply then the marketability of their produce and the overall perception of the industry by consumers would be greatly enhanced.

There is a wide range of agrichemicals available today which are approved for use on food crops. Vegetable produce is deemed safe to consume if Maximum Residual Levels (MRL’s) are adhered to. The sale of fresh produce in New Zealand and most other countries is strictly policed and samples of vegetables are randomly taken from supermarket shelves by food safety authorities and tested in the laboratory for agrichemical residues. Growers in breach of MRL limits can be severely fined or have their farms shut down altogether.

Growers who are repeatedly affected by insect pests infestations or crop diseases are encouraged to assess the likely causes of  these problems first rather than resort to continued agrichemical usage as a curative measure. Prevention is always much cheaper than a cure.

A healthy, stress free crop far less likely to be targeted by pests or diseases than one which is not. Problems will always strike the weakest plants first. If growers can ensure a greater proportion of their crop is healthy and strong then  there will be less likelihood of problems requiring agrichemical usage.

In many cases the use of agrichemicals can be reduced or eliminated by overseeing the following checklist:

  • Is the hydroponic system well designed? Are there aspects of the design that could be putting the crop under unnecessary stress? (E.g. Mixing tank is too small for a recirculating system, poor oxygenation of the nutrient solution, NFT gullies are too long, nutrient solution strength is too high, seedlings are being over watered).
  • Is the greenhouse & greenhouse environment well designed? Is there sufficient air movement, ventilation, humidification or shading? All of these aspects can put a crop under unnecessary stress if they are not properly controlled.
  • Have you chosen a good quality seed which is suitable for your climate? Modern seed breeding has allowed various types of vegetables to out perform varieties which were available only a few years prior. Many varieties are now bred to be resistant to a wide range of insects and are adapted to harsher climates. Growers are encouraged to talk to their local seed representative for samples of the latest varieties and experiment with them.
  • Are there weeds inside or outside of the greenhouse which could be hosting insect pests? Quite often if weeds are not properly controlled in the vicinity of the greenhouse they will attract a wide range of pests which will then move inside the greenhouse area and affect the crop.
  • Has the crop been properly maintained? Excessive vegetative growth or old plant material that has not been pruned can limit air movement and become a breeding ground for insect pests or fungal spores. This is particularly important for tomato crops. Excessive vegetation can also limit the penetration and coverage of sprays when they are used.
  • Are there areas of poor drainage or surface water inside or outside the greenhouse? These can attract insect pests such as gnat flies which can then colonise a crop.
  • Is the water source properly treated? Untreated water can host a range of pathogens which will result in a series of crop problems and plant losses.
  • Is the hydroponic system and harvesting equipment being properly sanitised after use? Contaminated pruning shears, seedling trays, growpots and biofilm laden NFT gullies are all high risk areas for transmitting diseases.
  • Has unwanted plant material been properly removed and disposed of away from the greenhouse area after pruning or harvesting? Plant materials left on the ground to decay alongside healthy crops are a high risk source for disease transmission.

Growers should do everything possible to ensure the above-mentioned checklist has been properly observed.

The hydroponic industry would benefit greatly if all growers took a proactive approach to reducing agrichemical usage.

Pure Hydroponics will soon be showcasing a range of organic sprays and agrichemical based sprays for controlling a wide range of insect pests and crop diseases.