Biological Control

Latest News

Biological Control

‘Biological control’ is a method of managing pest and disease populations in crops by utilising their natural enemies rather than synthetic chemicals. British cucumber growers have been using biological control agents for over 30 years and can proudly claim to be world leaders in the field.

Biological control is usually used as part of an integrated pest management (IPM) programme.

While largely based on biological techniques, IPM also draw on physical and cultural control measures integrated with strategic applications of target specific and short persistence pesticides. There are now many biological products available to growers including parasites and predators, as well as fungi, nematodes and bacteria. Physical controls include the use of screens, traps and barriers, while cultural controls make use of tolerant cultivars, good hygiene practices and manipulation of the growing environment. The key to success is to understand how to use these products singly or in combination to maintain the pest populations below economic damage thresholds.

Encarsia wasp attacking a whitefly scale

CGA Communications Officer, Rob Jacobson, and Technical Officer, Derek Hargreaves, have worked with the HDC to produce a ‘Crop Walkers Guide’ which illustrates the common pests, diseases and biological control agents.

Plants are usually propagated by specialist plants raisers in November/December and transferred to production glasshouses in December/January.

Fruit picking begins in late January/February and is continuous for the life of the crop.

Most growers now replace crops at least once and sometimes twice, enabling them to supply good quality produce throughout an extended season. Through careful management the break in cropping can be restricted to less than three weeks, and by staggering the timing of replants, many growers now have productive crops in their glasshouses from January to October.

Crops are grown in high quality Venlo-style glasshouses with computer controlled environments enriched with carbon dioxide to improve growth and yield. Day time temperature is maintained at a minimum of 21ºC via hot water pipe systems and the atmosphere is automatically ventilated at 23 – 24ºC.

Plants are grown in artificial, inert substrates, the most common being rockwool. These substrates are sterile and free from inherent disease problems. Nutrients are applied as liquid feeds through computer controlled irrigation systems.

Cucumbers are usually grown by the cordon training technique:

• The main stem is trained up a vertical string that is tied to a horizontal support wire positioned about 2m above the ground. Side shoots are removed from the main stem until it reaches the support wire.

• Three strong lateral shoot are then selected and the main growing point is removed.

• The side shoots are allowed to cascade downwards to a length of about 1m and their growing points are removed to encourage “sub-lateral” shoot development.

• Crop is performed every 7 – 14 days when any additional unwanted side shoots are removed.