General information
How does it work?
In sunny conditions, male thrips will settle on prominent objects within a crop, such as flowers, and begin to display aggressively towards each other. Whilst doing this, they produce a pheromone which attracts other males to the area so that the aggregation grows. Female thrips then enter these aggregations, mate, and leave.
The pheromone is not produced in advance and stored by the thrips, but is produced on demand. This makes the task of isolating and identifying the components very challenging, but techniques to achieve this difficult task were developed by researchers at Keele University in England. They developed a method of collecting very small amounts of pheromone from the air above groups of displaying thrips, and identified the molecules involved using gas chromatography and mass spectrometry. They were able to isolate 2 major components and five minor components which were produced by males but not females of Frankliniella occidentalis.
The sex pheromones of Lepidoptera have been used successfully for monitoring or control of pest moth species. In general, female moths remain in one place and produce relatively large quantities of pheromone. Male moths detect this pheromone at very low concentrations, and from quite long distances using their antennae. They then follow the concentration gradient until they reach its source, the female. Placing false sources of pheromone to distract males and prevent them mating has been one successful tactic used in control.
The Frankliniella occidentalis aggregation pheromone differs from this in several important ways. Males do not follow a concentration gradient of pheromone to find a female, but rather use the trigger provided by the pheromone to change their behaviour. In the presence of pheromone, they travel to prominent objects within their immediate area: they are using two stimuli – one olfactory and the other visual. The visual stimulus in this case is provided by a sticky trap, which attracts and captures males and females of Frankliniella occidentalis.
The presence of pheromone improves the sensitivity of blue and yellow sticky traps as monitoring tools for thrips. It has been reported to catch thrips at very low densities, when none had been detected by traps alone or by searching the crop. It thus helps growers detect populations of thrips in their crops earlier than is otherwise possible, and enables them to apply control methods, such as Amblyline cu CRS. By doing this, it helps to ensure that thrips populations do not grow to damaging levels. The pheromone is impregnated into rubber septa, and is released gradually over several weeks. Thrips continue to be attracted throughout this period.
When and where should you use it?
Thripline ams should ideally be used early in the life of a crop, to identify the presence of F. occidentalis and allow chemical or biological controls to be applied.
It can be used in any crop where F. occidentalis is a pest. The majority of thrips flight activity occurs above 20°C, so the number of thrips caught may be reduced at lower temperatures.
How should you use it?
On receipt of the product, place the sachets into a refrigerator unless they are to be used immediately.
When ready to use the product, tear open the sachet carefully in the crop, and place individual septa onto blue or yellow traps. You can fix the septa to Taki-traps®, sticky traps, or roll traps. The pheromone is placed into the central cup of the septum, and in crops with overhead irrigation this cup may fill with water, reducing the release rate of the pheromone. In such crops, place the septa horizontally on the trap, or with the cup facing downwards.
Because thrips do not move far within a crop once established, it is best to use a high density of traps, for instance one per 100m², to monitor the crop thoroughly. Lower numbers of traps will still be useful, but may not pick up localised infestations of thrips.
When thrips are seen on the traps, begin using Amblyseius cucumeris or Orius laevigatus in biological control programmes, or treat with the insecticide of choice in chemical control programmes.
When should you not use it?
Do not use the product to monitor thrips other than Frankliniella occidentalis. It was specifically identified from that species, and has not been tested against other thrips such as Thrips tabaci and Thrips palmi.
What will it do?
Used as recommended Thripline ams will detect populations of thrips more effectively than sticky traps alone. It will give earlier warning of potential problems by detecting low level populations, and providing sensitive indications of the first thrips to arrive in a crop.
Used in conjunction with either biological or chemical control programmes, it will allow improved timing of application to ensure optimum protection.
What will it not do, and what are the control options?
Thripline ams will not control populations of Frankliniella occidentalis when used alone. It is intended to supplement the control provided by biological control agents or conventional crop protection products.
Biological controls for thrips infestation include Orius spp, Amblyseius cucumeris, Amblyseius montdorensis, and Amblyseius swirskii. The majority of these will also consume pollen, and perform best on pollen rich crops. Hypoaspis species will contribute to control when used with other beneficials.
The Controlled Release System formulation of Amblyseius cucumeris (Amblyline cu. CRS) and Amblyseius montdorensis (Montyline m) performs well in cucumbers, many ornamentals and also in peppers. Because each sachet contains a breeding colony of mites, which are released onto the plants at a constant rate over a period of six or more weeks, the product can provide thrips control without the need for establishment. This would be the favoured option for control in most situations. Amblyseius swirskii is also now available in a CRS sachet, but this species is primarily intended for whitefly control.