General information
How does it work?
All mobile stages of Orius spp. are voracious predators. They will attack small arthropod prey of all types and will also feed and complete their development on pollen. Females insert eggs into plant tissue, so that only a small cap is visible at the surface. After a period of approximately 5 days at 20°C, the egg hatches and a small, orange nymph emerges. These first instar nymphs are superficially similar to thrips larvae, and can be mistaken for them with the naked eye when first seen.
There are five larval stages before the insects become adult and at 20°C development from egg laying to adulthood takes approximately 25 days. At 24°C development shortens to 15 days, while at 28°C this reduces to 9 days. All these figures are based on laboratory studies with an ample quantity of high quality food. The quality and availability of food will have a significant effect on the development time, so that the rate of development in the field may be slower than in the laboratory.
During the course of development, the larvae darken from a pale orange to a light brown colour. The overall shape remains the same throughout development. The head is narrow, with prominent eyes and a powerful needle like proboscis or rostrum, which is folded beneath the body when not in use. The thorax is slightly wider, while the abdomen broadens considerably, giving the insect an overall pear shape. The dorsal surface of the abdomen may carry darker spots centrally: these are glands which produce repellent liquid for defensive purposes. At each successive moult the wing buds become more prominent, until with the moult to adulthood the insect becomes winged.
The front pair of wings is partially hardened, and they are folded back over the body to cover the rear pair. They are two toned, being dark towards the base and paler or translucent towards the tip, giving the adult its characteristic appearance. The exact colour varies between species. Males of Orius are unusual in that the tip of the abdomen is twisted to one side, giving the appearance of some deformity at first sight.
Orius characteristically hide in flowers and terminal shoots of plants where the leaves are tightly pressed together. All the mobile stages feed in the same way. Having identified potential prey, they extend the proboscis and insert it into the victim. After a few minutes, the body contents of the prey are sucked out, causing it to deflate. Orius are known to abandon a partially consumed prey item if another is located, so that they actually kill far more than they need to reach maturity.
Orius attack and consume almost any small mite or insect. They are primarily used to control thrips, but also feed on the eggs of Lepidoptera, spider mites, whitefly and aphids, as well as on pollen. They will even feed on beneficial mites such as Amblyseius cucumeris, which are also used for thrips control. Whilst they do probe plant tissue and may use this as a source of liquid, they are not considered plant feeders and have never been reported to cause plant damage.
The product containing nymphs only is for use on crops where adult Orius tend to fly away, such as strawberries. The nymphs are unable to fly, and so are obliged to remain in the crop until adulthood.
When and where should you use it?
Orius will attack thrips at any stage of their development, including adults. It can thus be used to reduce established populations of thrips.
Because of the plentiful supply of pollen on pepper crops, which are in flower, Orius can establish on this crop before thrips arrive and offer a good level of protection. Orius has also been used on cucumbers, but establishment is slow unless thrips populations are unacceptably high.
Use on ornamental crops depends on the presence of pollen on the crop. In the presence of pollen, Orius will establish and offer protection. On cut flower crops, the tendency of Orius to roost and lay eggs in flowers may result in a large part of the population being exported with each harvest, and therefore poor establishment.
How should you use it?
On receipt of the product, lay the bottles on their side and keep them cool until ready to use. Because Orius adults are winged, and may be agitated by handling, application in high temperatures and bright light may result in many flying immediately to the roof of the greenhouse and being lost. It is important, therefore, to apply them during the early morning or late evening, when light levels and temperatures are lower. This reduces the risk of loss, and improves the chances of establishment on the crop.
When should you not use it?
Because Orius needs pollen or plentiful prey in order to establish, there is little point releasing it on crops which are sensitive to thrips damage, but which do not have pollen to facilitate establishment. This includes many ornamental crops, where there is low or zero tolerance of flower damage.
What will it do?
Used as directed, Oriline products will help to protect crops from damage by thrips, including thrips invading from outside. In limited circumstances, they may reduce existing populations of thrips when used as part of a control programme.
What will it not do, and what are the control options?
Oriline products will not totally prevent damage by thrips, particularly where large numbers invade from outside the crop. Neither will it work well in short day lengths and low temperatures. For Orius insidiosus and O. majusculus, this is due to the incidence of diapause. For O. laevigatus, the commercial strains do not enter diapause but there is a general slowing of development and reduction of survival at low temperatures.
Poor or delayed establishment occurs on some crops such as cucumber where pollen is not present. Alternatively, use Amblyline cu. CRS, which has been proven to provide optimum thrips control in these situations. This product ensures the presence of large numbers of predatory mites on the crop, without the need for establishment.
Chemical compatibility
There are few insecticides that can be used to reduce populations of thrips while Orius is present on a crop.
Populations of whitefly and spider mite can be reduced chemically, but note that Insect Growth Regulators tend to disrupt development of Orius.