Monitoring
Monitoring helps to identify when thrips are building up and establish whether it is necessary to spray, and if spraying has been effective.
Thrips are best collected from flowers. Collect 20-30 flowers from each area and place into labelled zip-lock bags. Blue sticky traps are useful for monitoring, but as thrips on sticky traps are often damaged, expertise is needed to identify them to species.
Control
Serious damage to the crop occurs only when there are more than 10 thrips per flower. Do not take western flower thrips infested material onto properties as this has been one of the main causes of crop infestation.
Chemical control
Where western flower thrips are present, it is important to avoid excessive use of pesticides as the species has developed resistance to a range of insecticide from different chemical classes. Unfortunately, there are very few insecticides effective against western flower thrips that may be used on strawberries. Growers should choose pesticides carefully.
The Australian Pesticides and Veterinary Medicines Authority has a searchable database with the latest registered pesticides and permits. However, if unsure of what to use, seek advice from DAFWA.
Strawberry growing regions in the south of the state such as Albany and Mount Barker have not needed to spray for western flower thrips over the last 10 years due to the presence of natural predators.
Biological control
Growers in the Perth region under Haygrove tunnels have largely moved towards the introduction of the predatory mite Neoseiulus cucumeris and predatory bugs (Orius) to control western flower thrips since the pest has become resistant to insecticides. The mite feeds on thrips larvae, while the bug feeds on all life stages including the adult. The Australian Biological Control suppliers website lists all currently available predators.
Care should be taken with the use of chemicals prior to releasing beneficial insects and mites. Insecticides should be avoided after release.
Orius bugs
Orius bugs are supplied to growers in units of 1000 adults and late instar nymphs, contained in 500mL plastic bottles of mixed vermiculite and buckwheat husks. Orius is released at two bugs per square metre as soon as there is enough flowering. Normally three to four releases are undertaken 10 days apart.
In areas of high thrips infestation, two to three times higher rates are required to gain quick control. In covered strawberries, Orius can be introduced in and around the hot spot areas at a rate of 10-20 bugs per square metre.
Neoseiulus cucumeris (cucumeris)
Cucumeris is dispatched in sachets of bran containing over 200 predatory mites.These include adults, nymphs and eggs, and tiny tyrophagus mites as food for the cucumeris.
The adult predatory mite is cream coloured, while the younger stages are clear. Both forms are pear-shaped and fast-moving. Predator eggs are clear and slightly oval and about 1.5 times the size of a two-spotted mite egg. Cucumeris feed on 1st and 2nd instar thrips larvae. Cucumeris should be released at a rate of 50-100 predators per square metre of cropping area (1 litre of diluted mix per 100-200 square metres).
When Orius is used in combination with the beneficial mite, Neoseiulus cucumeris, the increased population of predators will help protect the crop during the whole cropping season.