Plague thrips

Thrips imaginis

Plague thrips are native to Australia and are widespread across the southern mainland and Tasmania. Their main hosts are pome and stone fruit and will also feed on strawberries, legumes, tomatoes, Eucalyptus spp., grapes, ornamentals, grasses, weeds and a variety of native plants. They are frequently present in citrus trees but do not cause economic damage.

Refer to the links below on different thrips species.

Description

Plague thrips are a smaller species; females range from 1.1-1.3 mm in length, whilst males are even smaller at 0.8-1.1 mm in length. Females are light brown or grey with light brown legs and males are yellow, whilst the nymphs are either white or yellow. They are similar in appearance to onion thrips, except that their eyes are red. Plague thrips are usually always female, especially early in the season, and are most prevalent from mid-late spring to early summer. They are active fliers and can be carried long distances in the wind, therefore they can easily migrate and inhabit orchards.

They inhabit the flowers of plants and are the most common thrips species found during flowering. Eggs are laid as early as bud swell in the sepals and other parts of the flowers, which hatch by late flowering.

Both the adult and larval stages can damage the flowers and fruit of stone and pome fruit, resulting in bronzing of petals and in severe cases flower abortion. Damage from larvae feeding on the ovaries causes small scars which get bigger as the fruit grows, resulting in abnormalities on the skin and corkiness in the mature fruit. In strawberries, larval and adult feeding often reduces shelf life and fruit may take on a bronzed appearance, while in older fruit feeding damage produces russeting around the seeds, and deformed fruit.

Control

Plague thrips can be targeted using biological control options such as the predatory cucumeris mite (Neoseiulus cucumeris) and the predatory orius bug (Orius tantillus), which are released into areas of high thrips infestation. Both feed on the larvae of thrips, while orius bugs will also feed on adult thrips. Natural predators such as lacewing larvae ladybird beetles, predatory flies and parasitic wasps may also provide control, so it is important to limit the amount of broad-spectrum insecticides applied to preserve these beneficial species.

Although plague thrips generally migrate into a crop from outside the immediate area, the removal of host plants or weeds may help with control. In addition to this, monitoring of plants should be done regularly to ensure that control methods can be implemented early.

When moderate levels of thrips are present, an application of an insecticide may be required. Currently plague thrips are easily controlled with insecticides, however in order to reduce the likelihood of resistance developing, rotating insecticides with different modes of action is recommended.

When used as directed, Movento® provides a soft option on beneficial insects whilst still providing good pest control. It is registered for plague thrips control in celery, rhubarb, herbs, bulb vegetables (excluding bulb onions) and suppression only in grapes.

Related Pests

Thrips

Chaetanaphothrips signipennis (Banana rust thrips), Thrips imaginis (Plague thrips), Thrips tabaci (Onion thrips), Thrips safrus (Northern plague thrips), Frankliniella occidentalis (Western flower thrips), Frankliniella schultzei (Tomato thrips), Pezothrips kellyanus (Kelly’s citrus thrips)

While over 6000 species of thrips exist worldwide, only ten per cent are deemed to have an economic impact on crops. The most common group is Terebrantia, which includes many of the damaging species such as onion thrips, western flower thrips and plague thrips. Hosts include citrus, green beans, cotton, mungbeans, cereals, some vegetables, summer pulses, sunflowers, canola and peanuts. Thrips can be vectors for tobacco streak virus and tomato spotted wilt virus.

Refer to links below for a more detailed description on different thrips species.

Plague thrips imaginis

Thrips imaginis

Banana rust thrips

Chaetanaphothrips signipennis

Banana rust thrips are a widespread problem in the coastal areas of Queensland and northern New South Wales. Predominantly affecting bananas, they have also been found in citrus and some native plants. In bananas they cause superficial damage to the skin which can result in the fruit being downgraded or rejected at market. Banana rust thrips are notably troublesome in areas with red soil and where bunch bagging is not used. Fruit that grows in the early warmer months tends to be more at risk.

Refer to the links below on different thrips species.

Northern Plague Thrips

Western flower thrips

Frankliniella occidentalis

A more serious pest than other thrips species because it plays a major role in infecting tomato, potato, capsicum and lettuce crops with the tomato spotted wilt virus (TSWV).

Tomato Thrips

Frankliniella schultzei

Tomato thrips originate from South America and are widespread throughout Australia. They prefer to feed on flowers and have a wide range of hosts including tomatoes, tobacco, capsicums, lettuces, potatoes, grain legumes and several weed species. They are known vectors for tomato spotted wilt virus (TSWV) which can cause considerable yield losses in tomato, capsicum, potato and lettuce crops.

Kellys citrus thrips

Pezothrips kellyanus

Kelly’s citrus thrips (KCT) are a serious pest of citrus in inland Australia, where in the Riverland-Sunraysia region of South Australia alone, it is estimated to cost industry $10 million per annum in crop losses and control measures. KCT feed on the fruit, causing scurfing (or halo) damage at the stem end and rind blemish which results in quality downgrades and reduced pack-out rates. The most affected varieties are Navel and Valencia oranges, lemons and grapefruit.

Refer to the links below on different thrips species.

References

Biological Services (Viewed Oct 19), ‘Plague thrips’, https://www.biologicalservices.com.au/pests/plague-thrips-85.html

Broughton, S (2018), ‘Thrips in citrus’, Department of Primary Industries and Regional Development (DPIRD), https://www.agric.wa.gov.au/citrus/thrips-citrus

Broughton, S and Reid, A (2014), ‘Thrip infestations in strawberry crops’, Department of Primary Industries and Regional Development (DPIRD), https://www.agric.wa.gov.au/strawberries/thrips-infestations-strawberry-crops?nopaging=1

Duff, J and Manners, A (2016), ‘Thrips: A pest management plant for productions nurseries’, Horticulture Innovation Australia, https://www.horticulture.com.au/growers/help-your-business-grow/research-reports-publications-fact-sheets-and-more/thrips-a-pest-management-plan-for-production-nurseries/

Invasive Species Compendium (2018), ‘Thrips Imaginis (plague thrips)’, Centre of Agriculture and Biosciences International (CABI), https://www.cabi.org/isc/datasheet/53736#tosummaryOfInvasiveness

Steiner M, Hardy, S and Thwaite G (Viewed Oct 2019), ‘Which thrips is that? A guide to the key species damaging Stone and Pome fruit in NSW’, NSW Department of Primary Industries, https://www.dpi.nsw.gov.au/__data/assets/pdf_file/0011/177329/stone-and-pome-thrips.pdf