Kelly’s 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.

Description

Confusion can occur as to whether citrus fruit has been damaged by thrips or by wind. Thrips damage extends from under the calyx, or can occur in patches between touching fruit, whereas wind damage tends to result in single or multiple transverse or diagonal scars across the fruit.

KCT adults are black, 1-2 mm in length with fringed wings. They are commonly observed on citrus flowers, however don’t cause damage until after petal fall. Both adults and larvae can be found feeding around contact points of touching fruit later in the season, which causes rind bleaching at those points.

While there may be other black thrips in citrus, KCT is the most common. In addition, these other thrips such as plague thrips, have generally dispersed before damage occurs. KCT is thought to be the only thrips that cause halo damage.

KCT larvae can be observed through a hand lens and are wingless and pale yellow to bright orange.
These larvae cause most of the halo damage 4 to 5 weeks after petal fall. They gather under the calyces of young fruitlets and as they feed, their mouthparts burst the rind cells, initially leaving silvery scars under the calyx. As the fruit develops, this scurfing damage expands across the surface of the fruit.

Control

There are a number of natural enemies of KCT including a parasitic wasp (Ceranisus menes), spiders and lacewing larvae, however it is believed they can’t significantly control KCT. In the Riverland-Sunraysia citrus soils there are a number of predatory mite species which only develop and reproduce on KCT. Therefore, avoiding organophosphate (OP) insecticides, building up soil organic matter and adding mulch (to support these beneficial mites) may all help to reduce KCT pupae.

Orchards should be monitored for KCT larvae from petal fall onwards, with growers checking for larvae between the fruitlet and the calyx.

Some populations of KCT have developed resistance to organophosphate (OP) insecticides, so applying newer chemistry insecticides such as Movento® is an opportunity to mix up insecticide groups and apply an insecticide that is soft on many beneficial insects, including parasitic wasps, pirate bugs, hoverflies and lacewings.

Movento is registered for the control of Kelly’s citrus thrips larvae and should be applied after flowering when threshold levels have been reached. During summer, the KCT lifecycle can be as short as 14 days, so a second Movento spray may be warranted no less than 14 days after the first application, to control the next generation of larvae.

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.

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).

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.

Plague thrips imaginis

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.

Onion thrips

Thrips tabaci

Onion thrips infest a wide range of hosts, including onions, garlic, leek, beans, cabbage, cauliflower, broccoli, cotton, celery, tobacco, tomatoes, cucumber, strawberries, potatoes and a range of ornamentals. Onion thrips are known vectors of tomato spotted wilted virus (TSWV) and iris yellow spot virus (IYSV) which is a potentially destructive virus of onions.

Refer to the links below on different thrips species.

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.

References

DPIRD (2018), ‘Thrips in citrus’, https://www.agric.wa.gov.au/citrus/thrips-citrus

South Australia Research & Development Institute (2016), ‘Fact Sheet: Kelly’s citrus thrips management’, PIRSA, https://www.pir.sa.gov.au/__data/assets/pdf_file/0010/285517/Kellys_Citrus_Thrips_Management_Fact_Sheet.pdf