Western flower thrips (Thysanoptera: Thripidae

Western flower thrips

(Thysanoptera: Thripidae)

Western flower thrips is a pest of serious economic importance globally. It causes severe economic damage on strawberries in South Africa. Feeding damage on strawberry flowers can cause the petals to shrink and berries lose their shape and become distorted when this pest feeds on developing fruits. Fruits also become discoloured due to bronzing.

Nozibusiso Maphumulo

IPM-PROGRAM, NORTH-WEST UNIVERSITY

Western flower thrips classification: Class: Insecta (insects) Order: Thysanoptera (thrips) Family: Thripidae Genus: Frankliniella Species: occidentalis

Western flower thrips originates from the western regions of North America and has spread throughout the world. Its introduction into South Africa was first reported in 1987 and it became a dominant species of thrips in deciduous fruits orchards in Western Cape during 2001.

The host plant range of western flower thrips is extremely wide, since it is polyphagous and feeds on more than 200 plant species from approximately 50 families. In South Africa, its host plant range include various vegetables, grapevine, deciduous and subtropical fruit, berries (mainly blueberry and strawberry), cut flowers as well as different indigenous flowers and weeds.

Western flower thrips have six developmental stages, i.e., egg, two larval instars, prepupa, pupa and then the adult insect. Eggs are laid in the leaves, flower petals and also in the soft parts of the stems. A single female can lay between 20 to 40 eggs and uses a saw-like ovipositor to insert the eggs into the plant tissue.

After hatching, larvae immediately start feeding on the plant tissue. The 1st-instar larva then moults into a 2nd-instar larva which is much bigger with more colour. At the end of the 2nd-instar, larvae drop to the ground where pupation usually takes place. Pupation may, however, also take place on leaves, inside flowers and other places that are sheltered. After adults emerge from pupae, they move around, mate and reproduce rapidly, if environmental conditions are favourable.

Eggs of the western flower thrips are kidney-shaped and are minute in size (length = 0,2 mm). Larvae are up to 1 mm long with a spindled shape. They have an almost transparent white or yellowish to orange-yellow colour with a big head that has bright red eyes. Larvae are mobile but have a tendency of residing in hidden places on plants, such as within flowers or developing leaves.

Both the prepupa and pupa are usually white to cream

Figure 1: Larva of the western flower thrips.

https://apps.lucidcentral.org/pppw_v10/text/web_full/entities/western_flower_ thrips_183.htm

Figure 2: Western flower thrips adult. https://www.crop.bayer. com.au/pests/pests/western-flower-thrips

Figure 3: Western flower thrips damage on strawberry fruits.

https://www.crop.bayer.com.au/pests/pests/western-flower-thrips

Figure 4: Scarred tissue on leaf surfaces is typical of western flower thrips feeding damage. This is caused by the scraping of the leaf epidermis by thrips mouthparts during feeding. https://ucanr.edu/blogs/strawberries_caneberries//blogfiles/56603_original.jpg

coloured and can be distinguished based on the presence of wing buds. Adults are approximately 2 mm in length, slender and have narrow fringed wings. Females vary a lot in colour. They can be nearly white, while some can be yellowish-orange and others are almost black in colour. Adults have fully developed pairs of fringed wings. Males are smaller than females and are yellowish-white in colour.

Management of western flower thrips can be achieved through monitoring, using blue sticky traps before flowering, followed by chemical control when needed. However, this pest is known of developing resistance to pesticides very quickly and this minimises the available control options. Enquiries: mashimanenozi03@gmail.com