Melon thrips

Adults

• Tiny insect, up to 1.5mm long.
• Cigar-shaped.
• Pale yellow-green to orange.

Nymphs

• Resemble the adults but are smaller and lack wings.

Prepupae and pupae

• Similar to nymphs but inactive and have developing wing pads.

Eggs

• Difficult to see because they are tiny and are laid in leaf tissue.

Plant stage and plant parts affected

• Found mostly on the undersides of leaves.
• Also found on fruit (under calyx) and in flowers.
• On cucurbits, this pest is more commonly found towards the tip of a runner.

Plant damage

Melon thrips have piercing and sucking mouthparts which damage plants by killing surface cells during feeding. At low levels, there may be no visible sign of damage. In high numbers, melon thrips produce silvering, yellowing, bronzing and scarring of affected plant areas.

Leaves may crinkle and die, growing tips may become stunted, discoloured and deformed, and fruits may abort or develop scar tissue.

Difficult to distinguish from western flower thrips and onion thrips.

Melon thrips need to be properly managed to minimise damage so it is important that you have an expert correctly identify the pest. If the pest is not correctly identified, incorrect chemicals may be used. This can worsen the problem, leading to crop loss and increasing the chances of melon thrips spreading.

Melon thrips occurs in South-East Asia, Japan, Florida and the Caribbean. It was detected in the Northern Territory in 1989 and in Queensland in 1993. It is now present in South East Queensland as far north as Bundaberg and also some coastal areas of North Queensland from Ayr to Mossman, and the Atherton Tablelands.

Melon thrips can affect a variety of fruits, vegetables, ornamental plants and weeds. It is particularly damaging to eggplant, capsicum, chilli, rockmelon and cucumber. Weed hosts include billygoat weed (Ageratum conyzoides), pigweed, Amaranthus, gomphrena and potato weed, as well as a variety of plants in the cucurbit and solanum families, such as the tall weed shrub, devil's fig (Solanum torvum).

• The melon thrips life cycle has 6 stages.
• The eggs are laid in leaf tissue, developing flower buds and fruit.
• Within 3–5 days the newly hatched young melon thrips change from the first nymphal stage into a second nymphal stage, and are feeding and crawling.
• At the end of the second nymphal stage, the insect crawls to the ground to undergo the next 2 stages, pre-pupa and pupa, which occur in soil.
• These stages take around 2–3 days.
• The adult emerges and either climbs or flies to a host plant to commence feeding.

High levels of melon thrips infestation can result in yield loss due to scarring on fruit. Capsicums and eggplant are particularly susceptible to losses from melon thrips feeding damage.

Melon thrips also vector tospoviruses, in particular capsicum chlorosis virus (CaCV) that can cause serious yield losses, particularly when crops are infected early. In Australia, plants affected by CaCV include capsicum (including chilli types), tomato and peanut. The virus also infects several weeds, particularly billygoat weed, which plays an important role in the survival and dispersal of the virus.

Melon thrips can be spread long distances on infested seedlings and other plant material.

Old infested crops can act as a local source of infestation.

• Protect your farm from emergency plant pests
• Understand good farm biosecurity
• Visit the farm biosecurity website

Although difficult to control, growers in the Northern Territory and Queensland have successfully managed melon thrips through a variety of integrated pest management measures including:

• population monitoring
• avoiding overuse of broad spectrum insecticides
• controlling weeds along headlands, irrigation channels and in fallows near cropping land
• avoiding sequential plantings of susceptible crops
• implementing production breaks of susceptible crops
• maintaining a buffer zone of 25 metres or more
• using reflective mulches that reduce the number of thrips entering the cropping area
• releasing commercially available predators.

In the past, the overuse of broad spectrum insecticides has exacerbated the problem, killing natural enemies including predatory thrips, and resulting in a rapid increase in insecticide resistant thrips populations.

There are no legal requirements for movement of melon thrips hosts within Queensland.

The presence of melon thrips can affect the movement of fruit, vegetables and other plant products interstate.

Interstate movement restrictions may apply to the movement of plants and plant products from coastal North Queensland and South Queensland. View maps of the North Queensland restricted area and South East Queensland restricted area.

If you are moving plants and plant products from Queensland to other states and territories, check with the destination state/territory prior to consigning. Various methods are available to meet the restrictions that may apply:

1. Having an inspection for pest freedom.
2. Having the product certified under an ICA arrangement.
3. Having the produce treated to meet the interstate destinations entry requirements.

Find out about interstate quarantine requirements.