Thrips Integrated Pest Management

Thrips

Scientific name:

Over 6000 species described, common pest species include:

Frankliniella occidentalis,

Frankliniella schultzei,

Heliothrips haemorrhoidalis,

Thrips tabaci,

Thrips imaginis,

Thrips palmi,

Image of first and second lava instar and adult
Frankliniella occidentalis

Source: http://www.omafra.gov.on.ca/english/crops/facts/14-001.htm

Image of adult

Source: https://bugsforbugs.com.au/whats-your-pest/thrips/

Common name:

Thrips

Insect order:

Thysanoptera

Family:

Thripidae

Host range:

Thrips are known to feed upon a wide range of different plant genera, including: Allium, Apium, Brassica, Capsicum, Citrus, Cucumis, Nicotiana, Persea, Petunia, Rosa, Rhododendron, Solanum

Metamorphosis:

Incomplete metamorphosis

Life cycle and seasonal behaviour:

Adult females deposit their kidney-shaped eggs beneath leaf and stem tissue. The emerging first instar larva immediately begins feeding upon plant tissue, before moulting into a second instar larva. The second instar larva then fall to the ground or lower leaf canopy and pupate. During the propupa and pupa growth stages the insects have undeveloped wings that can be seen forming on their backs. Adult thrips emerge within 1-3 days of the pupal stage, these can be recognised by their developed and fully functioning wings. This life cycle can be completed within 2 weeks during the warmer spring and summer months.

Adult mouthparts:  

Adult and juvenile stages of thrips use rasping and sucking mouthparts to suck sap from leaf, stem and flower bud tissues.

Juvenile mouthparts:

Plant part affected:

Thrips feed upon the leaves, petals and fruit of host plants. Feeding damage creates a silvery stippled effect upon their surface and may cause deformed growth in new shoots and flowers. Excretion may also be visible as little black spots. Thrips can cause severe stunting of growth in their host plant. Thrips can also be host to plant pathogens such as Impatiens necrotic spot virus and Tomato spotted wilt virus.

Pest management options

Chemical:

Neem oil, horticultural soap, pyrethrum

Cultural:

Avoid over fertilising, as thrips are attracted to young lush growth.

Physical:

Yellow sticky traps to monitor and assist in the control of adult thrip population.

Plants can also be gently shaken over a white piece of paper if thrips are suspected but cannot be easily located, they will fall off onto the paper.

Biological control:

Typhlodromips montdorensis (Australian native predatory mite), Hypoapsis miles (predatory mite)

Integrated Pest Management (IPM)

Thrips can be difficult to manage, and are best controlled using a combination of cultural, physical and biological practices. Chemical management can be helpful in certain circumstances, however it can be difficult to apply effectively as by the time damage is visible on plants the thrips will often have moved on to another feeding location.

Monitor and reduce thrip populations using yellow sticky traps. Populations can build up within weeds surrounding the garden or nursery. Remove weeds as they occur.

Promote the presence of beneficial insects in the garden or nursery by planting species that will attract them alongside other crops. Pirate bugs, parasitic wasps, green lacewings, as well as predatory mites all feed upon the larval and adult stages of thrips and are excellent at controlling their populations.

If chemical control must be employed, use of environmentally friendly horticultural soaps is preferred as these products have very little to no impact upon beneficial insects. Spray plants thoroughly, being careful to target the undersides of leaves and any crevices around buds, flowers or leaves that the insects could be hidden within.

Although listed for control of thrips, pyrethrum based insecticides are avoided as they are known to impact beneficial insect populations, especially honeybees.