Thrips are a pest of many agricultural crops. Thrips belong to the order Thysanoptera and feed on plant sap.

There are over 5,500 species of thrips and about 75 species of them are pests of horticultural crops. They have an elongated body and most species are up to 1.5mm in length and have two pairs of narrow wings. Their color may range between light yellow to black.

Common thrips species in vegetables and flowers:

Banded greenhouse thrips (Echinothrips americanus)
Tomato thrips (Frankliniella schultzei)
Melon thrips (Thrips palmi)
Western flower thrips (Frankliniella occidentalis)
Plague thrips (Thrips imaginis)
Onion thrips (Thrips tabaci)

DAMAGES CAUSED BY THRIPS
Thrips have rasping and sucking mouth parts and during feeding, they first rasp the cells and then suck up plant sap. Therefore, the direct damage caused by thrips includes flecking or silver-grey patches on the leaves, fruits and flowers.

Another common direct damage caused by thrips is deformation of leaves and flowers. When thrips feed on young plant parts, that are still growing, deformations are formed as a result of undamaged cells that develop around cells that were damaged by the thrips. It is worth noting that when deformation symptoms show up, the pest may no longer be present.

Additional direct damages caused by thrips may include small fruits, fruit drop and leaf drop.

Thrips can also cause indirect damages. They act as a vector to various plant viruses.

THRIPS LIFE CYCLE
Development stages of thrips include eggs, two nymph stages, pre-pupa, pupa and adults. The duration of each development stage is temperature dependent.

Females may lay 2-10 eggs per day, depending upon species, host and temperature. They may lay eggs inside plant tissue, underside of the leaves, inside flowers or along the stems.

Adult thrips may live for 2-6 weeks.

SCOUTING METHODS
In crops that are susceptible to thrips, regular scouting and monitoring are important in order to detected infestation as early as possible.

Using blue or yellow sticky tapes as traps can help in monitoring thrips, as thrips are attracted to the colored traps. In greenhouses, it is recommended to use at least 1 trap per 1,000 square feet (or 100 square meters). Traps must be hanged just above the plants and inspected regularly.

It is also recommended to inspect individual plants. Slightly shaking plant leaves and flowers over a white paper sheet may reveal hiding thrips that will fall on the paper. A magnifier glass can be used to identify them.

Thrips can also be detected by their damage symptoms or signs they leave behind. Black small spots, which are the thrips feces, will usually appear next to damage symptoms.

THRIPS CONTROL

Biological Control
Beneficial insects. When thrips pressure is low or moderate, beneficial insects can provide good control. Predatory mites, such as Amblyseius cucumeris and Amblyseius swirskii feed on the nymph stages of thrips. The predatory bug, Orius, feed on all stages of thrips life cycle, including adults.

Cultural Practices
multiple cultural practices can greatly reduce thrips infestation. Such practices include eliminating weeds, using anti-insect nets and sticky traps, using mulch etc

Chemical Control
Chemical control of thrips can be difficult. They are resistant to most pesticides and feed deep within the flower head or on developing leaves. This makes them a difficult target for insecticides, so thorough coverage is essential. If you use pesticides to control thrips, follow these general guidelines:

a. Begin applications early, before the thrips population grows too large. Thrips are more easily managed when population levels are low.
b. Although it is important to rotate chemical classes, use only one chemical class for the duration of the thrips' life cycle. This generally means using a different class every 2-3 weeks, depending on the time of year.
c. Apply pesticides in early morning or late afternoon, when flight activity of thrips is at a peak. This increases exposure of the thrips to the pesticides

Insecticides – insecticides such as neem oil and Azadirachtin can provide moderate control of thrips and usually do not harm beneficial insects. Spinosad is a natural insecticide that was found to be very effective against thrips. Pyrethrins insecticides are also used to control thrips.

Thrips are usually difficult to control with insecticides, mainly due to the fact that in most of their development stages they are hard to reach with spray and protected from insecticides.

Drop your phone number or visit AGRO HORTIPONICS on www.agrohortiponics.com and leave us a message to get a list of common chemical in Nigeria that are effective against thrips