Thrips

Thrips order Thysanoptera, are tiny, slender insects. Their mode of feeding is through puncturing the epidermal layer of the host and sucking the cell contents. This leads to a discolored silvery leaf surface. The feeding is usually accompanied by black excrement.

Discolored leaf as a result of Thrips.

Thrips move by being transported on infested plants or by floating with the wind.

Most adults are 1/20 inch long and have long fringes on the margins of both pairs of their long, narrow wings. The larvae/nymphs are slender, elongate and lack wings.

An adult, egg, and two larvae of Cuban laurel thrips.

Thrips feeding results in scar formation and distorted growth. Fortunately, most thrips are susceptible to some of the same controls. Certain thrips occur on many different plants but damage only a few of the plant species on which they are found. Identifying the species of thrips may reveal that it is harmless in certain situations and no control action is needed. For example, avocado thrips and greenhouse thrips superficially scar avocado fruit skin. Citrus thrips and western flower thrips are also found in avocado but do not damage avocados. Citrus thrips occur on many species of plants but damage only blueberries and citrus.

Greenhouse thrips larvae (yellow) with black pupae and adult of the Thripobius parasitic wasp.

THRIPS LIFE CYCLE

Thrips hatch from an egg and develop through two actively feeding larval stages and two nonfeeding stages, the prepupa and pupa, before becoming an adult. Late-instar larvae change greatly in appearance and behavior and are called prepupae and pupae, even though thrips do not have a true pupal stage.

Females of most plant-feeding species lay their elongate, cylindrical to kidney-shaped eggs on or into leaves, buds, or other locations where larvae feed. The pale prepupae and pupae of most species drop to the soil or leaf litter or lodge within plant crevices. Greenhouse thrips pupate openly on lower leaf surfaces; while pupae (and eggs) of some gall-making species, such as Cuban laurel thrips and myoporum thrips, occur on leaf surfaces but are enclosed within distorted plant tissue. Thrips have several generations (up to about eight) a year. When the weather is warm, the life cycle from egg to adult may be completed in as short a time as 2 weeks.

MANAGEMENT

Thrips are difficult to control. If management is necessary, use an integrated program that combines the use of good cultural practices, natural enemies, and the most selective or least-toxic insecticides that are effective in that situation.

Thrips can be managed using any of the following combinations of insecticides

• Avermectins e.g Abamectin, Emamectin benzoate. Examples of brand names include; Oberon Speed, Escort, Prove, Dynamec
   
• Benzoylphenyl urea e.g Lufenuron such as Match, Emmaron, Sussita
   
• Neem oil eg Nimbecidine, Neemazal.
  Diafentiuron e.g Pegasus
   
• Neonicotinoids e.g imidacloprid, acetamiprid, thiamethoxam such as Confidor, Actara, Golan, Twiga Ace.
   
• Spyrroles e.g spinosad, spinetoram such as Radiant, Tracer