Rasmudk

Description (larval stages)

The larvae of onion thrips differ from other thrips species in that they have the shortest macrosetae of any thrips, observed as roughly 20 micrometer long bristles arranged on the prothorax of the larvae. The larvae of many other thrips feature gray chitinous markings on the back of their thorax, which is not seen in onion thrips larvae. They can also be differentiated by structures in the abdomen; with T.tabaci featuring geometric, pointed protrusions, which are  otherwise rounded in most other species of Thrips (Diaz-Montano).

The outward appearance of an adult Thrip is partially determined by its surrounding temperature in earlier stages of its life cycle. Body size is determined in the larval stage, while the adult Thrips body color is determined during pupal stage (Diaz-Montano)

Damage (cont.)

The microbiome of onion thrips is host to many microbes, including Streptococcus, Eriwina, and Pseudomonas, making them potentially catastrophic to crops for their ability to transmit disease  (Gawande). They act as a major vector of Iris Yellow Spot Virus (IYSV), which can increase yield loss from thrips damage from 50% to up to 100%. Damage from onion thrip feeding can transmit IYSV, leaving tan-colored, chlorotic lesions that can range from long streaks to diamond shaped, potentially killing the crop before it reaches maturity, while also reducing bulb size and yield (Diaz-montano, Inglesias). T.tabaci infected with IYSV have been shown to have an increased lifespan compared to those not vectoring the virus (Leach).

Crop management

Insecticides

Management of Thrips tabaci is often only treated by use of insecticides, which when used too regularly or in overabundance, can lead to the development of resistances in T. tabaci, rendering the chemicals useless. There have been reported resistances to organophosphates, carabamates, avermectins, milbemycins, and other chemicals commonly used to treat Thrips infestations (Iglesias). Currently effectively chemicals used for treatment of T.tabaci include Spirotetramat, which inhibits lipid production in the insect's cells, and Spinosad, which has been found to be harmless to other arthropods, many of which are natural predators of T.tabaci (Nault, Mautino).

Biodefenses

The use of cultural and organic practices to reduce infestation can be helpful in managing T. tabaci, and can support the general health of Allium crops in a more environmentally friendly way than repeated chemical use. Avoiding monocultures of crops which T.tabaci feed and reproduce on can aid in decreasing pest pressure, such as intercropping with ryegrass or clover (Belder). Selecting or rotating crops that are naturally resistant to thrips, such as cultivars with tight leaf axils, or leaves exhibiting a glossy, light green phenotype may help to deter the pest from establishing (Cramer, Inglesias). Natural chemicals such as neem oil, and other derivatives of neem / Indian Lilac, have proven effective against T.tabaci infestations (Iglesias)