Tropical thrips
Pest insect
- Presence of white or yellow larvae
- Silvery streaks on leaf surfaces
- Small black spots near damaged areas
- Presence of brown or black adults
- Leaf yellowing and necrosis
| Difficulty High |
| Frquency Very high |
| Reproductive rate Up to 100x |
| Lifecycle Up to 50 days |
Tropical thrips species are among the most common and dreaded pests for both professional and amateur gardeners. This soft-bodied, elongated insect causes significant damage to the foliage of infested plants. The species most likely to attack indoor plants include Hercinothrips femoralis, Echinothrips americanus, and Isoneurothrips parvispinus. Their complex life cycle makes treatment relatively demanding.
Host plants
While all types of plants are susceptible to infestation by these species, they are more prevalent on tropical plants, where the damage can be more severe.
Screening
These thrips species measure from 1 to 4 millimeters in length and appear as small black hyphen-like shapes to the naked eye. Similar to indigenous thrips, the damage they cause on leaf surfaces is characteristic, usually forming irregular silvery streaks. They also produce biological waste in the form of black spots stuck near the damaged areas.
Prevention
These species are not adapted to the continental climate, and their spread typically occurs from one indoor culture to another through people, plants, or other contaminated objects. Amblyseius swirskii sachets are recommended for prevention.
Treatment
Treating these species may involve removing heavily affected plants or leaves, repeated foliar treatments, and multiple introductions of natural predators to target different growth stages simultaneously. Unlike indigenous thrips, tropical thrips larvae do not pupate in the soil, so predator use on foliage is preferred. Amblyseius swirskii, as well as green lacewings or Orius insidiosus, are recommended for treatment.
In severe cases, treatment can be very difficult, even impossible, and complete elimination or pruning of the plant should be considered.
Products
Morphology
In Hercinothrips, also known as greenhouse thrips, the adult is dark brown. Its abdomen is wider than that of Echinothrips, and its head is slightly paler than its abdomen. Wing stripes are invisible to the naked eye, and its larvae are yellow and stout.
In Echinothrips, much more slender, the larva is yellow, the pupa is white, and the adult is black. It is recognizable by its two white spots at the base of the wings.
Parvispinus, on the other hand, is much smaller, measuring less than a millimeter and is hardly visible to the naked eye. Apart from its size, the physical characteristics of the female are very similar to those of Echinothrips. The male remains yellow in adulthood.
Their wings resemble feathers and are used more for short hops than flying.
Behaviour
Hercinothrips is native to South America. It causes the most severe damage and produces more black spots on leaves. Larvae and adults are present on both the upper and lower leaf surfaces.
Echinothrips causes slightly less damage than Hercinothrips and produces far fewer black spots on leaves. Adults are present on both leaf surfaces, while larvae and pupae concentrate below. This species is native to the southern United States.
Parvispinus infestations, although increasing, are rarer than those of other tropical species. The damage caused by this species is characterized by infinitely smaller punctures that cause corky brown marks and leaf deformations. This species is native to Asia.
Lifecycle
The majority of tropical thrips species have a four-stage development cycle, sometimes divided into sub-stages, which occur on foliage: egg, larva, pupa, and adult. Females lay their eggs inside leaves and stems. Larvae emerge after a few days and then transform into pupae and finally into adults.