The chilli thrips, Scirtothrips dorsalis Hood, is an important pest of various vegetable, ornamental and fruit crops. Thrips possess piercing and sucking mouthparts and cause damage by extracting the contents of individual epidermal cells leading to tissue necrosis. Chilli thrips feed on the meristems of host plant’s terminals and on other newly developing plant parts. Damage includes: feeding scars, distorted leaves, and discoloration of buds, flowers and young fruits.
Successful treatment of active Chili thrips is a two pronged approach:
- Foliar spray of new growth to knock down active populations.
- Systemic treatment to provide season long control of new infestations.
Other Treatment Practices
- Adequate water is a key factor in maintaining stress free plants. A slow, deep watering event once every few weeks during dry conditions will help maintain soil moisture levels and minimize stress.
- Mulch is very beneficial for all trees because it reduces competition with turf and moderates soil temperature and moisture levels. The addition of 3 inches of wood chips or shredded bark under the drip line can have a very beneficial effect by holding in moisture and promoting healthy fibrous roots.
- Cambistat can be also be used to promote tree health and reduce the incidence and severity of stress mediated diseases and insect problems on trees growing in urban areas.
Systemics have been reported to work well. May need to combine with foliar sprays for faster control.
Signs of Damage
- Chilli thrips are pale colored and the lengths of their first and second instar larvae and the pupae are 0.37-0.39, 0.68-0.71 and 0.78-0.80 mm, respectively
- Adults are about 1.2 mm long with dark wings and dark spots forming incomplete stripes which appear dorsally on the abdomen (Seal et al. 2009a)
- Silvering of the leaf surface
- Linear thickenings on the leaf surface
- Brown frass markings on the leaves and fruits
- Grey to black markings on fruits often forming a conspicuous ring of scarred tissue around the apex
- Fruit distortion and early senescence of leaves
Photo: Rose bush leaves damaged by Chilli Thrips
Photo: Rose bush flowers damaged by Chilli Thrips
Trees At Risk
Chilli thrips can effect over 100 different plant taxa. Common shrubs affected are; duranta, plumbeago, pittosporum, Indian hawthorn, snowbush, and rose
- Life cycle consists of egg, first and second instar larvae, prepupa, pupa and adult.
- Females insert the eggs inside plant tissues above the soil surface.
- Eggs hatch between two to seven days, depending upon temperature.
- Larvae and adults tend to gather near the mid-vein or borders of the host leaf.
- The two larval stages are completed in eight to ten days and the pupal stage lasts for 2-4 days.
- The life span of chilli thrips is influenced by the host plant species.
- For example, at 28°C it takes 11 days for first instar larva to progress to adult stage on pepper plants and 13.3 days on squash plants.
- The chilli thrips adult's life span lasts an average of 15.8 days on eggplant, but only 13.6 days on tomato plants (Seal et al. 2009a).
- 4-8 generations per year.
Always refer to product label for rates and approved uses. Some images courtesy of forestryimages.org or Wikimedia Commons. Use of the images does not imply endorsement of treatments.