Citrus thrips is originally described from various localities in South Africa and is indigenous. It occurs throughout Southern Africa, East Africa, Egypt and Yemen. Citrus thrips can survive on many different host plants but seem to be particularly attracted to those with aromatic oils and terpenoids.
Appearance and life cycle of Citrus thrips
When food availability is optimal, the life cycle lasts 20 days during October and November. When food is suboptimal and the weather is colder, the life cycle can be 45 days. Eggs are laid in soft leaf tissues or young fruit and can take 6-24 days to hatch depending on temperature. It is the second instar larvae that are responsible for most of the feeding damage, this stage can last 4-6 days. The larva will move towards the shady area of the tree to pupate, if a suitable site is not found, the larva will drop to the ground to pupate. Citrus thrips does not enter diapause during winter and all life stages may be present throughout the year.
Damage and symptoms
Citrus thrips larvae and adults feed on young leaves or fruit. They cannot survive on mature, hard foliage. They feed most often in narrow crevices created by folds in leaves or under the calyx of a fruit due to their thigmotactic behaviour. Damage around the calyx appears as silver white blemished areas when fruit is small, which may become brown when exposed to the sun later in the season. Severe scarring of fruit can occur up to 13 weeks after petal fall, after which the damage appears as scribbling and finally as stippling or russet in mature fruit. Young citrus plants can be stunted by severe foliage damage, all growth flushes must be protected for several years using chemical treatments. Even though citrus thrips is an important pest, it is unlikely to be on the fruit at harvest, so it’s not considered a quarantine risk on fresh fruit exports.
We would like to acknowledge the following for the photos of Scirtothrips aurantii (Citrus thrips) and their damage: Stephen, P.R & Citrus Research International. Citrus thrips and their damage. [Photograph] (P.R. Stephen and the Citrus Research International Collection).