Mulberry thrips

The mulberry thrips (Pseudodendrothrips mori) belongs to the order Thysanoptera and the family Thripidae, specializing in infesting mulberry tree foliage.

Adult thrips are very small, usually measuring less than 1 mm in length, and possess a slender body with a yellow-brown or dark coloration.

The wings of this species are characteristically narrow and lined with long, delicate hairs, which is a diagnostic feature of the Thysanoptera order.

Larvae are similar in appearance to adults but are wingless, smaller, and generally exhibit a lighter, paler body color during their developmental stages.

They are notoriously difficult to spot, as they remain hidden on the abaxial (lower) surface of leaves, often nestled along the veins of the plant.

Mulberry trees serve as the primary host for this pest, often experiencing significant foliage damage when thrips populations reach high densities.

By piercing the leaf tissue and extracting cell contents, these insects disrupt photosynthetic efficiency and overall plant vigor.

Heavy infestations can significantly reduce the biomass of leaves, posing a severe threat to sericulture operations that depend on foliage for feeding silkworms.

The damage is typically concentrated on younger, developing leaves at the top of the canopy, which are the most nutrient-rich for the pests.

Continued stress from feeding makes the trees more vulnerable to secondary infections and environmental stressors, leading to overall decline.

The life cycle of the mulberry thrips is strongly governed by ambient temperature, with activity commencing as soon as spring temperatures rise.

These insects can produce several generations during a single growing season, with the development time shortening significantly in hotter climates.

Adults overwinter in sheltered locations, such as crevices in tree bark, among leaf litter, or within the top layers of soil around the base.

Population peaks usually occur during the warm summer months, particularly during periods of dry weather which favor rapid reproduction and spread.

As temperatures drop in the autumn, activity decreases, and adults migrate to protected areas to enter their overwintering phase until the next spring.

The first observable sign of infestation is the appearance of tiny, light-colored spots or stippling on the leaves, which eventually coalesce into larger necrotic areas.

Affected leaf areas often develop a metallic, silvery, or bronzed sheen due to the presence of air in the empty cells after the sap has been extracted.

Examination of the underside of the leaf often reveals tiny black specks, which are the fecal droppings left behind by the feeding thrips.

Severe infestations cause the leaf edges to curl, deform, and become brittle, significantly impacting the aesthetic and physiological health of the canopy.

In extreme cases, widespread chlorosis and premature leaf drop occur, which can lead to stunted growth and reduced yields in commercial plantations.

Cultural management is the first line of defense, including the thorough tilling of soil around tree trunks to disrupt the overwintering habitat of the pests.

Regular pruning and removal of heavily infested branches can help reduce local population pressure and prevent further spread throughout the orchard.

Chemical control involving systemic or contact insecticides should be applied when thresholds are reached, ensuring proper coverage of the leaf undersides.

Resistance management is crucial, so rotate active ingredients belonging to different chemical classes to maintain the efficacy of pest control products.

Integrated pest management strategies should also prioritize the preservation and introduction of natural predators, such as lady beetles and predatory mites.