INTERESTING INSECTS

By N A Martin (2018 revised 2019)

Hydatothrips (Neohydatothrips) samayunkur Kudo 1995

The scientific name of the French marigold thrips is Neohydatothrips samayunkur (Kudo, 1995), but there has been confusion due to the use of other ‘scientific names’ all in the subfamily Sericothripinae.

This adventive species of thrips was first found in New Zealand in an Auckland garden by Nicholas Martin in 2009. The feeding damage to plants of French Marigold, Tagetes patula L. (Compositae), alerted him to the presence of the thrips. The thrips is recorded from Tagetes species in Mexico, El Salvador, California, Florida, Hawaii, Japan, Sri Lanka, Mauritius, Kenya, and eastern Australia. It feeds and breeds on the leaves and in flowers.

Conservation status: A pest of its host plants, Tagetes species, in gardens. The thrips can cause severe damage to plants and sometimes kill them.

Life cycle of a plant feeding Terebrantia thrips. © Plant & Food Research Figure 8 from Crop & Food Research Infosheet No3-16. [Image: 2J2N]

The French marigold thrips appears on French marigold bedding plants in the summer. It breeds in flowers and on leaves; capable of causing extensive damage to its host. It is not known how long it takes to complete its life cycle. It is also not known how the adult females overwinter.

Adults

Adults, like the other active stages of French marigold thrips, are relatively long and thin The bodies of adult thrips are bicoloured dark and mid brown. The wings are dark brown with three white bands. The head has two antennae, two compound eyes and on the underside the mouth cone contains a pair of short maxillary stylets and a single stout mandible. There are three pairs of legs and two pairs of wings that when not used for flying are held over the abdomen. The tip of the abdomen contains the genitalia. The end of the female abdomen also has an ovipositor for inserting eggs into leaves.

Eggs, Larvae and Pupae

Eggs are laid in in leaves and possibly flowers. A thin larva hatches from the egg. It is the shape of a tiny orange wingless adult. Like the adult it has three pairs of legs, a pair of antennae and the same structures for feeding. There are two larval stages and two non-feeding stages, a prepupa and a pupa. The juvenile thrips go to the next stage by moulting. This involves the dorsal skin splitting and the next stage pulling itself out of the old skin. The second larva looks like the first larva. The upper side of the body is covered in short, wide and flattened setae (spine-like hairs) that bear short spines. The first non-feeding stage, the prepupa, differs in appearance from the larva by having short wing buds. The next stage, the pupa, has longer wing buds and the antennae are folded back. The prepupa and pupa also live on leaves and flowers.

Feeding and plant damage

The thrips feed and breed on leaves and in flowers. Larvae and adults use the stylets in their mouth cone to feed. They puncture plant cells with their single mandible and suck up the plant cell contents with their maxillary stylets. Their feeding kills the surface cells of the leaves creating distinctive pale areas of dead cells. Leaves that have been fed on by the thrips exhibit scarring, silvering and distortion. They are also covered with black faecal droplets.

Upper side and underside of an adult French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJ8]

An adult French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a leaf of French marigold, Tagetes patula L. (Compositae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJ7]

Side view of an adult French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a leaf of French marigold, Tagetes patula L. (Compositae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SJ3]

A larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a French marigold, Tagetes patula L. (Compositae), leaf: note the tiny black setae (spines). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SJ5]

A larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae): note the tiny black setae (spines). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SJ6]

A microscope slide of a larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Landcare Research. [Image: 31ID]

A microscope slide of the abdomen of a larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae): note the dorsal setae. Creator: Nicholas A. Martin. © Landcare Research. [Image: 31IF]

A microscope slide of the abdomen of a larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae): note the dorsal setae. Creator: Nicholas A. Martin. © Landcare Research. [Image: 31IE]

A larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a leaf of French marigold, Tagetes patula L. (Compositae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJE]

Two mature larvae and a prepupa of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a French marigold, Tagetes patula L. (Compositae), leaf: note the prepupa (left) has short wing buds. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJH]

Two images of a larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJI]

Two sets of images of a pair of pupae of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae): note the long wing buds. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJG]

A pupa of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a leaf of French marigold, Tagetes patula L. (Compositae): note the long wing buds. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJF]

In New Zealand, the French marigold thrips is the only leaf feeding thrips that lives on French marigold, Tagetes patula L. (Compositae) and other species of Tagetes. The thrips feeds and breeds on the leaves and in flowers. The leaf damage is typical of thrips. There are white areas on the leaves where the thrips have been feeding and black faecal spots. The leaves may also become distorted The adult thrips are dark brown with white areas between segment. The wings are black and white. The nymphs, prepupae and pupae are a dark orange and have many short black setae (spines).

A plant of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2SJL]

Leaves of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae): note an out of focus adult on the main vein of the leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJC]

An adult French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a leaf of French marigold, Tagetes patula L. (Compositae). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SJ4]

A larval French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae) on a French marigold, Tagetes patula L. (Compositae), leaf: note the tiny black setae (spines). Creator: Tim Holmes. © Plant & Food Research. [Image: 2SJ5]

No natural enemies of the French marigold thrips have been found in New Zealand.

The host plants of the French marigold thrips are French marigold, Tagetes patula L. (Compositae) and other species of Tagetes. The thrips feeds and breeds on the leaves and in flowers.

Adult and larvae feed by inserting their stylets plant cells at or near the surface of the leaf. They suck out the cell contents. Their presence can be recognised by the distinctive appearance of their feeding damage on leaves.

A plant of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJJ]

A plant of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Nicholas A. Martin. [Image: 2SJK]

A shoot of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJD]

Leaves of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae): note an out of focus adult on the main vein of the leaf. Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJC]

A shoot of French marigold, Tagetes patula L. (Compositae), with leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJB]

A shoot of French marigold, Tagetes patula L. (Compositae), with severe leaf damage caused by the feeding of French marigold thrips, Neohydatothrips samayunkur (Thysanoptera: Thripidae). Creator: Nicholas A. Martin. © Plant & Food Research. [Image: 2SJA]

The French marigold thrips can cause severe damage to French Marigold bedding plants. If thrips feeding damage is seen on young plants, treatment with an insecticide may be warranted. Consult your local garden centre or horticultural supplier about suitable insecticides.

Research Project

There is little detailed information about the lifecycle and annual cycle of the French marigold thrips. It would be useful to know how it overwinters in New Zealand and details of the female’s egg laying preferences and the length of time needed by the egg, larval and pupal stages.

Mound LA, Tree DJ, Paris D. 2018. OZ Thrips, Thysanoptera in Australia.

Mound LA, Nielsen M, Hastings A. 2017. Thysanoptera Aotearoa - Thrips of New Zealand. Lucidcentral.org, Identic Pty Ltd, Queensland, Australia.

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

1 June 2019, NA Martin. Added photos of microscope slides of larvae.