Thrips
THRIPS PARVISPINUS: IDENTIFICATION AND BIOLOGICAL CONTROL WITH NEMATODES
Thrips parvispinus, also known as tobacco thrips, has become a serious threat to horticulture worldwide in recent years. Originally native to tropical Asia, this pest is spreading rapidly and now colonises large parts of Asia, Africa and North America.
It has also long since arrived in Europe: after initial findings in Greece (1998), it was also detected in Spain (2017), France (2018) and the Netherlands (2019). Since the end of 2021, the pest has also been present in Germany. Especially in protected cultivation, Thrips parvispinus finds ideal conditions for mass reproduction due to the warm and humid weather.
The life cycle of Thrips parvispinus
Understanding the pest's development is crucial to effectively controlling it. The life cycle comprises a total of six stages:
- Egg: Females lay their eggs directly in leaves, petals or soft stem tissue using a saw-like apparatus.
- Larval stages (L1 & L2): The larvae are almost transparent-whitish to orange-yellow with striking red eyes.
- Prepupa & pupa: These stages usually take place in the soil or substrate. They do not feed and only move when disturbed.
- Adult insect: Adult females are about 1 mm in size and brown in colour, while males are significantly smaller at about 0.6 mm and yellow-orange.
The development period is highly temperature-dependent: while development from egg to adult takes about 36 days at 20∘C, it is shortened to only 23 days at 25∘C.
Identification and damage
Early detection is key to control, as populations can explode rapidly due to their high reproduction rate.
- Where to look: Check the undersides of leaves and the inside of flowers in particular. Larvae prefer young leaves and flower buds.
- Behaviour: While larvae often feed openly on the plant, adults are usually very adept at hiding.
- Symptoms: The feeding damage leads to considerable quality losses and deformities and can render the plants unsaleable. Peppers, papayas and various ornamental plants are particularly affected.
Typical damage of Thrips parvispinus in pepper cultivation
Biological control with nematodes
Since Thrips parvispinus spends part of its development (prepupa and pupa) in the soil, entomopathogenic nematodes (EPN) offer a strategic advantage. These biological antagonists can specifically combat the soil dwelling stages, which are often inaccessible to conventional, surface-acting insecticides.
Research conducted by Michigan State University has confirmed the potential of various nematode species.
The EPN species Heterorhabditis bacteriophora and Steinernema carpocapsae achieved a mortality rate of up to 50% in the laboratory.
The use of nematodes reduces the number of adult thrips that hatch, thereby reducing the pressure on the above-ground parts of the plant. Ideally, EPNs are combined with other beneficial organisms as part of an integrated pest management (IPM) concept.
Outlook: Working together for better solutions
Although the results achieved so far with the use of nematodes against Thrips parvispinus are very promising, the overall trial situation is still quite limited compared to other pests. Further data from practical application is needed in order to optimise the application protocols and develop even more specific strategies for different crops.
e-nema is open to further trials and collaborations
If you are interested in testing the use of nematodes on your farm or working with us to gain new insights into the control of Thrips parvispinus, please contact us!
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