Thrips on Orchids: Identification, Damage, and Natural Treatment Methods for Growers

Nothing is more disappointing to an orchid grower than a plant that grows well and produces flower buds that fail to grow to a normal size, become misshapen or fail to bloom. The first warning can be missing from the flower. Leaves and petals are covered with silvery scars and brown spots appear on leaves and on petals while small black spots start to appear around the damaged area. They can indicate damage is occurring and thrips orchid are one of the pests that needs to be addressed.

Thrips on orchids are tiny insects, making them hard to detect prior to establishment. Frankliniella occidentalis and Hercinothrips femoralis can damage ornamental plants, such as orchids. They have narrow bodies which enable them to grow in protected sites such as the flower sheaths, developing buds, leaf axils, and other protected sites where conventional sprays may not be able to get to. They have a short generation time, which can enable populations to rapidly increase if conditions are favorable.

One problem is the re-exposure to insecticides as thrip control products. There are a number of groups of chemical insecticides that can be used against thrips and the repeated use of the same group can become less effective. The orchid thrips management starts with early identification of the pests followed by monitoring, sanitation, biological control, and judicious use of treatments will be the key to orchid thrips treatment for orchid growers.

Early Detection: thrips damage on Orchids

How to get rid of thrips naturally? Orchid growers have more options when it comes to controlling thrips on orchids the sooner they are identified. A conspicuous symptom is damage to flowers and developing buds. Brown streaks, whitened or water-soaked and discoloured areas and bent petals and buds may result from feeding. Under severe conditions, flower development can be affected by malformed flowers and/or premature flower drop before the flower can reach its ornamental value.

An infestation can also be detected by the leaves. Thrips have mouthparts that have a rasping sucking action which injures cells of the plant when feeding. This may leave behind patches of silvery, bleached or etched that might look like fine scratches on the surface. A small amount of black frass can also be seen on the leaves, petals or where they are feeding.

The white-paper test is a simple monitoring technique. When orchids are in the early stages of flowering, it is particularly important to inspect them regularly for damage since the damage may not be evident until after feeding.

Importance of timing – understanding the Orchid Thrip life cycle

The orchid thrip life cycle can help to understand why only a single application is not always effective. Thrips undergo a number of stages and each stage acts differently. Eggs are laid in plant tissue where they are shielded from many contact treatments. Upon hatching, the first and second larval stages actively feed on the tender leaves, flowers and developing buds.

Thrips later enter into the prepupal and pupal phase that are non-feeding. They can be protected (e.g. leaf axils and growing media or other protected areas), depending on the species and growing conditions. The adult plants eventually emerge and feed, reproduce and move from one plant to another.

This co-occurrence of the development stages results in a possibility of eggs, larvae, pupae and adults being present in the same orchid material. An orchid thrips treatment that kills exposed larvae/adults does not necessarily kill protected eggs/or non-feeding stages. Therefore, a good orchid thrips program involves surveillance and follow-up applications as needed to control the pest, based on the product label and the conditions when the pest is developing.

Instead of considering control as one application of a homemade insecticide for thrips spray, growers should consider breaking the pest's reproductive cycle. Usually repeated monitoring is also important as new adults may emerge following an initial monitoring.

Focus on Biological Control: Nature's Solutions to thrips problems

How to get rid of thrips naturally? In addition to reducing reliance on the repeated use of conventional insecticides, biological control is another method orchid growers can use to control thrips. The entomopathogenic fungi and predatory beneficial organisms are two key strategies.

Beauveria bassiana is a Fungal Approach

Beauveria bassiana is an entomopathogenic fungus which has been well studied for biological control of thrips. The fungus does not depend on chemical toxicity like an insecticide, but is able to infect susceptible insects after contact with viable fungus spores. Spores become attached to the outside of the insect and then grow when conditions are right and bore through the cuticle. The fungus can then grow in the insect and eventually kill it.

B. bassiana is an interesting biological mode of action that could be added to an IPM program. But it is dependent upon many factors such as contact with susceptible insect, coverage, environment and formulation quality and viability. It should, therefore, be regarded as a part of a larger program of biological controls, not automatically as a substitute for all other controls.

Novobac's Beveria WP is a Beauveria bassiana, biological insect-management product that may be used if specified on the label. To the growers of orchids, the usefulness of such a product is in its role in a comprehensive program of orchid management that includes a system of scouting, sanitation and environmental management.

Never use any product on valuable plants without following the product label and carrying out any required crop-safety testing since orchids have sensitive flowers and foliage.

The predator mites and beneficial insects are described

How to control thrips organically? Predaceous enemies may be an additional method of thrips control. Amblyseius cucumeris and Neoseiulus swirskii are species that are applied in a protected crop biological control program and that can consume immature thrips. Minute pirate bugs (Orius species) will also feed on thrips and other small arthropods.

The good thing about beneficial organisms is that they can help with a continual control of pest populations, instead of just when they are applied. However, factors like temperature, humidity, the availability of prey and compatibility with other pest control products play a part in their success.

Organic and “Low-Toxicity” Contact treatments for Hobby Growers

How to control thrips organically? The use of physical and less destructive methods may sometimes be effective to reduce thrips populations in small scale orchid collections. Exposed larvae and adults can be removed by gently washing with water. This method will not kill any hidden insects or eggs, but if properly done, will control the exposed insects.

Exposed soft bodied stages can be damaged by contact with insecticidal soap. Orchid leaves and flowers, however, are sensitive to some formulations and growers should test orchid thrips treatment on a small part of a plant before treating a whole collection of orchids; and read and follow label directions.

Other products that sometimes are incorporated into integrated programs contain azadirachtin, which is derived from the neem tree. They can act as feeding deterrents and disrupt insect development but will vary by insect stage and use. For any specific crop or ornamental use where they are legally registered and labeled for use, spinosad-based products can also be used against certain thrips.

How to get rid of thrips naturally? The key is that it is not just a matter of discovering one ‘organic spray' to control thrips. Physical removal, sanitation, monitoring, biological control and appropriate products are often used in combination with each other to achieve successful management. Some of the herbs used in making insecticide on their own can be toxic when not used properly, especially on the sensitive flowers of orchids.

Chemical Pesticides - When to consider them?

Chemical pesticides for thrips control can be used as a component of a total program of thrips control if biological and cultural control methods are proven ineffective, with heavy populations of thrips. Flowers, leaves and growing points are sensitive to phytotoxicity (toxic effects on plants) however, and special care should be exercised when using orchids.

Contact insecticides may be difficult to use because thrips will often be found in flowers, buds and protected places. Systemic products can also be restricted as a result of the feeding habits of pests, the physiology of the plant and the active ingredient. Therefore, insecticide use by itself does not ensure control and just selecting any product labeled as an insecticide does not ensure effective control.

Another important consideration is resistance management for orchid thrips treatment. Thrips on orchids have a strong tendency to build up resistance to poorly rotated groups of insecticides. When chemical control is required, turn to other chemistry (using different modes of action and IRAC recommendations) rather than re-apply the same chemistry.

Growers should always check the registration or label for the product to be used on or for the intended crop or ornamental and at the site. Always use in accordance with label directions for concentration, interval of use and protective equipment and plant safety precautions.

IPM Plan for an Active Orchid Thrips Problem

How to control thrips organically? If an active attack is seen the first priority is to make sure that the insects do not spread to healthy plants. Isolating newly affected orchids from the remaining orchids, especially in greenhouses, nurseries and indoor growing areas. This is a simple, but effective, quarantine measure that can make a big difference to the likelihood of containing a localized problem.

Next, it's time for sanitation. If the damage is extensive at the flower, bud or plant level, remove the damaged parts as necessary. Removing heavily infested tissue (HIT) will remove potential feeding and breeding areas, and facilitate subsequent monitoring.

A biological product, like Beauveria bassiana, most effective insecticide for thrips, - in this case, a product labeled to deal with the problems that it is intended for, Beveria WP can then be incorporated into an integrated program. The goal is to apply viable fungal spores to susceptible insects under the appropriate application rate, coverage and environmental conditions. General application information should be used in conjunction with product directions, and not instead of them.

Post-treatment monitoring should be carried out. Sticky traps and visual inspection and white-paper testing can be used to help identify if adult and larval activity is decreasing. Follow-up applications should be reserved for those made in response to pest problem or according to the instructions on the product label and not on a fixed schedule which may not be suitable for all orchid growing situations.

Last but not least, prevention should be incorporated into the regular orchid maintenance. When introducing new plants to the collection, inspect for pests, have good air movement, remove plant debris and watch closely for development of flowers. In protected growing areas, physical insect screens may also be used to limit the spread of insects.

However, orchid thrips treatment is most often not a one-shot deal. An integrated program of insect pest management that relies on a combination of early detection, sanitation, biological control of thrips and, if needed, selected other methods.

References:

1. Hotaka, Dararat, et al. “Efficacy of Purpureocillium lilacinum CKPL-053 in controlling Thrips palmi (Thysanoptera: Thripidae) in orchid farms in Thailand.” Applied Entomology and Zoology 50 (2015): 317-329.
2. Li, Dongwei, et al. “Soil application of Beauveria bassiana JEF-350 granules to control melon thrips, thrips palmi Karny (Thysanoptera: Thripidae).” Journal of Asia-Pacific Entomology 24.3 (2021): 636-644.