Bald cypress trees (Taxodium distichum) are prized for their attractive feathery foliage, interesting knobby knees and pyramidal shape when young. However, they can sometimes fall victim to infestations by an annoying sap-sucking pest called thrips. Thrips feed on tender new growth of bald cypress trees causing buds to distort and dieback. Left uncontrolled, thrips can severely weaken, defoliate, and even kill bald cypress trees. Getting rid of thrips in bald cypresses requires persistence and integrating multiple control strategies. Here is a comprehensive guide on effective methods for eliminating thrips in bald cypress trees.
Understanding Thrips
Thrips are tiny winged insects only 1-2mm long Two common species attacking bald cypress are quantum thrips and bald cypress thrips They have piercing tube-like mouthparts which they use to pierce plant cells and suck out sap. This causes stippling, discoloration, curling, and distortion of bald cypress foliage and shoots. Thrips also spread debilitating fungal diseases.
Thrips thrive in warm, dry conditions. Populations peak in mid to late summer. They can build up undetected on new growth before damage becomes visible. Once established, thrips are difficult to eradicate due to their short life cycle and prolific reproduction. A single female can lay hundreds of eggs. The winged adult stage also allows them to disperse widely.
Combining different control methods and thoroughness is key to successful thrips management in bald cypress trees.
Cultural and Mechanical Controls
Certain cultural practices and mechanical controls can help reduce thrips populations:
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Improve air circulation and light penetration through proper pruning and spacing of cypress trees. This reduces the shaded humid conditions thrips prefer.
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Use a strong spray of water to wash off and dislodge thrips from foliage. Repeat frequently.
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Apply a layer of reflective mulch around the base of trees which can deter thrips from colonizing on lower branches.
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Destroy severely infested branches and foliage to eliminate thrips breeding sites.
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Inspect new nursery trees thoroughly and quarantine if necessary before bringing onsite to avoid introducing thrips.
While helpful, these measures alone are usually not sufficient to solve persistent thrips problems. Using additional organic and chemical means is often needed.
Organic Thrips Treatments
Several organic and natural pest control products can be applied to bald cypress trees to kill thrips and deter re-infestations:
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Insecticidal soap – Spray trees thoroughly with insecticidal soap which kills thrips on contact through membrane disruption. Repeat applications every 5-7 days.
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Neem oil – Mix neem oil with insecticidal soap for added killing power and deterrent effects. Neem oil damages the hormonal system of thrips.
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Pyrethrins – Naturally derived pyrethrin insecticides quickly knock down thrips populations but can also kill beneficial insects. Use selectively.
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Diatomaceous earth – This abrasive dust abrades and desiccates thrips. Coat foliage, branches, and soil around trees. Reapply after rain.
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Horticultural oil – Apply dormant oil in late winter/early spring to coat trees and suffocate overwintering thrips nymphs.
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Beneficial insects – Release predator mites or minute pirate bugs which will devour thrips. May take time to establish.
Regular applications of these organic treatments can significantly reduce thrips on bald cypress trees. But rotating modes of action is important to prevent thrips from developing resistance.
Chemical Control Options
At times, bald cypress trees heavily infested with thrips may need treatment with synthetic insecticide sprays to gain control of the situation:
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Insect growth regulators – Products containing azadirachtin or kinoprene disrupt the molting and maturity process of thrips. This curbs reproduction and breaks the life cycle.
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Pyrethroids – Bifenthrin, permethrin, lambda-cyhalothrin containing pyrethroids provide quick knockdown of adult thrips. Use caution as they can kill beneficials.
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Organophosphates – While very effective, organophosphate insecticides like acephate have higher mammalian and environmental toxicity. Reserve as a last resort.
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Systemic insecticides – Systemic products like imidacloprid are absorbed and transported through the tree’s vascular system, providing residual control. Use only as directed.
While chemical insecticides are effective, they should be integrated with cultural and biological controls to formulate a comprehensive IPM program for long term, sustainable thrips management.
Preventative Measures
Implementing preventative measures can help avoid thrips from ever becoming established on your bald cypress trees:
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Select more resistant varieties – there are bald cypress cultivars less prone to thrips damage
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Maintain tree health and vigor through proper care and nutrition – healthy trees better withstand pests
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Prune strategically to open up tree canopies and reduce humidity
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Monitor young shoots and growth tips regularly for early signs of infestation
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Apply horticultural oil or insecticidal soap early spring to deter initial colonization
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Remove and destroy discarded plant debris and prunings promptly to eliminate breeding sites
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Consider protective trunk spray coatings that can prevent thrips from crawling up tree
With advanced preparation and preventative care, you may be able to spare your bald cypress trees from ever experiencing a thrips outbreak. But if an infestation does occur, implementing the control measures detailed above can help eliminate the pests and restore your trees back to health. Consistency and diligence are vital in the battle against stubborn thrips invasions.
Cypress Twig Gall Midge: Taxodiomyia cupressiananassa
Recognition: Heavy, spongy galls of varying sizes are created when female flies lay their eggs on newly developing leaves. The oval, green galls are heavy enough to cause branches to droop under their weight if there are too many on the branch. Each gall may contain up to 15 yellow-orange maggots in individual cells. In the autumn, the galls turn brown and drop to the ground with the leaves, and the larvae over-winter in the gall. The adults emerge as flies and can be found for about a month beginning in mid-May. There are two generations per year.
Contributing Factors: The main contributing factor of cypress twig gall midges is previous infestations of this insect.
Management Recommendations: To reduce the number of galls in a new season, rake and destroy the fallen leaves and galls. Sprays can be directed at adults when they are scouted, but there are many natural enemies and biological controls of this insect (Gomez and Mizell 2013).
Recognition: Mealybugs are soft-bodied insects with piercing-sucking mouthparts and a wooly, white, waxy covering. A byproduct of mealybug feeding is sticky honeydew, which coats infested foliage and provides a medium for growth of black sooty mold fungi. Mealybug reproduction is increased in humid and hot environments.
Contributing Factors: Contributing factors for mealybugs, specifically for Baldcypress, is unknown.
Management Recommendations: Predators (like lady bug larvae) can control many mealybug infestations in the landscape. The waxy covering protects the insects from sprays. Horticultural oils or systemic insecticides can be effective in controlling mealybugs, but because Baldcypress is very sensitive to horticultural oils, extreme caution should be used when making the decision to apply (UF/IFAS 2015).
Recognition: The Baldcypress Rust Mite is a microscopic eriophyid mite, most active during the warm season, which causes browning of interior needles. It overwinters in bark crevices, ready to reproduce and infest new growth in the spring. The mites mouthparts rasp the leaf cells, causing the needles to become yellowish and then brown. Mites can be seen with a 10-power hand lens, and their white cast skins are the best diagnostic.
Contributing Factors: Warm weather causes very rapid reproduction.
Management Recommendations: Carbaryl, dicofol, and oxythioquinox will knock down this mite with thorough foliage coverage (Nixon and Sheltar 1998). Please consult the most up-to-date regulations before applying any pesticides.
Key Plant: Baldcypress (Taxodium distichum)
Baldcypress (Taxodium distichum (L.) Rich.) are deciduous-needled pyramidal trees that can reach 100 to 150 feet in height. They grow at a moderately fast rate, reaching 40 to 50 feet in the first 15 to 25 years. They are commonly found throughout the state of Florida, particularly near lakes and rivers (as they are native to wetlands along running streams), and can also be found throughout most of the eastern United States in USDA hardiness zones 5A through 10B. Growth is fastest on moist, well-drained soils in full sun. Trees are highly tolerant of drought, although they are adapted to thrive in wetlands, where they will develop “knees,” a distinct structure that forms above the roots. They will also grow well in upland sites with few to no “knees” (Gilman and Watson 2014).
This series of Key Plant, Key Pests publications is designed for Florida gardeners, horticulturalists, and landscape professionals to help identify common pests associated with common Florida flora. This publication, the first in the Key Plant, Key Pests series, helps identify the most common pests found on the Baldcypress (Taxodium distichum).
This publication provides information and general management recommendations for the cypress leaf beetle, fall webworm, cypress twig gall midge, mealybugs, rust mites, and needle blights. For a more comprehensive guide of woody ornamental insect management, download the current Professional Disease Management Guide for Ornamental Plants here or the Integrated Pest Management in the Commercial Ornamental Nursery Guide here.
THRIPS?! How to kill thrips and save your grow.
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