How to Get Rid of Borers on Thuja Plant

Thuja plants, also known as arborvitaes, are popular evergreen shrubs that add beauty and privacy to any landscape. However, these plants are susceptible to borer infestations, which can cause significant damage if left untreated. Borers are insects that tunnel and feed on the wood of the plant, weakening it and potentially leading to its death. In this article, we will discuss how to identify borer infestations and provide effective methods to get rid of them.

Identifying Borer Infestations

Borer infestations can be identified through various signs and symptoms. Here are a few indicators that your Thuja plant may be affected by borers:

Wilting or yellowing foliage: Borers disrupt the plant’s nutrient flow, causing sections of the plant to wilt or turn yellow.
Holes or tunnels: Look for small holes in the bark of the Thuja plant. These are entry points where borers lay their eggs and eventually create tunnels within the wood.
Sawdust or frass: Sawdust-like material, known as frass, can be found near the entry points or on the ground around the base of the plant. This is a result of borers tunneling through the wood.

Getting Rid of Borers

Once you have identified a borer infestation on your Thuja plant, it’s crucial to take immediate action to prevent further damage. Here are some effective methods to get rid of borers:

1. Pruning and Destroying Infested Areas

Start by pruning off all the affected branches and stems. Make sure to cut a few inches below the visibly infested areas to ensure complete removal of borers. Dispose of the pruned material properly, away from other plants, to prevent spreading the infestation.

2. Insecticidal Soap or Oil

Insecticidal soaps or oils can be an effective method to control borers. These products suffocate and kill the insects upon contact. Dilute the soap or oil as per the instructions on the product label and spray it directly onto the infested areas of the Thuja plant. Repeat the treatment every one to two weeks, as necessary.

3. Biological Control

Introducing natural enemies of borers, such as parasitic wasps, can help control their population. These wasps lay eggs inside the borer larvae, ultimately killing them. You can purchase these beneficial insects from gardening supply stores and release them near the infested plants.

4. Systemic Insecticides

Systemic insecticides are absorbed by the plant, making it toxic to borers when they feed on it. These insecticides are available in liquid or granular form and can be applied to the soil around the base of the Thuja plant. Follow the instructions on the product label for proper application and dosage. It’s important to note that systemic insecticides may take some time to show results, so patience is key.

5. Cultural Methods

Implementing cultural methods can also help prevent borer infestations in the first place. Here are a few practices you can adopt:

Proper watering: Keep your Thuja plant well-watered but avoid overwatering, as excessive moisture can attract borers.
Mulching: Apply a layer of organic mulch around the base of the plant to conserve moisture and regulate soil temperature. This can deter borers from laying eggs near the plant.
Pruning: Regularly prune your Thuja plant to maintain its shape and remove any dead or weakened branches that may attract borers.
Monitor and inspect: Regularly inspect your Thuja plant for signs of borers or other pests. Early detection can help prevent the infestation from spreading and causing more damage.

Conclusion

Borer infestations can be detrimental to the health and longevity of your Thuja plants. Identifying the signs and symptoms of borers and implementing appropriate control methods is crucial to protect your plants. Remember to prune and destroy infested areas, use insecticidal soap or oil, introduce beneficial insects, apply systemic insecticides, and adopt cultural practices to prevent future infestations. With proper care and attention, you can successfully get rid of borers and keep your Thuja plants healthy and thriving.