False Cypress shrubs and trees are relatively low maintenance and easy to grow for most home gardens. The most common pets on these plants are sap-sucking insects (Aphids and scale insects) and caterpillars (fall webworms and other types of bagworms) which mainly cause cosmetic and easily repairable damage when diagnosed very early.
More serious pests such as Bark Beetles may only be an issue in certain parts of the United States but cause irreparable damage to the plant which in turn becomes a fire hazard during hot, dry summers.
Arborvitae Aphid
Aphids are sap-sucking insects that not only cause damage to the affected plant but over time when left untreated cause secondary infestations of ants due to large amounts of honeydew produced. The honeydew can also cause significant damage to outdoor furnishings and car finishes. On False Cypress, Arborvitae Aphid feeds on the fleshy scale-like foliage causing the tips to turn brown, eventually leading to the dieback of whole stems.
Fortunately, this Aphid is rather large and easily identified by its brown body often covered in a waxy film that protects it from predators. The waxy film also makes treating this aphid a bit more challenging.
Treating Arborvitae Aphid on False Cypress
Spraying with soap sprays into large shrubs and trees is not recommended as the treatment may only reach some of the affected areas properly. Try knocking the aphids off the shrub with a stiff stream of water from the hose. This may need to be repeated until no more aphids are present.
Heavy infestations on smaller false cypresses may require the use of an insecticide specifically labeled for use on your particular variety. Look for a formulation specifically labeled for use on false cypress, as well as approved by the Organic Materials Review Institute (OMRI).
Keep in mind that even though a pesticide is approved OMRI it is still a chemical and will need to be used according to all of the directions on the label. Pruning out affected areas also helps to remove all stages of the lifecycle and reduce populations of the insect.
Preventing Arborvitae Aphid on False Cypress
Encouraging beneficial predators in your yard is also a great way to balance the biome in your landscape and keep any outbreaks of pests small and easily manageable. Insects that prey on aphids are not restricted to just Lady Beetles. All types of Lacewing, Damsel bugs, Hoverflies, and Parasitoid Wasps are highly effective at keeping the populations of sap-sucking insects low and overall plant damage to a minimum.
Aphids also thrive on plants that have been weakened when planted in the wrong growing conditions. Ensure that your false cypress is receiving the right amount of sun and has very well-draining soil. Applications of high-nitrogen fertilizers encourage quick, dense growth of the foliage which is generally weak and susceptible to pests and disease.
Bark Beetles
Bark Beetles cause damage to the inner structures of trees and shrubs, eventually resulting in the complete death of the plant. Damage on false Cypress occurs just under the bark layer and appears as tracks of shallow engraving in random patterns. As the beetle eats away at the cambium layer the plant is not able to transport nutrients to other sections of the stem or tree.
Over time the affected branch will die back. The dead portions of a tree are favored for the females to lay eggs, which starts another cycle of infestation.
Treating Bark Beetles on False Cypress
There are no sprays or systemic insecticides approved for home use on bark beetles. The insect lives under the bark making application impossible. Encouraging beneficial predators such as sapsuckers and other woodpecker species into your yard will help to control the beetles. Over time damage from the birds can cause dieback as well but you will have prolonged the life of your plant.
Remove any affected branches as soon as signs of tip browning or dieback are noticed. This will keep the adult females from laying more eggs.
Preventing Bark Beetles on False Cypress
The number one way to protect false cypress from bark beetles is to grow the plants in their preferred conditions. Well-draining soil is imperative for any false cypress. Plants that are over-watered or have seasonally boggy soil conditions will grow weak over time.
Fertilizing is rarely recommended for false cypress growing in average garden soil. Plant any new shrubs in the fall to protect them if there have been previous bark beetle outbreaks in your area.
Juniper Scale
Scale is another sap-sucking insect that commonly attacks the scalelike foliage of false cypress. The ends of the shrub will start to brown and have a very untidy appearance from the scale insect which forms a protective armor over itself during the adult stage. Small dots that look like a sunny-side-up egg indicate where the females are.
Overwintering of the female adults happens in mild winter climates, with typically one generation produced a year. May is typically when the eggs hatch. Damage is not detrimental to fully established and mature plants and is easily reversed with good garden hygiene.
Treating Juniper Scale on False Cypress
Pruning out of affected branches is the best treatment for infected plants. The best time to prune is after the eggs have been laid in the spring to prevent further infestation and damage. Look for white and yellow flat dots and prune well below to remove any eggs that might have already been laid in the joints of the foliage and stems.
Applications of horticultural oil in the late winter are possible on smaller plants and will control females. Follow all manufacturer's directions exactly and ensure that your variety of false cypress is specifically listed on the product.
Preventing Juniper Scale on False Cypress
Scale insects are notorious for infesting badly grown or managed plants indoors and in the garden landscape. False cypress that is growing in too much shade, being over-watered or over-fertilized is guaranteed to decline in health over time, becoming susceptible not only to scale insects but to many diseases as well.
Ensure that your false cypress has plenty of full sun exposure and only water mature plants during periods of drought with drip irrigation or soaker hoses to get the water directly to the root zone.
Bagworms
Bagworms look exactly what they sound like. The larval, caterpillar, stage of a mature, hairy moth. The caterpillars are up to 2 inches in length and continually make strands of silk to add to the “bag’ they form around themselves as they grow and prepare to pupate. Conifer evergreens are the preferred food source for these caterpillars which add other bits of organic material to their bag as they eat away at the tips of the plant.
Often the webs are confused for pinecones. In mild winter climates, the larva overwinter and hatch in the spring. After hatching they grow one single silk strand which allows them to catch a breeze and blow to another tree or shrub nearby.
Treating Bagworms on False Cypress
Treatment for caterpillars involves manual extraction and possibly treatment with the parasitic spore Bacillus thuringiensis (Bt)bT. Remove webs at any time of the year, placing them in a bucket of soapy water to ensure the larvae inside die before throwing them in the trash. Cut out affected stems and branches to remove any eggs. Bt is most effective against newly hatched caterpillars and should be used early in the spring.
As the caterpillars grow the Bt develops in their body eventually destroying the caterpillar. The bacterial spores are less effective when the webs have grown late in the summer.
Preventing Bagworms on False Cypress
Removing webs at all times of the year prevents any remaining eggs from hatching and causing damage. Encouraging all species of native birds to your yard also helps keep the populations of caterpillars to a minimum. Growing small fruit trees and other plants that bear fruit and seed sis a great way to encourage birds to frequent your landscape.
Keeping pesticide use low or not all in the home garden also protects the beneficial insect population and any other wildlife to keep a balance of prey and predator.
Common False Cypress Pest Chart
| Pest | Identifying | Treating |
|---|---|---|
| Arborvitae Aphid |
Up to ⅛ inch long, brown Dieback on the tips of stems, whole branches browned |
Sharp spray from the hose, remove the affected plant material |
| Bark Beetles | Shallow random trails cut into the cambium layer under the bark, dieback of whole branches, or plant | Remove dead plant material to prevent the female from laying eggs |
| Juniper Scale | Female adults cover themselves in an armor shell that looks like a cooked egg, dusty or scraggly looking foliage at the ends of the branches | Cut out affected stems and branches, horticultural sprays on small plants late in the winter |
| Bagworms | Clusters of silk and other plant debris used to shelter caterpillars, dead growth at the tips of the branches | Remove web bags during the year, application of Bt early in the spring while the caterpillars are small |
Sources:
Plant Toolbox, North Carolina State Extension. www.plants.ces.ncsu.edu