The Leyland cypress is a lovely evergreen tree that is pyramidal in shape and commonly used as a hedge, privacy screen or windbreak due to its fast growth rate. It can grow up to 3 feet or more in a year. A mature Leyland cypress can reach a height of up to 70 feet. It can be infested by several insects such as bagworms, scale and spider mites.
The Leyland cypress' foliage (dark green in color) has a soft, feathery appearance, and its needles emit a wonderful fragrance when broken. It is a hybrid of the Monterey cypress and the Nootka false cypress. The Leyland cypress should be planted in organically rich, moist but well-drained soil. This cypress tree has a shallow root system, and care will need to be taken to ensure that it receives adequate water during any extreme drought conditions. Stressed trees are more susceptible to insect infestations.
Bagworms are by far the most damaging of the insects to infest the Leyland cypress tree, and they are extremely difficult to get rid of. These caterpillars/bagworms can devastate the cypress tree. The bagworms build a web or tent-like structure at a fork in the tree. They leave the web during the daylight hours (with the exception of rainy or cloudy days) to feed on the foliage of the tree. As they feed the tent gets larger.
Control of Bagworms
Bagworms should be controlled before they build their bag or tent--when the larvae are small (the first three months of spring). If the Leyland cypress tree is small, the bagworms can be picked off by hand. However, if the tree is large it will need to be chemically sprayed to rid the tree of the bagworms. Use Dipel or Thuricide to spray the tree.
Scales are small insects that appear as small, crusty flakes on the needles and branches of the the Leyland cypress. They are sapsuckers and suck the sap from the cypress tree, causing yellowing or chlorosis of the needles. The best way to treat scale is through a systemic insecticide, which means the insecticide is fed into the system of the cypress tree. As the scales feed on the sap they are also ingesting the insecticide and are killed. The best time to apply the systemic insecticide is during early spring as a preventive measure. Cygon is one systemic insecticide that can be used to rid the Leyland cypress of scales.
Spider mites are actually arachnids that attack the Leyland cypress tree by sucking on the foliage. Symptoms that the tree has spider mites will be yellowing/browning of the needles. Spider mites can only be seen through a magnifying glass due to their minuscule size. You will only know they are there when the symptoms become apparent. Spider mites do have some natural enemies: ladybugs, lacewing larvae, minute pirate bugs, and some predatory mites. The best means of control is to maintain a healthy tree. According to the Auckers Nursery, "Spider mites have become resistant to most of the old chemicals. Recommend using only true miticides for control."