Leyland Cypress normally have only a few insects that cause any real problems. Bag-worms are probably the worst pest. On small trees, Bag-worms can be picked by hand but larger trees need to be sprayed. Scale is another insect that attacks Leylands, they look like little crusty flakes covering the needles and branches. Scale feeds on sap causing a chlorosis (yellow) look to the needles. The most difficult insect to control on Leylands is Spider Mites. These are very small insects that can be seen with a magnifying glass. Feeding on the sap causes needles to turn yellow and later brown. Spidermites have become resistant to most of the old chemicals. We recommend using only true miticides for control.