Ask Mr. Smarty Plants

Cupressus arizonica (Arizona cypress) is native to North America; from our webpage on this tree:

"USA: AZ , CA , NM , NV , TX , UT
Native Distribution: W. TX to extreme s. NV, s. AZ & n. Mex.
Native Habitat: Hot, dry canyons & stream banks from 3000 to 7000 ft."

From the USDA Natural Resources Conservation Service on Cupressus arizonica:

"It is found naturally on dry, sterile, rocky mountain slopes and canyon walls, but does very well when planted on better soils or when irrigated. It requires a minimum of 10 to 12 inches of water annually. It is not recommended for soils with a high water table."

Doesn't sound much like extreme northeastern Illinois in USDA Hardiness Zone 4b, with average annual minimum temperatures of -20 to -25 deg F, does it? How long have you had that tree and did you buy it locally? Just because a plant is sold locally does not mean it will thrive locally. On top of everything else, you are very close to Lake Michigan and we are guessing you have a high water table, not recommended for this tree. This sort of situation is why the Lady Bird Johnson Wildflower Center is dedicated to the growth, propagation and protection of plants native not only to North America but to the area in which the plants are being grown.

Frankly, we don't think it possible for this tree to survive in your environment, and the bugs are probably just taking advantage of a weakened, dying tree. Before you purchase plants, we suggest you go to our Native Plant Database, do a Combination Search for Illinois, designating type of plant (tree, shrub,etc.) under General Appearance. You can also specify Light Requirements where the plant will go, Soil Moisture, even projected height as you search. You can go to our National Suppliers Directory, type your town and state name in the "Enter Search Location" box and you will get a list of native plant nurseries, seed companies and landscape professionals in your general area. All have contact information so you can find out if they have a plant you are looking for before you go shopping.