| Pest Management Tips: October
As temperatures cool this month, many types of mites become more active. Check your broad-leaved evergreens (azalea, holly, camellia, viburnum) for southern red mite. These pests suck sap from leaves, which destroys the chlorophyll, resulting in yellow, stippled leaves. Heavy populations form silky webbing on the undersides of the leaves. Under favorable conditions, one generation time is only two weeks, so populations can increase rapidly. Check for mites by holding a white sheet of paper underneath a branch and tap on the branch. Small, reddish specks, the size of a period, will appear on the paper and begin to crawl around. If you see ten or more mites (many times more, usually), then it is time to control these pests.
Spruce spider mites also become active this month. They favor conifers: arborvitae, firs, spruce, junipers, and pines and can be one of the most destructive pests of ornamental conifers. They feed on the underside of needles, causing the yellow, stippled appearance. Silky webbing may be present, and needles eventually turn brown and fall off. As with southern red mites, use a white sheet of paper and tap on a small branch. These mites will easily be spotted on the paper as red or blackish moving specks.
Boxwood mite may still be active in early October. They feed on the upper surface of boxwood leaves, producing stippled leaf symptoms. (photo at right) >>
Cryptomeria red mite, similar to spruce spider mites, attack Japanese red cedars, Cyrptomeria japonica. They prefer cooler weather and can severely damage needles, as the stippling symptoms can go unnoticed for a long period of time. These pests should be monitored by using the white paper beat test. If you see 20 or more mites on your paper, you should spray using a miticide labeled for cryptomeria. Do not use oil, as this will damage the leaves.
Juniper web worms can now be spotted on groundcover juniper varieties, particularly shore junipers. Look for webbing near yellowing leaves. Several tan caterpillars with brown stripes will be inside. If left untreated, these caterpillars can do serious damage by spring. Prune out webs and dead foliage, or if the infestation is extensive, use a pesticide containing Bacillus thuringiensis or spinosid.
Scale insects are difficult to control. The best time to control is when the juvenile or crawler stage is present. The crawlers of Magnolia scale are usually found in October. Adults are brown or powdery white bumps about ½ inch in diameter. When feeding, the scale produce much honeydew, which encourages the growth of sooty mold. Leaves become yellow, and whole branches can die in heavy infestations. Use the white paper beat test to determine if the crawlers are present. If found, spray with horticultural oil.
The best way to manage pests is to use a combination of chemical and non-chemical control. Only take action when the problem is serious enough to damage the plant. If we all use Integrated Pest Management (IPM), we can control pests in an environmentally conscious manner.
Last Updated June 11, 2009 2:58 PM
URL = http://www.usna.usda.gov/Gardens/IPM_2008-10.html