August 2008

Bald Cypress is a beautiful specimen tree that looks like a evergreen, but is actually a deciduous-needled conifer.  It is interesting to note that there are living Bald Cypress trees known to be over 1,000 years old!  These trees are possibly some of the oldest living things east of the Mississippi River. 

Native to southern swamps and rivers, found in coastal areas from Maryland to Texas and in the lower Mississippi River valley, Bald Cypress is considered indigenous as far north as the southeast corner of Missouri. In the deep South, it is a familiar sight growing directly in swampy water, with its branches heavily draped with Spanish moss. When growing in water, cypress trees often develop distinctive, knobby root growths known as "knees" which protrude above the water surface around the tree. In cultivation, however, it does quite well in drier conditions and has been grown successfully in cities as far north as Milwaukee and on hot, dry Texas hillsides.

Bald Cypress have no serious insect or disease problems, but bagworms and mites are occasional insect pests that can affect the vigor and appearance of trees in the landscape.  Bagworms are easily controlled with either thuricide or spinosad - both are readily available organic products.  Bacillus thuringiensis, known for years to savvy gardeners as "Bt" or thuricide, is a safe, selective product to kill caterpillars. However, it has only a one or two days' residual effect. Spinosad is not new either, having been granted organic status by the USDA National Organic Program (NOP) in 2003, but few home gardeners are aware of its potential uses.  It is especially effective against caterpillars (yes ... a bagworm is a caterpillar that turns into a moth!) but is safe for people and many beneficial insects.  (Click on the link for Wickman's Lawn & Garden page and find Ferti.lome Borer, Bagworm, Leafminer and Tent Caterpillar Spray - a spinosad concentrate!) 

Bald Cypress rust mites (Epitrimerus taxodii) are microscopic, light brown mites that feed on Bald Cypress foliage.  Most active during the summer, the mites'  mouthparts 'rasp' the leaf cells causing damage that appears first as very fine spots, or stippling. Needles become yellowish, and then reddish brown in color as the mite population grows and feeds on the tree.  Spider mites can also be found on some trees, but the horticultural oils or 'summer oils' often recommended to control spider mites should NOT be used.

Unlike evergreen hemlocks, spruces, and junipers, Bald Cypress is very sensitive to horticultural oils. So if you try to control this mite with oils, you'll do more damage to the tree than the mites will! Traditional pesticides such as Carbaryl (Sevin) are typically recommended to knock down Bald Cypress rust mites which are actually eriophyid mites - not spider mites.  Use a 10-power hand lens if you want to see the rust mites on the leaves, but their white cast off skins and rusty foliage color are two easy diagnostic characteristics.  Thorough spray coverage of the foliage is necessary to control all types of mites.

Author's note:
Spinosad is an excellent choice for control of bagworms and is listed in a number of studies as being an effective control for spider mites and some types of  eriophyid mites.  However, several hours of online searches have failed to yield any documentation as to the effectiveness of spinosad in controlling 'Epitrimerus taxodii' - the Bald Cypress rust mite.  Spinosad has been tested on over 200 different crops without phytotoxic side-effects (damage to plant health or foliage quality) so it might be worth testing for control of rust mites.

Oaks are the true conservatives. They hold old leaves till summer gives a green exchange.
~Roy Helton, Come Back to Earth