A New Spider in Miami-Dade County Cyrtophora citricola
Catharine Mannion, Divina Amalin, Jorge Pena, and G. B. Edwards
University of Florida, IFAS, Cooperative Extension Service
Tropical Research and Education Center
Cyrtophora citricola, also called the tropical tentweb orbweaver, is present throughout Africa, Asia and the southern part of Europe and is also in parts of South America (Colombia). It was discovered in Miami-Dade County in April 2000 and it appears to be spreading. The unusual thing about this spider is that it is linked with branch dieback and sometimes plant death. It is unknown if the spider itself causes plant damage or that the plant is affected by the presence of the dense web.
Background and Biology
If you take an early morning drive on a misty day, the presence of this spider will be evident. Dew-covered webs are easily seen on fences, ornamental plants, and fruit trees. The tightly spun webs are horizontal in shape and can cover large areas. The adult spiders and spiderlings generally stay within the web but may drop when disturbed. The spiders can change color from light to dark brown in response to their environment. The female spiders are considerably larger than the male, so mostly the large female spiders and juveniles are seen. The female will lay up to ten eggsacs, also called cocoons, which hang like large beads within the web. Each cocoon may contain 100-150 spider eggs. There is evidence this spider builds its web in areas of high insect abundance. Fences provide excellent support structure for their webs. Fences with the most webs are generally beside orchards or extensive landscape plantings that likely provide an abundance of insects for food. Bridges over canals may also be heavily infested with webs.
Damage and Management
The major concern for this spider is whether it actually causes plant damage. Young or small trees and shrubs have been completely covered with the web and have ultimately died. Some trees with webs have suffered branch dieback. It is unlikely that direct contact from the spider is causing the damage and more likely that the thick web is affecting the plant. Tests will be conducted to investigate this issue.
Tests are under way to determine what insecticides may be used to manage this spider. Numerous commercial and homeowner products are labeled for use against spiders, but at this time, the most effective products have not been determined. Any chemical control of this spider will need to be done very carefully so that other spiders or beneficial insects are not disrupted or killed. Before any control measure is used, it is very important to have the spider identified, so other spiders are not affected. Removing the webs will not work, because if the spider is not killed, it will rebuild the web.
For more information contact:
Catharine Mannion, University of Florida, IFAS, Cooperative Extension Service
Tropical Research and Education Center, 305-246-7001 ext 200