Dm Livini; Rcsoidvcx — Plants 



191 



Microt'ungi can also be harmful, causing the 

 irritating human aftliction known as athlete's 

 foot as well as disastrous diseases of crops and 

 trees. The potato famine in Ireland during the 

 mid- to late 1800"s was caused by a fungus 

 called Phytophthom infestans that rotted the 

 potato crops for several years (Large 1962). 

 Because of this disease, many Irish immigrated 

 to the United States. Once the nature of the dis- 

 ease was determined, a solution based on fungus 

 control was found. Knowing what fungi exist, 

 where they occur, and what they do is essential. 



Diversity of Microfungi 



The microfungi are the most diverse group of 

 all the fungi but the least understood or docu- 

 mented. Only about SVc-lO^ of all fungal 

 species have been described, much less charac- 

 terized and put to use or controlled. 

 Investigations to explore the diversity of micro- 

 fungi have shown that they are much more 

 diverse than previously thought. Very small sam- 

 ples of tropical rainforest leaf litter yielded up to 

 145 different species of microfungi (Bills and 

 Polishook 1994). About 200.000 fungal species 

 have been described worldwide (Reed and Fan- 

 1993). yet an estimated 1-1.5 million species 

 may exist (Hawksworth 1991; Rossman 1994). 



Within the United States, information has 

 been published about 13,000 species of micro- 

 fungi on plants or plant products (Farr et al. 

 1989). probably only a fraction of the species 

 thought to exist. Specimens of microfungi are 

 housed in the U.S. National Fungus Collections 

 and other institutions that serve as reservoirs of 

 information and documentation about our 

 nation's natural heritage. By comparing the 

 species reported in the literature with those rep- 

 resented in the collections, one can estimate the 

 number of microfungi known in the United States 

 at 29.000 species (Farret al. 1989). In areas of the 

 world where fungi have been well studied, the 

 ratio of vascular plants to fungi is about 6 to 1. 

 suggesting that there may actually be 120.000 

 species of fungi within the United States. 



Internet Information 



Although the numbers and kinds of fungi in 

 the United States are not known, information 

 about the microfungi associated with plants and 

 plant products in the United Stales is available 

 over Internet at this telnet address: 

 FUNGI.ARS-GRIN.GOV. After the word OK 

 appears on the screen, type login user; when 

 prompted for a password, type user. By doing 

 this, anyone can find out what fungi might occur 

 on the flowers in his or her own backyard. Data 

 can also be consulted on accurate scientific 



names of microfungi. recent literature on 

 plant-associated fungi, specimens in the U.S. 

 National Fungus Collections, and records of 

 microfungi on plants throughout the world. In an 

 instant, reports of fungi can be consulted by 

 those making land-management decisions or 

 helping a farmer control a disease. 



Survey and Inventory Needs 



Knowing which microfungi occur within the 

 United States provides infonnation upon which 

 plant quarantine decisions are made. A wrong 

 decision allowing entry of a harmful pathogen 

 can profoundly affect this nation's biological 

 resources. In the eastern United States, a devas- 

 tating disease called chestnut blight, caused by 

 Cryphonectria parasitica and unknowingly 

 imported from Europe on logs, killed virtually 

 all the towering chestnut trees that once domi- 

 nated our forests in the last century 

 (Anagnostakis 1987). Now on the forest floor 

 only skeletons of the trees can be seen with 

 decay fungi rotting the bleached "bones" of these 

 fallen giants. 



Another disease, dogwood anthracnose. 

 occurs on flowering dogwood trees in both the 

 eastern and western United States. The causal 

 fungus, Discula destructiva. was unknown until 

 199"l (Redlin 1991). Still unknown is whether 

 this fungus was imported or was already present 

 in the United States before its appearance as dog- 

 wood anthracnose. Because microfungi are 

 small, their existence may not be noticed until 

 they cause serious diseases. 



A program to inventory and monitor micro- 

 fungi in the United States does not exist at pre- 

 sent: thus it is impossible to determine if species 

 of microfungi are increasing or declining. Efforts 

 to document the biodiversity of microfungi in the 

 United States are limited to reports by plant 

 pathologists who encounter disease-causing 

 organisms or search for useful biological-control 

 organisms. Information about the occuirence and 

 biology of microfungi will increase the ability to 

 make accurate decisions about the importation of 

 agricultural products, to control microfungi 

 already present, and to determine if beneficial 

 microfungi are being lost because of habitat 

 destruction. With increased knowledge the unex- 

 plored world of microfungi can be put to work to 

 solve our most pressing environmental and agri- 

 cultural problems. 



References 



Anagncstakis. S. 1987. Ctiestnut blight: the classical problem 

 of an introduced pathogen. Mycologia 79( I ):23-37. 



CAB. 1993. Locust project enters phase two. Commonwealth 

 Agricultural Bureau (CAB) International News, June. p. 4. 



Bills, G.F.. and J.D, Polishook. 1994. Abundance and diver- 

 sity of microfungi in leaf litter of a lowland rain forest in 

 Costa Rica. Mycologia 86:187-198. 



