POOR APPLE GROWTH DISEASE IN MASSACHUSETTS 



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William J. Manning, Daniel R. Cooley, 



and Ted R. Bardinelli^ 

 Department of Plant Pathology 



Poor Apple Growth Disease (PAGD) is a new name for an old 

 problem. It refers to poor growth or even death of newly-planted 

 trees, whether planted in old orchard sites or in new orchard 

 sites (especially those formerly in woodland). Scattered trees, 

 or trees in small areas may make little growth and die during 

 the first season. Adjacent trees may be vigorous and healthy. 

 When new trees do not die, they differ in both size and vigor. 



The exact cause of PAGD is unknown. It is probably due to 

 a combination of factors, both biological and physical. It is 

 well-known that poorly-drained locations, and those high in or- 

 ganic matter, especially the remains of old apple root systems, 

 are especially subject to PAGD. Certain rootstocks, notably 

 MM106, are also more susceptible to PAGD. A number of nematodes 

 also contribute to PAGD. 



A team of scientists at the East Mailing Research Station 

 in England feel that PAGD there is caused by the common soilborne 

 fungus Pythium. Pythium does well in cool moist or wet soils 

 that are high in organic matter. Dr. Geoffrey Sewell, of EMRS , 

 feels that Pythium produces a toxic exudate in soil. This in- 

 hibits root hair growth and function and this in turn affects 

 the growth and extension of root tips. Growth of affected trees 

 is considerably reduced. 



We investigated PAGD in 6 new orchards in Massachusetts 

 last year. Red Delicious, Jerseymac and Mcintosh on M.7A, 

 MM. Ill, M.26, and MM. 106 rootstocks were involved. The trees 

 came from different nurseries in different parts of the country. 

 We brought typical PAGD trees as well as soil from around their 

 roots back to the laboratory and greenhouse. In the laboratory, 

 we isolated the following potential root disease fungi: Cylindro - 

 carpon, Cylindrocladium , Fusarium , Pythium , Rhizoctonia , and Verti - 

 cillium . These are being used in the greenhouse to determine 

 whether or not they can cause PAGD in apple rootstocks. Apple 

 rootstocks have been planted in these soil samples in the green- 

 house to allow us to follow PAGD under controlled conditions. 



We do not know what causes PAGD in Massachusetts. We plan 

 to continue our laboratory and greenhouse investigations and to 

 begin field studies in 1979. 



Note to Massachusetts Fruit Growers : If you have suspected PAGD 

 problems, please contact Dr. William J. Manning, Department of 

 Plant Pathology, University of Massachusetts, Amherst, 01003. 



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Associate Professor, and Extension Technicians, respectively. 

 Department of Plant Pathology, University of Massachusetts', Amherst 



