Development and Implementation of 

 Northeast Strawberry IPM 



Daniel R. Cooley, Sonia G. Schloemann, Mark Mazzola, 



and Barbara Schloemann 



Deptartment of Plant Pathology, University of Massachusetts 



The Strawberry IPM program in Massachusetts 

 began in 1987. The first step in the program was to 

 establish what the key pests were in Massachusetts, 

 and what growers were doing to manage them. 

 Through a survey, we found that growers considered 

 Botrytis gray mold their most important problem, 

 followed by tarnished plant bug (Lygus lineolaris), 

 strawberry bud weevil {Anthonomus signatus), two 

 spotted mite (Tetranychus urticae), and black root 

 rot (a disease complex caused by the lesion nematode 

 Pratylenchus and the fungus Rhizoctonia). Weeds 

 were also considered of major importance. Of course, 

 there are other pests which can be important, and 

 the situation changes from year to year. For ex- 

 ample, leaf spot, angular leaf spot, leaf scorch, and a 

 Phomopsis blight have all appeared as significant 

 problems in some fields over the past 2 seasons. 

 However, other than making sure that the growers 

 use effective techniques at the appropriate times, 

 there is no true IPM system for these problems. 



We were unsure of the pest management strate- 

 gies used by growers. The strawberry pest manage- 

 ment recommendations of 1987 suggested that 

 growers make 8 to 14 fungicide applications, 4 to 8 

 insecticide-miticide applications, 1 to 3 herbicide 

 applications, and fumigate before planting. A 1987 

 survey showed that Massachusetts strawberry 

 growers averaged 2.0 insecticide applications (range 

 of - 7), 5.6 fungicide applications (range of - 15), 

 and 2.7 herbicide applications (range of - 5). 



Given the pesticide use information and evalu- 

 ations of pest priorities, we began work in those 

 areas where we could deliver information quickly 

 with the most benefit. Conveniently, we had meth- 

 ods available for management of Botrytis , tarnished 

 plant bug, and mites and thus began the significant 

 portions of the program. 



Botrytis IPM 



Strawberry growers fealt that their most impor- 

 tant pest problem was gray mold. Since it is a 



disease, some of the techniques typically used in IPM 

 are not available. 



Organisms which cause disease, such as fungi 

 and bacteria, cannot easily be observed in the field. 

 Symptoms can be seen, but spores and hyphae gen- 

 erally cannot be seen with the unaided eye. So, it is 

 not easy to find the spores and bacteria which start 

 a disease epidemic. Growers are faced with the prob- 

 lem of either treating before symptoms appear on the 

 assumption that the spores and bacteria are there or 

 treating after symptoms appear at a time when it 

 may not be possible to stop the epidemic. In the 

 former case, the disease organism may not be pres- 

 ent, thus the grower may over-treat. In the latter 

 case treatment may have little impact on the prog- 

 ress of the disease, since with many diseases, by the 

 time symptoms are there, the disease has gone 

 beyond the action threshold. While some disease 

 may be tolerable, a lot of disease is not. Therefore, 

 action thresholds based on symptoms are generally 

 very low. Fortunately there are other things, be- 

 sides spores and infection symptoms, that can be 

 used to monitor the progress of a pathogen. In order 

 to do this, we must understand the disease more 

 thoroughly. 



Botrytis has a more complex life cycle than 

 scientists have generally assumed. In the past few 

 years, work by Dr. John Sutton and Dr. Gordon 

 Braun in Canada (Braun and Sutton, 1987; Sutton 

 and Braun, 1987) and Dr. Michael Ellis in Ohio, has 

 shown how Botrytis functions and suggests how to 

 best control it. Like many fungi, Bortryt is cinerea is 

 active under moist conditions. Rain, dew, or sprin- 

 klers can provide an environment for the disease to 

 become active. 



Symptoms on the fruit are largely as the com- 

 mon name suggests-a gray mold. Fruit may rot rap- 

 idly just before or just after the fuzzy gray fungus 

 growth appears. Much of the time, however, in- 

 fected parts of the plant appear normal. The fungus 

 remains dormant, but alive. Only when the plant 

 tissue nears the end of its natural life do symptoms 



Fruit Notes, Spring, 1991 



