Plant Pathology Research at The Kearneysville Tree Fruit Research and Education Center

The WVU Alternative Processing Apple Production Project: The Pest Management Phase, 1995 - 1997 Results Summary

Integrated orchard management systems offer the potential to reduce impacts on the environment while increasing net income to growers. This research is being conducted to compare an advanced, alternative integrated orchard management program and conventional management practices on a whole-orchard scale. Each main plot was divided into four subplots that were planted in April, 1992, with one of four apple cultivars, 'York', 'Golden Delicious', 'Liberty' (resistant to apple scab), or 'Fuji' on M. 26 rootstock. Trees were established at 2.5 x 5.5 meters with every tenth tree a pollinizing cultivar. Conventional and alternative strategies were identified in 1994 with a written survey of grower practices. During the pest management phase of this project, arthropod pests and diseases were managed with 14 and 13 pesticide applications in the conventional and alternative plots, respectively, from silver tip until near harvest. Conventional materials used for arthropod management included oil (1 application), Asana, Guthion, Penncap-M, Provado, and Lannate (only in year 1 of pest management phase). Alternative materials used included oil (4-5 applications), Bacillus thuringiensis (Bt), and Provado. For diseases, apple scab, powdery mildew, cedar-apple rust, and fire blight were managed similarly in the two treatments. Conventional plots received Ziram and Topsin-M, whereas alternative plots received calcium chloride to suppress summer diseases.

System observations:  Incidence of foliage-feeding arthropod pests was determined at various times during the growing season on each of five trees/cultivar/main plot. In all three years, the incidence of spirea aphid was lower in the alternative plots. This was most likely the result of increased predation, as ladybird beetles, spiders, black hunters, lacewings and minute pirate bugs were more numerous in the alternative plots in years 2 and 3. In year 1, the incidence of rosy apple aphid, white apple leafhopper (WALH), rose leafhopper, and European red mite (ERM), and injury from Japanese beetle did not differ between management systems. In year 2, ERM and injury from spotted tentiform leafminer (STLM) were less abundant in alternative plots.  In year 3, ERM and WALH were significantly less in the alternative system. The increased use of oil and lower toxicity of Bt to parasites are the most likely reasons for the reduced incidence of ERM in years 2 and 3 (and WALH in year 3) and leafminer (in year 2), respectively, in the alternative plots.  Also in year 3, injury from Japanese beetle was higher in the alternative system, whereas there were no significant differences between systems in incidence of predaceous mites, or injury from rosy apple aphid and STLM.  The incidence of injury to fruit from arthropod pests was determined by sampling 100 fruit/cultivar/main plot at normal harvest for each cultivar. In year 1, total insect injury was higher in the alternative system (41%) than in the conventional system (14%). This was the result of higher injury from tufted apple bud moth, redbanded leafroller, codling moth, oriental fruit moth, plum curculio, and apple maggot. Fruit injury did not differ among the cultivars, except for that caused by tufted apple bud moth, which was highest on York, followed by a similar level on Fuji and Liberty, and lowest on Golden Delicious.  In year 3, again there was significantly more injury from codling moth/Oriental fruit moth and tarnished plant bug in the alternative management system.  There were no differences between management systems in injury from tufted apple bud moth/redbanded leafroller and plum curculio, or in total injured fruit.  No injury from San Jose scale and apple maggot was found in year 3.  There were no fruit evaluations in year 2 due to a late spring freeze.

For diseases, in all three years of the study, the amount of apple scab on leaves was similar between systems in June, but was higher in the alternative system in September.  Powdery mildew was higher in the conventional system in June in year 1, but similar in other years.  Numbers of apple scab ascospores caught on Rotorod spore traps were higher in the alternative system in years 2 and 3.  At harvest in the first and third years, total diseased fruit was higher in the alternative system (87% in both years) compared to the conventional system (29 and 19% in years 1 and 3, respectively).  Percent fruit infected (incidence) and number of lesions/fruit (severity) for fruit scab were similar between systems; however, in alternative plots, both incidence and severity of sooty blotch and flyspeck exceeded that found in the conventional system. For rots, incidence was higher in the alternative system, whereas severity (proportion of fruit surface with rot) was similar between systems in year 1, and was higher in the alternative system in year 3.  The goal of reducing rot inoculum with flail mowing (versus rotary mowing) was not realized.   Briefly, a slightly (and significantly) greater amount of bark surface was removed from apple prunings by flail mowing.  The total amount of fungal reproduction on mowed twig and branch elements was inversely proportional to the amount of bark removed from twig and branch elements by mowing. The occurrence of physical damage to apple tissue that was mowed and damaged to any extent, even minimally (ca. 1%), with either mower, caused fungal reproduction to be reduced by about 40%. Additional levels of damage or bark removal did not render the remaining attached bark any less desirable as a substrate for fungal reproduction.  Differences in fungal reproduction due to mower treatment occurred. In general, stem pieces that were flail mowed supported about twice the number of fungal reproductive structures (1.14 vs 0.54 structures per sq cm bark surface area for flail and rotary, respectively). When examined across bark removal classes, significantly greater numbers of fungal structures were observed after flail mowing for classes 1 to 10%, 26 to 50%, and 91 to 100%. For other classes, fungal reproduction was similar on chopped material from the two mowers.

Processor evaluation of fruit:  At the commercial processor, percentages of fruit graded as US No. 1 2.75 inches and larger, US No. 1 2.5 to 2.75 inches, and US No. 1 2.25 to 2.5, and ciders were not significantly different between systems in both years.  In year 3, the conventional system had greater percentages of No. 2 (1.1% vs. 0.1% for the alternative system) and culls (5.2% vs. 3.7% for the alternative system).  In year 1, the alternative system had a greater percentage of cull fruit (3.7%  vs. 0.8% for the conventional system).  In both years, both systems exhibited similar levels of bruise, pressure, and brix.  Among cultivars, York yielded the highest number of US No. 1 2.75 inch fruit, followed by Golden Delicious.   Liberty had the highest levels of cull fruit, related to freeze injury in year 3, and all other cultivars were similar in the amount of cull fruit. York had the highest pressure values, and Fuji exhibited the highest brix.

A. R. Biggs and H. W. Hogmire (January, 1998)

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