Gail R. Nonnecke

Effect of Organic Pest Management Practices on Apple Productivity and Apple Food Safety

ABSTRACT Research was conducted in a certified organic apple (Malus x domestica Borkh.) orchard in 2000 to determine the effect of organic pest management techniques on pest control, apple yields and microbial populations on harvested apples. In Experiment 1, apple colouring bags, sticky red spheres, kaolin particle film, kaolin particle film plus sticky red spheres, or colouring bags plus sticky red spheres were applied to Redfree, Jonafree and Liberty apple trees in a split-plot design. Insects and diseases were sampled in the control and kaolin particle film treatments. Apple yields and insect damage ratings at harvest were determined for all treatments. There was a significant treatment x cultivar interaction related to insect damage on apples. Insect and disease damage ratings throughout the growing season and at harvest were lowest in Jonafree trees treated with kaolin particle film or colouring bags. There was no effect of treatment on beneficial insects during the growing season. Marketability was greatest in the Jonafree apples treated with colouring bags or kaolin particle film. In Experiment II, the effect of the organic management practices in Experiment I on the food safety of harvested organic apples was examined. Microbial populations on untreated apples and apples treated with kaolin particle film or colouring bags were enumerated post-harvest. No E. coli populations were observed on any apples. Low populations (225.0 ± 95.0 colony-forming units [CFU] apple−1) of coliform bacteria were observed on unwashed control apples. Postharvest yeast and mould populations were greatest on unwashed apples treated with kaolin particle film and lowest on apples protected by colouring bags. When kaolin particle film-treated apples were washed prior to analysis, yeast and mould populations were reduced by 50%.

Mulches Reduce Weeds, Maintain Yield, and Promote Soil Quality in a Continental-Climate Vineyard

Weeds reduce vineyard productivity by competing with grapevines for water and nutrients. To manage weeds, growers commonly apply herbicides and/or cultivate, which compromise soil quality. With the expansion of continental-climate viticulture, such as in the Midwest, there is a need for sustainable weed management strategies that maintain grapevine productivity, fruit quality, and soil quality. Our objective was to evaluate four weed management strategies in a Midwestern vineyard. Data were collected from an established vineyard in Iowa planted with Maréchal Foch grapevines (an interspecific hybrid). Treatments were established in a randomized complete block design. Treatments were replicated four times and included: (1) cultivation, (2) herbicide application, (3) straw mulch, and (4) a living mulch of creeping red fescue (Festuca rubra L. Pennlawn). Weed control, grapevine productivity, fruit quality, and soil quality were measured from 2004 to 2010. Straw and living mulches provided greater weed control than cultivation and herbicides. Grapevine yield was unaffected by the treatments, although pruning weights were reduced in cultivated and living mulch plots. Excluding titratable acidity and pH, no differences in fruit quality were detected. Straw mulch plots tended to have more phosphorus and potassium in analyzed soil samples. Water-filled pore space and water content were also higher in plots mulched with straw. Both types of mulched plots had higher organic matter, total organic carbon, and stable aggregate content. Biological activity, measured as soil enzymatic activity and earthworm counts, was enhanced in mulched plots. Our results demonstrate that straw and living mulch reduce weed populations, maintain grapevine productivity, improve several indicators of soil quality, and are viable weed management strategies for continental-climate viticulture.

Survival of Escherichia coli on strawberries grown under greenhouse conditions.

Strawberries are soft fruit that are not recommended to have a post-harvest wash due to quality concerns. Escherichia coli O157:H7 has been linked to outbreaks with strawberries but little is known about the survival of E. coli during the growth cycle of strawberries. The survival of E. coli on strawberry plants during growing under greenhouses conditions was evaluated. Soil, leaves, and strawberries (if present) were artificially contaminated with an E. coli surrogate either at the time of planting, first runner removal (4 wk), second runner removal (8 wk), or one week prior to harvest. At harvest E. coli was recovered from the leaves, soil, and strawberries regardless of the contamination time. Time of contamination influenced (P < 0.05) numbers of viable E. coli on the plant. The highest survival of E. coli (P < 0.0001) was detected in soil that was contaminated at planting (4.27 log10 CFU g soil(-1)), whereas, the survival of E. coli was maximal at later contamination times (8 wk and 1 wk prior to harvest) for the leaves (4.40 and 4.68 log10 CFU g leaves(-1)) and strawberries (3.37 and 3.53 log10 CFU strawberry(-1)). Cross contamination from leaves to fruit was observed during this study, with the presence of E. coli on strawberries which had not been present at the time of contamination. These results indicate that good agricultural best practices to avoid contamination are necessary to minimize the risk of contamination of these popular fruit with enteric pathogens. Practices should include soil testing prior to harvest and avoiding contamination of the leaves.

Assessing a Reciprocal International Student Travel Exchange: The Iowa State University and University of Costa Rica Intercambio

The creation and educational impact of a reciprocal travel exchange program for student groups in horticulture and allied sciences between Iowa State University (ISU) and the University of Costa Rica (UCR) are described. The program, called the “Intercambio,” (“exchange,” in English), has facilitated group travel for 10to 12-day periods to farms and agricultural research centers in the host country annually since 1999. The article explores how the Intercambio began and factors that have helped to sustain it, to provide ideas for educators interested in initiating similar exchanges. Analysis of responses to a 2015 written survey of student participants indicated that the Intercambio has exerted a strong impact on academic studies and career choices for 77% of the ISU students and 100% of the UCR students, as well as amplifying interest in the other country and raising cultural understanding and tolerance.

Canopy Management Practices and Light Interception of Northern Grape Cultivars

Introduction The recent development of Vitis riparia hybrids has allowed the expansion of the wine industry into Iowa and the Upper Midwest. These cultivars are more cold hardy and vigorous than traditional V. vinifera hybrids. During maturation the fruit tend to retain high levels of acids, exhibit a rapid rise in pH, accumulate high potassium levels, and possess a different profile of malic to tartaric acid than other hybrids. Wines from these grapes often have a “grassy” or “herbaceous” flavor. These same characteristics have been associated with fruit grown in shaded canopies. This study was undertaken as part of the USDA Northern Grapes Specialty Crops Research Initiative (SCRI) project to assess the effectiveness and cost benefit of various combinations of canopy management practices on improving the fruit quality characteristics of Frontenac, La Crescent, and Marquette wine grapes. This report summarizes part of the first year results.

Ethylene Involvement in Raspberry Fruit Ripening

Ethylene is involved in softening and abscission of raspberry drupes from receptacle tissue (Robbins et al., 1989; Burdon and Sexton, 1990a,b). The objective of this research was to determine the relationships between respiration rate, ethylene production rate, and ethylene action during raspberry ripening.

MODIFIED-ATMOSPHERE STORAGE DOES NOT SUBSTITUTE FOR LOW-TEMPERATURE STORAGE OF STRAWBERRY

INTRODUCTION LITERATURE REVIEW Characteristics and Postharvest Handling of Strawberry Importance of temperature Importance of precooling Modified Atmospheres for Transit and Holding Terminology Overview Low 0 2 High C02 Combined Low 0 2-High C02 MATERIALS AND METHODS RESULTS Weight Loss Fungal growth Respiration Ethylene Production DISCUSSION SUMMARY AND CONCLUSIONS