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Sylvie Jenni, Katrine A. Stewart, Gaétan Bourgeois, and Daniel C. Cloutier

A simple method to predict time from anthesis of perfect flowers to fruit maturity (full slip) and yield is presented here for muskmelon (Cucumis melo L.) grown in a northern climate. Developmental time for individual muskmelons from anthesis to full slip could be predicted from several heat unit formulas, depending on the temperature data set used. When temperature at 7.5 cm above soil level was used, the heat unit formula resulting in the lowest coefficient of variation (cv=6.9%) accumulated daily average temperatures with a base temperature of 11 °C and an upper threshold of 25 °C. With temperatures recorded at a meteorological station located 2 km from the experimental field, the method showing the lowest cv (8.9%) accumulated daily maximum temperatures with a base temperature of 15 °C. This latter method was improved by including a 60-degree-day lag for second cycle fruit. The proportion of fruit volume at full slip of 22 fruit from the first cycle could be described by a common Richards function (R 2=0.99). Although 65% of the plants produced two fruit cycles, fruit from the first cycle represented 72% of total yield in terms of number and mass. The blooming period of productive flowers lasted 34 days, each cycle overlapping and covering an equal period of 19 days. Counting the number of developing fruit >4 cm after 225 degree days from the start of anthesis (when 90% of the plants have at least one blooming perfect flower) could rapidly estimate the number of fruit that will reach maturity.

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Sylvie Jenni, Katrine A. Stewart, Gaétan Bourgeois, and Daniel C. Cloutier

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Djamila Rekika, Katrine A. Stewart, Guy Boivin, and Sylvie Jenni

A lightweight agrotextile floating rowcover (10 g·m−2) designed for insect control was evaluated for its potential to reduce carrot weevil [Listronotus oregonensis (Le conte)] damage and to improve germination and carrot (Daucus carota L.) yield. The floating rowcover had no effect on total emergence and spread on emergence time but decreased emergence time by 0.5 day. Although floating rowcovers generally increased fresh weight of carrot leaves and roots during early development, no effect was detected late in the season and at harvest time. Carrot weevil damage of uncovered plants was 0.4 tunnels per root in 2006 and 2.0 tunnels per root in 2005. In both years, covering carrots with a floating rowcover for a period of 35 days after sowing reduced carrot weevil damage by 65% to 75%. In most years with low or medium carrot weevil infestation, the use of a rowcover could eliminate the use of insecticide to control this pest.

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Maryse L. Leblanc, Daniel C. Cloutier, and Katrine A. Stewart

A 2-year study was conducted to assess sweet corn (Zea mays) susceptibility to mechanical weeding using a rotary hoe at preemergence to six-leaf stages of corn development and at different combinations of stages. Three sweet corn cultivars: early (`Quickie'), mid (`July Gem'), and late season (`Sensor') were seeded at two sowing dates. The experiment was conducted in a weed-free environment. In general, sweet corn could be cultivated with the rotary hoe at least once without yield reduction from preemergence to the six-leaf stage. Cob numbers were reduced and maturity delayed after three or four cultivations with the rotary hoe. The rotary hoe could be an effective tool in controlling weeds in an integrated weed management approach or for organic sweet corn production since it cultivates both within and between the rows. The rotary hoe, which covers a large area in a short time, can be used at later growth stages, extending the time period during which it can be used without damaging the crop and reducing yield.

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Maude Lachapelle, Gaétan Bourgeois, Jennifer R. DeEll, Katrine A. Stewart, and Philippe Séguin

‘Honeycrisp’ is a relatively new apple cultivar highly susceptible to physiological disorders, such as soggy breakdown. The overall objective of this study was to identify preharvest weather parameters that influence the incidence of soggy breakdown over the different phases of fruit development. Using weather data and evaluation of fruit quality from three sites in Ontario, two sites in Quebec, and one site in Nova Scotia from 2009 to 2011, and data from four sites in Ontario from 2002 to 2006, a model for soggy breakdown incidence (SBI) was developed to predict the level of susceptibility in ‘Honeycrisp’ apples. This model uses primarily two weather variables during the last phase of fruit development [91 days from full bloom (DFB) to harvest] to accumulate an SBI index during the growing season, from full bloom to harvest. Cool (temperature <5 °C) and wet conditions (precipitation >0.5 mm) during this last phase resulted in increased soggy breakdown susceptibility levels. The predictions of the SBI model resulted in 68% of well-estimated cases (threshold of ±5%) (RMSE = 6.45, EF = 0.28, E = −0.04). Furthermore, firmness was linked to soggy breakdown, in addition to weather conditions, revealing a positive effect of high firmness at harvest on the development of the disorder. However, the effect of fruit quality attributes (e.g., internal ethylene concentration, starch index, firmness, and soluble solid content) by themselves, without considering weather conditions, revealed no relationship with the incidence of soggy breakdown.