Much of cover crop research to date focuses on key indicators of impact without considering the implications over multiple years, in the absence of a systems-based approach. To evaluate the effect of three years of autumn cover crops on subsequent processing tomato (Solanum lycopersicum L.) production in 2010 and 2011, a field split-split-plot factorial design trial with effects of cover crop type, urea ammonium nitrate fertilizer rate (0 or 140 kg N ha -1 preplant broadcast incorporated) and tomato cultivar (early vs. late) was conducted. The main plot factor, cover crop, included a no cover crop control, oat (Avena sativa L.), winter cereal rye (hereafter referred to as rye) (Secale cereale L.), oilseed radish (OSR) (Raphanus sativus L. var. oleiferus Metzg Stokes), and mix of OSR and rye (OSR + rye) treatments. Cover crop biomass of 0.5 to 2.8 and 1.7 to 3.1 Mg ha -1 was attained in early Oct. and the following early May, respectively. In general, OSR increased soil mineral N during cover crop growth and into the succeeding summer tomato growing season, while the remaining cover crops did not differ from the no cover crop control. The lack of a cover crop by N rate interaction in soil and plant N analyses at harvest suggests that growers may not need to modify N fertilizer rates to tomatoes based on cover crop type. Processing tomato fruit quality at harvest (rots, insect or disease damage, Agtron colour, pH, or natural tomato soluble solids (NTSS)) was not affected by cover crop type. In both years, marketable yield in the no cover crop treatment was lower or not statistically different than all planted cover crops. Partial profit margins over both years were 1320 $ ha -1 higher with OSR and $960 higher with oat compared to the no cover crop control. Thus, results from a systems-based approach suggest that the cover crops tested had no observed negative impact on processing tomato production and have the potential to increase marketable yield and profit margins.

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While links between soil and plant health are implied, there are few opportunities to empirically evaluate this due to inherent differences among sites. An exception is a long-term experiment established in 2007 (repeated in 2008) in Ridgetown, ON, where improved soil health scores and changes in soil microbial communities were observed in the medium-term with annual cover crops (CC). This led us to hypothesize that CC-induced changes in soil health might affect bacterial spot (Xanthomonas hordorum pv. gardneri) and anthracnose (Colletotrichum coccodes) development in processing tomato. Five CC treatments (no CC control, winter cereal rye, oat, radish, and mix of radish+rye) planted after winter wheat harvest were evaluated in 2019 and 2020 (CC grown 9 times over 12 years). Fruit yields and net revenue were similar or greater with CC than without. In 2019, there was greater defoliation (area under the disease progress stairs = 4370±204), percent red fruit (71.0%±5.38) and rots (1.91%±0.5) in no CC than with radish (3410, 39.1%, 0.62%, respectively, P≤0.0366), indicating earlier fruit maturity in no CC plots. Similarly, no CC had a greater incidence of red fruits with anthracnose (25.8%±2.89) compared with all CCs but rye (7.4 to 12.1%±2.89) (P=0.0029). Environmental conditions in 2020 were less favourable for disease development. Defoliation was not affected by CC treatment (P=0.1254) and anthracnose incidence was low (≥90.3±1.22% healthy fruit), which may have limited the ability to detect treatment effects (P=0.2922). Long-term cover crops have the potential to produce greater or equivalent tomato yield with decreased defoliation and anthracnose fruit rot.

Septoria late blight caused by Septoria apiicola damages celery leaves (Apium graveolens), but its main impact is on the marketability of petioles. Three field trials (two in 2005 and one in 2006) were conducted at the Holland-Bradford Marsh, Ontario, to determine whether the number of fungicide applications required to manage septoria late blight could be reduced compared with the standard calendar spray program and whether disease management could be improved. Two disease forecasting programs (Tomcast at three disease severity value (DSV) thresholds and the Septoria Predictor) were assessed relative to a 7-day calendar spray program and a nonsprayed control. Each fungicide timing treatment, which entailed application of the fungicide Bravo 500 (chlorothalonil 50% a.i.) alternating with Champ 2FL (copper hydroxide 37.5% a.i.), was compared with Pristine WG (pyraclostrobin 12.8%, boscalid 25.2% a.i.) alternating with Champ 2FL on each of two celery cultivars. Pristine consistently provided superior control of septoria late blight compared with Bravo. Treatments were applied to two susceptible celery cultivars 'Florida 683' and 'Sabroso'. Both cultivars responded in a similar manner to the treatments. Fungicide applications timed according to Tomcast at a DSV threshold of 10 or the Septoria Predictor resulted in septoria late blight severity levels on leaves and petioles comparable to the calendar spray program. Fungicide applications were reduced by 1 for the Septoria Predictor, by 1 to 3 for Tomcast at DSV threshold 10, and by 2 to 4 for Tomcast at DSV threshold 15. However, a yield reduction of 15% occurred in one trial when application of Bravo/Champ were timed according to Tomcast at DSV 15, indicating that the DSV 15 threshold was not always adequate for septoria late blight management using Bravo. Résumé : La septoriose (brûlure tardive) (Septoria apiicola) endommage les feuilles de céleri (Apium graveolens), mais c'est sur la qualité marchande des pétioles que son impact principal se fait sentir. Trois essais au champ (deux en 2005 et un en 2006) furent effectués dans le marais Holland-Bradford, Ontario, afin de déterminer si le nombre d'applications de fongicides nécessaires pour lutter contre la septoriose pouvait être réduit comparativement au calendrier courant de pulvérisations et si la lutte contre la maladie pouvait être améliorée. Deux programmes de prévision des maladies (le Tomcast à trois seuils de valeur d'intensité de maladie (DSV) et le Septoria Predictor) furent évalués en ce qui a trait à un calendrier d'applications de 7 jours et un témoin non traité. Pour chaque traitement fongicide prévu, l'application du fongicide Bravo 500 (chlorothalonile à 50 % de matière active) en alternance avec le Champ 2FL (hydroxyde de cuivre à 37,5 % de matière active), fut comparée au Pristine WG (pyraclostrobine à 12,8 %, boscalide à 25,2 % de matière active) en alternance avec le Champ 2FL sur chacun des deux cultivars de céleri. Le Pristine a invariablement procuré une meilleure lutte contre la septoriose...

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