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The Onion 2017 Daily Calendar _TOP_ Download Pdf

The need as indicated by stakeholders. Onion crops are damaged by a spectrum of pests and pathogens throughout the U.S. For example, infestations of fly maggots (Delia spp.) can reduce plant stands by over 50% if not controlled (Nault et al. 2006), while a new invasive fly pest (Phytomyza gymnostoma) is raising concern (Barringer et al. 2018). Onion thrips (Thrips tabaci) feeding damage can reduce bulb yield by up to 30 to 50% (Fournier et al. 1995; Leach et al. 2020b) and it also spreads pathogens that cause devastating diseases like Iris yellow spot (IYS, caused by Iris yellow spot virus) (Gent et al. 2004, 2006; Bag et al. 2014), Stemphylium leaf blight (SLB, caused by Stemphylium vesicarium) (Leach et al. 2020a) and bacterial bulb rots (Grode et al. 2017, 2019). Multiple fungal and bacterial pathogens can cause onion yield losses in the field and in storage facilities throughout the U.S. (Schwartz and Mohan 2008). Each disease can cause up to 25 to 100% crop loss. The most important fungal diseases include SLB, purple blotch (Alternaria porri), downy mildew (Peronospora destructor), black mold (Aspergillis niger), Botrytis leaf blight (Botrytis squamosa) and neck rot (Botrytis species), Fusarium basal rot (FBR) (Fusarium oxysporum f. sp. cepae), white rot (Sclerotium cepivorum), pink root (Pyrenochaeta terrestris) and powdery mildew (Leveillula taurica). The most important bacterial diseases include sour skin (Burkholderia cepacia), slippery skin (Burkholderia gladioli pv. Alliicola), center rot (Pantoea ananatis and P. agglomerans), leaf streak (Pseudomonas viridiflava), soft rot (Pectobacterium carotovorum and Dickeya spp.), and Enterobacter bulb decay (Enterobacter cloacae). Serious weeds include yellow nutsedge (Cyperus esculentus), ragweeds (Ambrosia spp.), pigweeds (Amaranthus spp.), lamsquarters (Chenopodium album), perennial sowthistle (Sonchus arvensis) and others. Growers continue to abandon onion production in some regions because one or more of these organisms have caused catastrophic losses. Consequently, we propose to address managing the most serious pests, diseases and weeds of onion through the following objectives:

The Onion 2017 Daily Calendar download pdf

Importance of the work, and consequences if it is not done. The work proposed is critical for solving the most important pest, disease and weed problems facing the U.S. onion industry. We are not aware of other public or private entities that will be as organized across state borders to solve these problems as the W4008 group, particularly given the successful foundation set by the preceding multistate onion projects (W1008: Biology and Management of Iris yellow spot virus (IYSV) and Thrips in Onions, from 2005-2010; W2008: Biology and Management of Iris yellow spot virus (IYSV), Other Diseases and Thrips in Onions, from 2011-2016; and W3008: Integrated Onion Pest and Disease Management, from 2017 to 2022). The most significant change to our proposed multistate project is that we will include a weed biology and management objective. Similar networking successes are anticipated for weed scientists working in onion cropping systems across the country, just as they have occurred with entomologists and plant pathologists during our previous multistate projects.

Onion plants inoculated with the bacterial pathogen, P. ananatis, and then infested with varying densities of onion thrips in a controlled environment showed more symptoms of bacterial disease as thrips density increased (Grode et al. 2017). Similarly, onion thrips densities were positively correlated with increasing incidence of bacterial disease caused by the pathogen P. agglomerans in Michigan onion fields (Grode et al. 2019). While insecticide use to reduce onion thrips infestations was suggested as an approach to mitigate bacterial disease (Grode et al. 2019), the incidence of bacterial bulb rot in commercial onion fields in New York was reduced in only one of four trials when insecticides were used to reduce onion thrips infestations. More research is needed to elucidate the role that thrips management may have in reducing bacterial bulb rot incidence (Leach et al. 2020b).

Among the various IPM tactics evaluated for onion thrips control in conventional and organic onion production systems, insecticides continue to be the most effective and reliable tool (Leach et al. 2017, 2020b; Iglesias et al. 2021b). In most conventional onion fields, abamectin, cyantraniliprole, spinetoram, spirotetramat and co-applications of methomyl and lambda-cyhalothrin continue to work reasonably well (Harding and Nault 2021, Moretti and Nault 2019, Waters and Darner 2017). For onion thrips management in organic onion fields, spinosad is the most effective, especially when co-applied with neem oil (Iglesias et al. 2021a). No new, highly effective insecticide active ingredients were registered on onion for onion thrips control over the past five years. However, isocycloseram (PLINAZOLIN technology) has been highly effective in research trials and should be commercially available for thrips control in onion in the near future.

Onion thrips management has been improved by developing a program based on two insecticide resistance management (IRM) principles: rotating classes of insecticides during the growing season and applying insecticides following an action threshold (Leach et al. 2019b). In New York, onion growers (n=17) increased their adoption of insecticide class rotation from 76% to 100% and use of the action threshold for determining whether to apply insecticides from 57% to 82%. Growers who always used action thresholds successfully controlled onion thrips infestations, applied significantly fewer insecticide applications (1-4 fewer applications) and spent $148/hectare less on insecticides compared with growers who rarely used the action threshold. Growers who regularly used action thresholds and rotated insecticide classes did so because they were primarily concerned about insecticide resistance development in thrips populations. Similar success has occurred in eastern Oregon where this IRM-based thrips management strategy has resulted in fewer insecticide applications and similar yields compared with a calendar-based application strategy. More effort is needed to develop extension-based programs that involve regular and interactive meetings with growers in other production regions to increase their adoption of IRM and related integrated pest management tactics.

Bacterial bulb rots are difficult to manage when weather conditions favor bacterial pathogens because of the lack of highly effective, systemic bactericides. Coppers (e.g., copper hydroxide) are the most effective bactericides available to onion growers, but they have limited efficacy at best (Schwartz and Mohan 2008). These bactericides are purely protectant, i.e., they cannot cure existing infections, are not absorbed into plant tissues, and must be applied prior to colonization of plants by bacteria to prevent disease outbreaks. In multiple years of field trials in various states, applications of copper hydroxide and other bactericides, biocontrol products, and disinfectants either did not control bacterial bulb rots, even when applied weekly, or were inconsistent among seasons in their level of efficacy (e.g., Dutta and Foster 2021; Dutta et al. 2020; du Toit et al. 2021c; Hoepting et al. 2021). Additional management strategies are being evaluated to reduce losses from bacterial bulb rots, with a focus on late-season cultural practices such as the timing of topping, undercutting, and rolling of tops (du Toit et al. 2021b); careful irrigation frequency and quantity as well as nitrogen application quantity and timing during the second half of the season (Belo et al. 2021; Pfeufer 2014); selection of irrigation methods (da Silva et al. 2021); selection of bulb harvest equipment and methods (Dutta and Tyson 2021a, 2021b); effective control of thrips as mentioned above (Dutta et al. 2014; Stumpf et al. 2021.); and postharvest applications of disinfectants to onion bulbs (du Toit et al. 2021a). In plasticulture systems, reflective or silver-on-black plastic mulches reduce soil temperature, which reduces bacterial disease incidence at harvest (Pfeufer 2014). The relationship between in-season foliar nitrogen tissue levels and loss at harvest and post-harvest is being examined so that growers can make harvest timing and marketing decisions (Mazzone 2017). Similarly, if foliage is infected with bacteria late in the growing season, there is a possibility of preventing bulb infection by harvesting early; however, this often means sacrificing bulb size for marketability. In Pennsylvania, a visual bacterial disease severity rating scale on foliage effectively predicted disease incidence at harvest. This tool was validated on commercial farms and will help growers determine when to harvest to minimize rot.

Waters, T.D., and J.K. Darner. 2017. Thrips managment on dry bulb onions with the use of foliar insecticide applications, 2016. Arthropod Management Tests 2017; 42 (1): tsx081. doi: 10.1093/amt/tsx081.

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