Seed Coating Technologies and Treatments for Onion: Challenges and Progress

Abstract

<jats:p>Conventional methods to control the onion maggot or onion fly, <jats:italic>Delia antiqua</jats:italic> (Meigen), have relied on in-furrow applications of the toxicant pesticide, chlorpyrifos. The objective of this research was to develop an onion (<jats:italic>Allium cepa</jats:italic> L.) seed treatment that utilizes a new chemistry compound that is environmentally safe. Cyromazine is an insect growth regulator with a mode of action different from traditional pesticides used to control onion maggot. Cyromazine has low mammalian toxicity and is relatively nontoxic to other insects, including beneficials. High seed loading rates (50 g·kg<jats:sup>-1</jats:sup> active ingredient) are required for optimal efficacy, and conventional slurry methods are inadequate to apply these high loading rates. Film coating and pelleting were performed at Cornell Univ. to apply cyromazine and a registered fungicide (a formulation of thiram and carboxin) to onion seeds. Results of field studies performed over several years revealed that stand losses due to the onion maggot ranged from ≈20% to 60%. Cyromazine applied by either film coating or pelleting decreased the loss by onion maggot from 1% to 8%, and efficacy was comparable to an in-furrow application of chlorpyrifos. Cyromazine was registered as a seed treatment and is commercially used in the northeastern and midwestern United States, where onion maggot is a serious pest. Field emergence was not negatively affected by cyromazine coated onto the seeds when onion seeds are sown in organic (muck) soils. There is other evidence, however, that cyromazine seed treatments may cause phytotoxicity to germination and seedling growth. Testing seed quality in sand or on roll towels revealed a high percentage of abnormal seedlings. Retarded root growth was observed in seeds treated with cyromazine, resulting in an increase in abnormal seedling classifications. A finely ground sphagnum peatmoss applied over the seeds in a roll towel test ameliorated the abnormal root growth symptoms, and seedlings had robust growth. Collectively, film coating and pelleting were effective delivery systems for the application of plant protectants required at time of sowing. Modification of the standard germination test was needed to accurately assess onion seed quality. Moreover, this project was successful due to a team effort of a university seed scientist and entomologists working with onion growers and industry. Future registrations on small acreage, high-value horticultural crops are envisioned to require similar multi-partner approaches. Chemical name used: <jats:italic>N</jats:italic>-cyclopropyl-1,3,5-triazine-2,4,6-triamine (cyromazine).</jats:p>

Systemic Seed Treatment Uptake during Imbibition by Corn and Soybean

“…Dosage rates were expressed throughout this paper as milligrams per gram of seed and were converted to milligrams per seed (Table 1). High application rates of selected seed treatments may induce phytotoxicity during germination (Taylor et al, 2001), and the initial increase phase is of significance in seed testing when evaluating the risk of phytotoxicity of agrochemicals applied as seed treatments. In the case of commercially treated corn seed, this range would be in the saturated region (Fig.…”

Evaluation of insecticides and application methods to protect onions from onion maggot, Delia antiqua, and seedcorn maggot, Delia platura, damage

“…Both maggot species have multiple generations per year (Eckenrode et al, 1975;Rinehold et al, 2013). First generation larvae cause the greatest economic damage by feeding on developing epicotyl and roots of seedling onion often resulting in plant death and significant reduction in onion stand density (Taylor et al, 2001). Second and third generation onion maggots feed on expanding onion bulbs typically causing minimal economic loss unless onions are diseased, as maggots have difficulty penetrating healthy, older onion plants (Eckenrode and Nyrop, 1986).…”

“…Onion seed treatments with clothianidin, cyromazine, fipronil, and spinosad were shown to effectively control onion maggot in New York, USA and Ontario, Canada (Hoepting et al, 2004;Nault et al, 2006a;Taylor et al, 2001). Seed treatments offer several advantages including alternative modes of action to chlorpyrifos and less active ingredient per unit area compared to in-furrow drench.…”

Effects of neonicitinoid seed treatments on soybean aphid and its natural enemies

“…This delivery technology for crop protection chemicals has many benefits. In addition to directly protecting crops from seed and root feeders and early season foliar pests, these targeted applications can have other benefits such as decreasing applicator exposure and the amount of active ingredient used (Taylor et al 2001) and less exposure to nontarget organisms than foliar applications (Albajes et al 2003). Additionally, their ease of use can improve pest control in situations where foliar sprays are difficult to time or crop morphology prohibits adequate coverage (Nault et al 2004).…”