Other onion project reports

Rob Wilson (UCANR): Update of onion white rot and maggot research

White rot fungicide management: Tebuconazole and Fontelis were most effective for white rot management. In furrow fungicide application of Tebustar and Fontelis performed better compared to untreated check. Seedcorn and onion maggots have been an issue for onion growers in California. Seed treatment and in-furrow applications of insecticides are the two options against seedcorn and onion maggots. California lost Lorsban in-furrow. Seed treatment options include Sepresto 75WS, FarMore, and Regard were better than untreated control. Full size pellet and film coat on seeds performed better than encrustment seed treatment. Sepresto seems to reduce onion smut.

James Woodhall (University of Idaho): Onion pathology research in the Treasure Valley

The Woodhall lab provides diagnostic lab services and is interested in new diagnostic method development, characterizing soil-borne diseases and conducting field trials for disease management. MinIon sequencing for pathogen diagnostics is current under testing in Idaho. Predictive soil testing for pathogen presence and soil-microbial community analysis using NGS were conducted for:  Setophoma terrestis, Fusarium spp., Pythium, Rhizoctonia sp. Pink root was detected from 78% of the soils tested (n=139). Rotation with corn increases F. proliferatum outbreaks.  Late season application of Luna and Pristine reduced Botrytis neck rot in fungicide evaluations. For pink root management field trails were conducted to evaluate combination of fumigants, fungicide (Fontelis) and biologicals under field conditions.

Chris Cramer (New Mexico State University): NMSU onion breeding program update

Onion bulbs from different germplasms were evaluated for Fusarium basal rot resistance. The NuMex Mesa selections, FBR1-2 and FBR3 selections had considerably lower Fusarum basal rot severity compared to Serrana and NuMex. The NuMex Sweetpak selections FBR1-2, FBR1-3 and FBR4 also performed well when evaluated for Fusarium basal rot resistance.  These selections will further be evaluated under field conditions.

Christy Hoepting (Cornell Cooperative Extension): Highlights from NY onion research

In New York, insensitivity of Stemphylium leaf blight to FRAC 11 fungicides including Quadris and Cabrio, FRAC 9 fungicides including Scala and cyprodinil, and boscolid (in Pristine and Endura) of FRAC 7 were evaluated.  Early signs of fungicide resistance (e.g. 2% of isolates slightly tolerant) have been detected in Rovral and FRAC 7 in Merivon.  In field trials, FRAC 11 fails to control SLB and FRAC 9 and boscolid provided poor control. Epidemiological studies showed that although SLB spores may be detected in commercial onion fields during the end of June, this disease outbreak occurs during the second part of July  through the end of the growing season. Developing an effective and affordable fungicide program that implements best management practices for fungicide resistance is a challenge.  New York growers have had an extremely high adoption rate for fungicide resistance management practices. Managing onion thrips under high pressure continues to be a challenge with current roster of available products.  Brian Nault continues to look for new products and tweak thrips management plan to optimize efficacy and resistance management, which also includes reduced nitrogen and use of tolerant varieties.  Steve Beer’s lab identified a critical gene cluster for center rot, which will help in identification of pathogenic strains, and changed the label of Surchlor (pool chlorine) to disallow tank mixes any other products due to incompatibilities.

Hanu Pappu (Washington State University): Update on recently-funded SCRI onion project

Diversity and genetic analysis of IYSV were conducted. PCR and RFLP-based test identified and distinguished two major genotypes of IYSV: IYSV-Brazil and IYSV-Netherland. Phylogenetic studies of the global collection of IYSV sequences were also conducted. IYSV N gene-142 sequences from 19 countries were analyzed. Phylogenetic analysis using in silico RFLP was used to genotype IYSV into two groups. Based on Hinf1 recognition site, 142 IYSV isolates were divided into 79 Netherland genotype, 55 Brazil genotype and 8 other genotype. Recombination may be playing a role in IYSV evolution. 

Beth Gugino (Pennsylvania State University): Onion leafminer update (Shelby Fleischer)

Allium leafminer (ALM) update was presented. First specimen of ALM was collected in December 2015 in leeks. Feeding damage has been detected in wide range of hosts. Twisting and distortion of leaves are some of the major symptoms. Overwinter as pupae in onion. Insecticide efficacy trial was conducted in Leek (2018). Of 280 plants dissected, 18 plants had <10 and 3 plants had <20 ALM per plant. Foliar application of Scorpion and Exirel (neonic and diamide) significantly reduced ALM populations/plant compared to control. Oviposition marks of onion foliage predicted presence of ALM. Infestation rates higher in younger plants regardless of cultivar. Parasitoid collected from ALM pupae in Centre and Lancaster Co., PA. Currently, being identified by USDA/ARS.