June 23, 2017

Lindsey du Toit – WA State Commentary – Onion ipmPIPE

2013 WA – Onion ipmPIPE Commentary 7-24-2013



Onion Crop Growth Stage and Status Last Modified: 07/24/13

Onion crops are maturing rapidly with the very warm conditions in the Columbia Basin in July. Bulb crops in the north Columbia Basin are at the 5-6 growth stages (12 pairs of true leaves and bulb initiation), and in the south Basin most crops are at the 6-7 growth stages (bulb diameter of 1.0-1.75 inches and 1.75-3.0 inches = 2.0-4.0 cm and 4.0-7.5 cm diameter, respectively).


Seed crops of Allium fistulosum (bunching onion) have been harvested. A. cepa and CFC (‘cepa fistulosum cross’) seed crops are in late-bloom.


Weather Impacts (temperature, rain, hail, freezing) Last Modified: 07/24/13

July has been very warm in the Columbia Basin, with the result that thrips numbers have increased significantly.


Temperature Outlook* [next 2 – 4 weeks]:       average

Precipitation Outlook* [next 2 – 4 weeks]:        average to 30% below average

*Courtesy of Planalytics, Inc.


Insect Scouting, Outlook and Management Last Modified: 07/24/13


Thrips populations have increased very rapidly in onion crops with the onset of very warm conditions through most of July. 100% of plants were infested in Sentinel Plots in the north and south Columbia Basin, with 3 to 35 thrips/plant detected in the north Basin Sentinel Plots, and 5-69 thrips/plant in the south Basin Sentinel Plots.



No maggot problems reported at this time.


None reported.


Disease Scouting, Outlook and Management Last Modified: 07/24/13

Iris yellow spot virus

Iris yellow spot virus has been detected in several onion bulb fields in the north and south Columbia Basin. In the north Basin, the infected crops are in relatively close proximity to onion seed crops infected with IYSV. Samples were submitted to the NOVL on 7/16/2013. Growers leasing ground have been advised to consider the location of biennial onion seed crops in the region to try and avoid a green bridge effect for movement of thrips and IYSV from seed crops to bulb crops.


Soilborne Diseases (Damping-off, pink root, Fusarium basal rot, etc.)

Pink root observed on 2-6% of the plants in Sentinel Plots in the south Columbia Basin.


Fungal Foliar Diseases (purple blotch, downy mildew, Botrytis)

No surveys or reports at this time.


Bacterial Diseases (Xanthomonas, center rot, soft rots)

A few growers reported bacterial-like symptoms in center-pivot irrigated bulb crops in the south Columbia Basin, but there has not yet been verification of the cause of the symptoms on samples tested in one lab. The NOBL in Pullman requested samples for further evaluation.


State Contact for Project
Lindsey du Toit
Professor of Plant Pathology

Washington State University
Email: dutoit@wsu.edu


Collaborators: Tim Waters, Carrie Wohleb, Jordan Eggers, Hanu Pappu, Brenda Schroeder,

Bill Dean