Notes from our Grading Line | Vidalia Onion Extension Blog

Pictured above from l-r are Jason Edenfield, Toombs County Extension Agent, Savannah Tanner, Emanuel County Extension Agent, and Chris Tyson, Area Onion Agent. Here we are grading some “Vidora” onions earlier in the season, which looked great. The first few weeks of harvest we saw very few issues in growers’ fields and in our trial onions here at the VOVRC. Photo credit: Ross Greene, Candler/Evans County Extension Agent.

Hey onion folks,

I know many of you are trying to wrap up or are already finished with onion harvest. We are too here at VOVRC with onion trials. I am thankful we’ve had great harvest weather this season. It could have been a lot hotter and wetter than it was, and I think that has helped the quality of the crop tremendously.

Overall, this was a great crop year. A much lower incidence of internal rot this year, as compared to last year. I did want to share some pictures and document some isolated issues we’ve noted on the tail end of the crop. These are typical issues for us late season, and not cause for any widespread concern. I am just letting you know what has been reported to me and what I’ve seen. The incidence of the items below are isolated and not a widespread industry concern.

External Decay in Field

Here is a photo of some “white mold”, caused by the pathogen Sclerotium rolfsii, growing on the bottom of an onion still in the field. This is the same white mold that hurts peanuts. This is one of the issues that could cause onions to be culled on the grading line for external decay.

Some of the typical “External” onion problems can be found in some fields and grading sheds. This includes sour skin, sun damage, and even the white mold pictured above. By the way, this is the same white mold we see on peanuts and tomatoes. One important visual observation that we have noted in our plots is that there is less disease/decay in onions which were dug with a chain digger as compared to those which were just undercut with a blade.

This onion encountered some external decay in the field. It has been clipped and dried and this is what it looks like on the grading line. The decay started to eat away at the outer layer of onion skin and discolor it. In addition, some black mold can also be seen growing underneath the onion skin. Due to these issues, this onion will be culled. Photo credit: Savannah Tanner, Emanuel County Extension Agent.

Black Mold

Some Black Mold is starting to show up as well. Black mold is usually a later season problem, especially if we get temperatures into the 90’s during harvest. I wrote a previous post about black mold which can be viewed here: https://site.extension.uga.edu/vidaliaonion/2019/06/black-mold-in-vidalia-onions-quick-facts/

Center Rot and Internal Decay

Here is an onion we cut open on the grading line. The neck was dark and not dried down, so we cut it open to see if something was going on. Looks like either center rot or slippery skin, or both, has gotten into this bulb. Photo credit: Savannah Tanner, Emanuel County Extension Agent.

Some Center Rot and other internal decay pathogens have shown up late season. Many growers have noted that is only an issue in certain varieties. On the grading line, we often detect onions with internal rot by inspecting the neck. If the top of the neck is discolored (black or brown) where it was clipped, or the neck feels “slimy” or wet, this is often an indicator of something going on internally.