Bacterial wilt? Plants drowning! Onion maggots, oh my!

Long rows of Roma paste tomatoes. Photo Kathryn Simmons
Long rows of Roma paste tomatoes.
Photo Kathryn Simmons

Like many people in our area of the mid-Atlantic, we’ve had a lot of rain. 8″ in June, including a ten day dry spell, so 8″ over 20 days. Some of our 540 Roma paste tomatoes suddenly wilted, about ten days ago. Argh! Were our tomatoes drowning or was it the dreaded Bacterial Wilt?

My first response was to stop everyone touching them. No string-weaving till we figured out if the problem was contagious or not.  Then I read up about Bacterial Wilt (Ralstonia solanacearum, formerly called Pseudomonas solanacearum). ” Plants wilt and die rapidly without the presence of yellowing or spotting of the foliage”. We had the rapid wilting, with no yellowing or spotting. “The disease is most commonly found in low, wet areas of fields and is most active at temperatures above 75 degrees F.” Check, check. But drowning is most common in low, wet areas too! The affected plants were in the lowest areas, but that didn’t tell us whether it was drowning or bacteria causing the problem.

Next I counted the wilted plants in each row. The total was 81 plants the first day, 92 the second (uh-oh!), but 65 the third day, 51 the fourth day, up to 57 the next day, then 41. By this time I was concluding these plants were not dying rapidly, so maybe it wasn’t wilt. One site said plants could die within a few hours of starting to wilt. Other sites said plants could wilt a bit in the middle of the day, then recover at night. I don’t think that’s Bacterial Wilt.

The third day I sacrificed the worst plant and cut through the stem to look at the xylem (water conducting pipes). Yes they were brown, not happy. Does that happen in drowning plants or just those infected with bacteria? I don’t know. The cut ends weren’t sticky, as suggested for bacterial wilt, didn’t pull out sticky threads when pressed together and pulled apart. So next I tried the definitive test for tomato bacterial wilt: I cut a length of stem, stabbed it through with a knife and suspended it in a jar of water to watch for milky bacterial ooze streaming from the cut. Initially a small amount of something gently fell from the cut end. Then stopped. I watched for 5 minutes (some sites said it took several minutes for the ooze to leave). Nothing more happened. I’ve decided they were drowning, so we’re back to string-weaving.

Roma Virginia Select, grown at Twin Oaks. Credit Southern Exposure Seed Exchange
Roma Virginia Select, grown at Twin Oaks.
Credit Southern Exposure Seed Exchange

We transplanted these around May 5, and tomorrow we’ll do our first harvest (about 66 days from transplanting). These are listed in Southern Exposure Seed Exchange catalog as 75 days from transplanting to harvest. We grow these Virginia Select Romas here in our garden and sell the seed to SESE. I’ve been selecting for earliness (as well as good yields and tolerance to Septoria leaf spot) and I’ve been wondering what impact I’m having on the “earliness” part of the equation. Seems like it’s working well.

Meanwhile, the plants are recovering from near-drowning and assaults by all manner of other disease organisms that like warm damp weather. I see some Septoria, some early blight, but abundant healthy foliage too.I think they will outgrow the current issues.

Trimming garlic. Photo Brittany Lewis
Trimming garlic.
Photo Brittany Lewis

We have been making great progress trimming and sorting our garlic. We’ve trimmed it all! In just a couple of weeks! Yay for us!

But as soon as the tomato trouble gets resolved, another problem arises. Some of our softneck garlic bulbs have onion maggots! What to do? We also had a problem with helpers bagging up garlic before it was fully cured, so we’ve spread the trimmed bulbs back out on racks to finish drying. Is there anything we can do about the maggots? If you have suggestions, please add a comment! I know what to do to reduce our chances of getting them in future: pay attention to rotations, practice good sanitation by removing all allium bits from the plot when we harvest, control weeds ahead of planting garlic (and of course while it’s growing!).

My understanding of the life-cycle of the onion maggot is that pupae overwinter in the soil, adults emerge in spring. 9 days later they lay eggs at the base of plants. Eggs hatch in a week, maggots burrow into the roots of the plants, spending 2 or 3 weeks up to no good. Then they leave the bulbs and head back into the soil to pupate. If we leave our garlic on racks for three weeks, will the larvae just drop to the ground below the racks? Can we then sort the good bulbs from the bad? Will they all be infested by then? It seems biologically determined that the larvae leave after about 3 weeks. How much damage will they do while we wait?

Or can we try sorting good bulbs from bad now? We’ll need to take a closer look at the crop and see what we can do. We also wanted to save stock for replanting, and obviously don’t want to replant infested cloves. Any there any garlic experts reading this?

Measuring garlic bulbs to select good seed stock. Photo Brittany Lewis
Measuring garlic bulbs to select good seed stock.
Photo Brittany Lewis

3 thoughts on “Bacterial wilt? Plants drowning! Onion maggots, oh my!”

  1. We had onion maggots in our garlic in 2010, also a wet year, and we wrote about finding them here:

    Though we were very concerned at first, they turned out not to be as huge a problem as we initially thought. A relatively small percentage of heads were affected, and those that were could generally be identified by smell, so we could avoid selling them. It has been a while, but my memory is that the maggots rarely penetrated the cloves themselves, so infested heads were still mostly good enough to eat for our own use.

    We didn’t end up with any long term problems. I can’t remember another outbreak in our garlic, though we’ve been saving our own planting stock since before 2010. Maybe wet weather is to blame? We’ve certainly been blaming the wetness on lots of things (including a backlog on blog reading). Now I’m feeling like I should go and check on our heads, the majority of which are still curing in our barn….

    1. Thanks Joanna, good timing. I’m just about to go and investigate. We de-bagged the garlic and spread it out on the onion racks. My idea was that in three weeks the larvae would have pupated, perhaps unsuccessfully as there is no soil to burrow in. (Not like while the garlic is growing.) Also, frankly, I thought waiting and seeing was all I could manage at the time! Now it’s time to revisit the bulbs and make a plan. The tip about the small identifying the troubled bulbs is the best! So helpful.

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