by Trish Fox, New Farmer Academy Intern

Specifically, I’m speaking of the bacterial wilt that infects Cucurbits. At Old Trail Farm, we recently lost some cucumber plants in the hoop house to the disease. If you’ve been battling the wilt in your home garden, and you’ve experienced some cucumber casualties as a result, we can empathize with your loss.

 

Some Biology

For those who aren’t familiar with bacterial wilt of Cucurbits, it’s a vascular wilt disease that infects some members of the cucumber (Cucurbitaceae) family. The bacterium responsible for the wilt is Erwinia tracheiphila, and it’s spread by the striped and spotted cucumber beetles. This highly destructive disease affects certain members of the Cucurbitaceae Family more than others; with cucumber and muskmelon (cantaloupe) most highly susceptible, squash and pumpkins less so, and watermelon showing resistance to the disease.

 

How do I know it’s bacterial wilt? Maybe my plant just needs water!

You’ll notice the symptoms in just one of the plant’s leaves, but soon it will spread to adjacent leaves. Those leaves may become wilted beyond what you expect to see in a plant that just needs a bit of water. You may observe the leaves droop in the daytime heat, but they will be fine the next morning. Infected leaves will look dull green at first, the leaf margins will eventually turn yellow and brown and then die. The wilt will progress down the vine until it ultimately withers and dies, too. Most importantly, you will likely detect striped and/or spotted cucumber beetles in your garden. 

It may be tempting to try to save your plants by removing infected leaves. Sadly, the disease is systemic in the plant. The bacterium lives in the guts of the striped and spotted cucumber beetles. While not all these beetles are infected with the bacterium, they can pick up the bacteria when feeding on infected plants. Therefore, removal of infected plants is a must to limit disease transmission to healthy plants.

 

Okay. I’ve diagnosed my plants with the wilt, now what?

Management of the cucumber beetle population in your garden is the recommended solution. Ways that you can do this include:

  • Using yellow pan/bowl traps in your garden. This easy set-up involves placing a yellow bowl(s) with some water and a few drops of soap within your garden. Why does this work? Because the cucumber beetles are naturally attracted to the yellow flowers of the Cucurbits. In the same manner, the beetles are attracted to the yellow bowl. The beetles land in the bowl and drown due to the surface tension being broken by the soap in the water. 

  • Plant a “Trap Crop.” Plant a variety of cucurbit that is highly attractive to the cucumber beetle along the perimeter of your garden. This may lure the beetles to the trap crop, causing them to concentrate there rather than on your main cucurbit crop. Also, cucumber beetles tend to overwinter near garden edges in proximity of last year’s cucurbit crop. The trap crop may delay movement further into your garden. Just be sure to remove and dispose of the trap crop before any bacterial wilt can be passed on to healthy, desired plants by roving cucumber beetles.
  • Rotate your crops. This is a beneficial garden practice for soil health maintenance and management of garden pests, so we recommend that you implement good crop rotation practices! In the case of cucumber beetles, because they overwinter near where they were feeding and mating last season, it would behoove you to move your cucurbits to another site in the garden. Beware of volunteer plants, however. They may mess with careful crop rotation planning.
  • Consider delaying planting your crop until later. The idea here is that the cucumber beetles will be drawn to a crop in another location before your crops emerge from the ground.
  • Transplant rather than direct seed. This is a similar idea to the previous point. Transplants may attract fewer beetles because they are planted later and are at risk for a shorter amount of time. 
  • Use row cover. Cover your cucumbers with row cover until they are ready to flower. You’ll have to remove the row cover once the plants begin to flower so they can be pollinated.
  • Use mulching. Mulching can inhibit beetle movement between plants. It can also provide hiding spots for beneficial bugs like spiders. Organic mulches can also increase the presence of beneficial organisms in the soil.

No single management technique is likely to completely eradicate your cucumber beetle problem entirely, but the use of these management techniques can help to make the problem more controllable. This is especially true when more than one technique is used in conjunction with another.  

Have you found a successful strategy for managing Cucumber beetles in your home garden? Or do you just need to lament the loss of your cucumber plant? Either way, we’d love to hear from you! 

Sources:

“Bacterial Wilt.” Facts in Depth. The Ohio State University. 

https://u.osu.edu/vegetablediseasefacts/cucurbit-diseases/bacterial-wilt/advanced/  . Accessed August 11, 2021.

Michelle Grabowski. “Bacterial wilt of Cucurbits.” University of Minnesota Extension. 

https://extension.umn.edu/diseases/bacterial-wilt . Accessed August 11, 2021.

Snyder, William E., “Managing Cucumber Beetles in Organic Farming Systems.” eOrganic.

https://eorganic.org/node/5307 . Accessed August 11, 2021.

“Striped Cucumber Beetles.” Integrated Pest Management Program. University of Connecticut. 

http://ipm.uconn.edu/documents/raw2/Striped%20Cucumber%20Beetles/Striped%20Cucumber%20Beetles%20.php?aid=75 . Accessed August 11, 2021.

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