Zucchinis in Trouble

Question: My zucchini plants are in trouble. Although the tops of the plants are green, leafy and producing fruit, the bottoms of the stems are gnarly and all of the leaves have died (so I cut them off). The leaves at the top are rapidly dying also. I am worried that soon I won't have any leaves left. I spray them weekly with Neem and Daconil. Recently I saw a slug so I put down some slug bait (Ortho Bug-Geta with sulfur). I water them with an underground soaker hose. I switched this week from watering daily to every other day in case the issue is too much water. Your advice is greatly appreciated.

responder: Edward A.  Replied July 30, 2024, 9:52 PM EDT
response: Hello, Thank you for your question. In the first photo, I am pretty sure I see the results of a squash vine borer and I see a borer hole on one of the stems. You could have squash vine borers, but vines will split for other reasons – strong winds, heavy weight on the vine and inconsistent watering. Oakland county has had an unusual amount of rain this year. Are you making sure the soil is not too soggy when there is rain and you use the underground weeper as well? It could also be that you have a fungal disease. The weather has been very conducive to fungal growth this year. From a picture alone, it would be nearly impossible to determine the exact fungus and confirm that Neem or Daconil will be effective against it. In one of the pictures I am pretty sure I see mildew on the leaves, but without a laboratory test, there is no way to be sure what other fungal growth may be present. Do you plant your squash in the same place every year? This ensures that the fungus that over winters in the soil has a host to live on when the conditions are right the next year. Before you go full bore with slug bait, it is easy to determine if you have significant numbers of slugs to do damage. Bury small dishes in the ground and fill them with beer. The next morning you will find out how many slugs you have moving around your plants that end up drowning in the trap. Slugs are generally defoliators and are not really vectors for infections. I see at least some signs of Squash Vine Borer: https://extension.umn.edu/yard-and-garden-insects/squash-vine-borers#cultural-controls-3112161 Look for borer holes in the vine close to the root. Inside you should find a yellow to orange-ish mush and possibly the white borer larvae. The damage to the plants in the photo is likely terminal. If the vine is not completely dead, it my be possible to insert a piece of wire through the hole and up through the center of the vine to try and kill the borer. Please see the website given above for pesticides that are effective against the Squash Vine Borer. The pesticides need to be applied in June through early July. The following article also has a non-chemical method to prevent the borers from entering the vine – wrapping the stem with aluminum foil. There is also a suggestion for “layering” the stem to promote root growth if the borer is discovered before the entire vine dies. https://extension.umd.edu/resource/squash-vine-borer-vegetables/ I would conclude that you have multiple issues: vine borers and at least one fungal infection. If you want to plant zucchini again next year and you need to plant in the same location, you could benefit from sending a vine sample to the MSU Diagnostic Laboratory and have a positive identification of your squash issues. Information about the Diagnostic Service and fee structure can be found at: https://www.canr.msu.edu/pestid/ This website gives tips on how to effectively take a sample: https://www.canr.msu.edu/pestid/submit-samples/ Knowing exactly what is happening to your plants allows you to try a preventative application regimen next year. Hope this helps.

responder: The Question Asker Replied July 31, 2024, 12:49 PM EDT
response: Dear Edward,  Thank you very much for your thoughtful email. After I emailed you but before I received your response, I discovered that I did in fact have a squash borer infestation. I slit the stems and removed all the borers (I hope) then covered up the stems with dirt. I don't know if these plants will survive and also it was gross! I don't really have a big garden. I only had 2 zucchini plants, but they had a lot of vines (or at least they did before the borers chewed up most of them). Do you think it would be best if I would take a year off from squash or does it make sense to try again with foil, pesticides and other preventative measures? Also, I have one pickling cucumber plant but it is very large and tall. It is also having a die-off of leaves. I was wondering if the squash borers could have gotten into the cucumber, but it didn't make sense to split the stem at the bottom since it is very narrow. I will take photos of that later (since I am at my office now) and will send them in hopes you can identify the issue. I really appreciate your advice!  Sincerely, Beth   On Tuesday, July 30, 2024 at 09:52:22 PM EDT, Ask Extension <<personal data hidden>> wrote:

responder: Edward A.  Replied July 31, 2024, 10:30 PM EDT
response: Hello Beth, What you grow next year is totally up to you.  Just be prepared if you grow zucchini to treat with pesticides and possibly apply aluminum foil at the appropriate time to avoid borers. Cucmbers are always susceptible to powdery mildew.  Our weather in July has been favorable for powdery mildew development.  It is likely the problem that is affecting your cucumber plant.  https://extension.umn.edu/disease-management/powdery-mildew-cucurbits#:~:text=Powdery%20mildew%2C%20mainly%20caused%20by,and%20easily%20spread%20the%20disease. Powdery mildew is a large problem for cucumbers in Michigan.  One recommendation I heard lately is to try a resistant variety and plant early, to get the most yield from the vine before powdery mildew infects it. Happy gardening!

responder: The Question Asker Replied August 01, 2024, 7:09 AM EDT
response: Dear Edward,  Thank you for your advice. I have attached photos of my cucumber leaves. Does this look like powdery mildew or something else?  Sincerely, Beth    Sent from my T-Mobile 5G Device   -------- Original message -------- From: Ask Extension <<personal data hidden>>  Date: 7/31/24 10:30 PM (GMT-05:00)  To: bsnider67 <<personal data hidden>>  Subject: Re: Zucchinis in Trouble (#0149296)

responder: Edward A.  Replied August 03, 2024, 8:13 AM EDT
response: Hello Beth, I don’t think that is powdery mildew. It is possible it is a fungal or bacterial leaf spot. https://extension.umd.edu/resource/key-common-problems-cucumbers/ The spots are generally between the veins and it does not look like insect feeding (look under the leaves for any signs of mites or sucking insects). Considering Southeast Michigan has had exceptionally good conditions for fungus infections this year I would generally look there. Another concern is that the plant looks very “dense.” There is a lot of foliage which makes it very difficult for the plant leaves to dry out after rains or on dewy nights. Fungal diseases in cucumbers are so common that growers should watch for varieties that have disease tolerance and start the cucumber crop early before conditions are ripe for fungal growth. Finally, you could send leaf samples to the Diagnostic Laboratory or you can send these photos to <personal data hidden> for a second expert opinion. Hope this helps.