Hello Terry

I’m sorry for the delay in our reply due to the holiday.

Diatomaceous earth works by scraping the exoskeleton of insects, drying them out. Here is a publication that indicates that DE has some effect on flea beetles:

https://extension.colostate.edu/topic-areas/insects/flea-beetles-5-592/

Some references do not list diatomaceous earth for control of flea beetles.. Here is a publication that lists cultural and chemical controls for flea beetles in the garden:

https://extension.umn.edu/yard-and-garden-insects/flea-beetles#using-insecticides-3089113

Spinosad is an organic option, which you can read more about here:

https://extension.illinois.edu/blogs/garden-scoop/2018-07-26-organic-pest-control

It is important to only use garden chemicals labeled for the plants, and for the insects or condition, that you are treating. The “label is the law”  as it is required by regulations to be accurate and tell you what plants it is allowed on, how to apply, what it is effective on, and what precautions you must take.

So please read the label of the product you use and apply it exactly as directed. If you are using a dust, be sure to wear a respirator or other protection as listed on the label.

Thanks but this does not answer my question.  And I use d.e. for other things like radishes etc.  I have spinosad.  The question was which is better when applying de.  Dusting is on or

I’m sorry, we cannot recommend any application or use that is off-label. If your product has a slurry mixing direction you may then use the product mixed that way on the surfaces the label  states. 
I could find no studies that indicated which technique was better.

I will refer your question to an expert with pesticide application certification. He or she may have access to more information than I could find for you. I appreciate your patience.

Hi, I would agree with Laura's response that any off-label application methods are not recommended. If you are not seeing much control with diatomaceous earth, I'd recommend focusing on using other controls. Like Laura mentioned Spinosad is an option, but employing integrated pest management by using cultural practices in addition to any chemical or other treatments is recommended. For example, these are some recommendations from University of Minnesota:

-Control weeds in and around planting sites to limit food sources for flea beetles.
-Remove old crop debris so that beetles will not be able to get protection in the winter.
-Plant crops as late as possible. Plants grow faster in warmer temperatures and are more stable to resist damage from flea beetles.
-Use row covers or other screening to keep beetles out when the seedlings are growing.
-Remove row covers before the flowers come up so pollinating insects can reach the plants.
-Plant a highly-favored crop, such as radish, as a trap crop, before you plant your main crop.
-Adult flea beetles will be attracted to the tallest, earliest crops available.
-Once beetles are actively feeding on the trap crop, spray with a labeled pesticide.

Laura sent the link to that resource previously.

Hello again,
I did find a slurry vs dust reference, by a manufacturer, which indicates the slurry is used for ease of application and for applying to hard to reach places. While wet the slurry has no effect but once dry crawling insects will pick up the dust— this according to the manufacturer. 
Your product label should have a manufacturer toll-free number for questions. You may give them a call, they may have more information for your particular product.

Regards,
Laura