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pacmom23

Pity the beast that ravages my rose bush

pacmom23
16 years ago

I have several rose bushes of which I pruned down and fertilized just after the last frost. The new growth brought a bounty of new buds, and the anticipation of seeing and smelling what each bore was building with each passing day. Horrors! Wednesday afternoon I noticed holes appearing on the leaves, and by that evening, some were completely skeletonized. I inspected the leaves (top and bottom) but didn't see anything. In a panic, I rushed to my computer and looked for information in this forum. I learned it was probably a sawfly and went back to look - sure enough (with reading glasses in place) there were small green caterpillar looking things on the underside of nearly every leaf ugh! I also learned that people had tried flour, insecticidal soap, and poisons. However, most questions were left open and I could not find the definitive cure.

The next morning, I set up an experiment in my laboratory (master bath). I cut several leaves from the affected plants (now almost completely ravaged) and placed them on individual dishes and labled each. I looked at those beasts under a microscope and declared war. To each dish of leaves and stem, I did one of the following:

1. sprinkled flour on the underside

2 sprinkled flour on the topside

3. sprayed with a dilute mixture of water and dawn dish detergent to the underside.

4. sprayed with Pam vegetable oil.

5. nothing (for control)

Results:

1. all larvae stage dead; adult alive

2. they live

3. slow death (they stop eating)

4. all larvae dead, adult dead!

5. larvae stage alive; adult missing

Today is Sunday. Friday, 5am I opted to spray Pam on one plant, and dilute Dawn on another. This morning, both plants are doing well. I did not rinse off the Pam or dilute Dawn. I continue to get new growth, and the beasties are GONE! No buds have bloomed, and I will post again in a few days.

The science behind the above is simple:

The larvae has a soft membrane (tissue) protecting it from the environment. It is fluid-like on the inside and the membrane keeps it from dessicating (drying out).

Flour - causes the fluid to move from the larvae to the higher concentration of flour, and you are left with an empty shell. The adult has a more complex membrane that prevents this diffusion.

Pam (vegetable oil) solubizes (dissolves) the beast. Like dissolves like, and also solubizes the adult.

Again, I will post again after more time passes.

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