I think the aphids like the most tender juicy leaves. I think plants have immune systems and defense mechanisms that we probably don't fully understand yet but maybe the bugs know by sight, taste or smell who may be least resistant to their attacks.

Some caterpillars utilize plant toxicity to help protect themselves from predators. So bugs are pretty smart lol. Good topic!

Thank you, Dr. Manners! I had no idea that the aphid was such an extraordinary critter. I will have to show them more respect -- just before I turn the hose on 'em, haha. They pose little problem here. But every chance I get now, I am inspecting my roses for early signs of sawfly larvae,since they can be and have been brutally destructive. As they're late to arrive, I'm letting myself dream that perhaps they'll just pass us by this year.

Sultry, I agree, insects are fascinating! Very interesting re the caterpillars using toxic plants to keep safe!

Are there any other SF/SF Bay Area people out there? Are you seeing more or fewer or no rose slugs so far this year?

How fascinating,that stuff about aphids! Actually I heard /read somewhere that aphids play an important role in thrip control,but i don't remember what it was.

In any case, i really DO think that insects can sense if a plant is weak and IME do attack weaker plants. I think it is just part of the nature of predators-somehow they can and do sense weakness.

I practice what would be considered odd to most people... I leave well alone... not wishing to sound 'high and mighty' about it, it's just that I can't deal with killing anything out there... they've all got a right to their existence, most are food for something else, it's not my place to argue with that... and so I don't regard them as pests... I would consider myself a pest if I sought to kill them really..

If a rose or any other plant becomes unsightly on a continuing basis because of insect infestation.. I remove the plant, and put something else in that won't be so bothered by them... that means sometimes removing roses ...

I admit, it does horrify me when I hear people reaching for whatever spray they can get hold of, as if it's the done thing.. at the first sign...

I should apologise having realised that none of this answers the questions posed.. and I do not have to deal with deer, rabbits, Japanese beetles, rattlesnakes or gophers...

What Marlorena said. Our garden has lots of lady bugs, and in the Spring huge flocks of teeny, tiny, birds show up and feast on aphids. I was alarmed once by a lot of "soldier bugs", until I looked them up and found out that they were "good" bugs which ate the bad ones! So, after I realized all of that, I got much more relaxed about bugs in the garden. Our garden is full of birds and bird nests, and squirrels, and the occasional deer, and sometimes possums, raccoons, and skunks (it is only 4 blocks from the downtown of our town!). I let them all be, and enjoy them. Right now we have a lot of butterflies for some reason, and we always have a lot of several different kinds of bees, including honey bees. The roses are not perfect (and we do not get real scourges of bad bugs like Japanese beetles), but they seem happy and are beautiful, so I try to concentrate on giving them basic care.

Jackie

Yes, rose slugs seem to me to be worse this year than last year. I think yours moved from your yard to mine! Have not seen too many aphids this year. Of course, now I have jinxed myself and they will show up in droves. The awful Hoplia beetles were just horrible this year. I hope my spraying of beneficial nematodes in the soil will help with that next year. I really seem to have had more of an issue with thirps this year. Hate those things too! I don't spray and tend to leave things along except or what I can pick off (like those Hoplia beetles), I found a baby praying mantis the other day when I was deadheading! I tried to pick him up so I could get a better look and admire him but he wasn't having any of it, unfortunately. I am also finding those invader species of large cockroaches (dead) in my yard ever since my neighbor decided to "let them be free" when they moved. They used to feed them to their reptiles.

The worst bug in my yard has to be the Aedes Aegypti. I couldn't stand my yard the other day and went and deadheaded. Covered myself with clothing and the recommended lemon eucalyptus oil. Still got bit and one followed me into the house and is continuing to bite me. UGH! I have huge itchy welts everywhere--13 on my back alone! Don't recall how many on my legs, ankles, arms and feet. I do kill those things and unfortunately, the little sucker (literally) is too quick and small for me to catch. Cordisone cream is now my best friend. Yes, it is 110 degrees and I am in long sleeve shirts and long pants, double socks, gloves, hats with mosquito netting on them, etc., trying to avoid the things. I am now looking up things like the life cycle of the Aedes Aegypti mosquito to see how long that little sucker will live. Seems I have another week or so with it in the house before it goes to the big blood vein in the sky. I have no water in any of my bird baths for the birds in my yard but my neighbor just put a beautiful big one in the front yard and is keeping it filled with water. I have a feeling this is their breeding ground.