HELP with aphids!!!

We have a 9x12 greenhouse, partly shaded and ventilated so it won't get too hot. All works fine an everything grows great. Plants are in raised bed, soil is 1/2 Miracle-Gro garden soil and 1/2 Miracle-gro potting soil, well mixed.
We have tomatoes, cucumbers, squash, bell peppers and zucchini.
Problem: EVERYTHING is being eaten alive with tiny bugs of various colors, presumably aphids. These are tiny, maybe 1/2 a mm, mostly green, but some are black, white or "clear." They are destroying the plants, sucking the life out of them.
I've tried everything: soapy water, Sevin, Malathion, 91% alcohol, etc. and nothing works. A day or two later, you look on the underside of a leaf and they're back, hundreds of them. The tomatos are producing well, despite the problem. Bell peppers have been OK, but marginal. Everything else is either not producing, or produces little 1-inch fruit that dries up and falls off, from them sucking the juice out of it.
Again, I've tried everything short of setting fire to the place. Any suggestions?

Unfortunately soil mixes containing fertilizer high in nitrogen and ammonium promote insect population explosions. The rapid, lush growth attracts a host of problem insects with aphids at the top of the list. Add to that the use of chemicals such as Sevin and malathion, which are broad range insecticides, and you have wiped out potential beneficial insects. I didn't create this saying but feel it's basic to garden success...It all begins with the dirt. The reason why soil mixes contain fertilizer these days is because they are comprised most often of low nutrient compost, usually decayed wood bark, and not actually "soil" such as top soil which is a mix of organic and inorganic material. If I had a ground based greenhouse I would invest in having high quality top soil trucked in.

I don't think I mentioned it, but this is a raised-bed operation. The greenhouse is sitting on 16 inches of packed roadbase, so we use 2x12's to make raised beds. So whatever we put in the beds is what they're growing in. Naturally, of course, I wanted a good, rich bed, so I used the Miracle-Gro potting/garden soil mix. It DOES work great as far as growing the plants, but I had NO idea that it could also stimulate pest populations like this! The aphid population is just overwhelming. We've tried non-pesticide approaches such as oils, soaps, water spray, alcohol, etc. and it works for a day or two, then kaboom, they're all over the place again.
Perhaps it would be good, then, to remove the top 6-8 inches and mix in some topsoil.......? Or maybe just empty them and replace the dirt altogether.....


This message was edited Aug 17, 2022 6:54 AM

I'll start by sharing my garden also began on a granite gravel bed which the previous property owner used to park heavy equipment. It was very compacted ground. It is currently about 3,500 s.f. and sits on a stepped granite mountainside. A pickmatic and prybar were my best friends for many years. I screened the dirt out of the gravel and wheelbarrowed out the gravel. I've since spent decades ammending the soil. There are five gallon buckets placed throughout the garden during Spring so I can toss and haul rocks as I cultivate. It'll never be clear.

If you want to stay with raised beds try looking for free fill dirt which might be available where construction site work is happening. You'll probably have to pay for delivery. You might have a challenge since basements are not common in your area. Dirt is easy to come by here wherever home construction is happening. If you can find "real" soil, add it and go about testing through your extension service. Ammend according to their advice. Adding organic material is always desirable.

What I'm suggesting is obviously not an overnight fix but you will have a forever garden. I've been growing in mine for more than thirty years. And throw out those toxic chemicals. Promote a habitat conducive to beneficial insects. Open your greenhouse up during favorable weather. Yes, organic alternatives require maddeningly frequent application. That's because they're not hanging around poisoning the ecosystem. Aside from ladybugs, wasps, spiders a host of other insects feed on aphids but will not survive Sevin or malathion.

I appreciate the answers. We're planning to remove the Miracle-gro soil and replace it with just plain topsoil. But I'm nervous about what to add to the topsoil. For example, we can get "topsoil with compost" at a local supplier. But doesn't compost create nitrogen, like Miracle-gro?
As far as spraying, that was out of desperation. We tried all the "natural" approaches - neem, soap, water blasts, alcohol, etc. and NOTHING worked. So I moved to Sevin and Malathion. They would go down for a day or two, then you'd go out there and the leaves would have hundreds of aphids and other micro-critters on the underside, eating them alive. NOTHING would put those things down.

I don't think there were a significant number of beneficial insects to harm. This is screened-in pretty tight.

Tomatoes were OK, but the squash, cucumbers, okra and bell peppers were hopeless. I was ready to go in there with a flamethrower. We'd get rid of most of the parasites, then go out a couple of days later and they were back in force, all over everything. Over and over and over, no matter what we did.

As of right now, everything's been pulled up except for a couple of young tomato plants a couple of feet tall - they look very healthy (variety is "Bobcat").

Main thing we want to do is AVOID having this happen again! It's been a nightmare!

This message was edited Aug 31, 2022 9:21 AM

Hey folks, diving into this thread a bit late but really curious, did anyone try mixing their own soil for the citrus trees? I've heard blending some sand can help with drainage and avert the root rot problem common in standard potting soils. Also, any updates on how the trees held up during the winter? I’m venturing into growing a lemon tree indoors and could use all the tips!