g'day jesse,

i would as mealy bugs etc.,. don't exist in the soil as such, they are sap suckers and would be found on the roots of plants, and plants that are so badly affected do generally die.

len

Here is a link that might be useful: lens garden page

If they were dying of "no apparent reason," were the critters in the soil? If so, they may be root aphids -- bad news.

Or root mealybugs ....

"..... no apparent reason." Hmmm. Rather than worry about reusing the soil, perhaps you should take a closer look at it. In my experience, most of the difficulties you encounter in container culture stem from an inadequate soil. Poor soils stress plants. Stress leads to strain, which if uncorrected always leads to the death of the organism. Death usually comes by way of biotic pathogens or as a result of insect infestation, which, had the plant been growing robustly it could have fought off.

Plants mount a number of genetically encoded responses to (insect) wounding, ALL of which require energy allocation. In plant cells, there are genes that control proteins functioning in defense, sending defense signals, altering metabolism, controlling cellular maintenance, and regulating photosynthesis, as well as many genes of unknown function. In short, plant energy reallocation is prioritized in the plant's own defense, & other things, like every day metabolism and photosynthesis are put on the back burner.

When wounding occurs (insect attack) there is a "wound response" that occurs both at the site of injury as well as distally (in other plant parts). Plants can even differentiate between the wounds of a pin and those of insects and react in different fashion to the "attack". Without getting more technical, the plant produces various anti-feedants, anti-metabolites, and toxins that make the insects feel pretty unwelcome - as long as the plant is in good vitality, which means growing strongly, or has high energy reserves. In other words, as long as the plant is in good health. Stressed or strained plants cannot quickly or efficiently respond and ward off insect/disease attack.

The speed with which the response occurs, and the effectiveness of the defense response are also both energy driven, so it should be no surprise that plants grown under constant stress are highly susceptible to insect marauders. If you want to keep the bugs away - keep your plants growing with as much vitality as possible, which is almost always culturally dependent and very often originates with soil choice.

Al

Hey,

Thanks for the thoughts. Small correction, though: I said my plants died for a "variety of reasons", which include raccoons, deer, bugs, powdery mildew and (I'm guessing) inadequate container sizes. I don't think soil quality was an issue - I used a good organic Uni-Gro potting mix and amended it with compost and other things as needed; I watered them a good amount and they got a ton of sun. It does remain a mystery why some did so much better than others, so your point about stress is a good one.

In any case, my concern wasn't so much with why my plants were dying as it was with whether mealy bugs might somehow survive in the soil after I've uprooted the dead plants. I'm fairly certain they never got to the roots (is it a different kind of mealy bug entirely that gets to the roots, or can they simply travel downward?). Still now sure what the verdict is...

But thanks for all the info about plant defenses - very interesting anyway!

I wasn't suggesting that your plant's demise WAS from root mealies, only adding another remote possibility to what Jean opined.

It might have been helpful if you'd mentioned the deer & coons. Amending what you feel is a good soil with compost & 'other things as needed' doesn't necessarily mean you've improved the soil. Adding water-retentive compost to a soil that is already likely rather water-retentive from the bag, would not, in my mind, be an improvement. Had you said that you mixed your 'good soil' 50/50 with pine bark fines and some perlite (instead of compost .... care to share what else you felt was needed to amend what you started with?) to ensure there would be a minimal amount of soggy soil at the container's bottom, and to ensure that the soil would have adequate aeration for the expected life of the planting, I would agree that there probably is no issue.

I think you've discounted the probability, even the possibility of it being a soil issue in the end w/o seriously considering it from a perspective other than your own, but it's your decision, of course. Good luck.

Al

Hi Al,

It might have been a soil issue, but again, that's not what my post was about. You sure like to argue!

I don't mind arguing, and I don't argue a point when I don't know what I'm talking about or if I even suspect I'm not on firm footing. Even if the soil is completely free of potential insect AND biotic pathogens, it makes no sense to even consider reusing it if it's poor.

It's nothing to me how your plants fare, I was simply trying to help by pointing out that a very high % of problems in container culture originate with the soil. Since you reject that possibility in your case, and are clearly looking for a blame other than grower malfeasance, I'll happily move along.

Good growing.

Al

Al,

Retract your claws, buddy. Life is good!

I'm cheep to. Have to save all I can. Gonna use the soil. It's been a while with no plant and water. Thanks

This is such an old thread but I’m wondering the same. My very large planter that housed my 18 year old dracaena got mealy bugs and infested it to the point of no return after spraying and doing everything I could for 8 weeks but my 6’ foot plant just looked sad and puny and too risky for all my other 40+ houseplants.
That soil has been sitting in that container in garage for 1.5 years so can it be amended and reused? I want to use it outside for canna’s and it’s such a large pot and I’d like to be frugal as possible.

i know this thread is old. However, I have been wondering the same thong. i own a 3 tier green stalk with mealy bugs and now aphids. i would like to reuse that soil as well. i was thinking about using it in compost rotating bin. It gets plenty hot and may kill all bugs and pathogens.

To respond to the previous two recent postings......

You can certainly compost potting soil that has been exposed to either form of mealy bug (root mealies as well as foliage mealies).

The advisability of reusing mealy infested potting soil depends on several factors:

1. the quality of the potting soil to begin with. As Al clearly pointed out above (and was rather rudely dismissed by the OP), if the potting soil is not of sufficient quality, it is not recommended to be reused regardless of condition.
2. how long the soil has been sitting without any plants. Foliage mealies cannot survive more than a couple of weeks without a host plant. Potting soil that has been stored more than a month or two should be free of contamination.
3. root mealies require moist soil and warmish temps to survive for long. Keeping the potting soil dry or subjecting it to cold - or both, as in storing in an unheated but dry garage for several months/over winter - should also eliminate any mealy problems.

What Pam said ^^^; and, the most significant factors in determining whether or not a grow medium is appropriate are whether or not the soil contains anything phytotoxic and particle size. Container media do not wear out, even though this idea is often suggested. Soil particles just become smaller and smaller, which increases the amount of water a medium can hold while decreasing the amount of air porosity. There is no question it's better to err on the side of more porosity and water more frequently than to err on the side of too little porosity and see the planting suffer from poor root function or even wrecked root health.

One cannot take a quart of fine material, like peat, coir, or sand, and "amend it by adding coarse materials like pine bark. That practice actually DECREASES o/a air porosity until the fraction of coarse materials becomes so large there is no longer enough fine material to fill the larger spaces between the coarse particles. Two observations about mixture reaches the "threshold proportion", which occurs when there is exactly enough fine material to fill all spaces between large particles: 1) It will have less aeration and be more difficult to grow in than peat, coir, or sand or a mix thereof. 2) Adding additional coarse material to mixtures at or beyond the threshold proportion such that the coarse material becomes a very large fraction of the medium (around 80%) quickly increases o/a air porosity.

Container media is all about structure and its ability to retain that structure for the expected life of the planting. So, as Pam and I mentioned, there is little sense in reusing a medium, the structure of which is inappropriate. That seldom ends well. Used media can be used as the much smaller fine fraction we might add to coarser material when putting a medium together, but even then, particles of slightly larger size 1/20-1/10" (about the size of coarse ground pepper) would be the better choice.

As in life, our growing experience and how much reward we're able to realize from our efforts is a product of the decisions we make. There's no judgement to be made about what a grower does or doesn't do, we all order our priorities differently, but that doesn't change the fact that what the grower chooses will always have an impact on how the plant responds.

Al