Hey man, have a look at this article just in case, i stumbled across it a while back:
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~from the book "The Gardener's Monthly And Horticulturist V25", by Thomas Meehan.~
Hot Water To Kill Insects
In the first volume of the Gardeners' Monthly, probably one of the most valuable papers published was one on the use of hot water in destroying plant lice. Many have thanked us since for giving them such a simple and effectual plan. The following details have recently appeared in the London Gardeners' Magazine, and as there are some suggestions in it, not noted in our original paper where 130F was given as the degree of limit, it will be useful to reproduce it here :
"Water is a cheap insecticide insufficiently appreciated, but capable of more extended use than the majority of those who already believe in it are aware. It is quite certain that the best cultivation will not prevent the occurrence amongst plants of such pests as aphids, red spider, mealy bug, and a few of their near relatives. Therefore it will not do to dismiss the subject of plant vermin by saying that good cultivation is a sufficient preventive, though it is unquestionably true that the most natural conditions for vigorous growth are also just those which keep vermin at a distance. We do not intend here to enter upon a general consideration of the subject, but to relate a few particulars of experiments that have been made at Stoke Newington, with a view to determine the extent to which hot water may be employed for the destruction of the insects that most commonly infest plants. The few experiments made have been attended with such promising results that we shall hope to find opportunity soon for repeating them in a more extended and systematic manner. For the present we shall speak of aphids only, and as that is the most prevalent of plant pests, we trust that these remarks will be useful to many readers.
It appears, then, that aphids quickly perish if immersed in water heated to 120° Fah. We obtained from various sources plants infested with green fly, and cleansed them by the simple process of dipping. As the experiments were made in the month of February, we thought it probable that aphis might endure in June a temperature many degrees higher than that which proved fatal to them in the earlier and colder season. Hence it became desirable to ascertain the degree of heat the plants could endure in the dipping process. A number of herbaceous and soft-wooded plants were therefore subjected to the process of immersion in water heated to various degrees above 120. We found that fuchsias were unharmed at 140, but at 1500 the young leaves were slightly injured. Calceolarias suffered at 1400, but the plants were not killed, though their soft tops perished. Pelargoniums were unhurt up to 150, but the slightest rise beyond that figure killed the soft wood and the young leaves completely. Chinese primulas were injured by any rise beyond 140, and this at last proved to be the most general maximum, and may be cited as a rule for observance.
Centaureas, sedums, saxifragas, thyrsacan-thus, justicias, ferns, heliotropes, petunias, begonias, mignonette, and many other plants of soft texture, were unhurt by being dipped in water at 140, but the slightest rise beyond that point was followed by blackening of the leaves, and consequent disfigurement of the plant, and at 150 the process of killing commenced. About ten years ago we reported in the Floral World that Fairy or Lawrence roses, which are grown in quantities in pots for market, could be best kept clean by dipping in hot water, as at 120° the plant is not injured, and every aphis upon it is destroyed. This simple method of removing vermin from plants is, we are quite satisfied, capable of very general adoption, in place of more troublesome and more expensive plans. We shall be glad of any aid our readers can afford towards the reduction to system of the facts of the case. To what extent can we carry on an offensive warfare against scale, red spider, and all the rest of the little foes that plague us in the garden? The question can be better answered by many than a few.
It is eminently a question for those who have opportunity and a liking for experiments, and who can afford to kill a few plants, if need be, to make a sure test of the respective powers of endurance of high temperatures by various orders and genera.
Notwithstanding it is nearly twenty years ago since the Gardeners' Monthly published the fact that water heated to 120 or 130, was the easiest and best remedy against all sorts of insects which infest greenhouse plants, people are very much afraid of it. To encourage these timid people, we give the following bit of experience contributed by a correspondent of the Journal of Horticulture:
"Last spring I read in the Journal that the best way to get rid of insects destructive to Orchids was to plunge the pots in hot water at a temperature of I20°. I was rather in doubt whether it was safe to do this, consequently tried two or three pots that I knew were pretty well full of woodlice, or, perhaps I should say, appeared so from the condition of the roots. The contents of these pots all changed, the insects were killed, and the Orchids improved. Seeing that no injury was caused to the plants, I last August plunged every Orchid I had in water heated to 120. I have found that it has not injured one plant. Dendrobium densi-florum that I subjected to this treatment has now no less than forty-two spikes of bloom, and these in a few days will be fully expanded."
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Apparently, flushing thoroughly with hot water (120-125F or 48-52C) will kill root aphids... I don't know for sure as I haven't needed to try it for myself, but you could definitely use it as a last resort before closing down your grow. Best of luck :)
