I have very few reservations about using chemicals in my garden. I bet you did not expect to read that. It is the quick and easy explanation about my philosophy on garden chemicals. Almost all chemicals that are available to the general public are reasonably safe if handled and applied properly. I am actually more concerned about the larger volumes of chemicals used in the landscape industry, and applied by technicians who can not read the labels or write their use reports. Yes, it happens. Anyway, some of the sugars, salts, preservative and other components of some of the food I eat is more dangerous than chemicals I use in the garden.
That is because I use almost no synthetic chemicals. I have almost no use for them. I only occasionally use semi-synthetic fertilizers like fish emulsion. Just about every disease or insect problem I have encountered in my own garden was most efficiently controlled by cultural methods or simple home remedies that have been effective for centuries, or even thousands of years, long before the first and worst of the really nasty garden chemicals were invented less than two centuries ago.
That certainly does not mean that all home remedies are completely safe, or even any safer that some of what are considered to be ‘chemicals’. I mean, they are supposed to ‘kill’ things. Tobacco is unfortunately toxic, and kills many people quite regularly. That is precisely why a cigar butt or a few cigarette filters can be simmered into a tea to spray onto small potted plants, like fuchsias, to kill aphid. Adding a few drops of dish soap makes it even more effective (although in a different way). Is it toxic? Yes. Am I concerned about it? Not really. Although, it would be nice if no one used tobacco anymore.
Dish soap that so many of us use as a ‘natural’ remedy for aphid is almost as effective for immediate kill even without tobacco tea, but lacks residual toxicity. Because it is necessary to use a slight bit more soap if it is used alone, it is more likely to damage tender foliage. Also, most dish soap is actually less ‘natural’ than tobacco is! Homemade soap made from bacon fat may seem to be more natural, but the fat contains of all sorts of unnatural nitrates. It certainly does not bother me any; but those seeking totally natural remedies should know. (They probably should not eat bacon anyway.)
What do I do for peach leaf curl? Nothing. Well, nearly nothing while the disease is actively ruining foliage. However, while the trees are bare through winter, I prune them very aggressively. Pruning is done so that the trees do not overburden themselves with fruit, but it also stimulates vigorous vegetative growth the following spring and summer. After bloom, while peach leaf curl is busy ruining the first phase of foliage, vigorous vegetative (non-fruiting) stems are busy speeding beyond infection with reasonably healthy foliage. Inadequately pruned trees lack vigor, and are therefore more susceptible to the disease.
The worst of the damaged foliage lower in the canopy falls away as it gets replaced by healthier foliage. It should be raked and disposed of (not composted) because spores of the disease overwinter in the fallen foliage. I actually prefer to pluck much of the damaged foliage from the trees because, technically, it dispersed spores more efficiently while still viable and actively infected. Does this eliminate the disease? No; but neither does spraying chemicals.
Does putting ‘Tanglefoot’ or axle grease around the trunk of a lemon tree infested with scale eliminate the scale? Of course not. It merely keeps out the ants that cultivated the scale. (Ants have a symbiotic relationship with the scale because the ants consume the honeydew excreted by the aphid. Ick!) Without the ants to herd them around and protect them from natural predators, the scale are not so prolific. You might not even know they are there. ‘Controlling’ them just might be better than ‘eliminating’ them with a chemical insecticide. Besides, it leaves something for their natural predators to consume so that they are there when we need them.
After centuries of breeding plants to do what we want them to do and behave very unnaturally, we really should consider how to get nature to do some of the work it really wants to do ‘naturally’.