Home Is Where Your Trees Are

Spraying

The above account of tree parasites is necessarily oversimplified. Readers are again referred to the definitive literature listed on a later page. Besides describing symptoms and their causes, the best pest books carefully specify remedies, which can be summarized here, to give the reader a base of spray knowledge to build on. Spray materials have long been used to achieve five main effects: 1) When trees are still dormant in spring, to "burn" off by oxidation many nascent or emergent organisms; 2) to poison insect parasites internally; 3) to kill them by contact; 4) to combine effects (a) and (3); 5) to suppress fungi by poisoning their fresh spores. In the old tree-spray pharmacopoeia, standard materials for the purposes thus listed were: 1) Miscible oil, a petroleum fraction close to kerosene, for dormant sprays; 2) Ar-senate of lead, for stomachs; 3) Lime sulfur, for contact; 4) Nicotine sulfate ("Blackleaf 40"), for contact-and-stom-achs (some old-timers made it by soaking their cigar butts in a tub); 5) Copper sulfate and lime ("Bordeaux mixture"), as a fungicide.

Pyrethrum, an extract of chrysanthemums, was long used with a light grade of miscible oil as a stand-by stomach poison less dangerous to warm-blooded animals than lead arsenate. If your garden supply store is not up with the times, it may still carry all these remedies tried and true, and there is nothing wrong with any of them. But on modern shelves there is now a wide assortment of brave new formulations, of higher and often more specific potency. These change from year to year, as do the experts' opinions of them. DDT, an all-purpose killer, enjoyed a fifteen-year vogue which has now somewhat waned since its ill effects on unintended targets - birds, mammals, fish - became manifest and many of its insect targets developed immunities. Parathion too proved all too potent and is used now only by professionals. As of spring 1962 an adequate home arsenal of reliable, manageable spray materials might include the following:

Some basic ground rules about spraying are these: Do no spraying when the temperature is below 40° or above 8o°F. Spray materials can sometimes be mixed to obtain multiple effects with one application, but this should never be attempted without first checking that the materials are compatible. Manufacturers' charts will tell you about this. Wash out your rig after every use, to avoid an incompatibility next time. If you use any weed- or brush-killers (2-4-D; 2-4-5-T) on your grounds, apply them with separate equipment, not your tree-spray rig. Beware tree damage through root absorption or atmospheric drift of these killers, which over-stimulate broadleaf plant life into "growing itself to death."