Protecting crops from disease, weeds and pests
Insects (butterflies, beetles, flies, bugs), mites, slugs and rodents (mice, ground squirrels) do great harm to field crops. There are four ways to protect them: agrotechnical, chemical, mechanical and biological. Ecologically the agrotechnical and biological methods are best: the first ensures good growth and so cuts disease and pests, in the second helpful creatures (for example, birds called into the orchard and nests built for them) destroy pests. The mechanical method is catching pests in various devices. Plant diseases arise from unfavourable conditions (nutrients, heat, light, moisture) and from microorganisms; a disease from poor conditions is not contagious and goes away when conditions improve. The book names simple means: soapy water, an ash-and-lime mix against cabbage flea beetles, soap solution against aphids (late May–June), sticky flags. Weeds take nutrients from the soil and reduce fertility. Chemical and poisonous preparations (dusting, spraying) are very dangerous: only a trained specialist in protective clothing uses them; children do not touch them, do not enter a sprayed field and never reuse their containers. Even permanganate solution is used only with an adult.
Protection table: pair each problem (aphids, rodents, weeds) with a method (biological, mechanical, agrotechnical) in a table. This is a paper exercise only; no real chemicals are used.