Plant Hygiene 



By Arthur S. Brooks. 



The dread of plant diseases and pests is ever with us. 

 If for a time we are free from their attacks, we are con- 

 stantly being reminded of them by warnings, insecticides 

 and the investigations of the cx]jerimental stations. 



It is comparatively easy to give the orthodox remedy 

 for any specific case, but the trouble is to find out just 

 why this or that plant was attacked by rust, mildew, or 

 white fly. 



There are epidemics where whole sections of the country 

 are attacked by some insect, as, for instance, the Brown 

 Tail and Gypsy I\Ioth in the New England States, but 

 I speak more particularly of those attacks of disease and 

 insects which appear sometimes without due cause in 

 our greenhouses and gardens, and one has the feeling 

 that more real service could be given if it were possible 

 to investigate the predisposing causes. The important 

 question to my mind is : What are the predisposing 

 causes of disease? Why should this plant be attacked 

 first? or this one succumb quicker? Very frequently we 

 would find that at first no specific disease or pest was 

 present, but a general unthriftiness would reveal itself 

 and the plant weakened by climatic or soil conditions 

 readily fell a prey to the first pest that came that way. 

 The chief causes of unthriftiness in plants are : Heredity, 

 structural weakness, adverse physical conditions of cli- 

 mate, temperature, water and soil, and last, but not least, 

 malnutrition. 



A plant with a good constitution may be ruined by 

 such adverse conditions and fall an easy prey to all man- 

 ner of diseases. 



Plant breeding and selection will give us many types 

 with a strong constitution and immune to specific dis- 

 eases in the near future, and much already has been done 

 on that line, with both garden and farm plants. I would 

 endeavor, however, to induce growers to try everv pos- 

 sible method of making the plants self-resistant by hy- 

 gienic methods. 



It is almost impossible to grow certain plants in our 

 Eastern States, which would grow farther south, and so 

 it is with local aspect, certain [ilants like shade and others 

 sun. 



One cause of trouble is a draught in the greenhouse 

 through faulty joints or mismanaged ventilation ; this 

 chills off certain plants and non-resistance follows. 



Garden literature of years ago reveals to us one great 

 fact, that our forefathers grew hardier plants, and con- 

 sequently were less troubled with plant diseases ; we 

 have no new diseases, only they were not catalogued and 

 named by scientific investigators. Is it not that by our 

 cheap glass and chemical fertilizers our plants have lost 

 stamina ? Lack of balance between light and heat is re- 

 sponsible for a great deal. In forcing vegetables during 

 the winter, the grower often fails to regulate the heat 

 with the sunlight, of which he has a very limited supply ; 

 when the light is deficient the heat must be cut down to 

 correspond, or a weakly growth will be the result. 



Judicious watering is important, and using water sev- 

 eral degrees colder than the temperature of the house 

 gives the ])lants a decided check. 



A suitable condition of the soil is recognized by all 

 good cultivators, and the importance of a firm soil for 

 onions, strawberries, raspberries, etc., is a necessarv item 

 for success. A soil may be rendered acid by applying 

 too much organic manure year after year, without the ad- 

 dition of lime, which is a very necessary plant food in 

 itself, besides keeping the soil sweet and liberating the in- 



soluble phosphates and potash for plant use. The soil 

 must be studied as a living bed of bacteria, if we are to 

 understand it properly and not as mere inanimate dirt 

 with various chemical fertilizers mixed in. ^^onderful 

 progress has been made by science in isolating disease 

 germs, but, at present, we know comparatively little of the 

 bacteria or germs in the soil, they play a much more im- 

 portant part than we give them credit for. The de- 

 composing and nitrifying bacteria of the soil are about 

 the only ones we are at all familiar with, yet it is reason- 

 able to suppose many others exist in the soil, each with 

 their definite purpose. 



One of the most predisposing causes of plant disease 

 is an unbalanced plant food. Our forefathers used loam, 

 leafsoil, farmyard manure and lime, but little else, and _ 

 they grew hardy plants ; today we have numbers of highly 

 concentrated fertilizers which are very powerful forces 

 in the hands of the grower, and experience is needed to 

 get the proper balance of plant food. Where there is a 

 deficiency of available nitrogen the growth will be ar- 

 rested and turn pale, sickly looking ; whereas, an ex- 

 cess of nitrogen will force vegetative growth to an enor- 

 mous strength. It has been well said : "All other things 

 being equal, he will be the most successful cultivator who 

 always has sufficient available nitrogen for his plants and 

 none to spare." The nitrogen exists in unlimited quan- 

 tities in the air, but cannot be used for plants with the 

 exception, however, of the legumes, which by the aid of 

 bacteria that live in the roots, convert the free nitrogen 

 of the air into soluble nitrates. This peculiarity of legu- 

 minous plants was discovered about 1886 as being 

 due to an indirect supply of available nitrogen. This 

 property is extremely valuable for poor lands in bring- 

 ing them to a high degree of fertility. There is not much 

 need, however, to use the much boosted inoculation mix- 

 tures offered for sale as some type of legiune has been 

 growing on cultivated land for centuries, and the bac- 

 teria are numerous in the soil, with the exception, per- 

 haps, of reclaimed land. 



There are forms in which nitrogen is combined with 

 other elements, and of these the nitrates of potash and 

 soda and sulphate of ammonia are principally used. 



A few years ago some unrest was felt as to the future 

 supply of nitrogen, but science has again stepped in and 

 showed us how to manufacture it from the unlimited 

 sources in the air: it has come to us in the form of ni- 

 trate of lime or nitrolim (calcium cyanamide). These 

 forms of nitrogen are gigantic forces in the hands of the 

 cultivator, and should be used with care or weakened 

 plants will residt. 



The phosphatic manures are more important for the 

 production of the fructification of the plant, while the 

 nitrogen is responsible to a greater degree for leaf 

 growth. Crops grown for the seed or flowers would re- 

 quire, therefore, some phosphatic fertilizer, as phosphate 

 of potash or bone dust, to bring the crop to the highest 

 degree of perfection. 



The three fertilizers — nitrogen, potash and phosphates 

 — have been aptly described as the "Golden Tripod" of 

 manures. 



The potash section more directly affects the plants 

 which store food in their roots, such as carrots and tur- 

 nips, but which are not grown specially for their leaves 

 or seeds. 



The most important thing, however, to consider in 

 plant hvgieno '- rli-nnliness. Kcepinc vour fruit trees 



