Antibiotics, or the “wonder drugs,” which have proved sensational and successful in treating human diseases, are receiving wide study in the control of plant ailments.
A dozen or more are used in human medicine, while hundreds of others are under experimentation.
Background on Antibiotics
What are these so-called wonder drugs? They are substances produced by fungi (bacteria and molds), which possess antagonistic or destructive power over other fungi or their toxins.
Today, the chemical structure of many antibiotics has been discovered, thus making it possible to manufacture them synthetically in the chemical laboratory.
The search for new antibiotics represents a vast effort among scientists and biological laboratories.
Initial Antibiotics Used in Plant Disease Control
Some of the first antibiotics to receive attention in plant disease control were Gliotoxin from Gliochuhu, fimbriatum, Viridian from Trichodcrina vi-ride, Actidione from Streptomyces griseus and Penicillin from Penicillium notatum. Most of the research has been applied to human diseases.
Cost-Benefit Analysis of Using Antibiotics
Expensive as antibiotics are, they are worth many times their cost in curing human diseases and saving lives.
To the farmer and horticulturist, the investment in their use to control plant diseases can be too costly in proportion to the value of the plant or crop.
Cheaper control measures are preferred, but some diseases lack effective or practical control by recognized methods and traditional fungicides.
Case Study: Control of Fire-Blight Disease with Antibiotics
Some of these diseases have been successfully controlled with antibiotics.
A notable example is the fire-blight disease of apple, pear, hawthorn, and other plants – a bacterial disease that was first recognized in botanical science.
New outbreaks of fire blight in the current season appear in the blossoms as blossom blight, following the introduction of the bacteria into the blossoms by pollinating insects.
The infection is picked up by insects from overwintering fire blight cankers, which discharge the bacterial slime early in the season.
Streptomycin sprays are applied at four- to 5-day intervals in the blossoming period, the first when the first blossoms open and the last when in full bloom.
There are numerous other examples of successful control of bacterial diseases with antibiotics, such as the halo blight of bean, bacterial spot of pepper and tomato, tobacco wildfire, black leg of potato, bacterial soft rot of potato seed pieces, angular leaf spot of cucumber and celery bacterial blight.
Generally, the best results have been obtained with Streptomycin alone or in combination with another antibiotic, such as Terramycin.
Control of Fungus Diseases with Antibiotics
In other instances, the addition of glycerin has improved the effectiveness of the antibiotic by improving the absorption of the antibiotic by the foliage.
Glycerin also reduces the solubility of the antibiotic. Examples of the control of pathogenic diseases caused by fungus molds with antibiotics arc downy mildews of tobacco, crucifer, and cucurbit vegetables.
Using Antibiotics for Plant Pathology: Ongoing Research
The exact role of antibiotics and other chemicals, applied either as foliar spray or in the soil like a fertilizer or even artificially injected into the sap stream, represents a field of research in plant pathology far behind that of human and animal pathology.
44659 by Dr. E. F. Cuba