Principle of Eradication
The appropriate disease control action when pathogen has breached the exclusion barrier but is not yet widely distributed or well established. It aims at eliminating or reducing primary inoculums.
Eradication
Eradication method is accomplished by one of three (3) general means using different technologies applied in various ways:
Removal, Elimination, and Destruction
is the direct destruction of a pathogen together with all or part of the host or substrate.The action and results are immediate.
Removal
Removal of plants or Group of plants
Roughing
Removal of individuat defective plants and plants harboring pathogens; this extreme measure sacrifices the host to kill the pathogen; a common procedure in certification programs for propagative material.
Ex
a) removal of leaf roll and other virus infected potato plants b) excising swollen short virus infected cacao trees
Roughing
a) removal of leaf roll and other virus infected potato plants
b) excising swollen short virus infected cacao trees
Roughing
Eradication of parts or organs
Pruning, Therapeutic pruning, Surgery, Handpicking, Contact Herbicides, and Sanitation
–removal of stems, branches infected with blight cankers & gall rusts
Pruning
- is used to eliminate or retard some vascular patnogeis such as Verticillium and Ceratocystis in economically valuable trees.
Therapeutic pruning
-removal of diseased. or decayed tissue from tree stumps. SOP in maintenance of high value ornamental trees; cavities are filled with concrete to provide strength to support the trees.
Surgery
leaf wilt infected peach leaves, azalea, leaf galls, and galls of common smut of corn are done in limited scale by gardeners.
Handpicking
Such as dinitro compounds or flaming are used to destroy basal spikes of hoper to eliminate the initial flush of inoculums that starts the downy mildew infection cycles in early spring. Defoliating trees in rubber plantations with herbicides in the event that South American leaf blight is detected.
Contact herbicides
involves physical and'chemical measures to remove pathogen containing plant residues and exudates from equipment or other sources.
Sanitation
Cleaning grafting sheds to remove the rose black mold fungus
Washing grain to remove smut teliospore
Washing and disinfesting potato storage equipment and seed piece cutting knives to remove potato ring rot bacteria
Cleaning potato storage bins to remove tuber rot pathogens
Cleaning and disinfecting contaminated poles and stakes to remove bean rust spores.
Sanitation
is the indirect destruction of a pathogen. The pathogen is not immediately removed or destroyed and host tissue may or may not be involved.
Elimination
Elimination of alternative hosts, Crop rotation, and Trap and decoy crops, cultivation, Biological control, Stump removal, and Mechanical or chemical girdling of trees
Elimination
- some pathogens have a wide range of hosts while others have a few, common plants that serve as reservoirs of the pathogen. Many plant viruses have weed hosts. Some crops or weeds serve as bridge crops for pathogens that cannot survive without a living host.
Elimination of alternative hosts
with non-hosts eliminates the food source and starves a pathogen. To be effective crop rotation, must be clean. For example, all grass weeds for take-all, volunteer potatoes for late blight must be destroyed.
Crop rotation
The former allow a pathogen to invade the plant where it cannot complete its development. Eg. Marigolds (Tagetes species) take the root-knot nematode but no eggs are produced. The potato powdery scab fungus can infect roots of some Datura species but does not produce galls or resting spores. The latter stimulate pathogens to germinate but resist invasion. Encysted eggs of golden nematode can remain inactive for many years. The host, however, excretes hatching factors that stimulate emergence of larvae from cysts. Non-host hatching factors also stimulate emergence, but the plants are not suitable hosts and the larvae starve. Witchweed (striga) is a phanerogamic parasite of corn and its seeds usually germinate only in the presence of a host plant. However, some non-host plants such as soybean and cotton stimulate germination of seeds bút the seedlings are unable to produce haustoria and infect the decoy plants.
Trap and decoy crops
is one of the several routine farming practices that can eliminate inoculum. Plowing buries inoculums such as ergot sclerotia and rust teliospores. Crop residues such as corn stover infested with the stalk rot fungus are incorporated into the soil where they decompose.
Cultivation
relies on natural systems to eliminate pathogens by antagonism or other
actions.
Biological control
removes the food base required by some pathogens for infection of adjacent plants. It is used in forests and orchards to control Armillaria root rot of conifers and fruit trees and in landscaping to eliminate inotulums of the Dutch elm disease fungus.
Stump removal
done prior to feling to deplete stored food from roots and eliminate inoculums of various root rot fungi.
Mechanical or chemical girdling of trees
- is the direct destruction of a pathogen but not host or substrate. This is accomplished by physical methods of disinfection or disinfestation.
Destruction
- getting rid of established infections within the host by heat or chemical means.
Disinfection
- geting rid of pathogens on plant and other surfaces by heat or chemical
means.
Disinfestation
the simplest and least costly in time, material and money of any chemical or cultural control measure. Seed treatment chemicals include: copper sulfate, mercuric chloride and sodium chloride., benzimidazole fungicides, hypochlorite, andbiotics, carbamates, captan and copper fungicides.
Seed treatment
Easily applied but must be done properly - seeds must be completely and uniformly coated with the chemical. Stickers enhance adhesion of fungicides to seed and include natural materials such as milk casein, wheat flour, blood albumin, gelatin, oils, gums, resins and fine clays
or synthetic stickers such as methyl cellulose or latex.
Inexpensive compared to foliar sprays or soil drenches.
Very effective since every plant (seed) is protected. This stops development so that further cycles do not occur.
Can supplement other control measures and are frequently required in some quarantines.
Advantages of seed treatment
3.b. ERADICANTS OTHERTHAN SEED TREATMENTS
I.Organic mercury compounds
2. Formalin (1%) or mercuric chloride (0.1%)
3. Streptomycin sulfate solution (2g/L)
4. Benzimidazole fungicides
5. Oxytetracycline (Terramycin)
6. Kasumagycin
7. Methyl bromide
8. Nitrogen tricholride
9. Formaldehyde gas
used to treat vegetative propagative materials such as tubers, rhizomes, bulbs and corms. These compounds include Mersolite, phenylmercury acetate, merthiolate sanoseed, ethyl mercury chloride etc.
Organic mercury compounds
used to treat sugarcane sets by soaking setts for 5 minutes to control smut.
Formalin (1%) or mercuric chloride (0.1%).
used to treat apple budwood to treat fireblight bacteria.
Streptomycin sulfate solution (2g/L) -
used to eliminate crown, stem and finger rots.
4. Benzimidazole fungicides
used as chemotherapeutant for several mycoplasma diseases.
Oxytetracycline (Terramycin)
an antifungal antibiotic used to control rice blast and several vegetable diseases.
6. Kasumagycin
-soil fumigant used to control nematodes.
7. Methyl bromide
-a fumigant used to control blue and green molds on stored citrus fruits.
8. Nitrogen tricholride
- used to fumigate empty sweet potato houses.
9. Formaldehyde gas
Disinfectants used on quipment and other nonhost surfaces: a.Ca and Na hypochlorite
b. Fornalin solution (:3)
c.Quarternary ammonium compounds d.Alkyl dimethyl ammonium chloride (Roccal) e.Alkyl dimethyl benzylammonium chlofide f.Octyl docyl dimethylammonium chloride g Dimethyl benzylammonium chloride h. Copper-8-quinolinolate i.8-quinolinol
DISINFESTATION OF NONHOST SURFACES