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SEED TREATMENTS PROMOTE SEEDLINGS:
Seed treatment refers to the application of fungicide, insecticide, or a combination of both, to seeds to disinfect and disinfect them from seed-borne or soil-borne pathogenic organisms and storage insects. Seed treatment is a term that describes both products and processes. The usage of specific products and specific techniques can improve the growth environment for the seed, seedlings, and young plants. Seed treatment complexity ranges from a basic dressing to coating and pelleting.
Seed and seedling damage caused by soil-inhabiting insects can be prevented with insecticidal seed treatments. As well as controlling fungi on seed surfaces or inside seeds, fungicidal seed treatments work against pathogens in soil that causes seedling disease and root rot.
With effective seed treatments, smuts and bunts have been significantly reduced in severity in grain-growing regions around the world.
Seed treatments' ability to control diseases and insects depends on their dosage and environmental conditions. You'll maximize seed treatment benefits if you use recommended application rates and minimize environmental stress. Plant seeds as soon as possible after treating them, since some seed treatments don't work as well over time.
Benefits of Seed Treatment:
1) Prevents the spread of plant diseases
2) Protects seed from seed rot and seedling blights
3) Improves germination
4) Protects from storage insects
5) Controls soil insects.
Types of Seed Treatment:
1) Seed disinfection: Seed disinfection refers to the eradication of fungal spores that have become established within the seed coat or more deep-seated tissues. For effective control, the fungicidal treatment must penetrate the seed to kill the fungus that is present.
2) Seed disinfestation: Seed disinfestation refers to the destruction of surface-borne organisms that have contaminated the seed surface but not infected the seed surface. Chemical dips soak, and fungicides applied as a dust, slurry, or liquid have been found successful.
3) Seed Protection: The purpose of seed protection is to protect the seed and young seedlings from organisms in the soil that might otherwise cause the decay of the seed before germination.
Seed treatment complexity ranges from a basic dressing to coating and pelleting.
1. Seed dressing: This is the most common method of seed treatment. The seed is dressed in either a dry formulation or wet-treated with a slurry or liquid formulation. Dressings can be applied at both farms and industries. Low-cost earthen pots can be used for mixing pesticides with seeds or seeds can be spread on a polythene sheet and the required quantity of chemicals can be sprinkled on the seed lot and mixed mechanically by the farmers.
2. Seed coating: A special binder is used with a formulation to enhance adherence to the seed. The coating requires advanced treatment technology, by the industry.
3. Seed pelleting: The most sophisticated Seed Treatment Technology, resulting in changing the physical shape of the seed to enhance palatability and handling. Pelleting requires specialized application machinery and techniques and is the most expensive application.
Conditions under which seed must be treated.
1) Injured Seeds: Any break in the seed coat of a seed affords an excellent opportunity for fungi to enter the seed and either kill it or awaken the seedling that will be produced from it. Seeds suffer a mechanical injury during combining and threshing operations, or from being dropped from excessive heights. They may also be injured by weather or improper storage.
2) Diseased seed: Seed may be infected by disease organisms even at the time of harvest, or may become infected during processing, if processed on contaminated machinery, or if stored in contaminated containers or warehouses.
3) Undesirable soil conditions: Seeds are sometimes planted under unfavorable soil conditions such as cold and damp soils, or extremely dry soils. Such unfavorable soil conditions may be favorable to the growth and development of certain fungi spores enabling them to attack and damage the seeds.
4) Disease-free seed: Seeds are invariably infected, by disease organisms ranging from no economic consequence to severe economic consequences. Seed treatment provides good insurance against diseases, and soil-borne organisms and thus affords protection to weak seeds enabling them to germinate and produce seedlings.
Precautions in Seed Treatment:
Most products used in the treatment of seeds are harmful to humans, but they can also be harmful to seeds. Extreme care is required to ensure that treated seed is never used as human or animal food. To minimize this possibility, treated seeds should be clearly labeled as being dangerous, if consumed. The temptation to use unsold treated seed for human or animal feed can be avoided if care is taken to treat only the quantity for which sales are assured.
Care must also be taken to treat seed at the correct dosage rate; applying too much or too little material can be as damaging as never treating at all. Seed with very high moisture content is very susceptible to injury when treated with some of the concentrated liquid products.
If the seeds are to be treated with bacterial cultures also, the order in which seed treatments should be done shall be as follows.
i) Chemical treatments
ii) Insecticide and fungicide treatments
iii) Special treatments
Control of Fungal Diseases:
Pre-sowing seed treatment with systemic fungicides is a firmly entrenched practice for most crops worldwide.
The treatment is intended to protect the crop against seed- and soil-borne diseases. In recent years, there is increasing evidence that fungicidal applications to manage diseases might inadvertently also affect non-target organisms, such as endophytes.
Endophytes are ubiquitously present in plants and contribute to plant growth and development besides offering resistance to biotic and abiotic stresses. In seeds, endophytes may play a role in seed development, seed germination, seedling establishment, and crop performance.
FUNGAL ENDOPHYTES OF SEEDS:
The successful association between two eukaryotes belonging to two different Kingdoms (the fungal endophytes (FE) and their plant hosts) is not inconsequential.
FE residing in tissues of a plant can enhance the plant’s ecological fitness by increasing its tolerance to pests and pathogens, and abiotic stresses like salinity, high temperature, and drought.
In light of the increasing evidence of the role of endophytes on plant growth and stress tolerance, their use in real-world agriculture could be constrained by the practice of seed treatment with fungicide.
Although seed treatment could include the application of fungicides, insecticides, or rodenticides, the majority of seed treatments are with fungicides.
The major aim of seed treatments with fungicides is to bring down the pathogen load on the seed surface or inside without affecting seed viability and seedling fitness, several studies have cast doubts if this is indeed the case.
For example, fungicide treatment affects the diversity of epiphytic and endophytic fungi in Phaseolus vulgaris. Comparing soybean grown using conventional plant protection versus those cultivated organically, reported a one-third reduction in foliar endophytes in the former.
Seed treatment with fungicides could lead to similar loss or disruption of the seed microbiome including the endophytes compromising seed germination and early seedling development. For example, in ryegrass and tall fescue, seed treatment with fungicides reduced endophyte loads by over 60%.
Seed treatment with Insecticide:
Seed treatment as a method of local application of pesticides in precise agriculture reduces the number of pesticides used per unit area and is considered to be the safest, cheapest, and most ecologically acceptable method of protecting seeds and young plants from pests in the early stages of their development.
With the introduction of insecticides from the neonicotinoid group in the mid-1990s, the frequency of seed treatment increased.
Due to suspected negative effects on pollinators, most of these insecticides are banned in the European Union.
The ban has therefore led to a reduction in the number of active substances approved for seed treatment and to increased re-use of active substances from the group of pyrethroids as well as other organophosphorus insecticides, which pose potentially very serious risks, perhaps even greater than those of the banned neonicotinoids.
Nano capsulation achieves controlled release of the active ingredient over a long period, thus preventing premature degradation under adverse environmental conditions, which is crucial for reducing active ingredient doses. In addition to synthetic active ingredients, naturally derived active ingredients can also be encapsulated, such as insecticidal essential oils, which have low toxicity, and are environmentally friendly.
Insecticidal seed treatment is carried out to control soil pests such as wireworms (Agriotes spp.), white grubs (Melolontha spp.), and pests that attack plants in their early stages of development such as flea beetles, aphids, etc.
Sowing treated seeds is a measure of good and rational agricultural practice as it reduces the negative impact of insecticides on the environment. Control of stored-product pests by treating stored seeds with insecticides dates back to 60 AD. Vines and shredded cypress leaves were used for seed treatment.
In the middle of the last century, the insecticide lindane was developed from the chlorinated hydrocarbon group, mainly to control wireworms. Aldrin, dieldrin, and heptachlor were also developed in the same group.
At the same time, the systemic insecticide disulfoton was developed from the group of organophosphorus insecticides. Disulfoton was used extensively to treat cotton seeds.
Seed treatment with Spinosad is mainly used on onions, and good results are obtained in the control of onion flies. When Spinosad is used, adverse effects on bee communities and bumblebees are minimal when exposed to real concentrations of insecticides that would be expected in the environment.
The treatment of wheat seeds with Spinosad under laboratory conditions resulted in transient morbidity of larvae, which later recovered after treatment. Another laboratory experiment showed that spinosad at doses of 3.5 and 5 mg/kg of seed applied to maize seed achieved an efficacy on wireworms of about 70%.
In the same study, the application of spinosad by seed treatment did not show satisfactory efficacy against sugar beet weevil, while the results for sugar beet flea beetle were much better.
Application of 0.2 and 0.4 mg a.i./seed (corresponding to 40 mg/ha) resulted in more than 95% efficacy on the fourth day.
Spinosad is effective against sugar beet weevil under laboratory conditions. After foliar application of spinosad at a dose of 72 g a.i./ha, 80% efficacy was achieved on the fifth day after treatment.
Check out the previous article on pesticide exposure. https://www.seedlearner.com/post/pesticide-exposure-case-study-in-agriculture
