A seed carries the next crop.
It can also carry the next crop's diseases.
Smuts and bunts of wheat travel inside or on the seed from one season to the next, and many other diseases start from infected seed or from soil around the young seedling.
And young seedlings are easily killed, for example by damping-off.
Seed treatment puts protection, or a helpful microbe, right on the seed before sowing. In this video: starting with good seed, what seed carries, hot water, chemical treatments chosen by FRAC and IRAC group, biological agents, inoculating legumes with rhizobia, the right order when you combine them, doing it properly, and safety. The advice is general and global.
Your local extension service and the product label always come first.
No treatment turns poor seed into good seed.
Use clean, certified or tested seed where you can. If you save your own, take it from a healthy part of the field, not from a weedy or diseased corner.
Use big, plump seed. It comes up faster and stronger.
Seed cleaning removes light, shrivelled and discoloured grain.
And one rule from Laisha's wheat guide: never save seed from a field that showed smut or bunt. That is how it comes back next year.
Different problems need different treatments, so know what you are treating against.
Seed-borne fungi include the smuts and bunts of cereals. Karnal bunt of wheat, for example, survives for several years in soil and on seed, and seed treatment reduces that seed-borne source.
Damping-off kills seedlings at the soil line. It is caused either by water moulds such as Pythium, or by true fungi such as Rhizoctonia and Fusarium,
and different products act against each.
In maize and pearl millet, downy mildews infect young seedlings,
and seed treatment protects them through the most susceptible weeks.
Seed treatments are also used against some soil insects, such as white grubs, and against aphids that spread persistent viruses,
such as barley yellow dwarf in cereals. But a treatment on the seed cannot protect a crop through the whole season.
One kind of seed treatment uses no chemical at all.
Hot-water seed treatment is used in some programmes for vegetable brassica seed, for tomato and pepper seed against bacterial spot,
and for rice seed against brown spot.
It needs no chemical, but too much heat harms the seed itself.
So use a tested method from your seed programme or extension service, never a guess.
Laisha names chemicals only by their mode-of-action group:
FRAC for fungicides and IRAC for insecticides.
The group number is printed on labels in many countries.
Here are examples from Laisha's pest and disease encyclopedia.
FRAC group three, the demethylation inhibitors, are used as seed treatments against seed-borne fungi, for example in Karnal bunt and rice brown spot.
FRAC group four, the phenylamides, act on water moulds, for downy mildews and Pythium. They have been used for so long that resistant populations are widespread,
in Pythium in greenhouses and in maize downy mildew in parts of Southeast Asia.
FRAC group twelve, the phenylpyrroles, are seed treatments against true fungi.
Group M three, the dithiocarbamates, are multi-site protectants, with a very low risk of resistance.
And FRAC group one carries a resistance risk.
For insects, IRAC group four A, the neonicotinoids, has seed-treatment uses in some crops, but these have been restricted or withdrawn in some regions.
Know the limits.
In chickpea wilt, a seed-treatment fungicide reduces seed-borne infection and early wilt, but cannot protect the crop through the season against fungus in the soil.
Combine seed treatment with resistant varieties and rotation.
And if a seed treatment suddenly fails, report it. It may be resistance.
Seed can also carry living helpers.
Trichoderma fungi, and some Pseudomonas and Bacillus bacteria, protect roots from pathogens.
They produce antibiotics, compete for space and food, attack the pathogen directly, or prime the plant's own defences. In trials they have reduced chickpea wilt, rice brown spot and downy mildews, although results vary more than with fungicides.
They are living products, so the dose is a count of living cells.
Here is the worked example from Laisha's biocontrol guide. A Trichoderma product with two hundred million colony-forming units per gram, used at four grams per kilogram of wheat seed, gives about thirty-two thousand per seed. If the product was stored badly and its count has fallen tenfold, each seed gets far less. That is one reason biocontrol works in one field and not another.
Store these products cool, out of the sun, and use them before the expiry date.
For legumes, the most important seed treatment may be a biofertiliser.
Rhizobia are bacteria that form nodules on legume roots and fix nitrogen from the air. The partnership is specific: soybean needs Bradyrhizobium japonicum,
and chickpea needs Mesorhizobium ciceri. So use the right inoculant for your crop. It pays most where the legume is new to the field, or where the soil lacks effective strains.
The method is simple.
Moisten the seed with a sticker solution, such as a little sugar or gum. Mix in the inoculant until the seed is evenly coated.
Dry it in the shade, and sow it promptly. Seed sown hours later into hot, dry soil loses many of its bacteria.
For large-seeded legumes such as soybean, guidelines aim for at least about one hundred thousand living rhizobia on each seed.
And avoid heavy nitrogen fertiliser on an inoculated legume, because soil nitrate suppresses nodulation.
Here is where many farmers go wrong.
Some fungicides and insecticides kill rhizobia,
and many fungicide seed treatments kill Trichoderma. So do not mix them together in one go. If the seed must be treated with a chemical, apply the chemical first, and the inoculant just before sowing. Or use products that the labels say are compatible.
For Trichoderma, another option is to apply it to the soil, or at a different time, instead of on chemically treated seed.
Use only a product registered for your crop in your country, bought from a licensed dealer, at the dose on the label.
Never use an unlabelled powder from the market.
Seed-treatment products have their own formulation codes: F S is a flowable concentrate for seed treatment, and W S a powder for seed treatment.
Coat the seed evenly.
Seed treaters are made for exactly this job.
Then calibrate your seed drill with the treated seed. A seed treatment can change how seed flows through the drill, so the rate you set for untreated seed may be wrong.
Treated seed carries the pesticide with it, so handle it like the pesticide.
Wear the gloves and protection the label asks for. Handling the concentrate while mixing is the riskiest step, so mix outdoors or in a well-ventilated place,
and do not eat, drink or smoke while you work. Wash afterwards.
Store products and treated seed locked, away from food, feed, children and animals.
Never eat treated seed or feed it to animals.
Birds can be poisoned by treated seed, and bees can be exposed to dust from treated seed at sowing, so do not leave spilled seed on the surface.
Triple-rinse empty containers, puncture them, and never reuse them for food or water.
And remember: if you farm for an organic certificate,
seed treated with synthetic chemicals is not allowed.
To recap.
Start with clean, plump, tested seed, and never save seed from a field with smut or bunt. Know what you are treating against.
Choose chemical treatments by FRAC or IRAC group, registered for your crop, at the label dose.
Use hot water only with a tested method.
Treat living products as living: keep them cool, and check the count.
Inoculate legumes with the right rhizobia, dry in the shade, and sow promptly.
Chemical first, inoculant last.
And handle treated seed like the pesticide it carries.
For more on seeds, crops and every pest, visit laisha.ai. Thank you for watching.
