Seed Production of Vegetable, Tuber and Spice Crops (2+1)

Seed treating chemicals

Seed protectants

• Chemicals that can be directly applied to grains are formulations of chemicals having residual toxic or repellent action or both. Those are applied directly to the grain to prevent damage by stored product pests. Eg., clay minerals (red earth, Kaolin) before 1950. Now their use is restricted only to seeds and grains meant for animal feed. These grain protectants can be applied in the form of spray/ dust on the uninfested grain.
Example
1. Pyrethrum synergized with PBO

• Safest of the grain protectants available and approved for use. Available as powder 1 % PBO +0.8 % pyrethrum, 0.83 lb synergist+ 0.6 % pyrethrum also be applied in the form of spray 3-5 gallons/ 1000 bushel, 0.6 lb synergist+0.066 lb pyrethrum.
2. Premium grade Malathion

• Foul smell is removed. Can be directly applied over the grain as 1 % D or as a spray 57 EC. Other chemicals include: Carbaryl, Dichlorvos, Fenitrothion, Lindane, Malathion, PBO, Pyrethroids (Deltamethrin , Fenvalerate).
• Fungicides
• Insecticides
• Botanicals
Halogenation seed treatment

• It is the protective treatment given to seed in the production cycle of most of the seed. In this treatment, chlorine or iodine based halogen mixtures are prepared and treated with seed either dry or as slurry treatment.
Preparation of chlorine based halogen mixture

• Calcium carbonate (CaCO3)is dried in an oven at 100° C for 24 hours. Bleaching powder (Calcium Oxychloride) and arappu (Albizia amara) leaf powders are mixed with the CaCO3 in the ratio of 5:4:1 (CaCO3 : CaOCl2 : arappu leaf powder) and is kept in airtight container for impregnatim for 3-4 days. Then the mixture is used for treating the seed @ 3 g kg-1 of seeds. For slurry treatment, 5 ml of water per kg of seed is used for mixing the halogen mixture with the seed.
Iodine based halogen mixture

• 3 mg of iodine crystal is impregnated in 3 g of dry CaCO3 in an air tight container for 3-4 days.
  
• The iodinated mixture is used for seed treatment @ 3 g kg-1 of seed.
Advantages

• It is a dual purpose treatment where seed can be used as grain on non disposal.
• It gives protection against natural deterioration by reducing the free radical formation.
• It is less harmful to human and animals.
• Maintain high germination of seeds during storage.
• Growth & vigour improved significantly
• Protect seeds from storage pests.
• Significantly reduce storage fungi.
• Enhance field establishment.
• Early plant growth.
• Leaf area and chlrophyll content increased.
• Augment crop yield.
• Chemical is eco-friendly and cost effective.
Characteristics of a good seed protectants

1. It must be effective against all diseases.
2. Cheep and easy to handle.
3. Non injurious to seed under prolonged storage.
4. Non injurious to users and non-corrosive to machineries.
5. Stable in the package on the seed or in the soil.
6. Compatible with inoculants.
Bulk treatment for stored pests

• In cases of large quantities available for seed treatment ,gaseous treatment is recommended .Fumigation is the seed treatment given in the form of gas under air tight chamber. They have the advantage of (i) very rapid action against insects and (ii) it has high penetrability. The commonly used fumigants are:
• Solid form – Celphos, Quickphos,
• Liquid form – CTC – LB, ethylene dibromide.
The effect of fumigation depends upon

1. The moisture content of seed.
2. Concentration / dosage of fumigant.
3. Duration of treatment.
4. Degassing is important.
5. Type of fumigation.
   
• Spot fumigation – are done in godowns.
• Fumigatorium.
6. Frequency of treatment.
Advantages of seed protectants over fumigants

• Used as a prophylactic treatment
• Can be effective when the grains are stored in loose containers where fumigation is not possible
• Less dangerous than fumigants
• Don’t affect germination adversely
• One application at harvest time is sufficient for one year