Preparation before you Harvest Maize

This covers Maize harvesting right from the preparation before you harvest Maize, drying of the maize, threshing, storage until post-harvest management & storage pest management the Maize plants are finally harvested. Before the new maize harvest, maize farmers must be prepared for post-harvest activities.

1. They must ensure that equipment needed for the maize harvesting and post-harvest activities are available and in good condition.
2. They should decide where activities such as drying and threshing will take place
3. Ensure that there will be sufficient storage space for the crop.
4. Ensure the grain stores and sacks have been thoroughly cleaned before the new maize harvest so that residues of last season’s crop are removed from all cracks and crevices.
5. The new harvest should never be mixed with grain from the previous season as this will encourage the movement of pests from the old to the new maize harvest.
6. The old harvest can be stored in a separate place for consumption.
7. In addition, good hygiene should be ensured to prevent post-harvest losses.
   NB/: The new harvest should never be placed on, or with, grain from the previous season as this will encourage the movement of pests from the old to the new.

Harvesting

1. Harvest when cob husks turn brownish and dry the cobs adequately before storing and shelling.
2. The stalks are normally cut and stoked together to dry before de-husking.
3. Delayed harvesting is not encouraged as the crop may get spoiled, thus reducing the quality and quantity available for utilization.
4. Maize Harvesting is best done when the weather is dry because wet weather enhances the rotting of produce.
5. Avoid contact of the harvested maize produce with soil to reduce contamination

Post-harvest pest control and storage

Drying Maize

1. After harvesting, the maize must be dried before threshing and storage. Proper drying of maize enables grains to be stored for long and reduces conditions favorable for pest and mould infestation by lowering the moisture content.
2. Drying should be done by spreading the cobs on mats, tarpaulins or cribs.
3. When drying maize at the homestead, it should not be placed in direct contact with the soil and should be kept away from farm animals, or else the grain may be damaged or eaten. Maize cobs may be dried either with or without the husk cover.
4. The grain should be dried to a moisture content of about 13% -14% to avoid grain attack by fungal disease, especially aflatoxin.
5. Farmers need to judge when grain drying is complete, that is when grains reach a moisture content of 13%.
6. Farmers can test the moisture content of dry grain by biting or pinching with fingers. If the grain is dried sufficiently for storage it will be hard and does not break easily into many parts.

Another method is the ‘salt method‘ of checking grain moisture content which is quick and easy but only indicates that grain is above or below 15% moisture content. Dry salt will absorb moisture from grain. It should be noted that the ideal or recommended grain moisture content should be 13% or below. The salt must first be dried by spreading on a plastic sheet in the hot sun and leaving it for at least 3–4 hours until it is hard. It should be turned at intervals during this time. It can also be dried in an oven. The dry salt should be placed in a sealed container until it is ready for use. This method includes the following steps:

1. Shake the bottle vigorously for 1 minute to mix the salt and grain
2. Allow the grain to settle for about 15 minutes
3. If after 15 minutes the salt sticks to the side of the bottle then the moisture content of the grain is above about 15% and so is not safe for storage
4. If the salt does not stick to the bottle, then the moisture content is below 15% and so is safe for storage.
5. Shake the bottle vigorously for 1 minute to mix the salt and grain.
6. Allow the grain to settle for about 15 minutes
7. If after 15 minutes the salt sticks to the side of the bottle then the moisture content of the grain is above about 15% and so is not safe for storage.
8. If the salt does not stick to the bottle, then the moisture content is below 15% and so is safe for storage.

Moisture metres can also be used to determine the moisture present in the grain. Moisture meters are quick, portable, simple to use and fairly accurate. The procedure of testing moisture content using the Dickey-John multi-grain moisture tester is as below:

1. About 150 g of the grain is scooped by hand and poured into the moisture meter, which is then closed.
2. The device is given a few seconds to detect moisture and temperature.
3. The digital electronic machine will display the readings on the screen once the detection is over.

Mycotoxins and Aflatoxin Control

The most important mycotoxins in maize are produced by Aspergillus (which produces aflatoxin) and Fusarium species (which produces fumonisin).
Once these mycotoxins are produced on the grain, they cannot be destroyed by cooking or heating.
The only way to prevent moulds from growing and spreading is to dry maize grain quickly at harvest to moisture levels of less than 13%, keep them in clean bags, dry conditions and off the ground during storage.
Farmers should check their maize regularly, to ensure that moisture levels do not increase and allow fungus and mould to grow on it.

Storage

1. Dust the store with storage pesticides.
2. Ensure to treat shelled maize with the pesticide (e.g. Super Actellic) at a rate of 50g per 90Kg bag of maize against weevils and larger grain borer.
3. Keep a cat to control rats or use a chemical to control them.
4. You can also use PICS (Purdue Improved Crop Storage) bags to store your grain without the use of insecticides.

Storage Pests Management

Maize Weevil

Symptom/Damage

• Damaged kernels with ragged holes.
• Increased heat and humidity in sacks of grain.

Management and Recommendation

• Use of resistant maize hybrids
• Use of metal silos
• Use of grain protectants such as physical toxicants, botanicals, chitin synthesis inhibitors

Larger Grain Borer

Symptom/Damage

• Damaged kernels with ragged holes
• Increased heat and humidity in sacks of grain

Management and Recommendation

• Use of metal silos
• Use of Super Grain bag™ inside polypropylene bags/ hermetic bags
• Use of pre-fumigated seed with Gastoxin™ (a phosphine fumigant)
• Use of grain protectants such as physical toxicants, botanicals, chitin synthesis inhibitors
• Sundry and sieve infested grains before packing
• Place sticky traps in susceptible areas in the store

Angoumois grain moth (Sitotroga cerealella

Symptom/Damage

• Round exit holes in infested grains.

Management and Recommendation

• Use of hermetic bag for storage
• Cleaning of all equipment used to harvest
• Removal of the stored grain insect pests
• Protection in the store
• Use of Insecticides/tobacco dust/fumigants.

Step 4: Learn How to Manage Pests and Disease for Maize Farming in Kenya

Read our complete Guide on How To do Maize Farming in Kenya