Primary symptoms
Birds and rodents usually eat seeds or plants, especially early in the season, and thus reduce plant density. They can also damage maize late in the season by eating grain off the mature ear.
Confirm the problem by checking below.
Summary
| Causes of bird and rodent damage | Additional evidence required |
|---|---|
| Seed planted too shallow, or soil not firmed over the seed. | Dig up seed and measure planting depth. Ask farmer about planting method. |
| Poor husk cover, so the grain on the ear was easily attacked by birds. | Examine husk cover. |
| Lodging allowing rodents to reach ears. | Count lodging. |
| Maize planted out of season, or a very early variety, so it was the only food supply for birds and rodents in this area. | Observe the maturity of the crop and compare with that of other maize in the area. Check for damage in late-planted fields. |
Birds and rodents usually eat seeds or plants, especially early in the season, and thus reduce plant density. They can also damage maize late in the season by eating grain off the mature ear. Rodents can be a more severe problem if lodging has occurred, placing the ear within the animal's reach.
Is bird or rodent damage a problem?
Evidence: measurements.
Is the plant density low?
Evidence: observations.
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Before the V4 stage: Look for areas where seeds have been dug up. Often birds will pull the young plant out of the ground and eat the remaining seed. Look for the tracks or droppings of birds or rodents in areas where emergence is poor. The damage often occurs in distinct patches or along the margins of fields where shrubs or trees provide a habitat. The economic importance of this damage will be related to the effect on plant density.
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Around maturity: Examine the tips of ears in different areas of the field. Are the husks chewed or shredded? Estimate how much of the grain is lost. If more than 20% of the ears are more than 25% damaged, the yield reduction is over 5% and the problem may be of economic importance. Even if the damage is less than this, the problem may cause economic losses by allowing insects and disease to affect the ear.
Possible solutions
- Change the planting method.
- Apply a bird repellent to the seed.
- Poison rodents in burrows near the field.
- Plant a variety with improved seed cover.
- Double the maize (bend the stalks below the ear after the R5 stage) to limit bird damage.
- Plant varieties of similar maturity for the region.
- Employ a bird scarer.