Pest damage in maize

BY Makeli Phiri

Yes, maize is our staple food and no one can even dispute this fact. This can even be seen by mushroooming of so many milling companies all over the country in addition to grinding mills here and there.

This maize of ours is at risk each year from different types of pests. It is these pests that I would like to look at. Maize is attacked at different stages by different types of pests, starting from the time the seed is put into soil. The seed would be more prone to white ants attack these we call termites. Sometimes seeds would be dug out and eaten. Rats too would be at play.

Germinating seeds or seedlings are found to be attacked beneath the soil and the young plants rapidly wither. This can be due to a variety of pests such as cutworms, maize rootworm, Fat John, black maize beetles etc.

Damage to young plants causes withering of the central shoots and these can be caused by a numvmer of pests notably maize rootworm pink grubs, caterpillars boring in stem above ground can also cause havoc.

Irrigated maize is prone to to attacks by the pink stem borers.

In other maize should borers be seen in any part of the stem and damage seen on young leaves of funnel, then the maize stalk borer is doing its rounds.

When young maize stems are eaten at groung level then suspect cutworms, dusty  surface beetles or harvester termites. And if damage is beneath the ground level, suspect black maize beetles or white grubs.

If leaves are eaten by caterpillars  and are readily noticeable on plants and in large numbers one can sure that these are army worms.

If they have several fine yellow lines along sides and broad yellow or pale green band and feed on cereal crops and grasses then these are African armyworms.

However if they look brownish and have a longitudinal whitish black stripes and feed on crops other than the cereal and grasses, these are called lesser armyworm. All the same both types of catepillars do a lot of damage to maize.

On  seed heads or cob damage, the cause would be due to maize earworm and should tunnels be found on any part of the maize cob, this would be the work of maize stalk borer. Some grasshoppers would also do danmage when they feed at the tip of the cob.

Lets look at some specific pests that do a lot of damage.

African armyworm: it is the most important armyworm species in Africa.

These breed locally in some parts of Zambia however most of the serious invasions originate fronm outside the country. Outbreaks of this pest is influenced by environmental conditions.

Armyworms are leaf eating caterpillars and occur in very large numbers moving like an army through vegetation devouring as they advance. The newly germinated crop is at risk if all other vegetation is tough and dry.

During heavy outbreaks, these caterpillars are seen in large numbers crawling on the ground, migrating across fields and roads. It is this habit  that has given them their popular name of armyworms. Armyworms are easily killed by insecticides.

Cutworm: cutwornms are usually associatied  with the occurence of weedy conditions prior to seedbed preparations. Moths deposit eggs on newly emerging weeds at the onset of  the rainy season.

Damage causued by the cutworm can be recognized by maize seedlings being cut off just above ground level. Small cutworms larvae chew holes on maize leaves and so do not begin cutting until they are about 12 cm long.

Fat John:  Fat John is a weevil grub that attacks maize seedlings below ground level, causing damage similar to that  of the  maize rootworm. It chews into the sides of the underground portion of the maize stem, inside which it is found curled. Infestitation of maize by this pest is more severe on lighter sandy sopils that in the maize crop growing on heavier soils.

Maize Earworm(American Bollworm):  the caterpillar vary  a great deal in colour from pale green, pink, black, dark brown or a dirty yellow. Young caterpillars are whitish green. Maize earworm is an important pest of cotton, tomato, maize and tobacco. On cotton and tomato it is known as American bollworm; on maize it is called earworm and on tobacco is it  named budworm.

In tomato the pest, especially the larva prefers to bore into green or ripening tomato fruits, growing tobacco tips, cotton balls and tips of developing maize cobs. In our Zambian situation, the tobacco, maize and cotton crops are mainly attacked from February to April.

Maize rootworm: this is an important pest in many maize producing areas of Zambia. The larva bores into the underground stem of the portion of maize plant especially seedlings and feed on the growing points, causing the young plants to wilt and die. In older plants when they survive the attack, they usually produce suckers and the cobs are small.

Maize stalk border: it is a  pest that has been estimated to cause damage at approximately 10 per cent of the total maize crop. Plants are weakened by caterpillars tunnelling in the main stem and on the maturing maize cobs, the caterpillars spoil the plant by tunnelling and feeding on the grain.

The tunnelling of stems of the maize crop interfers with the movement of nutrients and water in the stalk rsulting in smaller cobs.

Termites or white ants: usually feed on timber and other dead  organic matter. Healthy and established crops are not usuallly attacked. However under certain farming conditions, especially in drier areas and low-fertility soils, termites cause damage to cereal crops in various ways.

In maize, the time of harvest is important, losses done due to termites increases rapidly.

This is because termites prefer their food to be  as dry as possible and with a high proportion of cellulose.

Some plants like soya  bean are easily attacked from the enmergence and damage is considerably higher than in maize. This is because the soya bean plant has a high fiber content and this attracts white ants and they dry  later in growing season. There is even more attraction to plant damage by termites.

These are just a few pests that do damage to our staple crop and if we are able to minimize the damage it would mean more grain in the nation and therefore an increase in the establishment of food procession industries since materials to feed these industriers would be readily available and it would mean more employment for those in need of work.

To the farmers, especially most maize farmers, when confronted wth unnecessary crop damage, always call on the department of agriculture to advise the way forward becuse we need food.



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