1. Crop: COCOA

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Type

Healthy Cocoa


Description

Healthy cocoa varies in color from green-white to yellow to purplish red. It has no form of deformity or discoloration. The pods are usually free from any form of disease and pest infestation.


Disease

Black Pod


Causative Agent

Fungus


Description

Black pod is the most important fungal disease of Cocoa worldwide and results in the browning, blackening, and rotting of pods and beans. The disease may also grow into the cushion through the pod stalk and enter the trunk to cause canker. Black pod is caused by the fungus Phytophthora sp.


Damage Pattern

Symptoms are a small brown spot on the pod that grows darker and expands rapidly. Whitish spores (seeds) are produced on the brown surface and the whole surface of the pod may become black within 14 days.


Mode of Transmission

  • Healthy pods in contact with infected plants.
  • Rain drops hitting infected pods splash spores onto healthy pods.
  • Drips of water from infected pods falling on healthy pods.
  • Rain splash from infected soil to lower healthy pods.
  • Through the activities of insect pests and rodents.
  • Through contamination from harvesting implements and dirty hands.
  • Through carrying infected pods from one farm to another.

Biological Control

Coming soon!!!


Cultural Control

  • Weed regularly.
  • Drain standing water.
  • Regular harvesting of matured pods.
  • Removal of shade trees, climbers and interlocking branches to enhance light penetration.
  • Phytosanitary harvesting (prompt removal of diseased pods) and burning them in a designated place. The ash could be used for soap making.
  • Remove soil and soil tunnels to the surface of the cocoa trunks. This eliminates two sources of disease: spores carried in infested soil and those carried by the ants themselves.

Chemical Control

  • Spray recommended fungicides to coat the pods against the fungus. Spraying must be done
  • Rationally. Effective control is achieved when combined with cultural control.
  • Spray early on a day when the weather is clear, for the chemical to get the chance to dry on the pods.
  • If it rains within 3 hours of spraying then spray again.

Disease

Stem Borer


Causative Agent

Pest


Description

Losses from this moth are usually low but a high number can seriously affect yield and tree health. Stem borer is reported to spread as a pest where there has been heavy pesticide misuse on trees. This kills off the natural predators of this pest. However, since the late 1990s, stem borers have become more noticeable, even on farms where no pesticides are used. A further problem is that the stem borer entrance holes also serves as entry points for diseases such as canker.


Damage Pattern

Symptoms are the presence of sticky sap on Cocoa tree bark, and silk threads on branches. Attacked branches lose their leaves, dry out and die off.


Cultural Control

  • Use pesticides rationally to keep insect pests in check and to preserve natural enemies.
  • Plant a barrier crop such as sweet potato, cocoyam, or leucaena sp. that is not attractive to stem borers.
  • Practice the spot application of pesticides.

2. Crop: MAIZE

Type

Healthy Maize


Description

Healthy corn also called maize usually has no form of deformity or discoloration on the leaf or cob. The Leaf or cob are usually free from any form of disease and pest infestation.

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Disease

Common Corn Smut


Causative Agent

Fungus


Description

Corn smut is a troublesome disease of corn plant disease caused by the fungus Ustilago maydis throughout most of the world. The disease reduces corn yields and can cause economic losses. Corn smut galls can develop on both the aboveground part and beneath the soil surface when the apical meristem of the corn.


Damage Pattern

Symptoms are localized to the site of infection. Corn smut galls are initially firm to spongy and are covered with a glistening, greenish-white to silvery-white membrane. As the gall ages, the interior turns dark, and the membrane eventually ruptures to expose a mass of powdery, dry, black, sooty fungal spores (teliospores). Galls on leaves are usually small, hard, and dry, and often do not rupture. The early signs of an attack are whitish galls that later rupture to release dark spores capable of infecting other corn plants. The galls vary in size from less than 1 cm to more than 30 cm (0.4-12 inch) in diameter and are found most frequently on ears, tassels, stalks, nodal shoots, and mid-ribs of leaves.


Mode of Transmission

  • Contact of healthy corn with infected ones.
  • Through the activities of insect pests and rodents.
  • Through mechanical injury to plants during cultivation.
  • Through carrying infected corn from one farm to another.

Management

  • Plant corn where common smut has not previously occurred or has not occurred for several year
  • Phytosanitary harvesting (prompt removal of galls before they mature) and burning them in a designated place.
  • Practice crop rotation
  • Planting of resistant varieties
  • Avoid mechanical injury to plants during cultivation, or any other practice that may wound plants. In seed production fields, avoid detasseling during wet weather.
  • Provide balanced fertilization. Excessive N tends to increase the incidence and severity of common smut

Disease

Common Rust


Causative Agent

Fungus


Description

Common rust is caused by the fungus Puccinia sorghi. Rust occurs every growing season. and is favored by high humidity with night temperatures of 65-70°F and moderate daytime temperatures.


Damage Pattern

Early symptoms of common rust are chlorotic flecks on the leaf surface. These soon develop into powdery, brick-red pustules as the spores break through the leaf surface. Pustules are oval or elongated, about 1/8 inch long, and scattered sparsely or clustered together. The leaf tissue around the pustules may become yellow or die, leaving lesions of dead tissue. The lesions sometimes form a band across the leaf and entire leaves will die if severely infected. As the pustules age, the red spores turn black, so the pustules appear black, and continue to erupt through the leaf surface. Husks, leaf sheaths, and stalks also may be infected. Common rust can be differentiated from Southern rust by the brown pustules occurring on both top and bottom leaf surfaces with common rust.


Mode of Transmission

spores are carried long distances by wind.

Management

  • Planting of resistant varieties
  • Application of recommended Foliar fungicides especially if applied early when few pustules have appeared on the leaves.
  • Timely planting of corn early during the growing season may help to avoid high inoculum levels or environmental conditions that would promote disease development.

Disease

Gray Leaf Spot


Causative Agent

Fungus


Description

Gray leaf spot, caused by the fungus Cercospora zeae-maydis, occurs virtually every growing season. If conditions favor disease development, economic losses can occur.


Damage Pattern

Symptoms first appear on lower leaves about two to three weeks before tasseling. The leaf lesions are long (up to 2 inches), narrow, rectangular, and are yellow to tan to brown in color. They look very similar to those of other diseases, except that they often have a faint watery halo which can be seen when held up to the light. Later, the lesions can turn gray. They are usually delimited by leaf veins but can join together and kill entire leaves.


Management

  • Plant resistance hybrids
  • Crop rotation and clean plowing are effective at reducing in-field inoculum buildup.
  • Use recommended fungicides and apply fungicides early in the season before significant leaf damage occurs. Check fungicide labels for appropriate timing of fungicide application.

Disease

Northern Corn Leaf Bright


Causative Agent

Fungus


Description

Northern corn leaf blight caused by the fungus Exerohilum turcicum can cause yield loss if it develops before or during the tasseling and silking phases of corn development


Damage Pattern

Symptoms usually appear first on the lower leaves. Leaf lesions are long (1 to 6 inches) and elliptical, gray-green at first but then turn pale gray or tan. Under moist conditions, dark gray spores are produced, usually on the lower leaf surface, which give lesions a "dirty" gray appearance. Entire leaves on severely blighted plants can die, so individual lesions are not visible. Lesions may occur on the outer husk of ears, but the kernels are not infected.


Management

  • Select Resistant Hybrids
  • Practice crop rotation and tillage
  • Timely planting
  • Use recommended Fungicides at appropriate quantity and timing

Disease

Southern Corn Leaf Bright


Causative Agent

Fungus


Description

Southern corn leaf blight is caused by the fungus Bipolaris maydis.


Damage Pattern

Lesions are generally from 1/8 to 1/4-inch-wide by 1/8 to 1-inch long tan in color rectangular to oblong in shape usually found on leaves variable, making identification more difficult than for other diseases. Its lesion type depends on hybrid genetics Lesions usually develop first on lower leaves and work up the plant


Management

  • Select Resistant Hybrids
  • Practice crop rotation and tillage
  • Use recommended Fungicides at appropriate quantity and timing

Disease

Northern Corn Leaf Spot


Causative Agent

Fungus


Description

Northern corn leaf spot, also known as Carbonum leaf spot, is caused by the fungus Bipolaris zeicola. It is occasionally seen in the lower canopy during periods of high humidity and moderate temperatures.


Damage Pattern

Symptoms of northern corn leaf spot usually appear at the time of silking or at full maturity. It consist of circular tan to brown lesions (1/8 to ½ inch) running in a line along the leaf vein. These lesions are often described as looking like a "string of pearls."


Management

  • Select Resistant Hybrids
  • Practice crop rotation and tillage
  • Use recommended Fungicides at appropriate quantity and timing