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Diseases to look out for in sweet peppers

By George Mbakahya

Sweet peppers. For a healthy yield, always plant disease resistant varieties. [Courtesy]

Sweet peppers are a high impact superior crop primarily grown in three colours; red, yellow and orange. No matter the final colour, all sweet peppers start out green and the final colour develops as the fruit ripens. The colour of the mature pepper is determined by the cultivar grown.

Harvesting fully sized peppers when they are still green is not profitable as the mature coloured peppers command a better price. However, common problems can lead to massive losses.

Common problems

The most common problem is where the seedling will be cut off near the soil surface. When this happens, it indicates the presence of cutworms. Handpick the worms from the soil around plants. Keep the garden free of plant debris. Leaves rolling downward with no indication of yellowing or stunting is a physiological leaf roll, not caused by pathogen; it may be a reaction to temperature or weather. Keep plants evenly watered.

Curling leaves

Curling leaves that are deformed, discoloured and stunted plants indicates presence of aphids. Aphids are small soft-bodied insects–green and gray–that cluster on undersides of leaves. The insects leave behind a sticky excrement where a black sooty mold grow. Spray away aphids with a blast of water or use insecticidal soap. Aphid predators include lacewing flies, ladybugs, and praying mantis.

Wilting leaves that turn yellow then brown indicates infestation of whiteflies. Whiteflies are tiny insects that will lift up in a cloud when an infected plant is disturbed. These insects suck juices from plants and weaken them. Spray with insecticidal soap. Trap whiteflies with a sticky bright yellow card.

Galls or knots on plant roots; plants wilt in dry weather; plants become stunted. Root knot nematodes are nearly microscopic, translucent worms that inject toxins and bacteria into plant roots. Remedy is to plant resistant varieties. You can also rotate crops. Companion plant with marigolds. If plants do not grow; blossoms drop off; fruit does not develop. Temperatures are too cold. Plant when the weather is warmer. Plant varieties recommended for your region.

Early blight

Plants with lush foliage do not fruit or have little fruit. The soil may be nitrogen rich and lack phosphorus. To remedy this, add aged compost to the planting bed before planting and side dress plants with aged compost. If night temperatures are cool, place a wire cage around peppers and drape the cage with plastic at night. Increase pollination and fruit production by lightly tapping plants to make sure pollen is distributed.

Black spots on leaves and lower stem; leaves turn yellow to brown is early blight. Early blight is a fungal disease spread by heavy rainfall and warm temperatures. Keep weeds down in the garden area; they harbour fungal spores. Also avoid overhead watering.

Bacterial leaf or fungal leaf spot cannot be cured. To counter it, plant treated seed. You can also prune away infected leaves. In addition, keep garden and tools clean and plant resistant varieties.

Blossom end rot

When fruit is normal-coloured but small and flattened; with few or no seed inside is a sign of Blossom end rot. It points to poor or incomplete pollination. To avoid this, plant when the weather has warmed and insects are active. You can also attract bees and other pollinators to the garden. Increase pollination and fruit production by lightly tapping plants to make sure pollen is distributed.

The remedies

Blossom end rot is caused by irregular watering or the irregular uptake of water by plants; this can happen when temperatures rise above 32°C. Keep soil evenly moist; mulch around plants. If the soil has calcium imbalance that inhibits the uptake of water; add limestone to the soil if the pH is below 6.0.

Anthracnose is a fungus disease that over-winters in infected seed and the soil. Remedy is to destroy rotting fruit; keep fruit off soil.

Spray or dust with a fixed copper- or sulfur-based fungicide every seven days. Do not collect infected seed. The sign for this is fruit has light-coloured areas that are soft before they become sunken and dry. Sunscald can affect peppers exposed to too hot sun. Prune plants so that blossoms and fruits have a leaf canopy above.

For a healthy crop, use shade-cloth or a lath screen to shade peppers during intense hot spells.

The writer is an expert on sustainable agriculture and agricultural solutions georgy.mike@yahoo.com

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