By Umar Nsubuga
Pawpaw, also known as papaya, is a widely cultivated fruit in Uganda, valued for its nutritional and economic significance.
However, pawpaw farmers face several challenges, including various diseases that threaten yields and fruit quality.
Muhammad Kyazze, a pawpaw farmer from Kamuli village, Kayunga district says managing these diseases effectively requires understanding their causes and implementing appropriate control measures.
For example, anthracnose, he says this disease is caused by the fungus colletotrichum gleosporoides, primarily affects ripe fruits.
It manifests as small, sunken, water-soaked lesions that grow larger and darker over time, making the fruit unmarketable. Anthracnose thrives in humid conditions, which are common in tropical climates.
With this kind of disease, he says it is important to remove and destroy infected plant parts to minimise the spread.
He also says to apply fungicides such as copper-based sprays or those containing chlorothalonil, especially during the wet season, you can choose anthracnose-resistant pawpaw varieties where possible.
Gideon Zakke, an agronomist says asperisporium black spot is caused by the fungus asperisporium caricae, this disease appears as small, dark spots on leaves, stems, and fruits.
According to Zakke, severe infections can lead to leaf drop, reduced photosynthesis, and lower yields.
He says when such disease affects your farm trim affected leaves to improve air circulation and reduce humidity.
Also, use systemic fungicides such as tebuconazole or azoxystrobin to manage the disease.
It’s also important to maintain sufficient space between plants to reduce the risk of fungal spread.
Black rot
Allan Kyambadde, another pawpaw farmer from Luwero district says the fungus mycosphaerella caricae causes black rot, which begins as small, dark spots on the fruit.
Over time, the spots enlarge, leading to cracking and rotting of the fruit. This disease can devastate fruit quality if not addressed.
“If you are to control black spots, avoid overhead watering to reduce moisture on the fruit. You can also use fungicides like mancozeb or thiophanate-methyl during critical growth stages.”
Harvest fruits as they ripen to reduce exposure to pathogens, he says.
Cercospora black spot
This disease, caused by cercospora papaya, affects leaves, causing dark spots that can lead to premature defoliation. Affected plants suffer reduced growth and productivity.
Regularly remove and destroy infected leaves, Zakke says avoid planting pawpaw in areas previously affected by Cercospora.
Apply foliar sprays containing propiconazole or difenoconazole.
Phytophthora fruit rot
Henry Sekyewa, an agronomist and crop expert says phytophthora fruit rot is caused by the oomycete Phytophthora spp.
He says this disease results in water-soaked lesions on fruits, leading to decay. It often occurs in poorly drained soils or during periods of heavy rainfall.
“If you are to control this ensure proper drainage to prevent waterlogging, use phosphonate-based fungicides to control outbreaks, remove infected fruits and improve field sanitation,” he explains.
Bacterial canker and decline
This disease is caused by bacteria, and leads to wilting, cankers on stems, and overall plant decline. It spreads through contaminated water, tools, or plant material.
Sekyewa says if you want to control it, sterilise tools and avoid using contaminated water.
Rotate crops to reduce bacterial buildup in the soil, and introduce beneficial microbes to suppress bacterial activity.
Pawpaw Ringspot Virus (PRSV)
This viral disease causes mosaic patterns on leaves, stunted growth, and malformed fruits. It spreads through insect vectors, primarily aphids.
Use insecticides or introduce natural predators to control aphids, and plant virus-resistant pawpaw cultivars. Remove and destroy infected plants to prevent the virus from spreading.
