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Seedlings are delicate and susceptible to attack by various pests and diseases as well as weather conditions. Such damages can seriously weaken or kill the seedlings. It is important that the damages be dealt with immediately.

Damage and disasters in the nursery may be categorized as below.

• Weather conditions: This is damage caused by adverse weather conditions. We can either regulate watering or shading to comply with prevailing weather conditions.
• Human: This is the stealing and/or intentional damaging of seedlings by human beings. Fencing and security are examples of options to overcome this. You remember that security is among the most important thing to consider when starting a nursery.
• Livestock and wild animals: Livestock and wild animals browse or graze on seedlings. Fencing can reduce attacks from livestock. Also, rodents like Field mice/rats frequently could damage to seedlings in the nursery when they eat them. Maintaining p[roper hygiene is one way of controlling the attacks. Additionally, a well-made fence could somehow protect them. I have seen people who keep cats in the proximity of their nurseries, and the biological control works for them!
• Insects: Termites are the most common recorded insects in the nursery. They eat the roots and stems of many tree species. Eucalyptus species is particularly prone to their attack. There are various methods that can be used to control termites:
• Spraying layers of ashes to deter them
• A manual approach could also be used where you can identify where the queen termite is and kill it. The termites will move when they have no queen. Somehow cruel!
• Using chemicals e.g., Dieldrin and Aldrin; As environmentalists, we do not advocate for the use of chemicals.
• If milk packets are used for potting, they need to be washed with soap and water or insecticide solution before potting, otherwise, your nursery is likely to attract termites.

Another insect that attacks tree nurseries is gall flies. The attack from gall flies worsens when the seedlings are water-stressed. As such, the condition is improved by providing the seedlings with an adequate amount of water.

• Weeds: Weeds will compete with the seedling for food, sunlight, and water. As a nursery manager, it is paramount that you protect the seedlings from weeds. Practices for weed protection include crop weedicides, mulching and planting cover crops. However, Silvica recommends the use of manual control of weeds in a nursery bed and seedbed.

Diseases in Tree nursery

Various diseases can occur in the tree nursery. The origins for disease in the nursery vary and they include:

Infested soils: Many pathogens occur in soils. Take great care while during the soil mixing and potting process

Plant debris: These could act as hosts to pathogens. Do you get why soil sieving is important?

Other plants: diseases can also emanate from other existing plants in the nursery; whether they are seedlings or mature plants. It is good to deal with any plant that shows a sign o disease in the nursery

Water: Water may contain pathogens. Also, under watering and over watering could lead to diseases.

Air: Most fungal diseases can be spread when air carries the spores.

The USDA classifies nursery diseases as follows:

• Roots and soilborne diseases
• Stem and branch diseases (Cankers)
• Foliage diseases
• And storage molds

A great resource on the nursery diseases of the United States from the USDA could be accessed here . Also, an overview of nursery diseases in New Zealand could be accessed here . The two resources could assist you understand the nature of disease in your nursery. 

Fungal Disease

Although there are various diseases, which attack seedlings in the nursery, damping-off, powdery mildew and wilt are described here since they are the most common fungal diseases in East Africa and areas with similar agro-climatic conditions.

Damping Off

This is a fungal disease mainly caused by Pythium spp., Rhizoctonia salani. Dampness in the nursery often increases the severity of attacks. Damping-off can occur before germination, after germination and at pricking out.

The fungi attack the seedlings at soil level and cause rotting of the part attacked consequently killing the seedling. Susceptible species include Eucalyptus, Casuarina, Dovyalis, etc.

Conditions favourable to spreading of the disease are;

• High sowing intensity
• Overwatering
• Using soil with under-composed material
• Damaging the bark of tender seedlings

Control measures: avoid sowing seeds too close to each other, Use of appropriate quantity of water or not damaging the bark of seedlings

Wilting

It is often caused by overcrowding as well.

It can be controlled by providing the seedlings with adequate space. Nursery managers could separate the seedlings through thinning or planting out.

Powdery mildew

It is recognized by the observation of small white powdery patches on the leaf that often spreads to the entire leaf area. The mycelial colonies lead to defoliation. The disease is common among young seedlings.

Control: As it is highly contagious. The fallen and infected leaves should be collected and buried in the soil. Better still, you can burn the affected leaves in a controlled environment. Chemicals (such as Benlate) can be used to control it too.

When it comes to nursery diseases or any diseases for that matter, prevention is better than cure. Many of the nursery diseases could be avoided by good husbandry in correct seed sourcing, adequate watering, correct spacings and general cleanliness of the nursery. Also, efforts should be made to protect seedlings from preventable damages.