Pests affecting tilapia fry are a significant challenge in freshwater fish farming, posing threats to the success of cultivation and reducing productivity. These pests often cause high mortality rates among tilapia fry, leading to economic losses for fish farmers. Pests not only decrease the number of fish that can be harvested but also increase operational costs due to the efforts required for pest control and the replacement of lost fry.

The high population of pests in tilapia ponds is caused by various environmental and technical factors that are less than optimal. Factors such as poor environmental conditions, inadequate land preparation, and insufficient water quality management are the primary reasons for pest infestations. For example, a dirty environment can become a breeding ground for various pests that threaten tilapia fry. Furthermore, neglecting water quality control can exacerbate the issue, as unclean water can harbor harmful pests that endanger the fish.

This article will explore in detail the factors leading to pest infestations in tilapia ponds, the types of pests commonly found, and effective methods for controlling them.

Causes of pest infestations

Several factors contribute to pest infestations in tilapia ponds, including:

1. Dirty environmental conditions

Dirty surroundings are often the main factor supporting pest presence in tilapia ponds. Unclean environments, such as overgrown grass or uncontrolled aquatic plants around the ponds, provide ideal hiding places for various pests. Untrimmed grass and unmanaged aquatic plants can become breeding grounds for insects and other organisms that may become pests for tilapia fry. Additionally, fallen and decaying leaves around the pond can also serve as breeding sites for pests, increasing the risk of attacks on the fry.

Unmanaged aquatic plants also create favorable conditions for certain pests to lay eggs and reproduce. For instance, dragonflies and some species of aquatic insects often lay their eggs on the leaves or stems of aquatic plants in the pond. When these eggs hatch, the larvae or nymphs that emerge become predators, feeding on and harming the tilapia fry population. Therefore, it is crucial for fish farmers to regularly clean and manage aquatic plants around the ponds to prevent them from becoming breeding grounds for pests.

2. Inadequate land preparation

Poor land preparation can be a key factor in the emergence of pests in tilapia ponds. One important step in land preparation is drying the pond, which aims to eliminate any pests that may be present. However, if the pond drying process is not properly carried out or fails to reach an optimal level, many pest larvae may survive and remain in the pond. These pests, though initially unseen, can quickly multiply when environmental conditions become favorable, leading to damaging infestations on tilapia fry.

The application of lime to tilapia ponds aims to clean the pond of harmful pests: BPBAT Tatelu

Mechanical or manual pest control, such as removing pests by hand or using nets, is often not effective enough to eliminate all pests in the pond. Many pests are small and well-hidden, making them difficult to reach with these methods. Additionally, some pests have life cycles that allow them to survive in unfavorable conditions and then multiply when conditions improve. For example, pest eggs left in the mud or crevices of the pond can hatch later and become a source of problems for tilapia fry.

3. Insufficient water quality control

Water entering fish ponds is often not filtered adequately, allowing pests to easily enter the system. Without proper screening, water channels can introduce small organisms, including pest larvae and eggs, along with the water flow. When the incoming water isn't properly filtered, these pests can rapidly multiply within the pond, attacking tilapia fry and causing significant losses. A proper filtration system not only prevents pests but also blocks organic materials and other particles that may foster pest growth and degrade water quality.

Furthermore, poor water quality can exacerbate pest issues, even under extreme conditions. Dirty and polluted water provides an ideal environment for various types of pests to thrive. For example, water enriched with organic matter and nutrients due to pollution can encourage the growth of algae and aquatic plants, which serve as shelters and breeding grounds for pests. This problem is compounded by insufficient circulation and aeration, leading to the accumulation of organic material and a decrease in oxygen levels in the water.

Common pests affecting tilapia fry

1. Odonata or Anisoptera (Dragonflies)

Dragonflies are common predators around tilapia ponds, especially in stagnant water with abundant aquatic plants. Female dragonflies lay their eggs on the water's surface, which then hatch into nymphs or larvae. Dragonfly larvae often attach themselves to aquatic plants, using these as hiding spots while waiting to prey on small tilapia fry. With a size of up to 2 cm, these larvae are highly effective predators, feeding on the small fry by sucking out their bodily fluids, leading to the fry's death.

Dragonfly larvae in a plastic bag: NPS

The presence of dragonfly larvae in fish nurseries can result in extremely high mortality rates, causing significant losses for fish farmers. The life cycle of dragonfly larvae is relatively short but effective; within 1-2 weeks, the larvae grow into adults, although they cannot fly at this stage. After reaching maturity in 2-3 weeks, the adult dragonflies are ready to lay eggs on the pond's surface, perpetuating the pest cycle and posing an ongoing threat to tilapia farming.

2. Cybister larvae (water beetle larvae)

Larva of Cybister lateralimarginalis, a beetle species native to the Palearctic region: Wim Rubers at Waarneming.nl 

Water beetle larvae, another aggressive predator of tilapia fry, range in size from 1.5 to 2.5 cm and are yellow-brown or greenish in color. Equipped with sharp mandibles and a venomous tail, these larvae can cause considerable damage to tilapia fry populations. They have two pairs of antennae on their heads and eyes positioned on either side, which help them locate their prey. The physical attributes of water beetle larvae make them effective and deadly predators of tilapia fry.

These larvae are commonly found in ponds rich in organic matter, often resulting from the use of dried chicken manure as fertilizer. The abundant organic material creates an ideal breeding environment for water beetle larvae. In such fertile ponds, these larvae prey on tilapia fry, especially those newly introduced and up to 30 days old, leading to high mortality rates in the fry population.

3. Notonecta (Backswimmer)

The insect Notonecta, commonly known as a backswimmer, is easily identifiable by its elongated, convex body and segmented beak that reaches its front legs. Its rice-grain-like shape and habit of swimming upside down make it recognizable. Found in stagnant ponds, backswimmers often gather in groups and exhibit positive phototaxis, meaning they are attracted to light. This tendency to congregate in well-lit areas makes them easy to spot near the water’s surface during the day.

Notonecta, commonly referred to as "backswimmers" due to their upside-down swimming position: Bj.schoenmakers

Backswimmers prey on tilapia fry by biting or stinging them. Their strong jaws grip the young fish, and with specialized enzymes in their bite, they liquefy the fish's body contents, making it easier to suck out the bodily fluids. This process causes severe damage to tilapia fry, often leading to death. Due to their efficiency in preying on tilapia fry, backswimmers pose a significant threat to tilapia farming.

Pest control for tilapia fry

To control pests affecting tilapia fry, several measures can be taken:

1. Environmental cleanliness

Maintaining a clean pond environment is crucial for preventing pests that harm tilapia cultivation. Grass and aquatic plants around the pond should be regularly cleaned and managed to avoid creating habitats for various pests. Uncontrolled vegetation can serve as breeding grounds for insects and other organisms that may prey on tilapia fry.

Periodic pond drying is another effective method to minimize pests. This process aims to kill pests that may be hiding in the pond bed, preventing them from continuing their life cycle. Drying also reduces the accumulation of organic material that can support pest life.

2. Installing filters on water inlets

Installing filters on water inlets is essential to prevent pests from entering the tilapia pond. These filters act as physical barriers, screening out small organisms, larvae, and pest eggs carried by the water flow. Proper filtration reduces the likelihood of pests entering and multiplying in the pond.

For filters to remain effective, they must be cleaned and replaced regularly. Clogged or dirty filters reduce water flow and filtration efficiency, allowing pests to slip through. Replacing worn or damaged filters ensures optimal filtering performance.

3. Water quality control

Good water quality is critical for maintaining healthy farmed fish, especially in tilapia ponds. Aerators and water filters are effective tools to keep water quality at optimal levels. Aerators increase dissolved oxygen levels, vital for fish respiration and metabolism, while filters remove small particles, organic matter, and contaminants that can degrade water quality and promote pest growth.

Regular monitoring of water parameters is also essential. Parameters such as pH, temperature, and dissolved oxygen should be checked frequently to ensure that the water conditions remain safe and conducive to fish growth. Extreme temperatures can add stress to fish and affect their metabolism.

4. Using natural pest control

Natural materials like neem leaves and garlic extract offer eco-friendly alternatives for pest control in tilapia ponds. Neem leaves, known for their natural insecticidal properties, help reduce pest populations without harming water quality. Compounds in neem, such as azadirachtin, effectively inhibit the growth and development of pest larvae, reducing the risk of infestation without adverse effects on fish or the pond ecosystem.

Garlic extract also provides similar benefits. It contains allicin, a compound with known antibacterial and insecticidal properties. When used in extract form, garlic can repel various pests without contaminating the water or harming fish health. Another advantage of natural pest control is that it preserves the ecological balance in the pond, ensuring that non-target organisms or beneficial microorganisms are not disrupted.