Pests and Diseases

Aphids, Whitefly, Mealybug, Scale and Thrip

Aphids are small insects that feed on plant sap, causing wilting, distortion, and the spread of viruses. Whiteflies are tiny, white-winged insects that suck sap from plants and can lead to yellowing, wilting, and the secretion of sticky honeydew. Mealybugs are soft-bodied insects covered in a white, waxy substance and can cause leaf yellowing, stunting, and sooty mould growth. Scale insects appear as small, immobile bumps on plant surfaces and feed on sap, causing leaf yellowing and weakening. Thrips are slender, winged insects that scrape and suck plant tissues, resulting in distorted leaves, silvering, and transmission of viruses.

Neem oil, derived from the neem tree, is a natural and organic solution that works well against all these pests. It acts as a repellent, suffocates insects, and disrupts their feeding and reproductive processes. Insecticidal soaps are another effective option, as they coat and smother pests while being safe for plants. Beneficial insects, such as ladybugs and lacewings, can be introduced to the system to control these pests biologically. Additionally, sticky traps can be used to monitor and catch flying insects like whiteflies and thrips.

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There are many types of caterpillars which are usually the larval stage of moths such as cabbage white butterfly. Cabbage white butterfly is white with distinct black spots on the wings and is around 40mm across.

The moths and butterflies lay their eggs on the underside of leaves. The larvae of caterpillars hatch from the eggs and then feed on the leaves or fruit, so it’s the caterpillar of the cabbage white butterfly.

The blue-green smooth textured caterpillar is that of the cabbage white butterfly. Look out for large holes in outer leaves. Bluey-green frass on the inside of the leaf, which is actually their droppings.

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Fungus Gnats

Fungus gnats pose a specific challenge in hydroponic and aquaponic systems. These small insects are attracted to the moisture and organic matter present in these setups. Fungus gnat larvae can cause significant damage by feeding on the delicate roots of hydroponic and aquaponic plants, disrupting nutrient uptake and leading to stunted growth or even plant death.

Controlling fungus gnats in these systems requires implementing preventive measures such as maintaining proper hygiene, including sterilizing growing media and equipment, and using pest-free water. Sticky traps can be used to catch adult gnats, and biological controls like predatory nematodes or beneficial bacteria can help manage larvae. Additionally, ensuring optimal drainage and airflow can reduce excessive moisture, making the environment less attractive to these pests.

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Mites (Spider Mite, Russet Mite)

Red Spider Mite generally live on the undersides of leaves of plants, where they may spin protective silk webs, and they can cause damage by puncturing the plant cells to feed.

Spider mites are known to feed on several hundred species of plants. Spider mites are less than 1 millimetre (0.04 in) in size and vary in colour. They lay small, spherical, initially transparent eggs and many species spin silk webbing to help protect the colony from predators; they get the “spider” part of their common name from this webbing.

Russet Mites can be the most difficult to control due to their size and lack of webbing that would indicate presence. Nearly impossible to see without the use of magnification, russet mites typically move in without being noticed and can build a large population even before damage symptoms become present.

Damage symptoms usually present themselves at the bottom of the plant and move upwards as the mite population does so. Russet mite damage begins with yellowing leaves (chlorosis) and leaf curl, which is often mistaken for a nutrient deficiency.

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Leaf Fungus

Leaf fungus, also known as foliar fungal diseases, can significantly impact hydroponic and aquaponic growers. It refers to various fungal infections that affect the leaves of plants, causing discoloration, spots, or patches.

These diseases thrive in moist environments, making them a common challenge in soilless systems. To address leaf fungus, growers should prioritize preventive measures such as ensuring proper airflow, controlling humidity levels, and practicing good sanitation to minimize the conditions favoring fungal growth. Timely detection and removal of infected leaves can prevent the spread of the disease.

Additionally, employing organic fungicides or biological controls, such as beneficial microbes, can help manage leaf fungus effectively. Regular monitoring, proper environmental management, and the use of appropriate interventions are key to mitigating leaf fungus and maintaining healthy plants in hydroponic and aquaponic setups.

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Soil Fungus

Soil fungus refers to fungal organisms that can infect plants’ roots, leading to root rot, nutrient deficiencies, and stunted growth. Soil fungus can be a concern for hydroponic and aquaponic growers, even though these systems typically don’t use soil. Soil-borne fungi can still find their way into the growing environment, causing various issues. 

Prevention is key, and growers should focus on maintaining a clean and sterile growing environment, including using sterilized equipment and disease-free planting materials. Implementing a strict sanitation regimen, such as regularly cleaning and disinfecting the system components, can help minimize the risk of soil fungus. Additionally, incorporating beneficial microbes or applying biological fungicides designed for hydroponic and aquaponic systems can support a healthy root zone and reduce the likelihood of soil fungal infections.

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