Pioneering Hydroponics

Since 1976

How to Deal with Spider Mites in Hydroponics

Part of the arachnid family and related to spiders, spider mites also have eight legs. They’re web spinners, building large networks and bridges between their colonies so they can travel all over plants. There are around 1,200 species of spider mites, with a few hundred species plaguing greenery.

A mere two to four weeks is all they need to completely destroy a crop. Similar to aphids, they’re a very common plant pest you should keep an eye out for. Plants often affected by spider mites are mint, strawberries, miniature roses, begonias, indoor houseplants, and beans.

Identifying Spider Mites

Although difficult to spot, you can identify them quite easily. They can be black, red, white, amongst other colours, measuring just a mm in both length and width. Leaf damage tends to be the first sign of a spider mite infestation, with leaves turning yellow and spotted. 

These areas are the spider mites’ feeding spots, where they already removed all the juices from the leaves. Webbing appears in more advanced infestations around nodes of flowers and leaves. At a late stage, the webbing spreads all over the top of the plants with thousands of spider mites walking around. The plants’ leaves will yellow and die.

Spider Mite Lifecycle

  • Egg. Spider mites’ lifecycle starts as very small eggs on the underside of leaves, usually overwintering until they emerge in spring.

  • Hatching. When they hatch, they become six-legged larvae and moult a few days later to enter their first nymphal stage. This is when they gain eight legs and start looking more like their adult counterparts. They go through two more moults before reaching adulthood.

  • Adulthood. Spider mites can damage your crops throughout all lifecycle stages after they hatch. Adulthood is their more mobile and longest-living time - and when they cause more damage to plants. 

  • Mating. A single female spider mite can lay up to around 300 eggs in just two to four weeks, which can cause the population to easily and quickly grow out of control. Warm and dry temperatures are ideal for this pest, even often doubling their growth rate. This can result in spider mites growing from egg to adult in just five days.

How Do Spider Mites Affect Hydroponics?

Spider mites can be extremely difficult to see in their early growth stages. They will feed on plant sap and effectively kill your plants. The webbing that provides them with protection and ease of movement also restricts plants’ air flow. This results in both fungal pathogens infecting plants and water loss.

These hitchhikers can infect your grow room very easily. You might simply brush up against an infected plant and carry them on your shoes, clothes, skin, and tools. Make sure you don’t reuse equipment or organic grow media from infected sources and quarantine any plant you suspect of.

Another pest to watch out for, the whitefly, can carry spider mites - or even just air! They can fashion parachutes from very small webbing and be carried by air currents. You should also make sure to always quarantine any new plants before adding them to your grow room so any existing pests or diseases have time to develop with visible symptoms.

What You Can Do to Deal with Spider Mites

Never use infected leaves, plants, or soil for either compost or as growing media - these will only serve as an easy way for spider mites to infect more of your plants. You may find that often the only way to contain a spider mite infestation is to throw all of the plants away.

  • Control humidity. Spider mites love dry surfaces. Make sure to always keep your grow room at the right humidity level.

  • Dust your plants. Make sure your plants are frequently dusted and cleaned so you can easily spot pests or diseases.

  • Balance water temperature. The warmer the water and the environment, the likelier the chance spider mites will grow into an infestation. They love temperatures above 28℃.

  • Apply Bugicide. Bugicide is a great way of keeping spider mites away. It can be used throughout all stages of plant growth, even right up to harvest.