Red Spider Mites

Severe Red spider infection

Severe Red spider infection

Red spider on Areca

Red spider on Areca

Red spider on Areca

Common name: Red Spider Mite

Family: Tetranychidae

Physical description

Red Spider is a mite, and not an insect and generally speaking almost immune to most commercial insecticides. The mites themselves are extremely small (0.1mm) and can normally just be seen with the naked eye. They develop into colonies on the underside of the leaves and enshroud themselves in a delicate "spider web". This web is quite noticeable if you are looking for it and often traps dust particles making it easier to spot. In really heavy infection, the webs will cover large portions of the plant and the adults can be seen moving across the web.

Description of damage

Spider mites are sap-sucking, causing chlorosis, wilting of the leaves, and deformation of new leaves and flower buds. In serious cases, the large populations of mires can cover the plant and make it appear almost white, in this case, photosynthesis is also physically impaired. Damage is normally visible on the upper side of the leaf to where the mites are feeding and will be observed as yellow mosaic, pin-prick speckling. Often on the underside of the leaves small black speckles of tar-like droplets are also found, this is the aggregated feces of the mites.

Life cycle description

Red Spider mites multiply incredibly quickly if the conditions are right; females lay clutches of up to 20 eggs at a time, once hatched the mites can develop into breeding adults within 5 days. This rapid population increase combined with the fact that mites are mobile can quickly cause serious damage to a plant.

Plants affected

Red Spider is a very common problem on indoor plants, where the plant is protected from wind and the air is relatively dry, there are few natural predators and the foliage may not be cleaned off very often.

A common problem on indoor plants such as Crysalodocarpus (Areca), Dieffenbachia, Dracaena, Syngonium, Ficus species, and cacti/ succulents.

A common occurrence on outdoor plants such as Ixora, Bougainvillea, Hibiscus, Terminalia, Jasmine, etc. Outdoors are commonly found in the summer months on Hibiscus, Ixora, Vitex, Acalypha, Ficus species, and many other soft tissue plants.

General comments

They normally increase in numbers in places where the relative humidity is very low, or there is dry air; their web structures are hydrophobic and help reduces the amount of moisture reaching them (this also reduces the affectivity of poisons).

The damage the mites cause (the speckling) is cosmetic and cannot be corrected once it is observed. This is direct physical damage to the plant tissue and has to grow out.

Affected indoor plants should be quarantined or moved away from unaffected plants as soon at an infection has been observed. The affected plant should then be treated and remain in isolation until the problem is completely resolved.

Control methods - Natural

They can however be reduced in numbers (to a point that the damage is barely visible) by regularly spraying the underside of the leaves with jets of water, or setting your watering nozzle to a medium-fine spray pattern so that it is able to get up and under the foliage of the plant, the droplets of water (or jet) destroy the web and drowns the insect. Occasionally spraying the underside of the leaves with a weak solution of soapy water also works in a similar manner.

The use of mineral plant oils (such as Neem mixed with a diluted soap water solution) can be used to control the population, this will normally kill off any mites that are on the plant (through suffocation) - a full cover spray application of the entire plant is required and needs to be repeated every 10- 14 days for at least 5 to 6 weeks. Encourage natural predators such as Ladybugs if possible.

Control methods - Cultural

Regular wiping of the foliage, the upper and lower surface will physically kill and remove the mites, although small pockets can be overlooked hidden in the terminal portions of the plant. Low-pressure washing of the foliage with a hose or even a spray bottle will dislodge and kills the mites, however, as they are mobile, this can simply spread the problem if they are not killed. As Spider mites thrive in dry air, increasing the humidity of the air around indoor plants can reduce infection.

Stick to fertilizers with a high Phosphate (P) level (e.g. 12-24-12 (NPK), which physically strengthens the cell walls of the plant and makes it harder for the mites to inflict damage.

Control methods - Chemical

Using general broad-spectrum poisons formulated for insects will have no visible effect and will only kill any beneficial insects (i.e. the Ladybirds); Red Spider is normally controlled with a product-specific insecticide.