Mites solutions guide
Ornamentals Advisory Blog

Mites are part of the Arachnida, a major class of arthropods. They are in the subclass, Acari hence the insecticides used to kill these pests are called acaricides. The Acari subclass consists of a wide range of Orders or groups of related mites – the main pest Order is the Prostigmata.

Development from egg to adult in mites usually includes a six-legged larva and two or three eight-legged nymphal stages; proto-deuto- and tritonymphs. Adults usually have eight legs. Red spider mite will be discussed in more detail, since it is the most polyphagous and a common pest in the East Africa, UK and worldwide.

The most common mites species found in the greenhouse are:

• Red spider mite (or two spotted mite) Tetranychus urticae

• Carmine spider mite Tetranychus cinnabarinus

• Bulb scale mite Stenotarsonemus laticeps

Susceptible crops

Many ornamental plants and herbs are prone to mites, including:

  • Alyssum
  • Alstroemeria
  • Roses
  • Geraniums
  • Chrysanthemum
  • Dahlia
  • Gerbera
  • Impatiens
  • Carnations
  • Hypericum
  • Verbena
  • Hederas
  • Hydrangea

Lifecycle 

Red spider is a successful pest because it reproduces rapidly by asexual means when environmental conditions are in its favor. Females can lay up to 100 eggs during their life, at rate of about 6 per day. Eggs are about 0.13 mm across, globular and translucent. The time it takes from egg to adult is accelerated by temperature so populations can increase dramatically as summer temperatures rise. At a temperature of 30°C a new generation would be produced every 8 days. Leaf canopy obviously increases as the plants grow, so the difficulty of controlling potential population explosions is compounded by the difficulty of achieving good under-leaf cover with sprays later in the season.

Damage

Mites suck sap from the leaf, causing them to look speckled with yellow marks. Heavily infested plants can be very chlorotic and become stunted and even die as a result of water stress under dry conditions. Heavy infestation can cause premature leaf drop. Red spider mite spins webs and this can not only disfigure plants but makes it more difficult for sprays to reach the leaf surface.

Speckling marks due to red spider mites damage in roses

Integrated Pest Management

Frequent, regular scouting is important because mites populations can build quickly.

  • Inspect new plants for mites before introducing them into production areas
  • Examine under leaf surfaces as well as any new growth on plants
  • Spider mites can be dislodged from plants during heavy rains. Growers can reduce mite problems by spraying affected plants with a steady stream of water twice a week during periods of peak mite activity.
  • Spider mites thrive on plants that are under stress. Be sure to keep plants watered and give them adequate light.
  • Avoid over-fertilizing with nitrogen-based fertilizers as this can increase aphid reproduction
  • Beneficial insects such as predatory mites (Phytoseiulus persimilis, Amblyseius cucumeris) and predatory midges (Feltiella acarisuga) work well but require early and frequent releases for adequate control and therefore very useful in finding and controlling spider mite hotspots.

Chemical control options 

Syngenta offers several products for mites’ control with different modes of action to minimize the onset of insect resistance. Insecticides, which kill mites, are called acaricides. Most acaricides provide some control of the Tetranychidae, whereas the Tarsonemidae and Eriophyidae may require acaricides with translaminar movement to complete the control of mites which are concealed in buds and tightly folded leaves.

Arima is a mitochondrial complex II electron transport inhibitor (IRAC group 25A which stops the production of ATP within mite cells, rapidly depleting the cell of energy, which leads to paralysis and death of the affected mites.

•          Provides an effective and noble control of spider mites.

•          Fast knockdown.

•          Long lasting activity for more than 30 days in greenhouses.

•          Highly effective against eggs, nymphs and adult stages of spider mites.

•          Safe to most beneficial insects, including predatory mites.

•          Excellent crop safety.

•          Labeled with a four-hour restricted-entry interval (REI) and no signal word

•          Use rates: 0.6L/Ha

Pegasus is a broad-spectrum insecticide and miticide (IRAC group 12A) that controls two-spotted mites, broad mites, aphids, whiteflies, thrips and caterpillars. It has translaminar activity and has excellent contact and /or stomach action with some ovicidal action.

•          Broad spectrum insecticide and miticide that controls of two-spotted mites, broad mites, aphids, whiteflies, thrips and caterpillars.

•          The product offers strong translaminar and vapor action, controlling hidden pests on the lower leaf surface.

•          Soft on beneficial insects therefore compatible in IPM and ICM programs.

•          Long lasting effect.

•          Strong phytotoxic effect which usually enhances yield.

•          Use rates: 0.6–1.0 L/Ha.

Dynamec insecticide (IRAC group 6) is a broad-spectrum insecticide/miticide, a superior solution for control of mites and leaf miners.

•          A proven standard in mite, Leafminer and thrips control and suppresses aphids and whiteflies.

•          Maximum leaf penetration and uptake provides longer residual control.

•          Pests stop feeding on plant tissue within hours of ingestion preventing or reducing damage.

•          Rain-fast within hours of application.

•          Ideal for rotation in resistance management programs.

•          Well suited for use in Integrated Crop Management programs.

Use rates: 0.5L/Ha.

Control of red spidermites on roses 

Control of red spidermites on roses