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SPIDER MITES
By Sherri-Lee Mathers
As many gardeners turn their green thumbs from the outdoors indoors they have company - Spider Mites also make their way inside to "garden". Spider Mites are one of the first and most damaging pests especially to indoor gardening.
In an outdoor garden the cold winters will kill most off, some eggs will survive and hatch in the spring to renew the outdoor colonies. Others migrate into the house or heated greenhouse and continue to grow, feed and breed. Outdoors, Spider Mites are not usually associated with large amounts of crop damage because of natural predation, which controls their population. Indoors is whole other story - without the presence of their natural predators and accessibility to virtually unlimited food sources such as in indoor hydroponic growing or greenhouses full of flowers and vegetables. Mites are able to breed and populate to numbers that can virtually obliterate plants if not controlled.
What are they? Life Cycle
Spider mites are so small that they are sometimes difficult to see without a magnifying glass, and individual spider mites are almost microscopic. Spider mites are not insects; they are closely related to spiders, harvestmen (daddy longlegs), and believe it or not ticks. There are many species of mites, yet the one most likely to attack the indoor garden is the 2 spotted spider mite. They can be identified by the two spots on their back, which can be seen under a magnifying glass.
However, unlike insects that have six legs and three body parts, spider mites have eight legs and a one-piece body. Mites are about 1/50" long, approximately the size of a grain of salt or slightly larger. They may be red, black or brown or pale green. In the summer, the adults and nymphs are white with two greenish spots.
Mites are triggered mainly by the cooler weather and shortened daylight hours in the fall, some or most of the mites turn red in color, stop feeding and egg laying, and then crawl off to protected nooks and crannies to hide or diapause through the winter. These eggs or adults overwinter in growing mediums, crevices or in ground debris, or on equipment that hasn't been properly cleaned, emerging when the climate conditions are again favorable to them and plant growth. If you had spider mites last year and didn't perform any preventative maintenance at the end or beginning of the season then, it's likely that they will return again.
A female lays about 100 eggs during her lifetime. Depending upon climate conditions, the eggs hatch in as little as 2-3 days, and the adult stage is reached in 7-10 days. The females reproduction is greatly affected by climate and humidity with a significant difference in the days till their maturity dependant upon the temperature i.e.) egg to adult. For instance at 60 degrees Fahrenheit, it takes 30 days for the egg to become an adult, at 70 degrees 14.5 days and here is the astounding number - 90 degrees Fahrenheit they reach adulthood in just 3.5 days! So now imagine those populations increases over a month when the offspring start to reproduce less than a week after hatching - at 70 degrees she and her offspring number 13,000; at 80 degrees she and her offspring represent a staggering potential of 13,000,000 individuals over a single month - huge population increases!
Mites evaporate large quantities of water from their bodies, so they must suck juices from the plants. This is easier for them to do in a dry environment. Humid environments (above 60% RH) slow down their metabolism, life span and reproductive rate. Mites may be controlled somewhat by lowering the temperatures (at about 50 degrees Fahrenheit they start to hibernate), thus slowing down their life process considerable. Even if you only decrease the temperature during the indoor dark cycle (when it is easier to lower temperatures), the progression rate of the infestation is slowed considerable.
Symptoms and Damage
Feeding marks are usually the first sign of a mite infestation and many confuse these as nutrient deficiencies. Spider mites lack chewing or piercing-sucking mouthparts. Instead they have a pair of needle-like structures that they use to rupture leaf cells. A feeding spider mite pushes its mouth into the torn tissue and draws up cell sap. Small patches of cells are killed, resulting in a stippling or fine flecking on the upper surface of leaves giving the leaves a "sandblasted" look, it also appears that the foliage is losing its green coloration. This injury generally becomes the most obvious first on the older established plant foliage. With heavy infestations the foliage become bronzed, bleached, yellow, or even gray.
As the pests spread over a plant they spin a spider-like webbing over and between the leaves generally at the stems, enabling them to move about the plant (and from plant to plant) more quickly. Mites tend to congregate on the leaves rather than the flowers or fruits of most plants. However, as their population increases, they can start colonizing these as well.
Spider Mites will walk down stems, across medium or equipment and across dry spaces in search of new host plants in which to set up house! They are also great hitchhikers who cling to your pets' fur, or your clothing, looking for a ride to more yummy plants. If left untreated these infected plants weaken to the point where they become susceptible to diseases such as viruses and bacteria, they can become sickly and may even eventually die.
Detection
Along with the plants symptoms, mites can be identified by shaking symptomatic leaves onto a sheet of white paper or by observing the underside of the leaf and stems infected leaf areas with a hand lens. In a hot dry climate, mites can cause plants to quickly drop leaves - in as short as a few weeks. Severely affected plants will yield poor quality fruiting and flowering.
Aphids or thrips can cause similar symptoms but they are usually clearly visible or else in the case of thrips leave dark specks of excrement behind right on the foliage as well as silvering.
Immediate Action
When an outbreak occurs you must act immediately:
1) Carefully examine plants - separate the infested plants from the uninfested plants. Light and heavily infested/damaged plants should also be separated. Do not let the foliage of the plants touch, as the mites will easily walk from plant to plant via the foliage. Separation is very important !
2) Install physical barriers such as sticky tape around the plant rims of the plant pots to prevent further migration of mites.
3) Don't forget to thoroughly wash your hands and change your clothing. Particularly if you have been working outdoors, visiting a nursery or fellow gardener (they will not be happy if you spread your problem to them), before nearing and tending to your own indoor garden. When tending and examining your plants, tend to your infested ones last - do not go back and forth between the uninfested and infested ones.
4)Be sure to remove any fallen debris to a plastic bag and immediately dispose of to the outdoor trash.
5) Wash down your plants with a forceful jet of water (but not so forceful it will damage the foliage), be sure to spray the underside of the leaves - sometimes the water will knock them off and kill them. Doing this in the shower works well for indoor, smaller plants.
6) Raise the relative humidity above 60% (the wash will help do this). If you don't have a automatic mister or humidifier, even misting the plants with a spray bottle several times a day will raise the humidity (be sure to do early in the day so that the water can evaporate under the lights. Hand misting is also an opportune time to foliar feed your plants !
By Sherri-Lee Mathers
As many gardeners turn their green thumbs from the outdoors indoors they have company - Spider Mites also make their way inside to "garden". Spider Mites are one of the first and most damaging pests especially to indoor gardening.
In an outdoor garden the cold winters will kill most off, some eggs will survive and hatch in the spring to renew the outdoor colonies. Others migrate into the house or heated greenhouse and continue to grow, feed and breed. Outdoors, Spider Mites are not usually associated with large amounts of crop damage because of natural predation, which controls their population. Indoors is whole other story - without the presence of their natural predators and accessibility to virtually unlimited food sources such as in indoor hydroponic growing or greenhouses full of flowers and vegetables. Mites are able to breed and populate to numbers that can virtually obliterate plants if not controlled.
What are they? Life Cycle
Spider mites are so small that they are sometimes difficult to see without a magnifying glass, and individual spider mites are almost microscopic. Spider mites are not insects; they are closely related to spiders, harvestmen (daddy longlegs), and believe it or not ticks. There are many species of mites, yet the one most likely to attack the indoor garden is the 2 spotted spider mite. They can be identified by the two spots on their back, which can be seen under a magnifying glass.
However, unlike insects that have six legs and three body parts, spider mites have eight legs and a one-piece body. Mites are about 1/50" long, approximately the size of a grain of salt or slightly larger. They may be red, black or brown or pale green. In the summer, the adults and nymphs are white with two greenish spots.
Mites are triggered mainly by the cooler weather and shortened daylight hours in the fall, some or most of the mites turn red in color, stop feeding and egg laying, and then crawl off to protected nooks and crannies to hide or diapause through the winter. These eggs or adults overwinter in growing mediums, crevices or in ground debris, or on equipment that hasn't been properly cleaned, emerging when the climate conditions are again favorable to them and plant growth. If you had spider mites last year and didn't perform any preventative maintenance at the end or beginning of the season then, it's likely that they will return again.
A female lays about 100 eggs during her lifetime. Depending upon climate conditions, the eggs hatch in as little as 2-3 days, and the adult stage is reached in 7-10 days. The females reproduction is greatly affected by climate and humidity with a significant difference in the days till their maturity dependant upon the temperature i.e.) egg to adult. For instance at 60 degrees Fahrenheit, it takes 30 days for the egg to become an adult, at 70 degrees 14.5 days and here is the astounding number - 90 degrees Fahrenheit they reach adulthood in just 3.5 days! So now imagine those populations increases over a month when the offspring start to reproduce less than a week after hatching - at 70 degrees she and her offspring number 13,000; at 80 degrees she and her offspring represent a staggering potential of 13,000,000 individuals over a single month - huge population increases!
Mites evaporate large quantities of water from their bodies, so they must suck juices from the plants. This is easier for them to do in a dry environment. Humid environments (above 60% RH) slow down their metabolism, life span and reproductive rate. Mites may be controlled somewhat by lowering the temperatures (at about 50 degrees Fahrenheit they start to hibernate), thus slowing down their life process considerable. Even if you only decrease the temperature during the indoor dark cycle (when it is easier to lower temperatures), the progression rate of the infestation is slowed considerable.
Symptoms and Damage
Feeding marks are usually the first sign of a mite infestation and many confuse these as nutrient deficiencies. Spider mites lack chewing or piercing-sucking mouthparts. Instead they have a pair of needle-like structures that they use to rupture leaf cells. A feeding spider mite pushes its mouth into the torn tissue and draws up cell sap. Small patches of cells are killed, resulting in a stippling or fine flecking on the upper surface of leaves giving the leaves a "sandblasted" look, it also appears that the foliage is losing its green coloration. This injury generally becomes the most obvious first on the older established plant foliage. With heavy infestations the foliage become bronzed, bleached, yellow, or even gray.
As the pests spread over a plant they spin a spider-like webbing over and between the leaves generally at the stems, enabling them to move about the plant (and from plant to plant) more quickly. Mites tend to congregate on the leaves rather than the flowers or fruits of most plants. However, as their population increases, they can start colonizing these as well.
Spider Mites will walk down stems, across medium or equipment and across dry spaces in search of new host plants in which to set up house! They are also great hitchhikers who cling to your pets' fur, or your clothing, looking for a ride to more yummy plants. If left untreated these infected plants weaken to the point where they become susceptible to diseases such as viruses and bacteria, they can become sickly and may even eventually die.
Detection
Along with the plants symptoms, mites can be identified by shaking symptomatic leaves onto a sheet of white paper or by observing the underside of the leaf and stems infected leaf areas with a hand lens. In a hot dry climate, mites can cause plants to quickly drop leaves - in as short as a few weeks. Severely affected plants will yield poor quality fruiting and flowering.
Aphids or thrips can cause similar symptoms but they are usually clearly visible or else in the case of thrips leave dark specks of excrement behind right on the foliage as well as silvering.
Immediate Action
When an outbreak occurs you must act immediately:
1) Carefully examine plants - separate the infested plants from the uninfested plants. Light and heavily infested/damaged plants should also be separated. Do not let the foliage of the plants touch, as the mites will easily walk from plant to plant via the foliage. Separation is very important !
2) Install physical barriers such as sticky tape around the plant rims of the plant pots to prevent further migration of mites.
3) Don't forget to thoroughly wash your hands and change your clothing. Particularly if you have been working outdoors, visiting a nursery or fellow gardener (they will not be happy if you spread your problem to them), before nearing and tending to your own indoor garden. When tending and examining your plants, tend to your infested ones last - do not go back and forth between the uninfested and infested ones.
4)Be sure to remove any fallen debris to a plastic bag and immediately dispose of to the outdoor trash.
5) Wash down your plants with a forceful jet of water (but not so forceful it will damage the foliage), be sure to spray the underside of the leaves - sometimes the water will knock them off and kill them. Doing this in the shower works well for indoor, smaller plants.
6) Raise the relative humidity above 60% (the wash will help do this). If you don't have a automatic mister or humidifier, even misting the plants with a spray bottle several times a day will raise the humidity (be sure to do early in the day so that the water can evaporate under the lights. Hand misting is also an opportune time to foliar feed your plants !
