At Brew & Grow we believe an integrated pest management (IPM) is by far the best method to control plant pests. IPM is a multi-pronged approach to dealing with pests that incorporates deterrence, monitoring, and pest control. It is always best to never have a pest infestation in the first place, and just a few simple steps can reduce your odds of developing a problem.
The first would be the installation of horticultural insect screen on your intake fans. This will help protect against airborne pests, but not pests like spider mites. You or your pets can easily, and unknowingly, introduce these pests to your garden. When I was in the mite producing business, I would even see pest eggs in the grooves of my fingerprints. Making your plants an inhospitable home is another tool in your arsenal. A weekly spraying with a mixture of a biosurfactant and neem is an excellent deterrent for a host of potential problems. Garlic Barrier is another popular spray deterrent.
Careful monitoring of the entire garden is an important habit to get into. Yellow sticky traps are a great way to discover the early stages of a fungus gnat or whitefly infestation. You will find them on the sticky traps before you notice your plants are infested. However, spider mites are a little trickier. Pay special attention to the general appearance of the leaves of your crop. If you notice any freckling of the leaves, or in later stages the beginning of webbing, it’s time to get out your magnifying glass. I’ve been using the same magnify glass for over 20 years.
If you discover an infestation, dealing with the problem promptly is very important. Your first decision is which path you’ll take to deal with the problem. Your first choice is to start over, and this is not a particularly popular choice. Even if you go this route, there is no guarantee that the pests won’t be lurking around just waiting for you to begin again. Your next option is to go the chemical route. This can be very effective, but many times a few tough ones will survive. These guys have super babies that can take what your dishing out, so it is advisable to mix up your approach with different chemicals. If you are growing food crops, be sure the sprays you are using are approved for vegetables. We carry a wide assortment of relatively safe products. My favorite course of action is biological control with one or more choices from the insectary. Before you introduce the beneficial insects, stop using the deterrent spray program. If you have an advanced infestation of a common indoor pest like spider mites, whitefly, aphids, or thrips we recommend using a soap spray to reduce the pest population prior to introducing the good guys. Soap spray is a contact kill, not a poison. It basically dissolves the pests’ exoskeleton, turning it to jelly. The good news is the bad guys can’t develop a resistance to the soap. Once the soap is dry, you can introduce the beneficial insects.
Multiple periodic introductions of beneficial insects are usually required to achieve the greatest control. For some pests, there are good guys that will stick around to take care of potential pest flare ups. An excellent resource on the biological control approach is the book “Knowing and Recognizing”. If you can’t afford it, let mom know you want it for your birthday! Below is a list of common pests and some ways to control it.
Problem – “Two-Spotted Spider Mites”
The spider mite is not an insect. It has eight legs, and an adult can vary in color from light green or yellow, to dark green, orange, red, brown, or even almost black. An adult will develop two spots on either side of its back, which can vary in form and size. The female two-spotted spider mite is an egg-laying machine, laying spherical eggs on the underside of leaves. Eggs will hatch in about three days into six-legged larvae. The larvae then develop into eight-legged nymphs, which later turn into adults. The life cycle, from egg to adult, varies from 8 to 28 days depending upon food availability, temperature, and humidity. In a hot, dry environment, they reproduce at an astonishing rate. With the exception of the egg, all stages of mite development will cause plant damage. A mite will pierce the plant cell wall and suck out the juices. These cells then turn yellow, producing the tell-tail freckling of the leaves. As mite populations swell, they produce webs that can cover the top of the entire plant. In severe cases of infestation, a plant will be swarming with a mass of the “mitey” bastards, just dripping off the plant in globs of insatiable hordes that go looking for more plants to devour and destroy. On top of that, the vast majority of spider mites are females. Spider mites reproduce so rapidly that subsequent generations quickly develop resistance to any chemical you are throwing at them.
Spider Mite Prevention and Detection
Cleanliness helps, as does not playing around outside and then going into your indoor garden with some hitchhikers on you and/or your clothing. Don’t bring new plants to your garden from an outside source. If you absolutely must, quarantine them for a few weeks and then carefully inspect each with a 5X or 10X magnifier before moving them into your garden. Try to keep your temperature from getting too hot. The low 70’s is a good target to shoot for. Weekly spraying with a biosurfactant and a neem product will help create an inhospitable environment. Do not use a spray if you are going to make preventive introductions of the predatory mite Amblyseius californicus. These predators are to be introduced every 3 weeks. This particular strain can survive for long periods in starvation conditions, so if/when the spider mites emerge, the predators are ready to dine. Getting into the habit of frequently inspecting the garden is extremely important. At the very least, do this once a week with magnifier in hand. Look for leaf freckling, or heaven forbid, webbing. If you have webbing, the mites have been around for a while.
Controlling A Spider Mite Infestation
Don’t panic, but you must act quickly! Although controlling a spider mite infestation can be costly and difficult, with a good war strategy and perseverance, you can prevail. If you have an established mite population, you must reduce it through non-poison means before introducing biological controls. Soap sprays are a contact-kill, not a poison, and pests do not build up a resistance to soaps. For pest control , I spray right before the lights go out. Safer Insecticidal Soap is a good choice. When spraying, do a thorough coverage, paying particular attention to the underside of the leaf. The soap will dissolve a mite’s exoskeleton causing it to turn into a jelly-like mush. Soaps are least effective on eggs, but will still get a fair number of them. When you spray something for the first time, begin with a test spray on a single plant. Sometimes a plant will have a bad reaction to a spray, so it is much better to make a small mistake instead of a big one. Once the soap has dried, it has little residual effect, so you won’t have to worry about it affecting the beneficial insects you may plan to introduce. I prefer to rinse off my plants with water the next morning after the soap has dried. Who wants to garnish their vegetables with soap?
You have a number of spider mite predators to choose from. Phytoseiulus persimilis will give you the most bang for the buck. They are aggressive feeders that require a ready food source to survive. The adult predatory mite, which is reddish-orange, consumes from 5 to 20 of the spider mite adults or eggs daily and is harmless to plants. At temperatures between 70 and 85 degrees, the female predator lays more eggs than a spider mite. The eggs reach maturity in half the time it takes spider mites to develop, and the offspring have an even higher proportion of females than spider mites. When the food source is gone, the predator will die off. Order a minimum of 5 per sq/ft for every foot of plant height. Introduce weekly (up to four weeks approximately) or until control is achieved. Amblyseius californicus also works well in combination with Phytoseiulus persimilis. Because of their ability to survive at low pest densities, they will be around to deal with a pest flare up should it occur. You can’t introduce too many or too often with either of these predators. Two other spider mite controls have the ability to fly; the predator beetle Stethorus punctillum (the Spider Mite Destroyer), applied every other week for 4 weeks at 1 per sq/ft, and the predatory midge Feltiella acarisuga applied every week for 3 weeks at 1 per sq/ ft. Both have a good reputation, and both are pricey. They would each complement an introduction of Phytoseiulus persimilis. It is important to read all biological controls instructions before use.
Problem – “Fungus Gnats (Sciarid Flies)”
Fungus gnats are small gray-black flies that measure about 1/10 of an inch long. They have long legs and antennae. The antennae are beaded with 14 segments. Their clear wings have a Y-shaped vein, which is easily visible with a 10X magnifier. Female gnats mate within hours of becoming an adult, and lay between 50 and 300 eggs on the growing media’s moist surface. Upon hatching, the Fungus gnats begin maturing, going through 4 maggot-looking larval stages over a 1 to 2 week period, before becoming pupae. The larvae will cause direct and indirect damage. Direct damage, caused by the larvae feeding on the roots, makes it harder for the plant to uptake water and nutrients. That’s bad enough, but it’s the possibility of indirect damage that is really scary. The damage done to the roots cause wounds, and these wounds can be an entry point for any number of viral or fungal attacks on the plant. The adult gnats as well as the larvae can be carriers of these pathogens.
Fungus Gnat Prevention and Detection
Use a horticultural insect screen over all intake fans. Avoid over-watering and try to minimize algae and mold growth. Adding a 2" layer of perlite to the top of growing media in a pot reduces the suitability for egg laying on its surface. Some growers, who know they are likely to develop a problem, will introduce the insect-killing nematode Steinernema feltiae to the growing media at a minimum rate of 60,000 per sq/ft. This helps stop an infestation before it gets started. The nematodes can remain in the growing media for long-lasting protection. Other options are the predatory mites Hypoaspis miles and Hypoaspis aculeifer. They are commonly introduced, prior to an outbreak, at a rate of 12 per sq/ft. They survive on other food sources in the absence of Fungus gnat larvae. Remove or do not use the perlite topping if you intend to introduce the Hypoaspis predator mites. Yellow sticky traps are a good way to discover the beginnings of an infestation. Every garden should have them. You will see gnats on a trap before you notice them around your plants. Use a 5X or 10X magnifier to verify their presence.
Controlling A Fungus Gnat Infestation
Bacillus thuringiensis israeliensis, the popular mosquito control, is effective against Fungus gnats. The bacteria, when active, are viable for approximately two days. When the larvae get a bite of the bacteria, their digestive tract becomes paralyzed and they starve to death. The nematode Steinernema feltiae is long-lasting and controls the larvae quickly. The nematode enters the larva of the Sciarid fly via mouth, anus, or respiratory openings and starts to feed. This causes specific bacteria to emerge from the intestinal tract of the nematode, which spread inside the insect and multiply very rapidly. The bacteria convert host tissue into products, which can easily be taken up by the nematodes. The Sciarid larva dies within a few days. Introduce the nematode Steinernema feltiae at a minimum rate of 60,000 per sq/ft to the growing media. For a heavy infestation, introduce the nematodes once a week for 2 to 3 weeks.
The predatory mites Hypoaspis miles and Hypoaspis aculeifer can feed on a number of foods, with Fungus gnat larvae as its food of choice. It will also feed on thrips pupae and springtails. It does feed on nematodes, but not if the pests are present. Both predator mites have introduction rates for a light infestation of at least 24 mites per sq/ft. Heavy infestations call for a minimum of 60 mites per sq/ft. You can’t add too many. The more you add, the quicker the control.
You can monitor the progress of your larva control by placing 1" in diameter by 1/2" thick peeled, raw potato slices on the surface of the growing media. The larvae are attracted to the potato and will accumulate under it. Check and replace the slices daily. As you achieve control, you will find fewer and fewer larvae. It is important to read all biological controls instructions before use.
Problem – “Thrips”
There are several thrips species that are indoor garden pests, with Frankliniella occidentalis (western flower thrips) being the most common. The tiny thrips are much longer than they are wide, and generally yellow to orange-yellow in color. Other colors do exist and are anywhere from light to very dark. Eggs are laid in the plant leaf, stem, or flower tissue, and mature through four stages of growth over a period of about 2 to 4 weeks before reaching adulthood. Most thrips pupate in the growing media. Adults are mostly female and have the ability to reproduce in the absence of males. Females can produce over 100 eggs. Thrips cause damage by piercing plant tissue and sucking out the juice, weakening the plant. Thrips can also transmit viral diseases.
Thrips Prevention and Detection
Use a horticultural insect screen over all intake fans. The nematode Steinernema feltiae can be applied to the growing media, at a minimum rate of 60,000 per sq/ft, as a precaution. A weekly spraying with a biosurfactant and a neem product will help create an inhospitable environment. Do not use a spray if you are going to make preventive introductions of a bio-control. Introduction of the predatory mite Amblyseius cucumeris, at 5 per sq/ft every two weeks, is sometimes used. They feed on the eggs and larvae on the plant. The Hypoaspis mite (which feeds on pupae in the growing media) can be introduced one time, at 12 per sq/ft. The predatory bug Orius insidiosus feeds on all stages of thrips as well as spider mites and aphids. They can be introduced two times, at 1 per sq/yd, two weeks apart. Yellow sticky traps are a good way to discover the beginnings of an infestation. Use a 5X or 10X magnifier to verify the presence of thrips. When monitoring the garden, look for plant damage in the form of silver-grey striations on the leaves or flowers as well as blackish fecal matter where the thrips have fed.
Controlling A Thrips Infestation
If you have an advanced thrips infestation, apply a soap spray (see Spider Mites). The nematode Steinernema feltiae will control the pupae when applied to the soil (see Fungus gnats) and adults and larvae on the plant when applied as a foliar spray. The predatory mites Hypoaspis miles and Hypoaspis aculeifer (see Fungus gnats) will eat pupae in the soil. Amblyseius cucumeris can be introduced once a week, at a rate of at least 12 per sq/ft for every foot of plant height, until control is achieved. Release Orius insidiosus at a rate of 1 per sq/ft, 3 to 4 times weekly. It is important to read all biological controls instructions before use.
Problem – “Mealybugs”
Mealybugs cause damage to several crops in indoor gardens, particularly many types of tropical plants. The most common indoor mealybugs belong to the genera Planococcus and Pseudococcus. The mealybug has five stages in its life cycle. The females go through the stages of egg, three nymphal stages and adult insect; the males go through egg, two nymphal stages, false pupa and adult insect. Nymphs and female adults feed on plant sap producing white wax-like secretions and honeydew. This reduces growth and causes deformation and/or yellowing of the leaf; sometimes leaves or flowers drop off the plant.
Mealybug Prevention And Detection
Use a horticultural insect screen over all intake fans. Always carefully inspect any plants, particularly tropical, before purchase.
Controlling A Mealybug Infestation
Soap or oil sprays are effective at reducing pest populations. The most commonly used predator is the Cryptolaemus montrouzieri (mealybug destroyer). Crypts are a specific type of ladybug. They are also used to control scale infestations. Release at a rate of 1 per sq/ft every other week for 2 to 4 releases.
Problem – “Aphids”
There are many aphid species that are indoor garden pests. They are usually pear-shaped with dual-exhaust like tubes on their top rear. They come in a rainbow of colors, such as yellow, green, pink, blue, gray, black, and more. If populations become large, some will grow wings and disperse. Indoors, they are virtually all females and they give birth to live young who are ready to eat. Females produce from 40 to 100 offspring, each of which starts producing its own offspring in about 7 days. Aphids feed by inserting a straw-like proboscis into the plant and sucking plant sap. This weakens the plant and potentially infects the plant with viral disease. They will also deposit honeydew, which encourages the growth of sooty molds.
Aphid Prevention and Detection
Use a horticultural insect screen over all intake fans. Don’t bring new plants into your garden from an outside source (see Spider Mites). Weekly spraying with a biosurfactant and a neem product will help create an inhospitable environment. Do not use a spray if you are going to make preventive introductions of bio-controls. Preventive introductions of the parasitic wasp Aphidius colemani, at a rate of 1 per sq/ft once a week, is often used in at-risk gardens. When monitoring the garden, look for dry, white skins left behind when the aphids molt, and look at the tips of the plants for groups of aphids. Ants are sometimes present as well.
Controlling An Aphid Infestation
If you have an advanced infestation, apply a soap spray (see Spider Mites) before you introduce any predators or parasites. The nematode Steinernema feltiae, applied as a foliar spray, may attack aphids, but I could not find any research to confirm this. However, research does show it is effective on the aphid’s cousin the whitefly. Common controls of aphids are Aphidoletes aphidimyza (1 per sq/ft once a week for 3 weeks), Aphidius colemani (1 per sq/ft twice a week for 3 weeks), Lacewing (5 per sq/ft every 2 weeks until control is achieved), and Ladybugs (2 per sq/ft twice a week for 5 weeks).
It is important to read all biological controls instructions before use.
Problem – “Whitefly”
There are several whitefly species that are indoor garden pests, with Trialeurodes vaporariorum (greenhouse whitefly) being the most common. The whitefly is tiny and white, and has a moth-like appearance. It has six life stages; egg, followed by four larval stages, and then the adult stage. A unique characteristic of the whitefly is their almost magnetic attraction to the leaves. When disturbed, the adults will fly out, but immediately return to the underside of the leaves. Larvae and adults both feed by piercing the leaves and sucking the plant sap. This weakens the plant and potentially infects the plant with viral disease. They will also deposit honeydew, which encourages the growth of sooty molds.
Whitefly Prevention and Detection
Use a horticultural insect screen over all intake fans. Don’t bring new plants into your garden from an outside source (see Spider Mites). Weekly spraying with a biosurfactant and a neem will help create an inhospitable environment. Do not use a spray if you are going to make preventive introductions of a bio-control. Preventive introductions of the parasitic wasps Encarsia formosa and/or Eretmocerus eremicus can be released at 1 per sq/ft every 2 weeks. Yellow sticky traps are a good way to discover the beginnings of an infestation, and whiteflies are very easy to identify.
Controlling A Whitefly Infestation
If you have an advanced infestation, apply a soap spray (see Spider Mites) before you introduce predators or parasites. The nematode Steinernema feltiae, applied as a foliar spray, will attack adults and larvae. Research shows to use 15,000 nematodes per liter of spray to be effective, though I would not hesitate to use many more than this. The parasitic wasps Encarsia formosa and Eretmocerus eremicus are effective weapons against whiteflies, but I was unable to find out whether nematodes would harm the beneficials. One or both of the parasitic wasps can be released at 1 per sq/ft on a weekly basis until control is achieved. Delphastus cataliniae (whitefly destroyer) is a tiny black ladybug that loves to eat whitefly eggs and larvae. Release 1 destroyer per sq/ft weekly, 3 to 5 times, and then just once a month thereafter.