Greenhouse & Indoor GardeningPest Control

A Checklist for Keeping the Bugs Out of a Greenhouse

An old saying says “An ounce of prevention is worth a pound of cure”; and, when it comes to greenhouse a pest problem, that is certainly true. The following list is meant to give you several ways to help ensure that your greenhouse is pest free. The more of these practices that you can integrate into your greenhouse gardening, the better chance you will have in winning the war against undesirable garden pests.

Start Plants from Seed

Consider starting plants from seed. There is an advantage of starting plants from seeds. Even if you buy plants at a nursery or a garden center, you can not be assured that the plants are perfectly clean.

Treated Seeds Have Benefits

Treated seeds aren’t for everyone but they may be safer for starting your greenhouse plants. Organic growers often require untreated or organically grown seed. These seeds could be more likely to carry a seed-borne bacterial or fungal disease.

Used Trusted Suppliers

If you have been getting plants from a good producer and have not had problems in the past, it would be a good idea to stick with that supplier, even if the prices are a little higher.

Repot Outside

Repot plants outside of the greenhouse and any used pots should be cleaned and disinfected with a 10% bleach solution before use.

Go Soilless

Use commercially available soilless mix as the media for seed starting and potting greenhouse plants. The purpose for this is to exclude insect and microbial pests that often live in soil.

Stay Off the Ground

Having some planting space on the floor of a greenhouse can be advantageous, but if the ground on the floor is not protected with a barrier, soil born pests may dig their way in from the outside.

The Greenhouse Comes First

Whenever possible, work in your greenhouse first before working in your outside garden. This helps you avoid bringing pests and diseases that live outside the greenhouse into the greenhouse.

Wash Your Hands

Washing your hands before going to the greenhouse should be a consistently practiced habit. This is particularly important after working with any plant, or even working with produce in the kitchen.

Change Your Clothes

A change of clothing may even be in order before entering the greenhouse if you have been in close contact with plants, grass, or dirt/mud. If you have been walking through grass or mud, it is a good idea to remove your footwear, before entering your greenhouse.

Limit Visitors

Consider possible contamination by visitors to your greenhouse. You and your visitors should not enter the greenhouse after being in another greenhouse, a garden, or an agricultural field.

Wash Your Tools

Sometimes insects, mites or diseases can be taken into the greenhouse on garden tools that have been used outside. Thoroughly wash all tools and disinfect them with a 10% bleach solution before bringing them in the greenhouse and in between working on separate plants.

Keep the Boxes Out

Materials or items that have been exposed to plants or produce are a source of contaminants. Used produce shipping boxes and plant shipping boxes may be very useful, but they should never be taken into the greenhouse.

No Pets

Sorry pet lovers! Dogs and cats, that live or spend time outdoors, should never be allowed in the greenhouse.

Screen Your Intakes

Air intakes to the greenhouse should be screened with a very fine mesh. A screening box will need to be built so the screen area can be at least five times the area of the greenhouse air intake, as to not restrict airflow.

Consider a Double Door

It may be difficult in some greenhouse applications but consider if a double door is possible. This is particularly helpful in keeping moths and butterflies out. Moths and butterflies are not generally a problem themselves, but when they lay their eggs on your plants, they will soon be caterpillars and start to eat their hosts. On your daily rounds remove any of them that are present.

Keep Plants Away From the Door

Outside plants should not be kept near the greenhouse door. These plants can be a safe harbor for bugs waiting for a chance to get in the greenhouse.

Use Bug Traps

Bug traps (sticky cards) can help in early detection of some flying and crawling pests.

Frequent Inspections

Take the time to inspect plants as often as possible for visual predators or damage caused by harmful pests, fungus, bacteria, or disease.

Beneficial Insects

Consider adding beneficial insects to the greenhouse. But keep in mind that to survive some of these require that food insects are already present in sufficient number. Vendors of these insects can help in selecting the right kind for the job. This is a good list of insects that are considered to be beneficial in a greenhouse environment.

Dr. Christopher J. Kline is a master gardener and writer living in Paradise Valley Arizona.

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