Shore Flies and Fungus Gnats: A Guide for Greenhouse Growers
Introduction
Greenhouses provide a perfect environment for a variety of insects, including shore flies and fungus gnats. While both insects can be a nuisance, only fungus gnats can cause damage to plants. This article will help you identify the differences between these two insects and provide tips for controlling them in your greenhouse.
Shore Flies vs. Fungus Gnats
Shore flies and fungus gnats are both small, flying insects that are commonly found in greenhouses. However, there are some key differences between the two insects:
- Appearance: Fungus gnats are dark brown to black and resemble mosquitoes. Shore flies, on the other hand, look like fruit flies with short antennae.
- Behavior: Fungus gnats are weak fliers and can often be spotted resting on top of potting soil. Shore flies are stronger fliers and will often be buzzing around the greenhouse.
- Diet: Fungus gnats feed on decaying organic matter, fungi, and algae in the soil. Shore flies feed on algae and are usually found in areas of standing water or underneath benches.
- Damage: Fungus gnats can damage plant roots by feeding on them. Shore flies do not damage plants.
Identifying Shore Flies and Fungus Gnats
The best way to identify shore flies and fungus gnats is by their physical characteristics.
Fungus Gnats
- Dark brown to black in color
- Resemble mosquitoes
- Weak fliers
- Often resting on top of potting soil
- Larvae are white to translucent with black heads
Shore Flies
- Look like fruit flies with short antennae
- Dark wings with five light dots
- Strong fliers
- Often buzzing around the greenhouse
- Larvae are opaque and lack a distinct head
Controlling Shore Flies and Fungus Gnats
There are a number of ways to control shore flies and fungus gnats in your greenhouse.
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Cultural Control:
- Remove any infested growing media and plant debris.
- Do not overwater plants, which can lead to algae growth.
- Avoid using fertilizers that contain high levels of nitrogen, which can also promote algae growth.
- Replace potting media that has a lot of organic matter with a mix that has less.
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Biological Control:
- Bacillus thuringiensis israelensis (Bti) is a bacterium that can be used to control fungus gnats.
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Chemical Control:
- There are a number of pesticides available for the control of shore flies and fungus gnats. Consult with your local extension agency for information on chemical controls.
Additional Tips
- Use yellow sticky traps to trap fungus gnats.
- Use blue sticky traps to trap shore flies.
- Place traps horizontally at the crop canopy.
- Use 10 traps per 1,000 square feet of greenhouse space.
By following these tips, you can effectively control shore flies and fungus gnats in your greenhouse and protect your plants from damage.
