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Being organized, clean and keeping a greenhouse and garden maintained will keep the plants mostly pest and disease free but you should lookout for common gardening challenges such as bugs, rodents, frosts, heat waves, and fungus.


Root maggots can infect radishes, onions, cauliflower, turnips and related crops. The simplest solution is to keep crops covered with a floating row cover for May and early June when the flies are out laying their eggs. Onions are particularly prone to root maggots and should remain covered from the time they sprout until they are harvested. Any roots with a maggot infestation should be put in the garbage, not in the compost where the larvae can live through the winter and return to attack plants next year.

Tip: Plant onions the first week of June to avoid the 1st crop of onion flies which is the most devastating. Do not plant onions in same place for 2 years. Try using cayenne, dill on the ground and moth balls in jars to fend of flies right from the start. Use a combination of deterrents.

Aphids are small sap-sucking insects which are among the most destructive pests in the garden. The removal of sap creates a lack of vigor in the plant, and aphid saliva is toxic to plants. Aphids frequently transmit disease-causing organisms like plant viruses, bacteria and fungi to their hosts. Symptoms of aphid damage can be as varied as decreased growth rates, mottled leaves, yellowing, stunted growth, curled leaves, browning, wilting, low yields and death. For limited infestations, using an insecticidal soap or simply spraying the plants thoroughly with a strong water jet every few days is generally sufficient to control the problem. Heavily infested plants should be removed and placed in the garbage.

Tip: Plant Marigolds in a pot and place around your plants. The aphids will be attracted to them and you can quickly and easily remove the pot and put in the garbage to avoid mass infestation.


Gophers can be an ongoing challenge throughout the summer. They can be trapped live and relocated to a different site away from your greenhouse and/or garden. It is important that the live traps are checked every few hours so that the animals are not harmed or unduly stressed for longer periods. Remember to pick them up at the end of the day.

There may be the odd mouse or vole around. Try to prohibit them with fine mesh chicken wire around the garden beds, and the bottom of the greenhouses.


The frost-free season is very short in the Yukon, usually from about mid-May or early June until mid-August or early September. If the morning air starts to feel cool and the forecast says it is going to get below 0 degrees overnight, it’s a good time to cover the outdoor garden beds. Start covering the outdoor garden beds in mid-August.

Tip: Use spare poly and cut it to size to cover the outdoor garden beds. Cover them over at the end of the day and open them up mid-morning the next day once it warmed up. This will protect the outdoor plants from frost before harvesting.

Heat Waves

Heat waves can dry surface soil quickly, which dehydrates shallow roots and water is also lost through the leaves in hot weather. The plants need thorough watering during a heatwave, which should be done early in the morning. In extreme hot weather a greenhouse and/ or garden may need a second watering later in the day.


Powdery mildew is a fungal disease that shows up as white, powdery spots on the leaves and stems of plants. It thrives in cool, humid conditions and cloudy weather can help it increase. Cucumbers, melons, strawberries and all types of squash are most affected by it. Powdery mildew can be controlled by spacing plants to allow for better air circulation, which will keep the humidity down. Aphids can carry powdery mildew and transmit it to surrounding garden plots, so monitoring and pest control are important.

Tip: To control or eliminate the powdery mildew, spray prone plants at the first sign of infection with milk diluted with water (mix 1:10 ratio of milk to water). Repeat applications weekly.

Damping off disease is a white mold that forms in the top of the soil. When starting bedding plants, little seeds are prone to this fungus. Damping off disease flourishes in cold, wet damp weather with little sunshine. It quickly spreads across the soil and wilts the seedling. Take its habitat away, and the disease cannot survive. The more you make conditions ideal for your plants, the more likely you will avoid damping off disease. Avoid starting the seeds in a basement and leaving them there for a couple of days. While the trays are conveniently out of the way, this is a perfect breeding ground for damping off disease.

Tip: If damping off disease does take hold in your seed trays, act immediately. Remove diseased sections to minimize the spread. If it has affected a significant number of plants, replant in new soil and clean containers. Do not reuse the soil.