“What’s that bug doing on my bean plants”? “Should I be worried by these droopy leaves”? “Help – the lower leaves on my container tomato plants are turning yellow. What should I do?”
HGIC is receiving many questions from first-time vegetable gardeners this year through our Ask an Expert service. It’s great to see more people growing some of their own food! We are trying to address specific concerns and help people learn how to prevent problems and garden sustainably and lovingly on Planet Earth. Our food gardens can be peaceful and restorative spaces and exciting laboratories where problems can be learning experiences.
Here are some of the major concerns of new vegetable gardeners:
Plants just don’t get big and healthy
The first step in IPM (integrated pest management) is to know and meet the needs of your plants. Healthy, resilient plants are better able to withstand pests, diseases, and challenging weather. When plants look weak, under-sized, and stressed we need to ask some basic questions: Is it the right plant for our climate? Does it get enough sunlight, and does it have enough room to grow? Is the container too small? Was it planted at the right time? Is the plant getting enough water and nutrients?
No fruits from summer squash and cucumber plants
Many gardeners are frustrated by plants that aren’t producing many (or any) fruits. This family of plants requires cross-pollination. Pollinating insects must move pollen from male to female flowers multiple times before a full-size fruit will form. Most of the first flowers are male flowers and when female flowers do appear (they can be identified by the small, undeveloped fruit below the flower) they may drop off. Small fruits may also dry up and drop off. This is caused by incomplete flower pollination or fertilization of the tiny undeveloped seeds (ovules), caused by low pollinator activity or heat stress. If the plants are healthy you will start to see more fruits as the season progresses. In the meantime, you can try hand-pollinating individual female flowers using a small, soft paintbrush or the male flower itself. There are many online videos to show you the way.
Spots, marks, blotches on leaves
Plant leaves do not need to be perfect to be healthy. Some leaf spots are indeed symptoms of a disease, insect or mite pest, and some of these can injure and kill plants. However, many leaf imperfections are not a cause for alarm. They may be caused by minor insect feeding, environmental conditions, and even misuse of fertilizers and pesticides.
Wilting leaves and stems
Plant leaves and stems that begin to go limp are a serious concern. A lack of moisture is the most common cause, especially for container vegetables or gardens planted in sandy soil. Root damage from cultivation, insect feeding, diseases, and waterlogged soil can also cause wilting symptoms. It’s important to quickly figure out why a plant is wilting.
Distinguishing major and minor insect pests
Hundreds of different insect species will visit your garden each year. Some are beneficial to gardeners, many are innocuous, a few are minor pests, and a very small number are serious pests. They are all fascinating and interesting to observe! Close monitoring of plants, including leaf undersides, will help you detect and manage the serious insect and mite pests:
These are examples of three relatively minor pests in vegetable gardens:
When to cut your losses?
Every growing season you will probably have some crops that fail for a variety of reasons. Your garden will be more productive if you learn when it makes sense to pull out ailing plants and re-plant the area. Of course, figuring out what caused the plants to fail is the key to preventing the same problem next year.
Tips for dealing with plant diseases
Many bacterial, fungal, and viral diseases attack vegetable crops in Maryland home gardens. Most of them can be managed without significant yield loss and in very few cases is spraying a fungicide recommended.
Foliar diseases can vary in severity from season to season according to rainfall and temperature. Regular plant inspection, especially on lower and inner leaves, will alert you to problems. Foliar diseases are progressive- they begin as small spots on a few leaves. Lesions grow and coalesce and may cause leaves to yellow and die. Identify problems early on to determine the cause of the problem.
- Select disease-resistant varieties, particularly for those diseases that appear in your garden each year.
- Purchase certified, disease-free potato tubers, garlic bulbs, and asparagus and rhubarb crowns.
- Avoid planting on wet, poorly drained sites. Plant in raised beds if drainage is not very good.
- Add organic matter to your soil each year.
- Grow healthy plants by providing adequate light, water, and nutrients. Give each plant adequate space to ensure good air circulation.
- Keep bare ground covered with an organic mulch.
- Avoid watering foliage in the evening. It is best to use soaker hoses and drip irrigation, or water around the plant base where it can quickly reach the root zone.
- Avoid handling wet foliage.
- Harvest your vegetables before they become over-ripe.
- Cut off and discard leaves and pull up and discard entire plants that are badly infected by disease.
- Clear your garden at the end of the season of all plant debris. This should be composted or tilled into the soil. Plant parts infected with especially damaging diseases, like late blight of tomato and potato, southern blight, and white rot (garlic and onions), should be bagged and put out with your trash.
- Keep weeds to a minimum and control those insect pests like thrips, aphids, flea beetles, and cucumber beetles that are most likely to spread diseases.
- When disease symptoms are observed it is often too late to apply a fungicide, although fungicide treatments can help to protect new or un-infected foliage. Fixed copper, sulfur, and horticultural oil are some organic fungicides used by home gardeners. Always, carefully read and follow all pesticide label information and test the spray on a small part of the crop to check for signs of leaf injury (phytotoxicity). Don’t spray on very hot and humid days.
Keep notes this year on plant issues to help you avoid them or manage them better next year. Keep planting and growing!
By Jon Traunfeld, Director, Home & Garden Information Center.