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I have been gardening in the Lehigh Valley for 11 years. Every year I grow garlic and assorted other onions. Last summer, I lost my whole garlic crop to allium leaf miners; it was the first time I have ever had a problem with my garlic or encountered this pest. It persisted through the summer on my Egyptian walking onions and chives. How do I prevent it from attacking the garlic I planted in October, when it warms up and starts growing? I read about crop covers but that won’t solve the problem if the pest is in my soil. I have looked into beneficial nematodes, been and other botanical oil preparations but I am unsure of timing of application and effectiveness.

Is this a new pest for the Lehigh Valley? The only change in my gardening practice is I spread a 8-10? layer of compost from Green Pond on my beds. I live in downtown Bethlehem with a small urban vegetable garden. These miners did not attack my globe alliums, interestingly. Thanks for your help.

The Allium leaf minor (Phytomyza gymnostoma) is a non-native pest, first located in the Lehigh Valley in 2015 according to Cornell University (news.cornell.edu/stories/2020/06/treatments-tested-invasive-pest-allium-crops).

As the name suggests, this pest attacks members of the allium family (chive, garlic, leeks, onions scallions and shallots), Adults are flies, about an eighth of an inch long, black with orange patches on the head. Both sexes feed on plant sap and the females puncture leaves and lay eggs.

The wounds appear in a line as a serious of round wounds. Larva hatch and grow in the stem and pupae emerge in late September. They winter over in the garden debris, weeds or nearby garden soil and emerge again in mid-March through April. Wild alliums, like wild garlic and onions, are a major source for spreading the pest.

Adults are most easily located on the tops of leaves during cool spring mornings.

Attacks against alliums last about five to seven weeks and occur in the spring and fall. Larvae eat from the tops of the leaves down toward the base, where they pupate.

Option one: Netting is a good option, but it must be in place before the adults emerge and take flight. The netting should remain in place for about seven weeks. For best results, net as soon as you set out transplants or greens emerge. Hand pick and destroy any infested leaves immediately.

Option Two: Crop rotation is another good control. Allow at least a year, preferably longer, before planting any allium family member in the same spot as a previous allium crop. This is to decrease any infestation from pests in the soil.

Option Three: Chemical control is effective, but must be limited to products safe for use on food crops. Sprays of dinotefuran, cycantraniliprole and spinetoram work well but are not acceptable for most home gardeners.

Spinosad is a naturally occurring ingredient in some insecticides and some products are approved for use in organic growing. It is applied to bare roots, or in plug trays for plant starts. See National Pesticide Information Center article (npic.orst.edu/factsheets/spinosadgen.html). Spinosad is produced by a soil bacterium and is used to control several pests including ants, fruit flies, leaf miners, mosquitoes and thrips.

So my suggestions would be to practice good sanitation in the garden, removing infested vegetation as soon as discovered and dead plant material at the end of the growing season. Gathered materials should be destroyed not composted.

Use fine netting to exclude adults from March through April. Consider using spinosad, dusted on leaves if your plants are already under attack.

For additional and more technical information, I suggest the Rodale Institute website article, Organic Management Practices for Allium Leafminer Pest (rodaleinstitute.org/science/articles/organic-management-allium-leafminer-pest/).

These brief but warm bursts of early spring are waking the garden, and gardeners often worry about spring bulbs that leaf out. As long as it is only the leaves or tightly closed buds, the cold temperatures between warm ones will not hurt the spring bulbs. It is when plants are leafed out and bud are blooming or at least showing color that we lose our spring flowers.

Sue Kittek is a freelance garden columnist, writer, and lecturer. Send questions to Garden Keeper at grdnkpr@gmail.com or mail: Garden Keeper, The Morning Call, PO Box 1260, Allentown, PA 18105.

Planting: Indoors, start seed for Dianthus. Finish sowing seeds for transplanting Ageratum, lobelia, scabiosa, torenia and verbena. Next week start Dahlia, larkspur and portulaca. Create and follow a schedule for starting seeds. Check packets for instructions such as start indoors four weeks before last frost date. Then, using a calendar, count back from your area’s date (May 10-15) for the appropriate starting time.

Seasonal: Cut back ornamental grasses. Divide when you see new green growth. Examine trees and shrubs. Note damaged limbs and candidates for winter pruning. Please check proper pruning information for each plant and prune as needed and recommended. Take cuttings of African violets and geraniums. Check germination rate for all stored seeds and replace those that perform badly with fresh seed this year. Check for heaved plants, particularly when soil temperatures are fluctuating between freezing and thawing. Get seeds for plants you intend to grow from seed. Keep pathways, driveways and guttering clear of dead plants and leaves.

Cut the flower stalks of amaryllis plants after the flowers fade but keep the greens warm and watered in a sunny area if you plan on keeping them until next year.

Move in some of those bulbs you potted this fall for forcing.

Chores: Keep de-icing materials, shovels, scrapers and other winter tools in a convenient space. Maintain winter equipment. Use fresh gas and check for damage before or after each use. Clean seed starting containers and other pots. Check supplies for spring and purchase as needed. Use a humidifier, humidity trays or misting to increase the humidity around your houseplants. Mark off beds, new plantings, plants that are late to break dormancy in the spring and delicate plants. Provide deer, rabbit and groundhog protection for vulnerable plants. Reapply taste or scent deterrents. Clean and fill bird feeders regularly. Clean up spilled seed and empty hulls. Dump, scrub and refill birdbaths at least once a week. Consider a heater to provide water during cold weather. Clear gutters and direct rainwater runoff away from house foundations.

Tools, equipment, and supplies: Inventory, clean, disinfect, restock, and store seed starting and potting supplies. Clean and repair spring/summer tools. Replace or send for service now.

Safety: Photograph storm damage before clearing or repairing for insurance claims and file promptly. Avoid tick and mosquito bites: Use an insect repellent containing Deet on the skin. Apply a permethrin product to clothing. Wear light-colored clothing, long sleeves, hats and long pants when working in the garden. Stay hydrated. Drink water or other non-caffeinated, nonalcoholic beverages. Apply sunscreen, wear hats and limit exposure to sun. Wear closed-toe shoes and gloves; use eye protection; and use ear protection when using any loud power tools.

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