Seedcorn Maggot
Delia platura
📖 Description
The seedcorn maggot is one of the most widespread and polyphagous root maggot species, attacking a broad range of crops including corn, beans, peas, and various vegetables. Unlike the onion maggot, which is a specialist on alliums, seedcorn maggots are generalists attracted to decaying organic matter and germinating seeds. They are most damaging in cool, wet spring conditions when germination is slow, giving larvae extended time to feed on seeds before they can establish. The flies are particularly attracted to freshly turned soil with high organic matter content, making spring-planted cover-cropped fields especially vulnerable.
⚠️ Symptoms to watch for
- Poor or patchy seed germination,Maggots found inside germinating seeds,Wilting and death of emerged seedlings,Hollowed-out seeds that fail to sprout,Reduced plant stand in early plantings
🩹 Treatment
- Plant seeds treated with an insecticide seed coating (chemical),Apply beneficial nematodes (Steinernema spp.) to soil before planting (organic),Use floating row covers after planting to prevent egg-laying (organic),Apply chlorpyrifos or terbufos granules in-furrow at planting (chemical)
🌿 Organic treatments
- Apply beneficial nematodes (Steinernema spp.) to soil before planting,Use floating row covers after planting to prevent egg-laying
🧪 Chemical treatments
- Plant seeds treated with an insecticide seed coating,Apply chlorpyrifos or terbufos granules in-furrow at planting
🛡️ Prevention
- Avoid planting in freshly tilled soil with high organic matter content,Allow tilled soil to settle for 1-2 weeks before planting,Plant when soil temperatures are warm enough for rapid germination,Remove and compost crop residues well before planting
🪴 Affected plants
- Corn,Beans,Peas,Squash
🦋 Natural predators
- Ground Beetles,Rove Beetles,Parasitic Wasps,Birds
🌱 Host plants
- Zea mays,Phaseolus spp.,Pisum sativum,Cucurbita spp.
🔄 Lifecycle
- Seedcorn maggots produce three to five generations per year.
- They overwinter as pupae in the soil.
- First-generation adults emerge in early spring and are attracted to decaying organic matter and germinating seeds for egg-laying.
- Larvae feed for 1-3 weeks before pupating in the soil.
- Subsequent generations follow through the summer, though later generations are generally less damaging.
- The lifecycle from egg to adult takes about 3-4 weeks in warm weather.
📅 Season
- Spring to Fall (most damaging in early spring)
🔎 Appearance
- Seedcorn maggot adults are small, grayish-brown flies closely resembling onion maggot flies but slightly smaller, with a more olive-gray body and dark legs.
- Their eyes are reddish-purple and the thorax has three dark stripes.
- Larvae are creamy white, legless maggots tapered at the head end, identical in general form to other Delia species.
- They are found inside germinating seeds or in the roots and stems of seedlings.
- Eggs are small, white, and elongated, laid in moist soil near germinating seeds or organic matter.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- North America
- Europe
- Asia
- South America
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