Onions, Green Onions, Garlic and Leeks | University of Maryland Extension

Updated: October 23, 2024

Garlic Bulb Mites

Bulb mites (usually Rhizoglyphus spp) are a problem of garlic that easily go unrecognized. Usually growers notice a general yellowing of their garlic plants with the tips of leaves often turning brown (fig 1). If you examine the bulb it can have feeding marks on the outside of the bulb (fig. 2) or the basal plate can separate easily from the bulb (fig. 3).

Garlic plants with early signs of root/bulb problems

Updated: October 23, 2024

Check for Allium Leaf Miner in Onions and Leeks

If you grow leeks or onions or other Allium species, you should already be checking for the tell-tale marks left by Allium leaf miner. Allium leaf miner Phytomyza gymnostoma tell-tale marks consist of many linear small white dots (made by the female’s ovipositor) that appear in the middle towards the end of leaf blades (fig. 1) of their preferred hosts of leeks, onions, garlic and other Allium species. Spring crops are usually not as hard hit as fall crops especially when looking at leeks, but this pest has been steadily increasing its geographical range each year and its damage potential. If you had some infestation last year you will especially want to be looking for the signs of this pest.

Updated: October 23, 2024

Allium (Onion) Leafminer

The allium leafminer Phytomyza gymnostoma (also known as the onion leafminer) has recently been detected and confirmed from infested leeks in Lancaster County, PA. This is the first confirmed infestation in the Western Hemisphere.

Updated: October 23, 2024

Allium Leaf Miner Active Soon

If you grow leeks or onions or other Allium species, now and for the next few weeks is the time to watch for the tell-tale marks left by Allium leaf miner. Allium leaf miner Phytomyza gymnostoma tell-tale marks consist of several small round white dots (made by the female’s ovipositor) in a row that appear on the middle towards the end of leaf blades (fig. 1) of their preferred hosts of leeks, onions, garlic and other Allium species.

Updated: October 23, 2024

Garlic Bloat Nematode Found in Several Garlic Samples

This must be a bad year for garlic because besides finding bulb mites we also have found garlic bloat nematode in several samples of damaged garlic. I wrote about this nematode last year and advised garlic growers to watch for it and to test any bad looking bulbs for it.

The lack of roots on one side of plate and bulb deformation can be indicators of bloat nematode infection.

Updated: October 22, 2024

Virus Problems Found in Garlic

Garlic growers may be noticing symptoms of virus infection in their plants that show yellowing tips on many leaves with some that are completely yellow (fig 1). If you look closely at the yellow leaves you will see mottling or striping on the leaves (fig 2). These symptoms are usually more pronounced on young leaves. Infected plants are stunted and bulb size can be reduced. Garlic crops infected with viruses are usually more susceptible to weather conditions like extreme heat, and do not keep well post-harvest.

Fig. 1 Garlic plants showing symptoms of infection with virus complex

Updated: October 22, 2024

White Rot of Onion and Garlic

The weather we had in May was great for seed maggots and for some soil diseases. One very serious soil disease that affects Allium species, especially onion and garlic, is white rot, caused by the fungus Stromatinia cepivorum (syn. Sclerotium cepivorum (fig. 1)), which was found in the last few weeks in Maryland.

Updated: October 22, 2024

Vegetable and Fruit News-April 2022

Fruit and Vegetable News, Volume 13, Issue 1 (April, 2022). Topic in this issue are: Check for Allium leaf miner in onions and leeks over the next few weeks, Edema problem in high tunnel tomatoes, Using Plant Growth Regulators to Improve Apple Return Bloom, Botryis Fruit Rot (Gray Mold) and Crown Rot in Strawberries, Spring Pest Scouting in Strawberries, and Early Spring Vegetable Insect Scouting Tips.

Fruit and Vegetable News April 2022 header

Updated: June 13, 2024

No-Till Spring Vegetables After Forage Radish Cover Crop (FS-1134)

Authors: Natalie Lounsbury - Ray Weil

A late August seeding of forage radish (Raphanus sativus L.) can eliminate the need for tillage before many early spring vegetable crops like spinach, beets, peas, onions, and even carrots under certain soil conditions in Maryland. In addition to reducing soil disturbance, not having to till prior to spring planting reduces labor requirements at a critical point in the season and may allow earlier planting. Forage radish, which winterkills when temperatures drop to 17-20°F, suppresses early spring weeds, allows soil to dry out and warm up, and provides an increased supply of N, S, P and other nutrients to crops in early spring. Because of the minimal amount of residue after forage radish, conventional planting equipment can effectively seed directly into the winterkilled cover crop without tillage. For early transplanted crops like onions, rows of radish can create holes into which transplants can be dropped. Experiment station results in Maryland and farmer trials throughout the mid-Atlantic and northeast have shown that this system requires a closed cover crop canopy in fall and may be ineffective in poorly structured, heavy soils. Authors: Natalie Lounsbury and Ray Weil; Title: No-Till Spring Vegetables After Forage Radish Cover Crop (FS-1134).

Updated: February 2, 2024

Vegetable and Fruit News-July 2022

Vegetable and Fruit News, Volume 13, Issue 4 (July 2022). Topics in this issue are: Disease of Garlic Scapes, Blossom End Rot, Preventing Bruising in Apples and Peaches, Corn Disease Identification, Tomato Spotted Wilt Virus, Tomato Pith Necrosis, July IPM Tips, Mowing: IWM Tool, and Upcoming Events