Symptoms, Treatment & Prevention Submitted by Asima Chaudhary
taken from the Fall 2016 newsletter
August Saint-Gaudens, the renowned American Sculptor, once said, “[w]hat garlic is to food, insanity is to art.” Before I began researching for this article, I did not know that there was a variety in the types of garlic. For example, I did not know that there existed the braided soft neck garlic, and the purple stripe hard neck garlic. Apparently, the garlic that I repeatedly purchased and used in cooking is called the fresh elephant garlic. This season, I am very excited to plant garlic since it will be my first time. I heard that planting garlic can be a very easy-to-grow herb in the garden but it is also prone to disease. So I decided that before planting, I research and share my findings about garlic disease. There are several different types of diseases that can infect garlic. These include, but are not limited to: Basal Rot, White Rot, and Downy Mildew. Botrytis Rot and Penicillium Decay.
Prevention: Most of the major garlic diseases stem from the soil, so prior to planting garlic; you must assess the condition of your soil and should rotate it yearly. A healthy garden is key to growing healthy garlic. Thus, the first step to preventing fungus, e.g. fusarium, and other soil borne diseases is to ensuring that you plant the garlic in well-drained fertile soil. Also, once planted, make sure that when you are weeding the garden, you do not injure the roots because this would allow diseases to pierce the garlic via the broken plant tissue. Furthermore, when covering the garlic, it is important to know which type of covering is best for the garlic. For instance, mulch is helpful for evening out the moisture in the soil between rains and snow. Consistent soil temperature prevents the separation of the young roots from the cloves that results from repeated freezing and thawing resulting in frost heaves.
Types of Diseases and Symptoms:
- Basal Rot: Basal rot is a slow developer that causes the garlic leaves to become yellow and slowly die. Fungal growth, an indicator of Basal Rot, occurring at the base of the garlic bulb can lead to rotting before and after the harvest. The best way to prevent the disease from spreading is to remove theinfected plants immediately upon discovery. Additionally, by treating the garlic cloves with a hot water treatment before planting can reduce the chances of infectious diseases by one-half.
- White Rot: White Rot is just like Basal Rot, but the disease develops much faster and thus causes the plant to die much quicker. If there exists “white, fluffy fungal growth on the stem that extends around the bulb base,” then remove the plants immediately. “It is advisable to not re-plant in infested fields, but application of some iprodione products (Rovral-an agricultural product-not to be used on residential sites) at planting may help reduce disease incidence. Also avoid planting infested cloves. Pre- treating garlic cloves before planting can help reduce white rot. Hot water pre-treatment includes dipping cloves in hot water before planting, though the water should not be above boiling as this will kill destroy the cloves.”
- Downy Mildew: Downy Mildew causes white furry growth on and yellowing of the plant leaves. The younger plants will die and older plants will not continue to grow. To reduce Downy Mildew, space out the planting of the garlic because good air circulation prevents and reduces Downy Mildew.
- Botrytis Rot: Botrytis Rot is also known as “neckrot” because it causes “water-soaked stems and gray fuzzy fungal growth.” To prevent the Botrytis Rot, space out the plants and use disease free bulbs. Disease free bulbs apt for planting result from proper storage the year before, including drying the harvest immediately and storing the garlic in cool and airy spaces.
- Penicillium Decay: Penicillium Decay eventually causes the seed clove itself to decay because the disease affected the plant by stunting its growth and the plant seems lifeless and yellow. The garlic glove will be a bluish-green. To prevent Penicillium Decay, plant the gloves immediately after they crack and ensure that you do not injure the bulb. Also, when storing, immediate dry the gloves beforehand.
- Nematodes: Nematodes disease has a variety of infections: Ditylenchus dipsaci, Pratylenchus penetrans (lesion), and Meloidogyne (root knot) species are most commonly associated with Allium crops. The best method for preventing Nematodes is prevention from the onset. Soil or even bulbs can be tested for Nematodes at diagnostic facilities. Treating the bulbs with hot water may kills the nematodes in the bulbs, but once the soil is infested, crop rotation without garlic may be the only cure, but not a guarantee because of the varying persistent forms of Nematodes.
- Ensure that the soil of the fields is clean
- Start by cleaning from the cleaner parts of the soil and then proceed to the soil infested with disease and/or fungus.
- When removing an infested plant, clean the equipment immediately
- Ensure that the seeds you intend to plant are not infected
- If infection of plants still persists, rotate away from planting garlic for a couple of years.
Moyer, Michelle M. “Diseases of Garlic: Various Pests.” Cornell University, College of Agriculture and Life Sciences, 11/11 http://plantclinic.cornell.edu/factsheets/garlicdiseases.pdf
Pleaseant, Barbara. “All About Growing Garlic.” Mother Earth News, Oct. / Nov. 2009. Web 17 Sept. 2016