Garlic Diseases and Problems

How to plant garlic profitably
Edilberto Santiago
Greenfields December 1992

Like other crops, garlic is attacked by a number of pests and disease.

Insect and their control.

1. Thrips (Thrips sp.) These are the most serious insect pests of garlic. Nymphs and adults suck plant sap, especially the young leaves and growing points. The leaves and growing points. The leaves turn yellow , curl slightly and become silvery-white or brown. Small black dots become visible. If the infestation is severe, the leaves wilt and die.

Thrips are small; adults measure 1 to 1.20 millimeters long. They are pale to light brown in colow with brown markings on the abdominal segments. The nymphs are pale yellowish or greenish and often dusky. The uniform white eggs are laid on the underside of leaves. The incubation period is three days. The life cycle of the insects is from three to five weeks.

Control: Nymphs usually hide in the angles of leaves, rendering their control difficult. Early planting is recommended in October to avoid heavy infestation which usually occurs in late January to March. Remove and burn badly infested leaves and bulbs.

For chemical control, use either Diazinon 20 EC, Malathion E 57, Lannate 20 EC or Mesurol R. Start treatment when the plants are 30 to 60 days old. For December planting, apply the insecticide 20 to 25 days after planting. Frequency of application is 5-10 day intervals, depending on degree of infestation.

2.Mites (Aceria tulipae) These are so small that their presence in plants often goes unnoticed. They are either seedborne or mulchborne. Mite damage to garlic is often called “tangle top.” Affected plants become twisted and distorted with yellowish or pale green streaks on the leaves. The leaves may also not emerge readily from the cloves; they separate poorly after emergence.

Control: Seed piece treatment to control mites has been discussed earlier. As the insect can be mulchborne, spray rice straw with insecticide before spreading this on the field.

Twisted and unextruded young leaves can also be stretched, but this should be done in the afternoon when the leaves are somewhat wilted to avoid breakage.

For chemical control, use either Malathion E 57 or Parapest M EC. Apply as soon as signs of infestation appear. Apply every 7 to 14 days, depending on extent of infestation.

3.Tobacco moth (Ephestia elutella). This is the most serious storage pest of garlic.
The larvae enter into individual cloves pf bulbs and feed on the contents, leaving the cloves empty and dry. In serious cases, the damaged cloves turn powdery.

Control: Bulbs selected for seed purposes should be treated with insecticides before storing. Any of the insecticides used to control mites can also be used against tobacco moth. Dip the bulbs in the insecticide solution, air-dry for one day, then store at room temperature or hang bundled in a well ventilated place. Do not treat bulbs intended for the market or for home consumption. Properly storing bulbs can also minimize moth damage.

Disease and Control:

1.Fusarium bulb rot. This is a soilborne diseasecaused by the fungus Fusarium oxyporum F cepae (Hanzwa), Snyder and Jausen. It attacks the basal part of garlic plants especially the roots and bulbs, which become semi-watery and rotten. This causes progressive yellowing and drying of leaves. Eventually, the top parts of the plants collapse. If left unattended, the fungus will continue to invade the bulbs until they shrink and dry up.

Control: Plant only disease-free bulbs. Burn all field refuse after harvesting. Practice crop rotation for at least four-year intervals. Plow or rotavate the area early and allow it to dry for at least three months before planting. For chemical control, spray the appropriate fungicide.

2.Cercospora leaf spot. This is caused by the fungus Cercospora duddiae.
Lesion which start as small circular, chlorotic spots about 3 to 5 millimeters in diameter penetrate through the young leaves. The disease progresses rapidly after the original lesion fuse. Affected leaves eventually die.

Control: Use only disease-free planting materials.

Practice crop rotation, remove and burn weeds and maintain good field drainage. For chemical control, use the appropriate fungicide. Apply at 7 to 10 days interval. Follow the recommended dosage (indicated on the label).

3.Purple blotch. This is caused by the fungus A;ternaria porri (Ellis). Early
symptoms are small to gray sunken spots. The spots become purplish as they enlarge. Infected leaves turn yellow and soon dry up completely.

Control: Use either Dithane 45 or Manzale 200. Follow manufacturer’s recommended dosage and intervals of application. Also eliminate thrips, which are the vector of the disease and plant only disease-free seedpieces.

Harvesting and drying

Garlic matures 90 to 120 days after planting. Generally, early planting in a longer maturity period than late planting. The crop is ready for harvest when the bulbs are fully developed.
A good index of maturity is when the main stem above the bulb softens, the top has fallen, and when 75 percent of the leaves turn yellow. Many farmers wait until the flowering parts have emerged, especially if they are after bulbs intended for planting the following reason.

To harvest, pull individual plants carefully by hand. Place the plants under shade with the tops laid over adjacent bulbs. Allow the bulbs to dry for two to three weeks.

For faster drying place the newly harvested crop directly under the sun for 3 to 4 days. Then grade and bundle the bulbs in groups of 50 pieces.

Bundled bulbs should then be air-dried under the shade to preserve their quality.


Usually, the bulk of the garlic produced by farmers is sold to middlemen who transport the produce to Manila and other parts of the country.

Much of the produce sold is unclassified. In the contract or “pakyaw system.” Garlic is sold while the crop is still standing in the field but about to be harvested. The buyer does the harvesting himself. In the “mandala” method, the farmer harvests the crop but sells the bulbs unclassified. These two selling methods do not require cleaning, sorting and grading of bulbs.

Garlic bulbs that have been classified are usually sold in garlic centers. To prepare the produce, the bulbs are bundled into twin 50-bulb bunches and then bundled in 10 to 100 pieces according to size. You will incur cost in cleaning, sorting and grading the bulbs but will usually get at least double the price of unclassified bulbs.


If the price is too low at the time of harvest, farmers may store the produce and wait for better prices. But they should store the bulbs properly to prevent significant weight loss and insect attack.

Farmers usually store their produce under ambient storage conditions. Many hang the bundles in rows with bamboo sticks or lumber as hanging materials in well ventilated areas. Others pile the bundles one on top of the other to form a pyramid or “mandala.” Still others pack the bundles in wooden crates arraned in a way as to allow free air circulation.

Studies conducted by M. Ines, A. Duropan and C. Sabuco of the MMSU in Batac, Ilocos Norte show that among the storing methods used by garlic farmers, piling is the best. It offers the least risk of pest infestation and weight loss.

The researchers also found that improperly stored bulbs are attacked by various insects. These include the tobacco moth, the angoumois moth, the cigarette beetle, the coffe bean weevil, the earwig, and ants. These insects can seriously reduce the quality of the bulbs.

Prospect and Problems.

The biggest problem of our garlic farmers is the wildly fluctuating price of the commodity. There is no regulatory government body that sets the price of garlic. Such a price-setting body can help farmers who today are at the mercy of price-dictating middlemen. The entry of foreign garlic into the country, much of which is smuggled, is also depressing the price

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