Leaf Miner (Liriomyza spp) – It’s Symptoms and Damage Prevention

Leaf Miner (Liriomyza spp) affects all species of crops. It is a black and yellow fly, it lays eggs in the leaves. Maggots later emerge from the eggs and dig mines on the leaf surface.

Larvae fall out to change into pupa from which will get out and transform into adult and all these leads to plant loss if the pest attacks at an early stage of the crop.

A leaf miner is any one of numerous species of insects in which the larval stage lives in, and eats, the leaf tissue of plants. The vast majority of leaf-mining insects are moths, sawflies, and flies, though some beetles also exhibit this behavior.

Leaf miner damage is unsightly and, if left untreated, can end up causing serious damage to a plant. Taking steps to rid plants of leaf miners will not only make them look better but will also improve their overall health. Let’s take a look at identifying leaf miners and how to kill leaf miners.

Found in greenhouses, home gardens and landscaped areas across the country, leafminers are the larval (maggot) stage of an insect family that feeds between the upper and lower surfaces of leaves. On heavily infested plants it is not uncommon to find 6 or more maggots per leaf.

Although damage can restrict plant growth, resulting in reduced yields and loss of vigor, healthy plants can tolerate considerable injury. Host plants include beans, blackberries, cabbage, lettuce, peppers, and a variety of ornamental flowers, citrus trees and shrubs.

In summary, The name “Leaf Miner” is used to refer to the larval or maggot stage of an insect that feeds upon the leaves and greenery of many valuable garden crops, including lettuce and cabbage, beans and peppers, berries, and a wide variety of flowers and citrus leafminer and shrubs, among others.

While most plants can withstand a great deal of damage and remain quite healthy, the damage from leaf miners can be unsightly. Moreover, they will reduce the saleable value of most crops quite quickly.

Continue reading to learn how to organically reduce these nuisance critters before they invade your plants and do noticeable damage.

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Leaf Miner (Liriomyza spp) – It's Symptoms and Damage Prevention
An adult Leaf miner attacking a crop

Life Cycle of Leaf Miner (Liriomyza spp)

Mature larvae overwinter in the soil under host plants. As temperatures warm in the spring larvae pass to the pupal stage and appear as young adults in late April.

Mated females use their needle-like ovipositor to lay up to 250 eggs just under the surface of the leaf epidermis. Deposited eggs may appear as small raised spots on the leaf.

Within 10 days hatching larvae tunnel through the mid-leaf tissue, feeding as they go and leaving tell-tale wavy lines that are visible on the surface. Larvae mature in 2-3 weeks, and when ready to pupate, leave the leaf and drop to the soil.

Once on the ground, they dig 1-2 inches into the soil and pupate. Adults emerge within 15 days as adult flies. There are several generations per year.

Identifying Leaf Miner (Liriomyza spp)

While there are several different kinds of leaf miners, for the most part, their looks and plant damage is similar. Leaf miners tend to be non-descript black flies. The flies do not directly cause damage to the plant; instead, it is the larva of these flies that causes the problems.

Most of the time, this pest is identified by the leaf miner damage. Frequently, it appears as yellow squiggly lines in the leaves. This is where the leaf miner larva have literally bored their way through the leaf. Leaf miner damage can also appear as spots or blotches.

Symptoms and Damage

It develops the presence of white marks on the leaf surface. Various types of leafminers attack various kinds of plants. They’re found on broadleaf trees, including elm, aspen, hawthorn, and poplar as well as shrubs and bushes, including lilacs.

Damage can be limited in initial stages of infestations but increase as leafminer numbers multiply, and even minor infestations, while not killing a plant, will cripple its hardiness.

Leafminers are a major cause of poor harvest numbers in home gardens as they weaken individual vegetable plants. They’re especially fond of spinach leaves and their tunneling severely decreases the attractiveness and value of the crop.

The larvae are small caterpillars which feed on the green tissue inside the leaf, leaving the transparent upper and lower membranes (epidermis) intact.

The young larvae enter the leaf and form serpentine mines (narrow, grey-brown or silvery tracks). As the larva matures, it consumes a broader patch of the leaf, forming blotch mines. 

Later holes are produced as the mined tissues are destroyed. The lower surface of the infested leaves become dirty with small grains of blackish frass and show silken webbings containing the small pupae.

During high infestation, the leaves become brown.  A serious outbreak can cut down the effective leaf surface for plant food production resulting in reduced storage root yield.

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How to Control Leaf Miner (Liriomyza spp)

Leaf Miner (Liriomyza spp) – It's Symptoms and Damage Prevention

Natural, and organic control methods work best when fighting leafminer problems. That’s because they don’t harm the naturally occurring beneficial insect populations that largely keep the leafminer and other harmful pests under control.

While pesticide use can encourage leafminer outbreaks, natural controls and beneficial insects prevent as well as cure these pest problems. Don’t wait until you spot leafminer tunnels in your plants’ leaves, especially if you’ve had problems with them in the past.

Be prepared with the products you’ll need to prevent and destroy infestations. Then stay vigilant.

  1. Install insect-proof nets to protect the nursery.
  2. Spraying repellent substances of garlic, onion or red pepper.
  3. Apply selective contact insecticide to kill adults and systemic insecticide to kill maggots.
  4. Perform a shallow ploughing.
  5. Remove crop residues.
  6. Monitor plant leaves closely. At the first sign of tunneling, squeeze the leaf at the tunnel between two fingers to crush any larvae. Done soon enough, this killing larvae can allow plants to survive minor outbreaks. Pick off and destroy badly infested leaves in small gardens.
  7. The more healthy the plant, the less chance that leafminers will hurt it. Maintain plant health with organic fertilizers and proper watering to allow plants to outgrow and tolerate pest damage. Keep your soil alive by using compost and other soil amendments.
  8. Use floating row covers (Harvest-Guard) to prevent fly stage from laying eggs on leaves.
  9. The parasitic wasp Diglyphus isaea is a commercially available beneficial insect that will kill leafminer larva in the mine. The wasp is especially beneficial to indoor growers of ornamentals and vegetables.
  10. Use yellow or blue sticky traps to catch egg laying adults. Cover soil under infested plants with plastic mulches to prevent larvae from reaching the ground and pupating.
  11. Fast-acting botanical insecticides should be used as a last resort. Derived from plants which have insecticidal properties, these natural pesticides have fewer harmful side effects than synthetic chemicals and break down more quickly in the environment.

5 Ways to Get Rid of Leaf Miners

As we always recommend with organic garden pest control, the best method for maintaining healthy crops is to encourage the vitality of your soil, and the life cycles of beneficial insects which help keep the environment in balance.

We discourage the use of pesticides, as this will destroy these beneficial insects and will almost surely lead to even more destructive outbreaks down the road.

(1) Check Your Plants Regularly

Monitor your plants closely and crush any tunnels between your fingers to kill any larvae present within. The best way to prevent an overabundance of leaf miners is early detection, so be vigilant. If you spot any infested leaves, pick them and toss in the trash away from the garden.

(2) Keep Plants Healthy

Maintain the health of your plant by composting and fertilizing as necessary according to the needs of your individual plant. We are here to help with specific instructions for fruits, vegetables, herbs, and more.

(3) Cover Your Crops

Physical remedies such as floating row covers or sticky traps can be utilized as necessary, but bear in mind the individual limitations of each. Row covers are not suitable for crops that require pollination, and sticky traps will not help in the larvae stage.

(4) Use Beneficial Insects

A better alternative may be to purchase beneficial insects such as the parasitic wasp diglyphus isaea. These little guys will handle your pest problem in no time. Plus, you can attract them naturally or purchase them to release in your garden.

We especially recommend this option for those growing indoors. 

(5) Use Botanical Insecticides

Botanical insecticides or neem oil can be used.  But, this should only be used as a last resort. These will break down faster in the environment than traditional pesticides. However, they will still repel your beneficial insects and disrupt the balance of your garden.

Remember that, while leaf miners are not the worst pest that could visit your garden, too many of them can make your plant susceptible to infection. Or worse, severely decrease its vitality. Early detection and prevention through a balance of beneficial insects and healthy soil are key.

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Benadine Nonye

An Agric. Consultant & a Writer. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education... Visit My Websites On: TheAgripedia.com - For Scientific Research Based Agricultural Knowledge and Innovations. Agric4profits.com - For Practical Agricultural Knowledge and Natural Health Benefits. WealthinWastes.com - For Proper Waste Management and Recycling Practices. Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4ProfitsTV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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