Common Lettuce Pests: Lettuce Pest Control Information

Lettuce aphid (Leafhopper Aphid)

The leafhopper aphid feeds on the leaves of most lettuces including iceberg, arugula, basil, bok choy, cabbage, cauliflower, chicory root and kale. They are not aggressive towards other plants so they do not pose a problem to your vegetable garden. However, their feeding habits can cause problems when they infest the roots of lettuces such as romaine or baby spinach. Leafhoppers feed on plant juices and nutrients which causes them to become overgrown with green and brownish-black growths. These black spots are called nits.

Nits may appear anywhere along the stem but tend to cluster around the base of leaves where there is less moisture and sunlight. Leaves may turn yellow and drop off leaving the plant vulnerable to attack.

Symptoms of Leafhopper Aphid Infestation

Yellowing leaves and stems, especially near the base of the plant. Leaves may fall off completely if left untreated. If leaves die back completely, it means that all of the foliage has been eaten away and no new shoots will grow out from under it.

How to Prevent Leafhopper Aphid Infestation?

Look for eggs, grayish-brown nits attached somewhat to the leaves or young plant stems. Also look for adults, winged insects with pointed rear ends and are light green in color.Thoroughly wash off the affected areas and dispose of the infested plant material. If you are growing your own vegetables indoors or under protective netting, check your plants regularly. Also make sure that soil is kept moist but not wet and that there is lots of fresh air and sunlight.

How to Get Rid of Leafhopper Aphids?

If you catch leafhoppers early on, you can wipe them off by hand or use a strong jet of water to knock them off. Parathion or Malathion at the rate of one teaspoon per gallon of water can be used as a last resort. Make sure that the chemical is well diluted before using it.

Lettuce Aphid Thrips

Thrips are small, slender insects that have a dark colored body and wings. They also give off a yellow secretion when threatened. Larger thrips may be yellowish or grayish and shorter in length. Thrips do not usually fly far when disturbed, but they can move quickly over the surface of the plants. Additionally, they can fold their wings back and walk across the surface of the plants without being detected.

Lettuce thrips feed on all kinds of lettuce and can be found in all stages of life on the leaves. They pierce the plant tissue and suck out the juice. This feeding habit is harmful to young plants and may cause the growth of distorted tissue.

Common Lettuce Pests: Lettuce Pest Control Information - Image

Symptoms of Thrips Infestation

Thrips feed in groups and produce serpentine feeding scars or silvery spots on the leaves. There are black flecks in the spots that are excrement. These black spots are actually eggs or the larvae of the thrips. Thrips can cause distorted growth on young plants. In addition to these effects, they cause discoloration and a reduction in the quality of the leaves.

These insects also carry several species of bacteria that can be transferred to humans through their bites.

How to Prevent Thrips Infestation?

Keep weeds under control as thrips tend to thrive in areas with lots of weeds. Also avoid cultivating the soil around lettuce plants when thrips are at their peak. Effective mulches help to deter these pests. A thick growth of crop is more effective than a bare patch.

How to Get Rid of Thrips?

Handpicking can be an effective way of controlling thrips. They are slow moving insects and you can scrape them off with your fingers or scoop them off with a glass or a cup. You can also blast them off with a strong jet of water. Yellow sticky traps are good at catching them. A few predators, like the minute pirate bug, might help in keeping their population under check.

Root Maggot

The root maggot is a type of fly that attacks many different types of plants, prefer leafy vegetables like lettuce, but it is especially fond of plants in the cabbage family. This is a serious pest in many areas that can reduce crop yields by as much as 50%. The maggots are creamy white colored with a brown head and have three pairs of legs. Fully grown root maggots are about 4 to 6 millimeters long.

Symptoms of Root Maggot Infestation

These young flies prefer to feed on the roots of their host plants, hence the name root maggots.

Sources & references used in this article:

Inheritance of resistance to common lettuce mosaic. by EJ Ryder – Journal of the American Society of Horticultural …, 1970 – cabdirect.org

Impact of ultraviolet-blocking plastic films on insect vectors of virus diseases infesting crisp lettuce by BM Díaz, R Biurrún, A Moreno, M Nebreda… – HortScience, 2006 – journals.ashs.org

The impact of aphicide drenches on Micromus tasmaniae (Walker) (Neuroptera: Hemerobiidae) and the implications for pest control in lettuce crops by PG Cole, PA Horne – Australian Journal of Entomology, 2006 – Wiley Online Library

Biological control of aphids in lettuce using in-field insectaries by WE Chaney – … control: habitat management to promote natural …, 1998 – books.google.com

Nitric oxide fumigation for postharvest pest control on lettuce by X Yang, YB Liu – Pest management science, 2019 – Wiley Online Library

Iceberg lettuce production in California by T Turini, M Cahn, M Cantwell, L Jackson, S Koike… – 2011 – escholarship.org

Responses of lettuce cultivars to insect pests in southern Florida by H Lu, AL Wright, D Sui – HortTechnology, 2011 – journals.ashs.org

Leaf lettuce production in California by R Smith, M Cahn, O Daugovish, S Koike – 2011 – books.google.com

Compendium of lettuce diseases and pests by KV Subbarao, RM Davis, RL Gilbertson, RN Raid – 2017 – Am Phytopath Society

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