Aphids on Lettuce: How to Identify, Prevent, and Control Garden Infestations

For removing aphids from lettuce, look carefully for aphids on the undersides of leaves and on inside of lettuce leaves; spray easily-defendable aphid infestations with a gentle wash of water; remove heavily-infested leaves, and encourage natural enemies. Repeat with a biological insecticide (registered for use) or with a low-risk chemical contact insecticide - For repeated infestations, depending on lettuce harvest instructions on the label, use a product containing Beauveria bassiana.

Identification of Aphids on Lettuces Plants

When inspecting the lettuce patch I give particular attention to the growing tips and tender leaves where I might first see signs of insects without seeing the actual damage. Lettuce aphids can be green, yellow, grey or dark-colored and are frequently found on the underside of leaves or between close growing and developing leaf surfaces. When I see that colonies are growing, I might see signs of curling leaves, yellow leaves, sticky honeydew and slower growth. Lettuce with aphid damage on leaves may be less marketable or difficult to clean before harvesting due to the visible symptoms. I have a good way of finding aphids on lettuce plants early if there is an infestation, when they are easily accessible in the center of the head of lettuce, but as they grow bigger, it will be hard to reach.

Solving Aphid Problem in a Lettuce Garden

What causes aphid infestation? I've come to find out that an aphid problem is generally not caused by only one thing. Form flighted aphids in gardens can reach the plants in the field via the wind or by being carried on infected nursery plants or adjacent weeds and host plants. The populations of these insects can rapidly increase given adequate conditions on tender growing lettuce. Phagylishing lush growth may be caused by excess nitrogen fertiliser, which will be used by aphids. Ants may also shelter aphid colonies, in return for the honeydew, to block out natural predators. Once I understand the causes of aphid infestation I am not looking at the lettuce and thinking "why do aphids get on this plant?," but only asking myself “why do these aphids NEED to be on this plant?” in my garden environment.

How to Get Rid of Aphids on Lettuce Naturally

If I see a small aphid population I go with the simplest option: running water to foliage and thoroughly wet the inside and undersides of the outer leaves. It's a way to remove numerous aphids without applications of a pesticide in the garden. I prune leaves if necessary that are infested with a lot of the pest and search surrounding plants for new infestations. I use a variety of plants to attract beneficial insects and refrain from using spray insecticides that could harm their beneficial insect predators, which include lacewing larvae, lady beetles and hoverfly larvae. Inspection regularly is vital as surviving aphids will breed rapidly. Practical suggestions and make a useful starting point to eliminate aphids from lettuce and controlling aphids in garden beds while not being concerned about a fast application of a chemical insecticide.

Keep Aphids Out of Lettuces

To minimize repeat invasions I screen seedlings before planting and visit new lettuce shoots and undersides in spring for signs of new growth, as well as seedlings. I take off very infested plants, control weed that can be an alternate host, and don't over fertilize plants with N fertilizer. Nectar and pollen plants can offer nectar and pollen for good insects, creating a more well-rounded garden environment. These practices will not ensure aphid free lettuce, but will help minimize the risk for a large infestation. Routine scouting and garden clean up is useful for reducing aphids on lettuce plants, keeping an eye on colonies in garden areas, and working towards controlling aphids in garden areas before they become loose.

What insecticide kills aphids on lettuce?

If the aphids remain after a wash and prun, then I would think about a product that is targeted towards aphids and lettuces. Insecticidal soaps and horticultural oils are good contact insecticides for aphids when they’re sprayed directly on the insects. Good cover is a must, particularly under foliage and in folded growth. If the label permits these applications can be repeated since there is a possibility that they may not have impacted aphids that were past their threshold. When evaluating the edible lettuce, I review the crop and pest listed on the label as well as the application rate, protective precautions and pre-harvest interval. When selecting an aphids control insecticide, or just conducting a bit of research and asking what insecticide kills aphids, it is especially important to remember this since not all aphid products are approved for use in food crops.

How Beveria WP Can Help with Aphids on Lettuce?

What insecticide kills aphids? Beveria WP, aphids control insecticide, a wettable powder insecticide containing the naturally occurring fungus Beauveria bassiana, is an option for gardeners interested in biological ways to control insects. Novobac is labelled as ‘controlling aphids and other soft-bodied insect pests'. It binds to the external surface of the insect, germinates and enters the insect's cuticle. The fungus then begins to spread in the host plant. Novobac gives directions for foliar applications and indicates that it is recommended as an IPM choice. 

As with Beveria WP for lettuce, I would make sure that it is registered as a spray for aphids in edible lettuce in my specific area. The age, coverage, environment, pest pressure and handling can all affect performance. I would adhere to the dosage, protective measures and harvest restrictions already listed on the current product label instead of assuming that they are the same as those for the general product.

What is the best way to use Beauveria bassiana to control aphids?

What insecticide kills aphids? Beauveria bassiana is an entomopathogenic fungus which forms the basis of some bioagents for biological control. Spores can be pathogenic on susceptible insects if they come in contact with them and germinate to penetrate the insect's outer covering to create an infection.

The fungus grows on the inside of the insect, leading to its death. Beauveria bassiana is not an "instant knockdown" pesticide, but rather may take a longer period of time for its visible effect to appear. The performance depends on type of fungus, formulation, coverage, humidity, sunlight and environmental conditions. 

I also separated the active ingredient with the finished good. Beauveria bassiana products vary in formulation, concentration, direction and allowed crop use. For controlling aphids in garden beds, I look for one which is labeled to control aphids and what it says to control lettuce, and follow all application and harvest recommendations. This assists me to consider which aphids control insecticide and to consider simultaneously the safety of food crops and suitability of products to flight control.

How to Plan for a Gardener to Have Good, Rosy, Aphid-Free Vegetables of Key Crops

How to get rid of aphids on lettuce? Regular scouting and letting me know that aphids are actually causing the problem is part of my healthy lettuce approach, before I treat. Small colonies are washed off, leaves that are heavily infested are removed when necessary, and broad-spectrum insecticides are avoided to be used in the vicinity of beneficial insects. With the continuing population, I believe a label application for lettuce and aphids is adequate to control the problem. Unfortunately, no one method yields the same results in every garden, particularly when the aphids nestle in small heads. I have simple notes made when infestations are noted where and when I make some treatment and what effect it has had to help me respond earlier next planting. All of these practices assist in managing aphids on lettuce plants, controlling aphids in garden beds, and in implementing useful techniques for garden lettuce aphid control.

A next step for gardeners thinking about using a biological control is to read the information on the Gardelabel related to Beveria WP or Beauveria bassiana; however the local-use label must always be followed to determine the use or non-use of a product in the garden.

References:

1. Shrestha, Govinda, Annie Enkegaard, and Tove Steenberg. “Laboratory and semi-field evaluation of Beauveria bassiana (Ascomycota: Hypocreales) against the lettuce aphid, Nasonovia ribisnigri (Hemiptera: Aphididae).” Biological Control 85 (2015): 37-45.
2. Macuphe, Neo. The effect of the entomopathogenic fungus Beauveria bassiana on growth, physiological responses and control of aphid (Myzus persicae) infestation on Lactuca sativa L. Diss. Cape Peninsula University of Technology, 2020.