It’s usually an unpleasant surprise to find anything crawling around the produce you put so much into growing and protecting. While there are certain insects that you do want around your vegetable garden, it would be nice to be able to tell the difference between the good and bad bugs.
Common bugs or insects found on lettuce that a gardener doesn’t want include types of aphids, armyworms, crickets, caterpillars, earworms, grasshoppers, weevils, and more. Good bugs that might be found on lettuce include ladybugs and spined soldier bugs.
In this article, we’ll check out a short list of the most common problematic bugs you’ll find on lettuce, how to know they’ve infested your crop, and how to get rid of them.
Easily the #1 problem to a garden, aphids that you find on lettuce will either be black, green-grey with a waxy coating, or pale-apple green. Aphids are extremely tiny, have long bodies (for their size), are often semi-transparent, and always show up in groups.
It’s easy to tell if you have an aphid infestation even if you can’t see the aphids themselves yet. Signs of aphid infestation include
- Your lettuce is growing malformed
- There are mishaped, curled, or yellowing leaves
- There is a sticky substance on the stem of the lettuce
- There are galls on the roots and/or leaves
- There are clusters of little bugs along the stem or underside of the lettuce leaves.
There are a number of ways to terminate aphids from brushing them off, to chemicals compositions. Two tried-and-true methods of aphid extermination are to use organic cold-pressed neem oil with warm water, or to use a mixture of 1 tsp. of mild dishsoap, 1 tsp. of cayenne pepper, and 1 quart of warm water, in a spray bottle.
Armyworms as larvea are devastating to lettuce. They are a type of moth caterpillar and are either green or brown with brown stripes and dark speckles in groups of four along its body.
You won’t catch armyworms in the act of devouring your lettuce because they are most active at night. You can expect them to show up if your area has had a few weeks of cool, wet weather, which they love. You’ll know your lettuce was a victim of armyworms if you see signs of chewing around the crown, midrib, and growing point on lettuce seedlings. On fully grown lettuce, they will bore into the lettuce heads.
To get rid of armyworms that aren’t yet chronic infestations, it’s recommended that you should use products with Bacillus thuringiensis (Bt) on your crops. Bt strains are in a variety of pesticide products.
Garden Symphlans are entirely white, semi-transparent, and look similar to centipedes with long antennae, long bodies with many legs, and two stingers at the end.
Garden symphlans will damage sprouting seeds, seedlings, and mature lettuces by feeding on root hairs, and the pitting they cause can bring in pathogens. In young transplants, you may notice stunted growth, but for adults, it’s very hard to tell that any damage has been done.
Managing these microdisasters is very difficult, but usually includes the use of soil insecticides, careful soil tilling, moisture control, and sending out natural predators and parasites of the symphyla such as actual centipedes and predatory mites.
Leaf miners don’t actually have one consistent appearance. The name “leaf miner,” can be applied to various larvae. However, where your lettuce is concerned, they are always diptera fly larvae that will probably look like black and yellow flies with red eyes.
Leaf miners were given their name for the tunnel-looking damage they leave on leaves. Instead of chomping on the entire leaf, they will eat the leafy tissue in between the upper and lower epidermal layers of the leaves in wild directions, and all you see are white lines all over your lettuce leaves.
Leaf miners have shown they are immune to organophosphate insecticides as adults, but what you can do is plow in early spring to destroy infected weeds and covering leafy crops with floating row covers early.
You don’t have to worry about identifying nematodes because you won’t be able to see them. These are microscopic parasites and there is no single variety of nematode that targets lettuce. What you have may be one of 50 different varieties.
Nematodes usually target the roots of your lettuce and each species will cause different damages. Root-know nematodes, which are very common, will create spherical and distinct galls in the roots that cause stunted or uneven growth. Unfortunately, there are no obvious exterior signs that you have nematodes other than lettuces that grew small or poorly.
Preventative measures such as crop rotation with crops that don’t host nematodes, are usually the best way to go. If you suspect you have nematodes, you can try giving your lettuces more fertilizer and water to make up for the deficiencies the parasites are causing.
Thrips, such as the western flower thrip have long yellow-brown bodies, red eyes, white wings, and six legs.
Thrips damage your lettuce by puncturing them and sucking on the sap inside. When a thrip is feeding on your lettuce, the lettuce leaf will turn silver and then form brown scarring. The brown scarring might look like common damages caused by sand or the wind, so if you see small black flecks in the damaged area, you know its thrips.
When you first notice the silvery leaf appearance, that is the time to apply insecticide during the afternoon, when thrips are usually at their most active.
Vegetable weevils are a problem in both the larval and adult stages. Adult weevils have tiny, all-brown, beetle-like bodies with six legs and long head. Weevil larvae will look like little maggots, except typically green in color. It will be very difficult to actually see these pests because they only come out at night.
You’ll know you have a weevil problem if on your lettuce you see signs of chewing on the leaves of your lettuce. The larvae and adult weevils will also feast on the roots of your lettuce and any damages will appear spotty.
For young lettuce, you can try to cover them with a cloth, but for mature crops, you might have to resort to removing infected crops. Neither the larvae or adults can fly, so infestation will be slow and will give you time to get rid of compromised crops.
Whiteflies look a lot like white aphids, with long, pear-shaped bodies that are light greenish yellow or white and they are always in clusters. However, they also have bright white wings, so that you can easily distinguish them from aphids. They can be found on the undersides of leaves.
Whiteflies, like aphids, suck the sap from leaves, causing discolored patches to form on lettuce leaves. They leave toxic substance in the plant that causes chlorosis, yellowing leaves. They will also pepper leaves with holes, often on one side.
Biological controls such as Delphastus catalinae beetles, parasite wasps specific to whiteflies, and Entomopathogenic fungi such as Verticillium lecanii fungus are used to control whitefly populations.
Now you will be able to easily spot at least 8 insects that you absolutely do not want to have in your garden, and especially your lettuce, and you’ll know at least one treatment method to try in order to get rid of them. With this information you can rest assured and be more confident in the idea that your lettuce will be safe and sound.