Pests are simply creatures that are going about their business, but their business happens to involve damaging a plant we have put our hearts and hard work into growing. One advantage to urban gardening is not having to worry about common garden pests like deer and rabbits, but unfortunately insects and other small creatures can make their way anywhere. Most are harmless, some are beneficial (pollination, eating other insects), but a few can cause real damage to our gardens and need attention.
The trick is figuring out which creatures are on your plants, and if something needs to be done to get rid of them, or if they are harmless and should be left alone. The old mindset of get rid of every pest no matter what it takes is out, and get a good harvest without hurting the environment or yourself is in. This article outlines five of the most common pests found in balcony and rooftop gardens, how to identify them, and how to deal with them in the least-harmful way possible.
Identification: Slugs are soft bodied animals that flourish in moist conditions and come out to eat at night. They leave slime trails, so the presence of these are a giveaway.
Plant signs: Large irregular holes in leaves or whole seedlings simply vanishing overnight are signs of their presence. They will also target the fruits of plants like strawberries and courgettes.
Favorite plants: lettuce, cabbage, strawberries, pepper, courgettes, cucumbers, and beans
Methods to try:
- Going on a nightime slug hunt is often the most effective solution. Go after it rains with a flashlight and be as thorough as possible – you may not get all of them but it is a good start.
- Copper barrier: many slugs will not cross copper because of the minor electrical current it produces. Try surrounding your plants with copper coins or lay down copper tape which is made specifically for this problem
- Traps: Funnily enough, slugs are attracted to beer, so placing a bowl or other short container at the base of your plants with some stale beer will entice them in. Alternatively, placing half orange or other melon peels, which they are also drawn to, will capture them without killing them.
- If you are concerned about this pest, be aware of growing plants from seed as slugs can demolish small seedlings. Only transplant once plants are hardy, as they will have a better chance of survival.
Identification: Aphids are tiny (1-7 mm long) insects that can be green, black, yellow, pink, or white. They are usually able to be seen with the naked eye because they come in large numbers. Check on the underside of leaves, especially younger ones, and on flower buds and stems.
Plant signs: Aphids suck the sap out of all plant parts, so if you have an aphid problem you will notice stunted growth and weakened plants as well as distorted leaves. Mold will also grow on the honeydew that aphids secrete.
Favorite plants: Unfortunately, they will feed on anything and everything
Methods to try:
- Biological control: if you see insects like ladybugs, praying mantis and hoverflies in your garden, welcome them in! They especially enjoy eating aphids and will help you in your efforts. Dill and fennel deter aphids and other pests while attracting ladybugs.
- Plant traps: Aphids love certain flowers like nasturtium, mustard, cosmos, zinnias, and dahlias, so while it’s sad to sacrifice them, planting them nearby will help keep aphids away from fruits and veggies.
- Recipe: Aphids, as well as many other pests do not enjoy garlic. Add 100 g of crushed garlic to 4 liters of water and let it sit for 24 hours. Then boil it for 20 minutes and once it has cooled put in a spray bottle and lightly spray on your plants.
Adult vine weevil and vine weevil grub
Identification: The vine weevil is about 10 mm long, black with mottled brown patches and bearing long antennae. They are active in the spring and summer. Grubs are the vine weevil’s offspring and are active from late summer through the winter. They can be more problematic due to the fact that they live in the soil where they are hard to spot and eat roots which are vital to plant health. They are also about 10 mm long, white with a brown head, legless and c-shaped.
Plant signs: The vine weevil eat leaves and symptoms are irregular-shaped notches along leaf margins. Because the grub targets roots, it will be hard to see the damage. Instead look for them at the base of the plant. If undetected the whole plant might begin to weaken.
Favorite plants: Strawberries, cabbage, carrots, beets, onions, radishes, tomatoes, and spinach as well as a wide range of flowers
Methods to try:
- Physical barrier: If you have had a problem with weevils in the past, it might be a good idea to put netting or sticky barrier around individual plants (only applicable if you mostly grow potted plants). As they do not fly, this will prevent infestation.
- Removal: Inspect plants at night as this is when they are most active and remove them by hand. Putting them in a jar of soapy water is an easy (although still sad) way to say bye to our little friends.
- Soil inspection: If reusing soil, check it thoroughly in the spring for grubs, and remove them before planting anything.
Identification: Spider mites are the tiniest of the tiny, about the size of the period at the end of this sentence. They are reddish-brown or pale in color, which would not be helpful in identifying one on its own because of how small they are, but “luckily” they live in colonies so are identifiable.
Plant signs: They usually hangout on the underside of leaves, sucking out the plant’s fluids. If they go undetected, you will notice leaves turning yellow or pale, drying up, and eventually falling off. As they are closely related to spiders, they will also create a cottony webbing that will appear under leaves and on stems.
Favorite plants: many including tomatoes, eggplants, strawberries, beans, and ornamental flowers
Methods to try:
- Dust and water stress will encourage mites. Pouring water over your plants (giving them a little shower) a few times a season will remove dust and keeping plants well-watered in general will prevent water stress. If mites are already present, spraying the plant should also wash away the mites.
- If there are a lot of them, remove all infested parts of plant. If possible, move the plant away from others so that the mites can’t spread, and if not consider sacrificing the whole plant. For the well-being of all!
Identification: Leaf miners are the larval stage of some moths, sawflies, and flies, as well as some beetles. Keep an eye out for eggs on the underside of leaves, and the larvae that hatch out of them which are about 1 cm in length, pale green or yellow.
Plant signs: This is one of the most distinguishable signs in the garden – the pale winding line on leaves that is rather mesmerizing as it shows how the larvae ate within the leaf without ever creating a hole all the way through.
Favorite plants: Lettuce, cabbage, spinach, beans, beets, peppers, ornamental flowers, and citrus trees
Methods to try:
- At the first sign of a tunnel being formed, squeeze the leaf between two fingers at that spot. This should kill the miner before it can do real damage. If there is substantial damage, pick off infested leaves.
- A healthy plant can withstand a good amount of this type of damage, so it is really only a problem for leafy vegetables where you are meant to eat the damaged part. So if you do not grow lettuce, spinach, etc. there is no real worry here.
- Write it all down. Documenting when pests arrive, how long they stay, the extent of damage they cause, and what works for improving the situation is the best way to prepare for the next season. Each garden will be present a unique set of conditions and pests, and therefore only you can be in charge of the necessary problem-solving.
- Having healthy plants is the best preventative measure out there. Pests are much more likely to attack a stressed plant as it presents an easier target. This can be a particularly interesting thing to record: do you notice weak-link plants getting targeted? If so, then the problem-solving changes to how do I improve my general plant health?
- Most infestations will not cause a plant to die. Don’t jump into a panic at the first site of a pest. Monitor it and wait to see if the problem solves itself (time to come out and feed ladybugs!).
- Sometimes, however, even the strongest plants get attacked and serious damage does occur. A very effective, albeit slightly more harmful natural insecticide recipe might be in your cards. Mix 6 mL Neem oil and 3 mL dish soap into 4.5 liters of warm water. Pour into a spray bottle and spray a generous amount on all leaf surfaces whenever you notice mites. Neem oil is extracted from the Neem tree, so it is natural, but it affects 400 species of insects, so be aware it will harm good ones too. It is non-harmful, however to plants, bees, birds, and mammals (including us).
Happy and (hopefully) pest free gardening!