30 Sep

Insects and your crops: how to prevent serious damage

Warmer weather brings out the insects, and Queensland’s high temperatures and humidity make it an ideal environment for many different types of insects.

Whether you grow, harvest and sell crops for a living or you simply find joy in growing your own fruit and vegetables, insects can pose very real threats to the life and quality of your produce. Certain insects can cause the spread of plant-based diseases, whereas others may cause significant damage through direct behaviour.

Insects and crops

Not all insects pose a threat to crops, but there are those that pose either a direct or indirect threat (or both). For example, caterpillars and grasshoppers can pose a direct threat as they are known for eating through plants and crops. It’s all part of their natural means of staying alive, of course, but even a small number of these insects can cause substantial, if not irreparable, damage.

While they can also cause direct damage, aphids (commonly known as whiteflies in Australia) are an example of an insect/pest that can also cause indirect damage to crops. Aphids are notorious for transmitting plant viruses to their hosts. These hosts, of course, are usually plants or crops. There are several plant viruses that these aphids can carry, which ultimately cause bacterial, viral or fungal infections on different crops (e.g. potatoes).

Keeping insects away from your crops

When it comes to deterring insects from damaging your crops, you can approach this situation in a number of ways. There are organic/natural methods or, if all else fails, there’s also the pesticide route. However, the latter should only be used as a last resort. Even then, you’ll need to ensure the type of pesticide you’re using will not have any adverse effect on your crops (both in terms of its growth and that the final product will be safe for consumption).

The natural methods

There are several natural methods of repelling insects, but the success of each is never 100% guaranteed. What may deter one insect may be ineffective against another.

One method can be to protect your crops is to grow them with plants that naturally repel insects and other pests. For example, if you’re growing tomatoes, you can then grow oregano and basil plants around your tomatoes. The strong scent of oregano and basil plants often deters a large number of insects. A different approach could be to surround your vulnerable crops with harsher plants – such as those with thorns or tougher leaves. It’s the same principle as building a strong fort around an otherwise vulnerable city.

If necessary, you may need to burn certain affected crops to prevent a destructive insect from spreading to other healthy crops. This also marks the importance of not having your crops/plants too close together. All of them need room to properly breathe. More distance also makes it harder for diseases to spread. And if it does come down to the wire where some crops need to be destroyed, it reduces the likelihood of other crops being accidentally destroyed in the process.

Consistently mulching your crop keeps it healthy, promotes greater growth and makes it harder for insects to get a foothold. The healthier your crop is, the harder it becomes for insects to make any substantial impact – although this is not a foolproof plan. Under certain situations, you can prevent an insect from damaging your crops by introducing another insect into the mix. Think of it as fighting fire with fire. You get rid of the offending insect by having its natural enemy, which doesn’t pose a threat your crops, take care of it.

There are other, more quirky, natural solutions such as placing coffee grounds into the soil or placing copper near certain crops/plants. A sizeable number of insects hate coffee grounds, and copper has been known to keep slugs at bay. When using these solutions, just make sure you’re implementing them in a way that won’t directly inhibit the growth or health of your crops.


As we said, you should be careful when using pesticides. No matter how plant or crop-friendly a particular pesticide or toxin is noted as being, there is always going to be an element of risk. All we can say here is to ensure that any pesticide you use has been proven to repel/kill insects while posing very little risk to your crops. If you do ultimately use a pesticide or numerous pesticides, don’t forget to properly clean your harvested crops so that all pesticide remnants are removed before human consumption.

* Image source:

Kite aerial photo of crop marks at Nesley, near Tetbury, Gloucestershire” by Dr John WellsOwn workPreviously published: http://www.armadale.org.uk/archeoscan.htmCC-BY West Lothian Archaeology. Licensed under CC BY 3.0 via Wikimedia Commons.

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