Whiteflies are a common garden and greenhouse pest and, as anyone who’s encountered these insects will tell you, they can be very difficult to get rid of. Recurrent whitefly infestations can cause significant damage to flowers, fruits, and vegetables, and at times they can seem impossible to control. But where are all these whiteflies coming from, and how can you stop them from making themselves at home? Read on to find out what causes whiteflies, and what steps you can take to effectively prevent them from invading your garden.
What Are the Most Common Causes of Whitefly Infestation?
Plants that are suffering from stress, especially water stress, are naturally more susceptible to whitefly infestations. If you live in an area that typically has hot, dry summers, or you simply keep forgetting to water your plants, there’s a good chance they’re dehydrated.
Drought stress can increase the prevalence of pests, such as whitefly, for a few reasons. Higher temperatures can boost reproduction and development rates, meaning there are more of these insects around. What’s more, dry conditions are naturally more beneficial for insects with piercing, sucking mouthparts, so whiteflies often flourish during periods of drought. Drought can also negatively impact the development and survival of ladybug larvae. Ladybugs are natural whitefly predators, so smaller numbers of these beetles can spell bad news for your plants during those dry summer months.
Overuse of Insecticides
Insecticides may seem like the obvious answer to your whitefly problems; however, these can often do more harm than good. Many insecticides are non-specific, meaning they don’t target any particular type of insect. Dousing your garden with copious amounts of pesticide can wipe out every bug around – including beneficial, predatory species.
Insects such as ladybug beetles, spiders, and parasitic wasps are natural enemies of the whitefly and can usually be counted upon to help exterminate the insects. Unfortunately, these predators are often killed off during insecticide treatment, allowing whiteflies to come back with full force. What’s more, many insecticides kill essential pollinators, such as bees, which can harm the overall health of your garden’s ecosystem.
Use of Nitrogen Fertilizer
Nitrogen-rich fertilizers can improve the health and vitality of your plants, so you may not think twice about spreading it on your flower beds. However, what you may not realize is that these fertilizers can also encourage whitefly to attack your plants! Studies have shown that excessive use of nitrogen fertilizers leads to a higher concentration of nitrogen in plant tissues. This makes them more attractive to whitefly and may be the reason for your frequent re-infestations.
Ladybug beetles are natural enemies of the whitefly and are handy insects to have around if you’re trying to keep infestations at bay. Unfortunately, ladybugs are not at the top of the food chain and often fall prey to other species. Birds such as swifts and swallows, certain types of spiders and larger, predatory beetles can all make a meal out of ladybugs. If you have lots of these creatures living in and around your garden, they may be responsible for your recurrent whitefly problems.
How to Prevent Whiteflies
If your plants are under constant attack from whiteflies, it can be a good idea to investigate methods of whitefly prevention. This can help to keep them out of your garden, houseplants, and greenhouse, without the use of potentially harmful insecticides.
Staying on top of your whitefly population is the best way to prevent their numbers from booming. Whitefly breed very quickly, and large infestations can develop in no time at all, which can make them very difficult to control. Routinely checking the underside of leaves on commonly affected plants can help you to stay one step ahead! If you notice large numbers of whitefly on your plants, blast the leaves with a high-pressure hose to remove them. This can help to keep infestations at bay and reduce the overall number of whiteflies on your plants.
Reflective, plastic mulch can be a highly effective way of keeping whitefly off your plants. Spreading it around the base of commonly affected plants can reduce whitefly populations and help to guard them against attack by confusing the bugs. This can stop them from landing on your plants and makes it more difficult for infestations to take hold.
Placing yellow sticky traps near plants can also help to reduce the numbers of whitefly in your garden and greenhouse. Sticky traps can effectively capture any whitefly that venture near your plants, stopping them from landing and forming infestations. These glue traps are also a great way to monitor your whitefly populations, so you can easily tell if their numbers are growing without the need to closely inspect plants.
There are several insect species, such as ladybugs, that eat whitefly. Buying and releasing large numbers of these natural predators can be an effective way of controlling a persistent whitefly problem and can help to keep their numbers low. Small, parasitic wasps like Encarsia Formosa are also extremely effective against whitefly (and are nowhere near as scary as their name suggests)!
As mentioned previously, insecticides may not be the best way to deal with whitefly infestations due to their negative effects on beneficial insect species. However, neem oil can provide an attractive, non-toxic alternative to chemical pesticides. This natural plant extract can be applied as a spray to plant foliage where it effectively kills whitefly and larvae; however, it has very low toxicity in ladybugs, spiders, and pollinators. Spritz your plants with a neem oil solution at least once a week to effectively reduce whitefly numbers, and to deter these insects from making themselves at home in your garden.
Recurrent whitefly infestations can be a nightmare. These tiny, sap-sucking insects can cause widespread damage in greenhouses and gardens, and they’re often difficult to eradicate.
Having to deal with whitefly over and over again can be very frustrating, and their persistence may leave gardeners baffled. Identifying the cause of your whitefly troubles is the first step to solving the problem! Once you’ve worked out why you have so many whiteflies, be it down to your choice of fertilizer, overuse of pesticides, or the lack of natural predators, you can take the necessary action to banish them for good.