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Pests On Ornamentals And Vegetables: Whitefly Treatment In The Garden

Pests On Ornamentals And Vegetables: Whitefly Treatment In The Garden


By: Heather Rhoades

In terms of garden pests, whiteflies are one of the most bothersome gardeners can have in their gardens. Whether they’re on ornamentals or vegetables, whitefly control can be tricky and difficult. But controlling whiteflies in the garden is not impossible. Let’s take a look at the answer to the question, “How do you get rid of whiteflies?”

Identifying the Garden Pests Whiteflies

Whiteflies are part of a group of sap sucking insects that can cause problems in the garden. Other sap sucking insects include aphids, scale and mealybugs. The effects of these insects, including whiteflies, are nearly all the same.

The signs that you may have whiteflies or one of its cousins are a sticky film on the leaves, yellow leaves and stunted growth. The way to determine if you specifically have whiteflies is to inspect the insects you find on the plant. Typically, the insects can be found on the undersides of the leaves.

The garden pests whiteflies look just like their name. They will look like a tiny whitefly or moth. There will be several in one area.

Controlling Whiteflies in the Garden

Normally whiteflies become a problem when their natural predators, such as ladybugs, are not present in the area. This can happen for many reasons, ranging from pesticide use to bad weather.

Controlling whiteflies in the garden becomes difficult without help from their natural predators. Therefore, making sure that the area is good for their predators is important. Whitefly predators include:

  • Green Lacewings
  • Pirate Bugs
  • Big-eyed Bugs
  • Ladybugs

Using these beneficial insects are the best way how to kill whiteflies.

You can also try spraying the affected plant with a lightly pressurized stream of water. This will knock the insects off the plant and will reduce, but not eliminate their numbers.

Also, for ornamentals and vegetables, whitefly problems and damage can be reduced if the plants are kept as healthy as possible, which means that you need to regularly feed and water the plants.

You can also try controlling whiteflies in the garden by using reflective surfaces, like foil or discarded CDs, around the plants. This can have a repelling effect on the whiteflies and may keep them off the plant. Alternately, you can try sticky tape, which will help to eliminate the current population of whiteflies on your plants and prevent them from laying more eggs.

Do not use insecticides as a way to kill whiteflies. They are resistant to most insecticides and you will only make the problem worse by killing their natural enemies. That being said, neem oil can be effective against these pests and is generally deemed safe for beneficials.

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Controlling Pests Organically: Aphids, Whiteflies, and Thrips

Most gardeners have had to fight off a pest infestation in their garden at one time or another. The good news is that there is a wide range of pest control options that allow you to deal with common plant pests without unleashing harmful chemicals and potentially exposing you, your family and your environment to harm. Mother Nature has already figured out how to deal with many of the pests that are bad for our gardens, we just need to let her be our guide. Read on to learn more about some of the most common plant pests out there and how you can effectively deal with them the natural way.

Controlling Aphids in Indoor Growing

Aphids, which are sometimes referred to as plant lice, damage plants by sucking out the sap from their leaves. Although they are large enough to be seen without magnification, their presence can go undetected until after significant damage has been done. There are many different kinds of aphids, but their modus operandi is generally the same.

Damage from aphids generally appears as a puckered or blister-like appearance on leaves, which can lead to leaf distortion or stunted growth. To add insult to injury, aphid frass (insect excrement), more commonly known as honeydew, attracts ants. Honeydew is a sweet substance made primarily of the sap aphids have consumed. Plants that have been contaminated with honeydew can develop a disease known as sooty mold, which creates a tar-like appearance on plant leaves that inhibits photosynthesis.

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Aphids are prolific reproducers. Female aphids are born pregnant and can start laying their own young within a week of their own birth. Due to their rapid population growth, multiple strategies often have to be employed to effectively control them.

Many different beneficial insects will either feed upon or parasitize aphids, or do both. One of the most effective biological controls that can be unleashed upon an aphid army is the common lady beetle, Hippodamia convergens. Lady beetles are carnivores that will seek out aphids and consume plenty of them every day. Lady beetle larvae will consume aphids and other pests in greater numbers than their adult counterparts.

Aphidoletes aphidimyza and Aphidius colemani are two parasitic wasps that seek out aphids in which to inject their eggs. Their eggs develop inside the aphids and feed on them from within. When they emerge as adult insects, they seek out other aphids to continue the cycle. The remaining hollow aphid carcass that these wasps leave in their wake is known as an aphid mummy.

If using beneficial insects makes you a bit queasy or sounds too much like science fiction, you can use a variety of liquid applications that are naturally derived from plants to effectively kill aphids by suffocating them or interfering with their body functions. Pyrethrins, not to be confused with the man-made pyrethroids, is an extract from the chrysanthemum plant. It is a common ingredient in many organic insecticides. It works by confusing the nervous system of the aphids, leading to paralysis and death.

Azadirachta indica or the neem tree of India is the source of another bio-pesticide, neem oil. Neem-based products can be applied to infested plants as either a foliar spray or as a soil drench.

Regardless of the method you have selected to control your aphid problem, multiple applications will be required. If you are using bio-controls such as lady beetles or parasitic wasps, it is important to release them on a regular basis to keep their populations sufficient for pest control. If you opt for a spray treatment, plan on applying the product two or three times every seven to 10 days, making sure to get thorough leaf coverage, both on the undersides as well as the tops and stems.

Controlling Whiteflies in Indoor Growing

Whiteflies, as their name implies, are white, flying insects. There are several species of whiteflies out there, all of which are closely related to aphids. Like aphids, whiteflies are visible without magnification. They damage plants by sucking the sap from them, but their damage appears differently than the damage from aphids. Leaves damaged during whitefly feeding will turn yellow or brown and drop off prematurely. They may get a speckled appearance before turning color.

Like aphids, whiteflies also secrete honeydew with the same potential results of attracting ants and fostering the development of black, sooty mold on leaves that may be below where the whiteflies are feeding. These pests are also prolific reproducers and each female whitefly can lay up to 400 eggs in her lifetime. Her nymphs will immediately begin sucking on leaves once they have hatched and can stay fixed in one spot, feeding for up to four weeks as they pupate into adult whiteflies. A heavy infestation of whiteflies will appear as a burst of smoke when disturbed. Care should be taken to not wear light-colored clothing when working around plants with whiteflies as they can easily be transported to other plants unknowingly.

Whiteflies can be controlled with beetles and parasitic wasps, like their aphid cousins, but different beneficial species are better at controlling them. A small, black beetle, known as delphastus pusillus, which is about the same size as the whiteflies themselves, will feed on all stages of whiteflies, but they prefer the eggs and nymphs. They are especially useful in high-infestation areas, as they require consuming up to 200 whitefly eggs per day in order to reproduce.

Whiteflies also can be controlled via the parasitic wasps found within the genus Encarsia. Encarsia formosa is the most prevalent beneficial wasp used to control greenhouse whiteflies. These tiny insects inject their eggs into the bodies of whiteflies in the same manner as the Aphidoletes aphidimyza and Aphidius colemani do with aphids. Whitefly hosts generally die 10 days after being parasitized. The adult Encarsia will emerge from the dead whitefly in about another 10 days.

To get a handle on whitefly infestations using sprays, pyrethrins and neem are two good options - insecticidal soap is another. For whitefly control, use a combination of different controls in successive sprays. It is nearly impossible to get full coverage in one application given the whitefly’s ability to spook easily and fly off. Plan on at least three applications, possibly more.

Controlling Thrips in Indoor Growing

Thrips are similar to aphids and whiteflies in that they cause their damage by sucking as opposed to chewing. These small flying insects can be anywhere from clear, to black, to reddish orange in color. Along with their black deposits of frass, they are often found on the undersides of leaves. Like the other pests described here, there are numerous thrip species out there, each with their preferred host plants.

Damage from thrips appears as a dappled, stippled or speckled leaf surface. Thrips will also feed on many fruits, which ends up causing damage to the entire crop. Thrips usually don’t kill their host plants they often cause stunted growth or poor performance as a result of the plant’s cellular losses and reduced ability to photosynthesize.

Controlling thrips using beneficial insects depends on the species you’re tackling. There are actually predatory thrip species that can be released to control the pest thrips. A positive identification of the pest species should be made before deciding on a beneficial insect to release. Predators such as the green lacewing (Chrysoperla rufilabris) and the minute pirate bug (Macrotracheliella nigra) will generally feed on multiple species of thrips. However, you cannot expect stellar results if you are releasing beneficial insects to control thrips on outdoor plants. They are much more effective when used to control thrip infestations of indoor crops.

The most effective spray for controlling thrips is spinosad, a naturally occurring fermented bacterium. This is the active ingredient in many insecticides approved for organic gardening. Unlike many non-synthetic pesticides, spinosad penetrates the leaf surface to reach the undersides where the thrips are feeding.


Identification

How to Identify Whiteflies

Like aphids, whiteflies use their piercing mouthparts to suck up plant juices and, in turn, produce a sticky substance known as honeydew. Honeydew left on its own can cause fungal diseases such as sooty mold to form on leaves.

With heavy whitefly feeding, plants will quickly become extremely weak and may be unable to carry out photosynthesis. Leaves will wilt, turn pale or yellow, growth will be stunted, and eventually leaves may shrivel and drop off the plant.

Honeydew is a sign that the whiteflies have been feeding for several days. You might also see ants, which are attracted to the sweet honeydew.

Where to Find Whiteflies on Plants

Whiteflies tend to prefer to feed on new growth, so check around any newly unfurled leaves first.

Check the undersides of leaves—especially around the veins—for white insects, even if they aren’t immediately visible, and feel leaf surfaces for sticky honeydew. If the whiteflies are feeding, they’ll suddenly all fly off the leaves in a swarm, so it’s very obvious.

You may also find eggs laid on the undersides of leaves. This is the beginning of a new generation! When the eggs hatch, the larvae will look like teeny white ovals without legs they don’t move but they immediately start sucking the plant juice. This is why gardeners often miss whiteflies until it’s too late. Adult females can produce up to 400 eggs, which hatch in about one week to a month after laying. They are usually laid in a circular pattern. Eggs are pale yellow when newly laid and brown when about to hatch.


Whiteflies congregate on the undersides of leaves and lay their tiny white eggs in this secure spot. Photo Credit: University of Florida.


How to Get Rid of the Whitefly

Last Updated: September 2, 2020 References Approved

This article was co-authored by Lauren Kurtz. Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.

There are 13 references cited in this article, which can be found at the bottom of the page.

wikiHow marks an article as reader-approved once it receives enough positive feedback. This article received 15 testimonials and 86% of readers who voted found it helpful, earning it our reader-approved status.

This article has been viewed 516,963 times.

There are over 1,000 types of whiteflies, insects that look like small white moths or aphids. They group and breed in large numbers on the undersides of leaves. The nymphs and adults damage plants directly by sucking the sap and by transmitting disease. Once an infestation has taken root, it is difficult to remove. You may need to apply multiple treatments over a period of weeks, and you may even need to trim back your plants.


More Advice on Organic Whitefly Control

Gardens that host an abundance of beneficial insects make poor homes for whiteflies. In areas where whiteflies are common and your neighbors use a lot of pesticides, monitor populations with sticky traps and use a vacuum to keep small outbreaks under control. In seasons following whitefly problems, avoid planting attractive annuals such as lantana, salvia and hibiscus.

More information on organic whitefly control is available from the University of California, Mississippi State University and the University of Missouri.


Conclusion

Whiteflies are an especially pesky group of creatures. They might seem harmless individually, but that’s where the gardener gets caught out. These pests multiply very quickly and before you know it you have an infestation on your hands. You want to do all you can to remove them from your plants and out of your garden, but like with most things, it requires some effort.

These options I have laid out can provide the most effective of results. I believe that in order to more effectively control whiteflies, a combination of these options will provide the best possible outcome. Mixing these options will enable you to see a reduction of the pests in your garden.

Each garden is different and has its own set of growing conditions. Some of this may make it easier for this pest species to multiply. It may be worth looking at your husbandry or even the way you water which may all help in tackling this pest.

I trust you found this post helpful and are ready to get those bugs off your plants. Subscribe to the blog for more helpful posts like this.

Remember folks You Reap What You Sow!

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I am Tony O'Neill, A full-time firefighter and long term gardener. I have spent most of my life gardening. From the age of 7 until the present day at 45. My goal is to use my love and knowledge of gardening to support you and to simplify the gardening process so you are more productive

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How to Control Whiteflies

Last Updated: February 6, 2020 References

This article was co-authored by Andrew Carberry, MPH. Andrew Carberry has been working in food systems since 2008. He has a Masters in Public Health Nutrition and Public Health Planning and Administration from the University of Tennessee-Knoxville.

There are 13 references cited in this article, which can be found at the bottom of the page.

This article has been viewed 47,234 times.

Whiteflies are an unsightly and destructive blight on a garden, covering plants with a cloud of white, moth-like insects and masses of white eggs. They are usually found on the underside of leaves, sucking the sap out of the infested plants. Besides taking the plant's nutrients, these bugs can also encourage the development of mold and spread certain plant viruses. Fight these insects through several angles of attack if possible, introducing their natural enemies to your garden, hanging traps, and inspecting infested plants regularly for manual whitefly removal.


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