Whitefly

Whitefly                           Family: Aleyrodidae

Host plant(s): multiple species

Adult size: varies by species, but generally – 
                        body length: 0.04-0.08 inch (1-2 mm)
                        wingspan: > 0.12 inch (3 mm)

Type: Pest

Life cycle: 
            Generations per year: multiple
            Egg: one week
            Nymph: 4 instar stages
            Pupa: unknown duration
            Adult: about 30 days

 

Description & Life Cycle: Whiteflies are not true flies. They are more closely related to aphids, mealybugs and scale. This puts them in the order of Hemiptera rather than in the order Diptera with the true flies. The name “whitefly” comes from the white wax covering on the wings and body of the adults.

Females lay 200 to 400 eggs in groups of 30 to 40. Eggs hatch in about a week into flattened nymphs with tiny legs. These crawlers, as they are called, will wander around the plant before settling in one spot and inserting their mouth part into the plant to start feeding on its sap. This crawler stays in one place through the next three instar stages…growing larger and losing its tiny legs as it grows larger. At the end of the 4th instar stage, the nymph enters the pupa stage, although technically it does not go through a true complete metamorphosis. Adults emerge to mate and live about a month.

Some adult whitefly species have distinctive markings on their wings but many have no markings. In the nymph stage, colour can be black with a white fringe, transparent yellow or white depending on species.

Whiteflies typically overwinter on plant debris and in branch crevices…although I could not find any mention in which life cycle stage this occurs.

  

Special Notes: There are over 1500 species of whitefly, most of which will feed on only one or a few species of plants. All whitefly species are sap-sucking feeders and a few are responsible for transporting viruses from plant to plant. They are difficult to identify in their specific species designation but are easily recognizable by the cloud of white which will erupt when an infested plant is disturbed. Another indication of a whitefly problem is sticky patches on the upper side of leaves caused by the honeydew excretions from whiteflies feeding in the undersides of leaves higher up on the plant. Another clue can be black sooty mold on the upper side of leaves which develops on the honeydew. While this looks unsightly, it rarely does any serious harm to the plant.

 

Remedial Actions: Whiteflies have many natural enemies in the garden including ladybugs, lacewings, spiders and predator bees as long as you do not use chemical sprays. These sprays are also harmful to beneficial insects.

Another solution is to use yellow sticky traps…although these will catch beneficial insects as well as the pests.

Best remedy of all is to provide appropriate water and nutrients to your plants to guard against pest infestation. Healthy plants are much, much better at thwarting pests from attacking them than those plants which are struggling because they are underfed or underwatered.

 

Posted on February 26, 2020

 

 

Stephanitis takeyai (pieris lacebug)

Stephanitis takeyai (pieris lace bug) - photo by RHS Stephanitis takeyai        Family: Tingidae

Common name: pieris lacebug; andromeda lacebug
Host plant(s): Pieris spp.; Rhododendron spp. (Found on Lindera benzoin & Sassafras albidum in Washington, D.C. in 1977)

Adult size:0.08 – 0.2 inch (2.0 – 5.0 mm)

Type: Pest     

Now found in areas of the Comox Valley but not in our garden, as yet

 

Life cycle: possibly as many as five generations per year, depending on region
                   egg – overwinters
                   nymph – 5 instars, or growth stages, lasting about one month
                   adult – lays up to 300 eggs; does not overwinter

 

Description & life cycle details: Eggs…inserted into, or alongside, the mid-rib on the underside of the leaves and covered by a dark-coloured, varnish-like secretion…overwinter on the underside of pieris leaves. Hatching begins sometime in late April or early May, depending on temperature in your region. Egg hatching can extend over a period of roughly one month.

Emerging nymphs are relatively clear in colour…beginning to darken within a few days. Initially, the young nymphs will remain clustered together but start spreading out into new feeding territories after the second or third moult. They go through 5 instars, or growth stages…the whole growing and moulting process taking roughly about one month. By the time the nymphs reach the 4th instar, they have darkened to brown-black in colour and have grown spines on their bodies. At 5th instar, nymphs are half the size of an adult lace bug.

Adults are up to 0.2 of an inch (5.0 mm) long. Bodies are slightly flattened and black in colour. Clear wings, conspicuous because of the black, lace-like veining and prominent black X-shaped marking, lay flat along the body. Females lay five to seven eggs per day…as many as 300 in their lifespan. There are multiple generations per year, depending on the temperatures and length of the growing season in your region. (Research conducted by the entomolgy department at Pennsylvania State University revealed two to three generations of Stephanitis takeyai occur in that state. The University of Connecticut claims four to five generations are produced every year in their state. No reference found for number of generations in BC.)

 

Special Notes: Native to Japan, this pest was accidentally introduced into the United States around 1945…according to the University of Connecticut. And yet, reports from England claim the pieris lace bug was not discovered in that country until 1998 when it was spotted in a garden near Windsor. In truth, it is definitely on the move.

Both nymphs and adult lace bugs feed on the underside of Pieris spp. leaves…piercing the epidermis layer and sucking up the plant sap. Early clues this pest may be present are the yellowing and mottled appearance on the upper side of the leaves. This mottling and discolouration impacts on the photosynthesis process…reducing overall plant vigour and causing premature leaf drop.

Of special note, the Entymological Society of Washington reported their discovery of two new host plants for Stephanitis takeyai. This pest was found on Lindera benzoin (spicebush) and Sassafras albidum (sassafras) in parts of D.C. in 1977.

 

Remedial Action: During winter months, check underside of pieris leaves for a line of varnish-like substance along the midrib. This is an indication there are hibernating eggs. Treat with horticultural oil at this stage. Keep an eye on shrubs in late April through into May for any signs of hatching light-coloured nymphs. If spotted, and while they are still in a cluster, spray leaves with either horticultural oil or an insecticidal soap. Best results are treating the nymphs while their body is still soft. It will begin to harden by the third moult or so. Repeat spraying in ten to fourteen days to catch newly hatching nymphs…and continue to monitor the shrub for any further pest activity.

 

Posted on January 31, 2015; updated on November 26, 2018

 

 

Stephanitis pyrioides (azalea lace bug)

Photo coming soon

Stephanitis pyrioides        Family: Tingidae

Common name: azalea lace bug
Host plant: azalea; rhododendron

Adult size: 2.5 mm (0.1 inch)

Type: Pest

Life cycle: Generations per year: two to four
                    Egg: 12 – 22 days
                    Nymph: 10 – 23 days through 5 instars
                    Adult: 1 – 4 months

Description & life cycle: Adult lace bugs are roughly 2.5 mm (0.1 in) long. Their cream-coloured body is slightly flat and elongated. The clear wings are laced throughout with tan-brown veins and they lay neatly folded and flat over the abdomen, extending just over the extremities. Given their colour and clear wings, these adult lace bugs can be rather difficult to spot with the naked eye on an infested shrub. Adult longevity is variable; one to four months within a temperature range of 20.5 °C (69 °F) and 32 °C (89.5 °F).

Each day, a female lace bug pierces the lower epidermis layer along the leaf midrib or margin in which to lay 5 – 7 eggs. She then covers them with a brown secretion which hardens to protect the eggs from damage and predators. Over their lifetime, females can lay about 300 eggs, or more.

The white eggs are tiny at a mere 0.36 – 0.43 mm (0.014 – 0.017 in) long and 0.16 – 0.23 mm (0.006 – 0.009 in) wide. They are oval-shaped with a slightly curled neck, resembling a tiny flask. The egg incubation period generally lasts for about 22 days when temperatures hover around 20.5 °C (69 °F); shorter at about 12 days when temperatures rise to around 32 °C (89 °F).

The young nymphs stay together and feed near the egg remnants for the first couple of instar stages before seeking out other feeding spots as they develop through the remaining three instars. They are very pale in their initial instar stages, gradually darkening to dark brown or black and forming spines around the lateral edge of their body. Nymphs are extremely minute at 0.1 mm (0.004 in) in their first instar to 1.8 mm (0.07 in) in their fifth instar. Nymph stage lasts for about 11 days at 32 °C (89 °F), up to 23 days at 20.5 °C (69 °F).

Special Notes: Native to Japan, the azalea lace bug has spread quite widely through the global movement of its very popular, and desirable, host plant. It was positively identified in New Jersey as early as 1915, and more recently in Washington State in 2008 and Oregon in 2009.

The young lace bugs develop on the underside of the leaves, inserting their stylet into the stomata and sucking the sap from the inner leaf tissue. As their population increases, the effects of this feeding results in a yellow mottled appearance on the upper side of the leaves.

Azalea lace bugs feed on both evergreen and deciduous azaleas and rhododendrons. Large populations of this pest can cause serious stress to the plant, even causing death.

Typically, lace bug populations are higher on plants situated in a sunny location versus a plant in a shadier area.

Remedial actions: Spray the upper- and undersides of the leaves with horticultural oil during the winter. This is to minimize killing any beneficial insects which may be nearby, feasting on the lace bugs. Beneficial insects include: ladybugs, lacewings, earwigs and spiders. Repeat to ensure all eggs have been coated with oil and thoroughly smothered.

Through the growing season, provide adequate water and fertilizer for the benefit of healthier plants which are better able to withstand pest damage. Placing mulch underneath the plant will help to keep the soil moist.

 

Posted on December 3, 2018

Blog Archive
Categories
Don’t be a stranger…