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Home , Aphid, Aphididae, Spider mite

Aphids and Scale

Western Colorado Management Workshop

Whitney Cranshaw Colorado State University : Aphids can range in size, shape and patterning Aphids associated with Prunus spp. Aphids associated with Acer spp. Rose Aphids Aphids associated with (Salix spp.) Largest in RM Region – Giant Willow Aphid Giant aphids

Different species are present on junipers, spruce and pines Some aphids are covered with finely powdered wax Some aphids – known as “woolly aphids” – have wax that form long filaments and may cover their body Woolly Aphid Leafcurl Ash Aphid Some aphids are associated with roots of

Sugarbeet root aphid

Rice root aphid Aphids on dandelion roots Root-infesting aphids are often surrounded by wax Aphid life cycles – All aphids go through three feeding stages, each punctuated with a molting event

Aphids will molt 3 or 4 times in their life, becoming an adult after the last molt Diagnostic: Cast skins remain after aphids molt Toothache infested with green peach aphid

Aphids on stem (left) and cast skins dropped onto (right) Asexual – giving live to a genetically identical daughter – is the norm for aphid reproduction Aphid populations can increase rapidly Live birth and are the norm with aphids Adults may be winged or wingless Developing wing pads on aphid Adults may be winged or wingless How do aphids survive winter in areas with freezing temperatures?

• Outdoors – that remain dormant through winter • Survives on perennial host or debris – Nymphs, adults in continuous reproduction • Rare and requires living hosts through winter • Indoors – Nymphs, adults in continuous reproduction Outdoors, almost all aphids have a holocyclic life cycle and produce eggs in autumn. That is normally the stage that survives between seasons.

Overwintered eggs of rose aphid Rose aphids on flower buds Late September on a hemp leaf Sexual forms of aphid and eggs producing form Egg producing form female mating with female with recently winged male Winged male laid eggs Most aphids lay the overwintering eggs on a perennial (often woody) plant

Holocyclic Life Cycle – with host alternation

Life cycle involves a winter host plant and a different summer host plant(s) Green Peach Aphid persicae

An example of an aphid that undergoes a holocyclic life cycle outdoors – and alternates hosts

Overwintering egg laid near the bud Stem mother, the stage that hatches from the overwintering egg On the winter host plant the first generations may cause leaf curling injuries to the new growth Sometime, usually in June, the green peach aphids on the winter host switch to becoming all winged forms – that then disperse to the “summer hosts” Summer hosts include various vegetables and weeds

Spinach, , peppers, , , pigweed, and lambsquarters are common summer hosts

Willow-Carrot Aphid Caveriella aegopodii

Winter Host: Certain European

Summer Hosts: Various Carrot Family (Apiaceae) plants (parsley, dill, carrot) Lysimachia Aphid lysimachiae

Winter Host: Black poplar (P. nigra)

Summer Host: Lysimachia (moneywort, creeping jenny) Cabbage Aphid brassicae One of the very few aphids that may survive Idaho winters outdoors as actively developing stages (nymphs, adults)

No eggs are produced no males and mating occurs – anholocyclic life cycle Life History of Aphids • Holocyclic life cycle – Involves one sexual generation (sexual form female and male) – Results in externally laid egg to survive winter – Often involves alternation of host plants • Winter host (Fall-late Spring) • Summer host • Anholocyclic life cycle – Continuous reproduction without or externally laid eggs How Do Aphids Survive Winter in Areas with Freezing Temperatures?

• Outdoors – Eggs that remain dormant through winter • Survives on perennial host or crop debris – Nymphs, adults in continuous reproduction • Rare and requires living hosts through winter • Indoors – Nymphs, adults in continuous reproduction Primary aphid species found in

Green peach aphid

Cotton-melon aphid Potato aphid

Indoors there is continuous, asexual reproduction. There are no eggs produced, nor sexual forms (males, sexual form females) [anholocyclic life cycle] Plant Injuries Aphids May Produce • Contamination of produce • Reduced vigor from heavy, sustained feeding – Leaf yellowing, premature • Nuisance problems with • Leafcurl distortions of new growth • Vectors of some viral diseases Piercing-sucking mouthparts of Hemiptera In Hemiptera, the mandibles and maxillae become extremely elongated to produce a stylet bundle.

The stylet bundle is sheltered within the labium to produce a “beak” (proboscis). Some sort of “beak” is present on the underside of the head Probocis containing aphid mouthparts

Stylet bundle (mandibles and maxillae) meandering through plant en route to

Aphids use their mouthparts to access the fluids of the phloem.

Little, if any, injury is produced by most aphids. Important Note: Presence of aphids does not always equate to occurrence of plant injury! Sustained feeding by high populations of aphids can produce wilting, leaf yellowing, retarded growth Outdoors there are normally numerous natural enemies usually control aphids before serious damage occurs

Flower fly Lady larva

Green lacewing larva Honeydew production Uptake of phloem fluids here Emergence of “honeydew” here Leaf with sparkles of honeydew – and cast skins The leaf above the honeydew – an aphid colony Leaf with sparkles of honeydew – and cast skins Honeydew Producing Insects* • Aphids • Soft scales • • • Psyllids (some) • (phloem feeding species)

*All suck sap from the phloem Mealybugs Whiteflies Soft Scales Psyllids (some) Sooty Molds Fungi that grow on honeydew-contaminated surfaces Sooty mold growing on linden aphid honeydew

Ants are commonly associated with honeydew producing insects and Aphids A Mutualistic Relationship

-Aphids provide food – honeydew

-Ants provide protection Leafcurl Injuries Produced by aphid feeding on emergent growth, producing distortion Leafcurl Plum Aphid Injury Hawthorn Chokecherry

Peach Leafcurl Ash Aphid

Honeysuckle Witches’ Broom Aphid Leaf curling produced by snowball (viburnum) aphid Aphid Control - Scenario One Aphids are Exposed on the Plant Different Levels of Control Response to Aphids • Do nothing. Natural controls will ultimately take care of things. – Indoor production will require introduction of natural enemies • Treat the plants with a strong jet of water to kill aphids • Use a soap/detergent spray to kill aphids • Use some other effective ‘aphicide’ Check for aphid natural enemies! Photograph courtesy of David Cappaert

Diagnostic: Cast Skins Remain after Aphids Molt

Aphid

Aphid mummies

Parasitized aphids – Photographs courtesy of “aphid mummies” Brian Valentine larva inside aphid mummy

Parasitoid wasp emerging from aphid mummy

Old aphid mummy with exit hole made by emerging wasp

Lady beetle larvae Adults

Eggs

Lady Beetle Life Stages

Pupae

There can be different levels of response to an aphids infestation

• Do nothing. Natural controls will ultimately take care of things. • Treat the plants with a strong jet of water to kill aphids • Use an effective ‘aphicide’ – Contact sprays – Systemic Hosing for aphid control Rose Aphids - Before

Rose Aphids - After Some aphid control products – Exposed Aphids • Insecticidal Soaps • –Bifenthrin, cyhalothrin, cyfluthrin, etc. • Neonicotinoids – –Acetamiprid Aphids have already produced a leaf curl?

Insects that work by contact will not control this problem – and can easily make it worse For control of aphids in existing leafcurls only an that moves systemically in plants will provide control

Systemic insecticides Systemic insecticides applied to applied to soil Insecticide control options for aphids

Acetamiprid for Aphid Control

• Best used as a spray • Has systemic activity in plant – May kill through ingestion or contact • Extended residual activity – May kill aphids for days-week? – Fairly conservative of natural enemies Commercial formulation for ornamentals

Retail formulation

Acetamiprid Commercial formulation formulations for fruits and vegetables Comparison of UV Stability among Neonicotinoid Insecticides

35

30 25 Acetamiprid 20 Imidacloprid Thiamethoxam 15

Half life (days) 10 Clothianidin 5 0 Aquatic Photolysis

Data obtained from published EPA registration documents

Slide Credit: R. Fletcher UV Stability

Neonictoinoids are generally not UV stable. Foliar persistence can be shortened by this feature.

Acetamiprid is an exception. Acute Toxicity of Neonicotinoids to Adult (Oral LD50 – micrograms/) • Acetamiprid 14.53 • Imidacloprid 0.005 • Dinotefuran 0.056 • Thiamethoxam 0.005 • Chlothianidin 0.0003 Insecticide control options for aphids

Imidacloprid for Aphid Control

• Best used as a soil application • Has systemic activity in plant • Slow uptake/Extended residual activity – May kill aphids for weeks- months? – Conservative of some natural enemies Dormant Oils? May manage many spring aphid problems – if they spend winter as eggs on the plant Oils can kill overwintering eggs of aphids. The application must cover the egg, which can then be killed by suffocation.

Aphid egg No overwintered egg – no stem mother No overwintering egg, no spring leaf curl : Tetranychidae

Photograph by Ward Strong Photograph by Eric Day Spider mites pierce cells with their whip-like chelicerae

Typically they will destroy 1 to 2 dozen cells at each feeding site – then move on “Rototill and Suck” Each feeding site produces a small area of dead cells – a type of stippling injury With high populations, the stippling injuries may cover much of the leaf area. Leaf bronzing A response seen in many plants in reaction to spider mite damage Symptoms on evergreens are more subtle – A duller, grayer color is typical In high populations, some spider mites will produce visible silk Silk can protect the spider mites and provide pathways for movement across a plant. Life Stages of the Twospotted Spider Mite Male spider mite

Female spider mite with eggs Photographs courtesy of David Shetlar Spider mites lay eggs that are quite large in proportion to their body Honeylocust spider mites, eggs and discarded skins Mites can disperse by -borne ‘ballooning’ Color change in mites going into dormancy (Diapause) Green summer form on leaves

Orange-red overwintering form around buds

Seasonal color changes in honeylocust spider mite

Honeylocust Spider Mite Platytetranychus gleditsiae Conifer spider mites Colorado species are common on junipers, arborvitae, and ponderosa pine Spruce Webbing on Spider Mite needles

Photograph by Petr Kapitola

Photograph by Bruce Watt Adult and discarded skins

Eggs on twigs Photograph by and needles Petra Kapitola Mites on are “cool- season” species

Peak activity of mites - fall, spring Peak expression of symptoms - summer Spider Mite Management

• Monitor high risk plants • Minimize drought stress • Maintain fairly high humidity • Take particular care with pesticide use on mite sensitive plants Sample plants to detect potential outbreaks Spider mites always leave behind cast skins and egg shells – great for diagnostics!

Cast skins

Live spider mites, eggs and cast skins Interactions of Drought, Drying and Spider Mites on Landscape Plants • Physiological effects acting through host plant –Changes in host suitability –Changes in tolerance to mite injuries • Alteration of leaf surface temperatures • Interactions with relative humidity • Physical effects of irrigation Interactions of Drought and Spider Mites

Drought-stressed plants may be more nutritionally suitable hosts.

Leaf surface temperatures increase on drought stressed plants Interactions of Dry Air/Low Humidity and Spider Mites

• Dry air allows spider mites to more rapidly evaporate waste fluid • Dry air is often seriously stressful to spider mite predators Minute pirate bug (feeding on

Predatory thrips Natural enemies of spider mites

Predatory mite feeding on spider mite “Spider mite destroyer” lady Predatory Mite: Galendromus occidentalis

Optimal environmental conditions

80-100 degrees F > 50% RH Predatory Mite: Mesoseiulus longipes

Can only tolerate the very low humidity of 40% when the temperature is 70°F.

Requires increasing humidity as temperature rises. Drought stress greatly contributes to spider mite problems

About 6 feet from building, Next to house, SW exposure on support trellis of porch Another example. Honeylocust spider mites primarily are pests on street trees in Colorado. A strong jet of water can wash off many spider mites from plants Mite Control Products • Least disruptive of natural enemies – Floramite (bifenazate) – TetraSan (extoxazole) – Hexygon (hexythiazox) – Horticultural oils • Moderately disruptive of natural enemies – Forbid (spiromesifan) – Avid (abamectin) • Highly destructive to natural enemies – All pyrethroids (Onyx, Talstar, Scimitar…) Use of many pesticides can aggravate (‘flare’) problems with spider mites Predators of spider mites include minute pirate bugs (left), predatory mites (below left) and predatory thrips (below) Mite Control Products Least disruptive of natural enemies Floramite (bifenazate) TetraSan (extoxazole) Hexygon (hexythiazox) Horticultural oils • Moderately disruptive of natural enemies – Forbid (spiromesifan) – Avid (abamectin) • Highly destructive to natural enemies – All pyrethroids (Onyx, Astro, Tempo, Scimitar…) Horticultural Oils Mite Control Products

• Least disruptive of natural enemies – Floramite (bifenazate) – TetraSan (extoxazole) – Hexygon (hexythiazox) – Horticultural oils • Moderately disruptive of natural enemies –Forbid (spiromesifan) –Avid (abamectin) • Highly destructive to natural enemies –All pyrethroids (Onyx, Tempo, Astro, Scimitar…) Imidacloprid and Spider Mites

Observation, mid 1990s – Spider mites seemed to be a new problem on many plants treated with imidacloprid Far more spider mites and injury occurred on plants treated with imidacloprid Why? Original thought was that imidacloprid was killing the natural enemies of spider mites. Some neonicotinoids (imidacloprid, chlothianidin) can suppress the jasmonic acid pathway – a primary plant defense mechanism Spider Mite Management

• Monitor high risk plants • Minimize drought stress • Increase humidity • Take particular care with pesticide use on mite sensitive plants