Rose Insects: What arethey are doing?

Whitney CranshawColorado State University

Photo courtesy Mike Klein

Some Topics for Today

• Review a few rose insects that have a bit of surrounding mystery

• Provide a few notes of diagnosis• Identify issues of landscape plantings

that allow “cross-talk” of rose insect pests

• Cover some of the newer insecticide options

Some Rose Insects with a Bit of Mystery

• Borers vs. Pith nesters• Leafcutter bees• Rose curculio• Rose midge• Rose leafhopper

“True” borers have larvae that feed and develop by

tunneling plants

There are few true borers associated with garden roses

Pith-nesters utilize the pithy area of canes to

rear their young

Pith-nesters enter through cuts or breaks and largely limit

tunneling to non-living tissues

There are few true borers of rose

• Raspberry horntail• Rose stem girdler (Bronze

cane borer)

Photo by James Amrine

Rose stem girdlerAgrilus aurichalceus

Occasional borer of roses

Adults are a metallic wood borer. They emerge in midSpring and lay eggs on the surface of branches.

Photo by William Ciesla

Larvae are a type of flatheaded borer that girdles the cambium

Larvae develop by girdling the stem, feeding on the cambium

Photo by James Amrine

Girdling weakens stems and can produce stem dieback

Photo by James Amrine

Rose Stem Girdler Control

• Prune plants to remove developing stages before adult emergence (midMayin Colorado)

• Applications of the soil systemic insecticide imidacloprid in spring should provide control.

Rose Stem GirdlerGarden “Cross Talk”

Rose stem girdler is also a common insect associated with

Ribes and Rubus, as well as various Rosa spp.

Raspberry HorntailHartigia cressoni

Occasional borer of roses

Rose stem sawfly, Hartigia trimaculata, is reported from the eastern US

Larvae tunnel primarily in the pith, but will cut into tissues that move water, nutrients

Wilting of raspberry tips from raspberry horntail larval tunneling

Wilting of rose terminal by raspberry horntail

Raspberry Horntail Control

• Prune plants to remove developing stages before adult emergence (early May in Colorado)

Raspberry HorntailGarden “Cross Talk”

Raspberry horntail is primarily an insect

associated with brambles (Rubus

spp.) and only incidentally affects

rose

Pith NestersBees and wasps that use canes for rearing young

Pemphredon hunting wasp

Small carpenter bee

Small diameter entrance used by Pemphredonhunting wasps

Adult wasp visiting old rose cut

Hunting WaspsFamilies Sphecidae,

Pompilidae

Ammophila wasp digging nest (left), carrying caterpillar prey (lower left), at nest entrance with prey (below)

Bembix wasp digging while holding horse fly prey

Photo courtesy Howard Ensign Evans

Pemphredon wasps hunt small insects such as aphids. These are paralyzed and cached within the tunnels to feed their young.

Young wasps develop in chambers within the pith

Small carpenter bees nest in broken twigs – or pruned roses and brambles.

The cells for rearing young are provisioned with nectar and pollen.

Control: Cover pruning cuts with a thumb tack or….

… or a bit of glue

Entrance holes for pith nesters in canes

Using old prunings to provide condominiums for pith nesting insects

Leafcutter BeesSolitary Bees

Hymenoptera: Megachilidae

Leafcutter Bee Excavating Rotten Porch Board

Leafcutter Bee Damage to Rose, Lilac and Virginia Creeper

Leafcutter Bee Carrying Leaf Fragment

Sawdust from workings of leafcutter bees on a partially rotted log

Returning bee with leaf fragment

Leafcutter bee carrying leaf fragment

Photo courtesy VWR

Leafcutter bee collecting pollen

Leafcutter bee nest cells in pith of weed

Courtesy Ken Gray

Courtesy Ken Gray Collection – Oregon State University

Courtesy Ken Gray Collection – Oregon State University

For nest construction:

3-4 rectangular pieces, crimped for the base

Oval pieces along the sides of the cell

Near perfect circles used to cap the cell

All leaf fragments are oriented with the smooth side inwards

Leafcutter Bee Boards

Leafcutter bees working sweet pea

Alfalfa leafcutter bees are used to produce alfalfa that is grown for seed

Markings on the bee blocks guide the bees to their individual nest tunnel

Rose curculioRose CurculioMerhynchites bicolor

Ken Gray Collection

Adults are present in spring on the buds of shrub roses

Rose curculio feeding punctures rose buds

Earlier bud feeding results in emergence of punctured petals

Feeding punctures are also used for egg laying. Larvae develop in blossoms, then drop to the soil to pupate.

Rose Curculio Control

• Knock of adults into collecting container and destroy

• Prune – and remove – spent blossoms to prevent development of larvae

Rose MidgeDasineura rhodophaga

All rose midge photos courtesy of Robin Rosetta

A related species of gall midge, honeylocust podgallmidge, Dasineuragleditschiae

Rose midge larvae develop under the sepals of flower buds. Bud tissues are sliced by the feeding midge larvae.

Degree of injury can vary depending on insect pressure and plant growth stage infested

All rose midge photos by Robin Rosetta

Key Aspects of Rose Midge Biology

• Adults overwinter as pupae in soil• Larval development on plants is

rapid (less than a couple of weeks)• Pupation occurs in soil• Multiple generations (5+) may

occur during a growing season

Rose Midge Control• Exclusion of potentially infested

material from midge-free plantings• Rigorous pruning and destruction

symptomatic buds• Management of insect stages on

plants• Management of insect stages in

soil

Rose Midge Control

• Exclusion of potentially infested material from midge-free plantings

• Rigorous pruning and destruction symptomatic buds• Management of insect stages on plants• Management of insect stages in soil

Rose Midge Control• Exclusion of potentially infested material from midge-free

plantings

• Rigorous pruning and destruction symptomatic buds

• Management of insect stages on plants

• Management of insect stages in soil

Rose Midge Control• Exclusion of potentially infested material from midge-free

plantings

• Rigorous pruning and destruction symptomatic buds–Prunings must be destroyed–Consider “host-free” period?

• Management of insect stages on plants

• Management of insect stages in soil

Rose Midge Control• Exclusion of potentially infested material from midge-free

plantings• Rigorous pruning and destruction symptomatic buds

• Management of insect stages on plants

• Management of insect stages in soil

Rose midge control:Combination imidacloprid and beta-cyfluthrin.

Contains a systemic neonicotinoidinsecticide (imidacloprid) and a persisting pyrethroid(beta-cyfluthrin)

Rose midge control: Bifenthrin (persisting pyrethroid)

Spinosad for rose midge?

Rose Midge Control• Exclusion of potentially infested material from midge-free plantings• Rigorous pruning and destruction symptomatic buds• Management of insect stages on plants

• Management of insect stages in soil– Insect parasitic nematodes– Imidacloprid– Persisting pyrethroid insecticides

(beta-cyfluthrin, permethrin, bifenthrin, etc.)

Rose LeafhopperEdwardsiana rosae

Nymphs emerge in spring from eggs inserted into twigs

Brambles are other overwintering hosts for this insect

Rose leafhopper nymphs (immature stage)

Rose leafhopper injury – “stippling”produced by mesophyll feeding

Adult rose leafhopper and old cast skin of nymphal stage

Adult rose leafhoppers disperse from rose and develop in summer on various fruit trees

Insect may be gone – but stippling and sometimes old nymphal skins remain diagnostic

Rose LeafhopperGarden “Cross Talk”

Brambles are alternate overwintering hosts. Summer

hosts include apple, stone fruits and other rosaceous family plants.

Rose Aphid (Macrosiphum rosae)

Rose aphid overwinters as eggs located in protected areas of the plant

This is the only period during the year when aphids produce and external egg.

Rose aphid sequence courtesy Ken Gray Collection/Oregon State

Different Levels of Control Response

• Do nothing. Natural controls will ultimately take care of things.

• Treat the plants with a strong jet of water to kill aphids

• Use a soap/detergent spray to kill aphids

• Use an effective ‘aphicide’

Check for aphid natural enemies!

Aphid natural enemies include:

• Lady beetles• Larvae of syrphid

(flower) flies• Green and brown

lacewings• Parasitic wasps

Lady beetle larvae

Lady beetle prepupae and pupae

Flower (Syrphid) Flies

Flower (Syrphid) Flies

Honey Bees

Syrphid flies are excellent mimics of bees and wasps

Syrphid egg in aphid colony

Flower fly larvae

Aphid-feeding syrphid larvae excrete a tarry material

Hosing for aphid control

Rose Aphids - Before

Rose Aphids - After

Some Aphid Control Products

• Insecticidal Soaps• Orthene• Imidacloprid• Malathion• Esfenvalerate

Soaps as Insecticides

Systemic insecticides can move with the plant.

Some older insecticides with systemic activity

Some Disyston containing products for use on roses

Imidacloprid

A combination product -

Imidacloprid plus cyfluthrin

Combination products with a fungicide and/or miticide (tau-fluvalinate)

Spider Mites

Spider Mite Management

• Monitor high risk plants• Minimize drought stress• Increase humidity• Take particular care with

pesticide use on mite sensitive plants

Interactions of Drought and Spider Mites

Drought-stressed plants may be more nutritionally suitable hosts.

Free amino acids may increase in the sap of drought stressed plants.

Interactions of Dry Air/Aridity and Spider Mites

• Dry air allows spider mites to more rapidly evaporate waste fluid

• Dry air is often seriously stressful to spider mite predators.

Drought stress greatly contributes to spider mite problems

Use of many pesticides can aggravate (‘flare’) problems with spider mites

Imidacloprid and spider mites – a concern for rose growers?

Imidacloprid can increase problems with spider mites (“flare mites”) on many ornamental plants

Predators of spider mites include minute pirate bugs (left), predatory mites (below left) and predatory thrips (below)

Currently, there are few over-the-counter miticides

• Horticultural oils• Sulfur dusts• Bifenthrin• Hexakis (found in some

Orthenex combination products)

Oil-containing insecticidesAbove: Mineral oil

Right: Neem seed oil

A product containing bifenthrin as the active ingredient

3-in-1 combination products contains imidaclopridand a marginal miticide (tau-fluvalinate)

A new publication from the American PhytopathologicalSociety (APS)

A book we use locally for Master Gardener training

A book to get kids interested in the insects that occur in this region

A general reference for insects

Buy lots of copies! Help me get my kids through college!

bugbooksdirect@yahoo.com