Download Pest of Perennials with Notes 2006

Major Insects & Mites
That Attack Ohio
Landscape Perennials
Dr. David Shetlar (the BugDoc)
The Ohio State University
OARDC/OSU Extension
Columbus, OH
© D.J. Shetlar, 2006, all rights reserved
Major Insects & Mites
That Attack Ohio
Landscape Perennials
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Plant bugs, Aphids & Psyllids
Sawflies & Caterpillars
Twospotted spider mite
Leafminers
Slugs (not arthropods!)
Notes:
Each perennial plant has its own set of insect and mite
pests, but many of these pests are very similar in their life
cycles and/or feeding habits (e.g., aphids, plant bugs,
caterpillars, sawflies, borers, spider mites, etc.). This
presentation will cover some examples of generalist pests
(ones that attack a wide variety of perennials), and pests
that can serve as examples of their group type. These are
herein considered to be “major” pests.
The presentation will also cover some non-arthropod pests
– such as snails and slugs.
“Bugs” & Aphids
On Perennials
 Fourlined plant bug - one generation.
• Most damage in May & early June.
• Prefers mint family.
 Aphids – many species, several
generations per season.
• Look for predators – be patient!
• Syringe (hose off with water).
Notes:
Most people think that all “bugs” suck, but actually only
certain kinds of insects have sucking mouthparts. The
“bug” group (Order Hemiptera) contains plant and leaf bugs,
seed bugs, stink bugs, aphids, scales, spittlebugs,
whiteflies, and plant hoppers. All have gradual life cycles
with egg, nymph and adult stages though this type of life
cycle can be highly modified (e.g., scales and whiteflies) or
complicated by different forms that move from plant to plant
over the season (e.g., aphids).
Fourlined plant bug
(damage above), late instar
nymph (above right), and
adult (right).
Notes:
While the fourlined plant bug prefers perennials in the mint
family, it is known to attack several hundred perennials,
annuals and small woody shrubs. There is only one
generation per year with the small red and black nymphs
causing noticeable twisting and distortion of expanding
leaves and shoots as well as making distinctive black or
purple sunken areas in the leaves. These are spots where
the bugs have inserted their sucking mouthparts, injected
saliva to liquefy the plant tissues and removed this
predigested material. In young tissues, the scars that
remain cause the plant distortion.
Since this bug overwinters as eggs inserted into remaining
plant stems, cutting and removal of these parts in the fall
can help control the pest.
Tarnished plant bugs also
damage various perennials
as well as several shrubs.
Tarnished plant bug
nymph (above), and
adult (right).
Notes:
The tarnished plant bug is another generalist feeder in
landscapes and while the green and brown nymphs can
cause damage to expanding foliage that is similar to the
fourlined plant bug, the major damage caused by the
tarnished plant bug is to flower ovaries. Larger nymphs
and adults feed at the bases of flowers, thereby killing
developing seeds. This is usually only important where
seeds are being collected from the plants. This pest can
have several generations over the summer and adults
commonly overwinter in litter.
Other
Miscellaneous
Bugs
Many stink bug species
feed on seeds and
flowers.
Chrysanthemum lace
bugs are unique in that
they prefer leaf upper
surfaces!
Notes:
There are dozens of small species of stink bugs that tend to
feed on the flowers of perennials. This often causes the
flowers to wilt earlier than normal and causes a lack of seed
set or development. Most stink bugs are mere nuisances.
The chrysanthemum lace bug is unique in that the adults
and nymphs are often located on the upper leaf surfaces of
perennials in the mum and goldenrod families. They can
cause blanching of the foliage and poor overall growth.
Other sucking insects that
attack perennials include tree
hoppers (left) and leafhoppers
(below). The painted
sharpshooters (a kind of
leafhopper) cause puckering of
leaves. The nymphs (below)
run sideways.
Notes:
There are several species of treehoppers, planthoppers and
leafhoppers that may be found infesting perennials. Some
are very host specific and others feed on a variety of plants.
The treehoppers and planthoppers rarely cause any
noticeable damage, but the insects jumping around when
disturbed can annoy gardeners.
Leafhoppers are wedge-shaped insects that run sideways
and readily jump and fly when disturbed. These insect often
distort the growth of expanding leaves or stems and some
transmit diseases that can slow the growth of infested
plants.
Rudbeckia psyllids cause
disease like purple blotches
on the leaves of host plants.
The psyllid nymphs
and pupae look like
scales.
Notes:
Psyllids (jumping plant lice) are fairly common pests of
landscape plants, but many go unnoticed. Recently, the
brown-eyed Susan psyllid was discovered in Ohio because
the nymphs make distinctive purple blotches on the leaves.
This blotch was thought to be a disease until the nymphs
were discovered on the undersides of the affected leaves.
Since its discovery, this psyllid is now found across Ohio and
most of North America. Not much is known about this pest,
but is appears that adults overwinter in leaf litter, so cleaning
out perennial beds may help in reducing the survival of these
adult psyllids.
Most perennials have one
or two species of aphids
that may feed on them.
The goldenrod aphid
(above) feeds on a variety
of daisy and composite
flowers. The milkweed
aphid (right) feeds
exclusively on plants in the
milkweed family.
Generalized diagram of an aphid life cycle showing a species that alternates
asexual and sexual forms along with alternation of hosts.
Notes:
There are hundreds of species of aphids! Almost every perennial has its
own species, but there are also some generalist species that can infest
several different perennials.
Aphids often have complicated annual life cycles in which the alternate
from asexual to sexual reproduction and they may use two alternate host
plants during the season. Most aphids overwinter as eggs attached to a
woody perennial plant. These eggs hatch into “stem mothers” that give
live birth only to females. These females also give live birth
(ovoviviparous) without mating (parthenogenic) and development can be
completed in five to 10 days. In June and July, these aphids often
develop wings and fly to alternate, summer hosts where they continue
their asexual reproduction, but their forms can change! In September
and October, these aphids give birth to sexual forms (males and
females) that mate, fly back to the spring host plant, lay eggs and die!
These alternations of hosts and reproduction types probably inhibit
predators and parasites, and also help explain the sudden appearance
and disappearance of aphids during the season.
Plant Bug & Aphid Control
(for homeowners)
Traditional
• Diazinon
X
• Dursban
X
• Sevin
• Orthene
?
• DiSyston
(Bayer
Advanced 2-in-1
Rose Systemic
Granules)
Still/Now Available
• Pyrethroids
(permethrin, resmethrin,
esfenvalerate,
bifenthrin, cyfluthrin)
• Soaps & Oils
• Sevin, Malathion
• Imidalcoprid (Bayer
Advanced Tree & Shrub
Concentrate)
Sawflies & Caterpillars
On Perennials
 Columbine sawfly – one generation
(May to June).
 Hollyhock sawfly – 3-4 generations.
 “Generalist” caterpillars – cabbage
looper, European corn borer, green
fruitworm.
 Stalk Borer & Iris Borer – not much
you can do other than remove!
Notes:
While sawflies and caterpillars may look alike, they are the
larvae of completely different types of insects – wasp-like
insects and butterflies or moths. In the past, this wasn’t too
important as insecticides usually killed either one. However,
newer insecticides may kill sawflies, but have little action
against caterpillars! Both larva have fleshy leg-like
structures on the abdomen, called prolegs. Sawflies have
seven to nine pairs of prolegs while caterpillars will have five
pairs of prolegs or fewer. Caterpillars with only two or three
pairs of prolegs are usually called inchworms or loopers.
Most sawflies are very host specific, but several caterpillars
are generalists, feeding on a wide variety of hosts.
Columbine sawflies can
completely defoliate
plants by the time they
are ready to flower.
Columbine sawflies hide on
the undersides of host
leaves during the day.
Though the larvae look like
caterpillars, they have more
than 5 pairs of prolegs on
the abdomen – a sawfly
characteristic.
Hollyhock sawfly larvae
skeletonize leaves and
the damage is often
mistaken for Japanese
beetle damage.
Larva (below)
Adults
look like
small
wasps or
flies.
Lysimachia sawfly larvae
are covered with a white
powdery material.
The violet sawfly
produces damage that
often looks like slug
damage – look on leaf
undersurfaces to
determine if the sawfly
larvae are hiding there.
The cabbage looper
may be found on a
variety of annual or
perennial flowers as
well as vegetable
crops.
Fruitworms
usually attack
fruit tree foliage,
but they may be
found on roses
and perennials.
The milkweed tiger
moth has a striking
caterpillar that feed on
all plants in the
milkweed family.
American painted lady
caterpillar feeding on
perennial.
Sawfly Insecticides
(for homeowners)
Traditional
• Dursban
X
• Diazinon
X
• Sevin
• Orthene
Still/Now Available
• Pyrethroids
(permethrin,
resmethrin,
esfenvalerate,
bifenthrin, cyfluthrin)
• Merit
• Sevin & Orthene
• Soaps or Oils
Caterpillar Insecticides
(for homeowners)
Traditional
• Dursban
X
• Sevin
• Orthene
X
• Malathion
Still/Now Available
• Sevin & Orthene
• Pyrethroids (permethrin,
resmethrin, esfenvalerate,
bifenthrin, cyfluthrin)
• Merit (imidachloprid – not
recommended)
• Bt
• Soaps or Oils
The iris borer overwinters in the egg stage attached to old
leaves. The eggs hatch in spring and the larvae burrow
down the leaves to the rhizomes. They continue feeding all
summer, nearly eating all the rhizome internal tissues. The
larvae drop out in August, pupate in the soil and the adult
moths emerge in October into November.
Notes:
The iris borer is actually a caterpillar of a moth that is in the
same family as cutworms. However, this larva burrows into
the stems and rhizomes of iris, feeding inside them. By late
July and August, the mature larvae can have completely
hollowed out the rhizomes and killed the iris plants. While
this pest prefers bearded iris, it will attack almost all species,
except for the bulb-type iris.
Iris Borer Insecticides
(for homeowners)
Traditional
• Dursban
X
• Lindane
X
• Cygon
(dimethoate)
• DiSyston
X
Still/Now Available
• Cygon (dimethoate, Bayer
Advanced 2-in-1 Rose
Systemic Granules)
• ???
Twospotted Spider Mite
On Perennials
 Prefer hot-dry conditions.
 Females overwinter in mulch &
protected areas OFF THE PLANT.
 Often “reinstalled” on new bedding
plants.
 Often resistant to common miticides.
Twospotted spider mites can
completely web over the
foliage of their hosts.
Twospotted spider mite
eggs, nymphs and adults
generally reside on leaf
undersurfaces unless they
have completely covered
their host foliage.
Miticides
(for homeowners)
Traditional
• Kelthane
X
• Cygon
?
• Soaps & Oils
• Orthene
NO! ?
Still/Now Available
• Pyrethroids??
NO!
• Soaps or Oils
• DiSyston (Rose
Systemic Granules) ?
• Conserve (=Naturalite)
??
Notes:
At present, we have lost all true miticides that used to be
available in the over-the-counter market! While some of
the pyrethroids and Orthene claim spider mite control on
their labels, these tend to make spider mite infestations
worse, not better! Insecticidal/miticidal soaps and
horticultural oils work well, but these can damage flowers
when plants are in full bloom. Products containing
Spinosad are available on the Internet and these can
provide some suppression of spider mites.
Coneflower flowergall
mites are eriophyids.
Eriophyids are often not
susceptible to regular
miticides.
Notes:
There are few eriophyid mites (gall and rust mites) that
seem to cause much damage in perennials. This
coneflower flowergall mite is commonly found in Ohio
plantings, but the damage can be mistaken for disease or
herbicide damage. There are no insecticide or miticides
available to control this mite, but thorough cleaning of the
flower bed in the fall can help reduce the infestation for the
next season.
Leafminers on Perennials
 Columbine leafminer(s) – several
species with multiple generations
per year - dipterous.
 Serpentine leafminers – several
species that attack Phlox,
hollyhocks and others - dipterous.
Notes:
Leafminers are insects that have small, flat larvae that can
live between the epidermal layers of leaves. These flat
larvae “mine” the spongy tissues, leaving behind a
characteristic trail or blotch that is visible on the leaf surface.
There are leafminers that are sawflies (hymenopterous),
flies (dipterous), beetles (coleopterous), or moths
(lepidopterous). Most of the leafminers that attack
perennials are dipterous leafminers.
Columbine leafminer adults
(above left) feed by making
“pinholes” in leaves (left). Eggs
are inserted into leaves and the
larval maggots make winding
mines which may end in a large
blotch.
Leafminer Insecticides
(for homeowners)
Traditional
• Dursban
X
• Lindane
X
• Cygon
X
(dimethoate)
• DiSyston
• Orthene
• Neem
(azadirachtin)
Still/Now Available
• Pyrethroids
(permethrin,
resmethrin,
esfenvalerate,
bifenthrin, cyfluthrin)
• Merit ?
• Neem ?
• Conserve ?
• DiSyston & Orthene ?
Notes:
Since most leafminer larvae are not discovered until they
have started feeding within their host’s leaves, systemic
insecticides are needed in order to reach them. Surface
applications of pyrethroids are used to knock out the adults
that are laying eggs into the leaves, but these types of
applications are difficult to time and several applications may
be needed in order to cover the time that the adults are
active.
A half dozen species of
slugs can be found in
Ohio landscapes and
most will feed on the
leaves of plants while
others specialize on
feeding on fungi.
Garden snails are not
common in Ohio, but
they occasionally
become established
through recent plantings
of new plants. Most
can’t survive Ohio
winters.
Notes:
There are about a half dozen species of slugs in Ohio and
these are the most common mollusk pests of perennials.
Snails can be damaging, but these are rarely found in Ohio
landscapes. Since slugs and snails are not arthropods,
special pesticides are usually needed for their control.
Over mulching and over watering commonly contribute to
slug buildup in landscapes. For every slug you see on the
surface, there are probably five to 10 in the mulch and soil
profile! Therefore, several applications of a slug bait may be
needed in order to greatly reduce this pest. Most baits also
loose their attractiveness if wetted by rain or irrigation.
Molluscicides
(for homeowners)
Traditional
• Metaldehyde
• Methiocarb
X
Still/Now Available
• Iron Phosphate
(Sluggo)
• Metaldehyde (Deadline)
Black Vine Weevil
On Perennials
 Not a common landscape pest of
perennials, mainly in container
production areas.
 One generation per year, females
lay eggs over long period of June
& July.
 Larvae overwinter in soil or pots.
Black vine weevils are
commonly called the Taxus
Weevil because this is one
of their favorite hosts.
Black vine weevil larvae look
like scarab white grubs, but
weevil larvae have no
obvious legs (right).
Black Vine Weevil
(adults only)
(for homeowners)
Traditional
Still/Now Available
• Dursban
• Pyrethroids (cyfluthrin,
X
resmethrin, bifenthrin)???
• Turcam
X
(professionals only) • Cygon & DiSyston?
• Orthene
X
Simple Black Vine Weevil Management
Merit! (home owner product
available, Bayer Advanced
Tree & Shrub Concentrate)
apply to soil for larval control,
NOT mulch, not for adults!)