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Stem Pests: (some Homoptera). Before we move on to stem pests, there are still some basic entomological topics to discuss. In particular, the digestive system. Why?. In order to better understand your favorite aphid and other homopterans. Remember Aphid Feeding. Hindgut. Midgut. Foregut.

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Stem Pests:

(some Homoptera)

Before we move on to stem pests, there are still some basic entomological topics to discuss.

In particular, the digestive system. Why?

In order to better understand your

favorite aphid and other homopterans

Remember Aphid Feeding entomological topics to discuss.

Hindgut entomological topics to discuss.








Generalized insect digestive


Foregut entomological topics to discuss.





Filter chamber

of aphids and

other homopterans


Honey dew

Honeydew from aphids
Honeydew from aphids entomological topics to discuss.

0.5mm entomological topics to discuss.

Now we can move on to the stem

pests, starting with the balsam

woolly adelgid1

1 Really belong to the family Phylloxeridae

The Balsam Woolly Adelgid entomological topics to discuss.1,

Adelges piceae.



1 Phylloxerid

1905 in a small coastal town in Maine, a Quarantine Inspector.

These European fir trees have only female

Adelges piceae -- I’ll let them pass.

“Males? We don’t need Inspector.

males; we’re


BWA Inspector.

Dead Fraser-fir

Unfettered population growth by the BWA began and in a few decades; they killed fir trees in the Canadian Maritime Provinces and today are into the Appalachian Mtns. destroying Fraser fir across thousands of acres.

The Balsam Inspector.

Woolly Adelgid

Comes West in



The BWA infest and kill: Inspector.

No. 1 subalpine fir, No. 2 grand fir,

No.3 silver fir & noble fir, and No. 4

Shasta-red fir is barely attacked.

Life Cycle of the BWA Inspector.

(1) The BWA overwinter as a diapausing

1st instar, the winter form.

(2) In early spring, the 1st instar swells and

begins to produce honey dew as the tree

sap starts flowing.

(3) The immature female molts several times

and becomes an adult in ± 3 weeks.

(4) Each female then lays ± 100 eggs.

BWA laying


BWA crawlers Inspector.

(5) Eggs hatch in about a week and each

motile nymph crawl rapidly around the

new foliage, twigs and branches.

(6) These motile nymphs then thread their Inspector.

stylets through the bark and tap a vascular

bundle -- they are stuck for life, a life of

sucking sap, the summer form.

(7) This summer generation, then aestivates

for 1 - 2 months.

(8) In July they “wake up” and quickly

molt to adults. These summer-generation

adults lay ± 50 eggs apiece.

(9) Depending

on the climate,

elevation, site,

aspect etc., there

maybe 2 - 3


The BWA in action! Inspector.

One mm

Motile nymph



Bark surface

Nymph stuck

in the phloem

As BWA feed they inject a toxin into Inspector.

the actively growing tissues, which

causes hyperactive growth & galls

A few Inspector.




The BWA Disaster

Subalpine Inspector.

fir near

the town of


More BWA Damage

In order to understand why its so Inspector.

difficult to control the BWA, let’s

discuss the Mortality Quotient.

The Mq asks: “how many individuals of an insect population must be killed to prevent the population from


Mq depends on: (1) fecundity

number of eggs a female will lay, &

(2) sex ratio.

Mq = (F)(SR) - 1 Inspector.


Mq = Mortality Quotient

F = Average No. Eggs

SR = No. Females

No. Females + Males

(75) - 1 Inspector.


= 0.986

The iris bulb fly:

Fecundity = 150

Out of 1000 puparia you collected, 500

are males.

There is one generation/yr

of the gladiola bulb fly.

Mq = (150)(0.5) - 1

( 150)(0.5)

150 X 0.986 = 148

So: 150 - 148 = 2 (a male and a female)

150 eggs

BWA Inspector.

(100)(1) - 1

Mq =

= 0.99/generation


i.e., 100 eggs - 99 killed = 1 female!

  • Management of BWA in the urban environment Inspector.:

  • Avoid planting subalpine fir

  • Maintain a high vigor in plantings

  • of other Abies spp.

  • Consider applied control of BWA-infested firs if they have special intrinsic value, e.g. a historical fir planting within the Japanese Garden.

  • Consider applied control when the aesthetic value of a commercial Abies spp. planting is threatened,

  • e.g. the Christmas tree industry.

Apply insecticide bud-break time.

at time of budburst,

you should see tiny



The balsam twig aphid, bud-break time.Mindarus abietinus


new growth

Stem mothers


BTA on the stem

April - May: stem mothers sucking on stem next to new buds or on new foliage – needles twist.


May - Mid June:

vivipary in action:

2 or more generations

of wingless females.










June: a winged generation or on new foliage – needles twist.

flies off to an alternate


Unknown or on new foliage – needles twist.


July - August:

both males and females

are produced and they

fly back to true firs

Late summer:

males & females




True fir: primary


Mating Aphids or on new foliage – needles twist.

August - September: egg laying and the winter is spent in the egg stage. Early next spring eggs hatch and stem mothers start inserting their stylets at the bases of buds.

The bowlegged aphid, or on new foliage – needles twist. Cinara curvipes; occurs in California Oregon, Washington, Colorado

and Utah -- on firs, Engelmann spruce,

and deodar cedar.

The Cinara spp. aphids have a typical conifer-aphid life cycle and they feed on trunks, stems, and roots. These aphids often are herded by ants, typically

Formica spp. (e.g. western thatching ants)

and Camponotus spp., the carpenter ants.

Ants tending Cinara aphids

and Cinara curvipes on

bark of white pine.

What to do? or on new foliage – needles twist.

  • Aphids: or on new foliage – needles twist.

  • Pest description and crop damage: Soft-bodied insects that suck sap on stems, branches, leaves etc.

  • Biological control: Aphids have many natural enemies.

  • Cultural control: A strong spray of water often effectively removes these suckers.

  • Chemical control: It’s important to cover foliage thoroughly

  • as well as stem and branches with:

  • azadirachtin

  • insecticidal soap

  • acephate

  • horticultural oils as dormant sprays

  • imidacloprid