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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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
Generalized insect digestive
of aphids and
Now we can move on to the stem
pests, starting with the balsam
1 Really belong to the family Phylloxeridae
These European fir trees have only female
Adelges piceae -- I’ll let them pass.
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.
Comes West in
No. 1 subalpine fir, No. 2 grand fir,
No.3 silver fir & noble fir, and No. 4
Shasta-red fir is barely attacked.
(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.
(5) Eggs hatch in about a week and each
motile nymph crawl rapidly around the
new foliage, twigs and branches.
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.
on the climate,
aspect etc., there
maybe 2 - 3
in the phloem
the actively growing tissues, which
causes hyperactive growth & galls
The BWA Disaster
the town of
More BWA Damage
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 = Mortality Quotient
F = Average No. Eggs
SR = No. Females
No. Females + Males
The iris bulb fly:
Fecundity = 150
Out of 1000 puparia you collected, 500
There is one generation/yr
of the gladiola bulb fly.
Mq = (150)(0.5) - 1
150 X 0.986 = 148
So: 150 - 148 = 2 (a male and a female)
(100)(1) - 1
i.e., 100 eggs - 99 killed = 1 female!
With valuable trees, you may have to treat -- about bud-break time.
at time of budburst,
you should see tiny
BTA on the stem
mold -- firs become unsightly.
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.
flies off to an alternate
July - August:
both males and females
are produced and they
fly back to true firs
males & females
True fir: primary
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, 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.