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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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Presentation Transcript
slide1

Stem Pests:

(some Homoptera)

slide2

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

slide4

Hindgut

Midgut

Foregut

Rectal

area

Mouth

Malpighian

tubules

Generalized insect digestive

system

slide5

Foregut

Midgut

Midgut

Malpighian

tubule

Filter chamber

of aphids and

other homopterans

Hindgut

Honey dew

slide7

0.5mm

Now we can move on to the stem

pests, starting with the balsam

woolly adelgid1

1 Really belong to the family Phylloxeridae

slide8

The Balsam Woolly Adelgid1,

Adelges piceae.

Galls

Galls

1 Phylloxerid

slide9

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.

slide10

“Males? We don’t need

males; we’re

parthenogenic.”

slide11

BWA

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.

slide12

The Balsam

Woolly Adelgid

Comes West in

1950

Adelgid

slide13

The BWA infest and kill:

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

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

Shasta-red fir is barely attacked.

slide14

Life Cycle of the BWA

(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

eggs

slide15

BWA crawlers

(5) Eggs hatch in about a week and each

motile nymph crawl rapidly around the

new foliage, twigs and branches.

slide16

(6) These motile nymphs then thread their

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

generations/yr.

slide17

The BWA in action!

One mm

Motile nymph

Egg

Adult

Bark surface

Nymph stuck

in the phloem

slide18

As BWA feed they inject a toxin into

the actively growing tissues, which

causes hyperactive growth & galls

slide19

A few

BWA

Millions

BWA

The BWA Disaster

slide20

Subalpine

fir near

the town of

Concrete

More BWA Damage

slide21

In order to understand why its so

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

increasing.”

Mq depends on: (1) fecundity

number of eggs a female will lay, &

(2) sex ratio.

slide22

Mq = (F)(SR) - 1

(F)(SR)

Mq = Mortality Quotient

F = Average No. Eggs

SR = No. Females

No. Females + Males

slide23

(75) - 1

(75)

= 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

slide24

BWA

(100)(1) - 1

Mq =

= 0.99/generation

(100)(1)

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

slide25

Management of BWA in the urban environment:

  • 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.
slide27

Apply insecticide

at time of budburst,

you should see tiny

crawlers.

7

slide28

The balsam twig aphid, Mindarus abietinus

Twisting

new growth

Stem mothers

Eggs

BTA on the stem

slide29

The balsam twig aphid can severely damage true firs:

  • In nurseries, the terminal needles twist and become deformed.
  • In urban plantings, BTA suck on twigs and foliage producing great amounts of honey dew and sooty

mold -- firs become unsightly.

slide30

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

Mom?

May - Mid June:

vivipary in action:

2 or more generations

of wingless females.

Mom?

Mom?

Mom?

Mom?

Mom?

Mom?

Mom?

Mom?

Mom?

slide31

June: a winged generation

flies off to an alternate

host.

slide32

Unknown

host?

July - August:

both males and females

are produced and they

fly back to true firs

Late summer:

males & females

occur

Male

Female

True fir: primary

host

slide33

Mating Aphids

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.

slide34

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.

slide36

Aphids:

  • 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
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