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

Mouth ForegutMidgutHindgut Malpighian tubules Rectal area Generalized insect digestive system

Foregut Midgut Hindgut Malpighian tubule Midgut Filter chamber of aphids and other homopterans Honey dew

Honeydew from aphids

Now we can move on to the stem pests, starting with the balsam woolly adelgid 1 1 Really belong to the family Phylloxeridae 0.5mm

The Balsam Woolly Adelgid 1, Adelges piceae. 1 Phylloxerid Galls

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 males; we’re parthenogenic.”

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. Dead Fraser-fir BWA

Adelgid The Balsam Woolly Adelgid Comes West in 1950

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.

(1) The BWA overwinter as a diapausing 1 st instar, the winter form. (2) In early spring, the 1 st 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 Life Cycle of the BWA

(5) Eggs hatch in about a week and each motile nymph crawl rapidly around the new foliage, twigs and branches. BWA crawlers

(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 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 generations/yr.

Egg Adult Motile nymph Nymph stuck in the phloem One mm The BWA in action! Bark surface

As BWA feed they inject a toxin into the actively growing tissues, which causes hyperactive growth & galls

A few BWA Millions BWA The BWA Disaster

Subalpine fir near the town of Concrete More BWA Damage

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.

Mq = (F)(SR) - 1 (F)(SR) 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 are males. There is one generation/yr of the gladiola bulb fly. Mq = (150)(0.5) - 1 ( 150)(0.5) 150 X = 148 So: = 2 (a male and a female) 150 eggs = (75) - 1 (75)

Mq = (100)(1) - 1 (100)(1) = 0.99/generation i.e., 100 eggs - 99 killed = 1 female! BWA

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.

With valuable trees, you may have to treat -- about bud- break time.

Apply insecticide at time of budburst, you should see tiny crawlers. 7

The balsam twig aphid, Mindarus abietinus Eggs Stem mothers Twisting new growth BTA on the stem

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.

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. Mom?

June: a winged generation flies off to an alternate host.

July - August: both males and females are produced and they fly back to true firs Male Female Unknown host? True fir: primary host Late summer: males & females occur

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. Mating Aphids

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.

What to do?

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: o azadirachtin o insecticidal soap o acephate o horticultural oils as dormant sprays o imidacloprid