Stem Pests Continued

The spruce gall adelgid, Adelgis cooleyi, another phylloxerid

Galls on spruce

Overwinteringeggs at base ofneedles

Winter

Sp

rin

g

Eggshatch andnymphs feedat base of newneedles -- galls begin.

Spruce

Adelges cooleyi

Nymphs develop withinthe galls and mature intoparthenogenic females.

These females produce another population of winged femalesthat fly to Douglas-fir.

Adelges cooleyion Douglas-fir

Summer

Male

Female

Winged males& females fly backto spruce.

Femaleslay overwinteringeggs

Late Summer-Fall

(1)

(2)

Douglas-fir

Gall adelgids are easy to manage:1. pick off the new, developing galls2. apply the systemic Merit®3. on Douglas-fir, apply Orthene® as

crawlers are detected.

Scales

These are sometruly weirdhomopterans.

Many scales are stem-infestingpests

Underside of scale

100’s eggs

The San Jose Scale

“He was an honest, industrious man, of much common sense, though noted for many eccentricities and whims and in his later years, of irritability and thoroughly disagreeable temperament. His great and well merited fame rests on the final disposition of his millions, which after provision for his relatives, were devoted to various scientific, charitable and educational enterprises for the benefit of the donor’s adopted State of California: the Lick Observatory for example.”

James Lick, the richest man in Californiaduring the 1800’s

All true, but he introduced the San Joséscale in 1870 on citrus trees importedfrom China.

San José Scale

There she is

MaleCrawler Male adult

Female

Fem.adult

Fem.adult

Scale removed

Tree surface

San José Scale (Quadraspidiotus perniciousus)

San José Scale

pseudo-pupa of male

Control of scales is aimed at the crawler stage.

Apply to control the immaturecrawler stage, usually in late springto early summer. Scout forcrawlers and gather life history datafor your JOURNAL. Oils are effectiveearly-late spring.

Scales can also be treated just before budbreakwith a dormant spray of horticultural oils. Theoil suffocates the overwintering insect stage.

The Lecanium scales

Lecanium scales suck the sap of stems and foliage of many ornamental plant species, e.g. Daphne, dogwood, holly, yew, Prunus spp. etc.

The Lecanium scales belong to a large group of scales called the soft scales, and the soft scales belong to the family, Coccidae.Coccidae.

Hmmmm?

The coccids themselves are divided into those that have ovisacs and those that lay eggs under a brittle covering -- the scale cover.

Originally, nearly all of the non-ovisac coccids were belonged to a huge genus Lecanium spp. Over time this large genus was divided into several genera,for example the genera Eulecanium, Mesolecanium, Neolecanium, Parthenolecanium and others.

Scale taxonomycontinued!

Just as an example, this is thecamellia scale – it has an ovisac,therefore, notnot a Lecanium scale.

Mom

Ovisac

But horticulturists still call all scales with a brittle covering, “the Lecanium scales.”

Eggs from LecaniumEggs from Lecaniumscalesscales

Male

Nymph

Scale

Female Eggs

Typical Lecanium Scale

June

Crusty deadfemale withmany eggs underher “scale.”

Later in June, crawlers marchingto the leaves

Lecanium Scale

July

Still crawlingto the foliage

July - August

Immature males & femalessucking sap from the leaves

August- September

Migration back tostems

Lecaniumscale (continued)

Lecaniumscale(continued)

September

back on stems and twigs

Males

FemalesMate

September

Overwintering Lecanium Scale

Next spring - June

Females lay eggs

Control of Scales

Washington, Oregon & Idaho Insect Control Handbook

Adult scales are immobile while the immature crawler is active. Many types exist, including the soft and hard scales. Consult a reference book for scale identification

Use: fenoxycarb, chlorpyrifos, metasystox-R, cyfluthrin, insecticidal soap, horticultural oils, acephate, imidacloprid.

Apply to control the immature crawler stage, usually in latespring to early summer. Look for crawlers and gather lifehistory data for your journal. Oils are most effective inearly - late spring.

The Oystershell Scale, Lepidosaphes ulmi (l.)

A scale of European origin that infests manyurban plants

Oyster shell scale

Male

Adult Female

Crawler

Lastinstarfemale

The most familiar stage of the oystershell scale is the covering of the full-grown female scale that overwinters attached to the bark. The mother scale is about 1/8th in long and shaped like an oyster.

• Eggs are underneath the old scale covering of the mother.

• Eggs hatch in early June and the egg-hatchmay last two weeks.

• The newly hatched crawlers are tiny, the size of a pin head.

• After a few hours of crawling around they thread their stylets into the plant, begin to feed and soon molt.

• In July, winged males find the last-instar-female and mate. Females then live on until early winter when they die, but leave behind eggs. There may be two generations/yr.

Oystershell scale (cont.)

Many predators and parasitoids attack oystershell scales. These can reduce scale populations, but usually such reductions are not enough to preventdamage.

Apply insecticidal soap when crawlers are active. To determine when crawlers are active, turn over the mature scale covers at weekly intervals starting in early May.

With aid of a hand lens determine when crawlers have left the protection of the scale cover; that’s the time to treat with pesticides or horticultural oils.

More I’d like you to know about control of the oystershell scale

(Professional handbook on insecticides: farmers, horticulturists, foresters, researchers etc.)

“Here’s a book you haveto use if your going tobe a professional urbanhorticulturist.”

The cottony cushion scale, Icerya purchasi

“we feel you must reallyknow the famous researchand control of the cottonycushion scale”

In 1880 the cottonycushion scale was introduced intosouthern California from Australia

Citrus farmers were desperate, as I. purchasi devastated the citrus industry. HCN gas was blown under tents placed on orange trees to kill the scale.

All to no avail!

In 1898 C.V. Riley went to Australiaand brought back the vedalia beetle, Rodolia cardinalis.

This fierce predator of I. purchasi, thislady-bird beetle, brought the cottony cushion scale populations crashing down –the scale was regulated!

The first great case of successfulBiological Control !

Vedalia beetles were reared by the millions in California. Then millions of these little lady-bird beetles were sent all over the world, wherever the cottony cushion scale was introduced.

Even to Spain !

1 de Australia

1

Vedalia beetle

“The perfect fit”Icerya purchasi

No

. P

ests

No

. P

red

ato

rs

Years

Pest

Predator

The heart of successful biological control: a case of complete density dependence. The numbers of predators at any given time depends on the number of pests. This kind of relationship is typically established when a pest species is introduced acrossgeographic bounderies without its natural controls. Then, when an important predator of that pest also is introduced we may see this permanent biological control being established.

I just can’t leave C.V. Riley yet.

Phylloxera on French grape root

C.V. Riley

Chilean wines:Real French Root Stocks

Another stem invading insect:the shothole borer, Scolytus rugulosus Fam. Scolytidae

This is a barkbeetle that infests weakened fruit trees, wild plums, cherries, serviceberry, mountain ash, hawthorn and elms.

• Females are attracted by odors given off by the weakening and dying trees.

• These females enter the phloem of the tree and sends out a pheromone that attracts males and females to the selected trees.

• Females cut egg galleries in the subcortical area and lay eggs in niches.

• Larvae then feed in the phloem, pupate and new adults emerge from the now-dead tree and find new hosts.

The shothole borer

Host selection behavior of theshothole borer, S. rugulosus

The shothole borerstarting to bore intoa tree and the exudation of resinfrom a tree underattack.

Shothole borer adult extending egg galleries in the subcortical region of the bark.

Emergence of the shothole borer: why it’s called the shothole borer!

Control? Maintain healthy trees.

The main pest of weakening Douglas-firs, the Douglas-fir beetle, Dendroctonus pseudotsugae.

This tree isdead!

As with all Dendroctonus, the Douglas-fir beetle attacks weakened host material – in particular weakened, isolated trees or trees with root damage (soil compaction).

• First flight begin in April. • Pioneering females find this scattered, degrading windthrows or other downed material. • These pioneering females and the rest of the flying population have an exquisite “game plan” to find these scattered, weakened hosts.

1.After mating, females cut egg galleries in the fresh phloem and lay eggs on alternate side of the inner bark (phloem).

2. The larvae feed in the phloem to the last instar, then they cut pupal cells and pupate next spring around March.

3.The new generation of adults then cuts its way out of the bark and they fly once again in a dispersal flight.

Upon peeling away the barkwe see the egg galleries andlarval mines

Peel away the bark withan axe and we see the egggalleries and larval mines, andeven larvae.

If Douglas-firs are dying all around you (neighbors’ yards), then, try a repelling pheromone, MCH.