Type: minimal pest  

Life cycle:
            Generations per year: 2 to 3
            Egg: unknown
            Larva: unknown
            Pupa: unknown
            Adult: unknown

Description: A medium-sized moth with white head, thorax, abdomen, and wings. The forewing has two black dots; the hindwing has several black dots, mostly located in a row in the  marginal area. Anterior legs are marked with yellow and black; remaining legs are white and black. The white abdomen is characteristically marked with yellow-orange and black dots arranged symmetrically.

Larva is woolly-looking, covered densely with long yellow and white hairs.

Adult moths begin to appear in late spring…typically May. After mating, females will lay 20 – 100 eggs grouped in a single layer on the underside of a leaf. When larvae hatch, they stay together for a brief period, feeding, and then disperse singly to other plants. Larvae defoliate host plant by skeletonizing its leaves, but usually does not harm the plant. Most larval damage occurs in the last generation as fall approaches. This generation will overwinter in the pupa stage. There are two to three generations per year.

Special Notes: Native throughout the temperate regions of North America. Here in the Pacific Northwest, it is generally found at low elevations from the northern parts of central British Columbia to central California.

Remedial Actions: None needed. Not a serious pest.

Re-posted on July 17, 2018

Catocala briseis                Family: Erebidae
(kah-TOCK-uh-lah  bree-SAY-iss)
Common name: Briseis underwing; ribbed underwing
Host plants: Populus sp. (incl. aspen, poplar,
                           cottonwood); Salix sp. (willow)
Adult size: wingspan 2.5 – 2.75 in (6-7 cm)
Flight time: June through late August

Type: Pest

Life cycle:

            Generations per year: one
            Egg:
            Larva:
            Pupa:
            Adult:

Description: Large moth with dark mottled forewings and orange-red hindwings. Forewings are primarily a dark grey colour with some pale scale patches, in particular a whitish patch above the subreniform spot. Hindwings have two black bands across the orange-red. The median black band is variable, typically ending before the inner margin making it invisible when forewings are only slightly open.

Larva is mostly smooth skinned, grey and tan in colour with small orange-red subdorsal spots, an orange-red and black patch in the middle of the back, and a ventral fringe of whisker-like hairs below the lateral line.

Special Notes: This moth species is very similar to Catocala californica (western underwing moth) so are difficult to differentiate, particularly as they can both be found in the Pacific Northwest. Some scientists believe they represent ecotypes of the same species.

Remedial Actions: None needed with this underwing species. Not generally considered to be too much of a pest as far as I can tell from my research. However, some species of the gardener’s nemesis, the cutworm, are underwing moths in their adult form.

Posted on January 10, 2018

Common name(s): small cabbage white butterfly; small white; imported cabbageworm; cabbage white; small cabbage white
Host plant(s): plants which contain glucosinolates, a chemical which cues female to lay eggs (See list of some of the host plants below.) 

Adult size: wingspan: 1.5 – 2.5 in (3.8-6.5 cm) 
Larva length: to 1.4 inches (3.5 cm)

Life cycle:
            Generations per year: 2 to 3 in southern Canada; several further south
            Egg: 3-7 days
            Larva: five instar stages; 11-33 days depending on time of year
            Pupa: 12 days in summer generation; months in winter generation
            Adult: 5-20 days

Description: Wings of adult butterfly are white above with black on the forewing tip and one black dot in centre area of each forewing on males and two black dots in same area on females. Hind wings of both sexes has a black dot on the front edge. Underside of wings is generally a yellowish hue; black dots can be seen faintly through wings. The body is covered with substantial hair…white in females, darker in males.

Early adults emerging from diapaused pupae in early spring in the Pacific Northwest region are typically a little smaller in size with fewer black markings on the upper wings but with an additional edging of black on the underside at the base of the hindwing.

Each female produces 300-400 eggs in their life span.

The egg is 0.04 inches (1.0 mm) long and 0.02 inches (0.5 mm) wide. Laid on end, singly, on the underside of leaves of host plants, the bullet-shaped egg is pale white in colour initially, turning yellowish. Ridges running the length of the egg are visible.

Larva develops through 5 instar stages. It is a velvety green colour with 5 pairs of prolegs and a narrow yellow line running down the centre of its back. (This line is missing in the first instar stage and can be broken up in early instars.) Dashes of narrow yellow lines, or several yellow spots can also be distinguished on both sides.

The chrysalis varies in colour…yellow, green, grey, speckled brown…and is roughly 0.7 – 0.8 inches (1.8-2.0 cm) long. Angled, keel-like ridges are prominently visible. In summer generations, pupation lasts about 11 days. As the chrysalis is the overwintering stage of this insect, the numbers of pupae entering diapause increases as autumn progresses.

In the Pacific Northwest, small white cabbage butterflies are active from early spring through until temperatures dip below 0 °C (32 °F), typically sometime in October or early November.

Special Notes: Originally native to Europe, Asia, and North Africa, this insect has now become well-established throughout much of the temperate regions in the world. It was accidentally introduced in the Montreal area of Canada in the 1860s. From there, it gradually spread throughout North America…although it is scarce or non-existent in semi-desert and desert regions. Nowadays it is classified as an important pest species.

Its life cycle and duration of all stages is governed by temperature. Whereas there are only two or three generations per year in Canada, there are three in the New England area of eastern United States, three to five in California, six to eight generations in the southern states with the exception of Florida where this pest is active year-round.

Remedial Actions: The small cabbage white has several natural predators including ambush bugs, shield bugs, predatory wasps and flies, as well as insect-eating birds. There are also various naturally occurring fungal and virus diseases which are detrimental to this pest, including glanulosis disease (GV)…a disease which acts quickly, inducing diarrhea in insect larvae and typically leading to a mortality rate of over 90%.

There are some crucifer crops which exhibit less susceptibility to damage by foraging cabbageworm larvae. These include: Chinese cabbage, kale, mustard, rutabaga, and turnip. Crucifer crops with glossy, dark green leaves seem to also be less susceptible to cabbageworm damage.

Female small white cabbage butterflies appear to avoid laying their eggs on all red cabbage varieties…although it is has been proven larval survival is indeed favoured by red cabbage.

Covering vegetable varieties which suffer cabbageworm damage with row covers is effective in preventing egg-laying.

List of host plants:

In the Cruciferae family:

• Arabis glabra – tower mustard
• Armoracia lapthifolia – horse radish
• Armoracia aquatic – lakecress
• Barbarea vulgaris – bittercress
• Barbarea orthoceras – American yellowrocket
• Barbarea verna – land cress
• Brassica oleracea – wild cabbage
• Brassica rapa – field mustard
• Brassica napus – rapeseed
• Brassica juncea – brown mustard
• Brassica hirta – white mustard
• Brassica nigra – black mustard
• Cardaria draba – hoary cress
• Capsella bursa-pastoris – shepherd’s purse (females lay eggs on this plant but larvae will not eat it)
• Dentaria diphylla – two-leaved toothwort
• Descurainia sophia – tansy mustard
• Eruca sativa – arugula
• Erysimum capitatum perenne – sand dune wallflower
• Lobularia maritima – sweet alyssum
• Lunaria annua – money plant; moonwort (larvae who eat this plant mature slower)
• Matthiola incana – hoary stock
• Nasturtium officinale – watercress
• Raphanus sativus – radish
• Rorippa curvisiliqua – curvepod yellowcress
• Rorippa islandica – northern marsh yellowcress
• Sisymbrium officinale – hedge mustard
• Streptanthus tortuosus – shieldplant; mountain jewelflower
• Thlaspi arvense – pennycress (larvae will not eat, or if they do, maturity is slowed)

In the Capparidaceae family:

• Capparis sandwichiana – Hawaiian caper
• Cleome serrulata – Rocky Mountain beeweed

In the Tropaeolaceae family:

• Tropaeolum majus – garden nasturtium

In the Resedaceae family:

• Reseda odorata – common mignonette

Posted on November 8, 2017

Common name: elder aphid
Host plant(s): Sambucus (elderberry); Rumex (docks); Silene (campion)
Adult size: wingless = 0.14 inch (3.5 mm)
                        winged = 0.07 inch (1.8 mm)

Type: Pest

Life cycle: Generations per year: multiple; generation length 20-40 days
                      Egg: overwinters
                      Nymph: unknown
                      Adult: unknown

Description: A minute, soft-bodied, sap-sucking insect; elliptical in shape, becoming more round as it matures through the nymph stages. Has six, long, thin legs; two long, six-segmented antennae which are carried over the body; sucking mouthparts called stylets which are enclosed in a sheath called a rostrum; a pair of short, upright, backward-pointing tubes called cornicles (or siphunculi) located on the 5th or 6th segment of the abdomen; a shorter projection called cauda located above the anal plate. Colour can be variable from black-green to yellow-brown, depending on which host plant they are on.

Aphids have a complicated life cycle. In temperate climates, overwintering eggs hatch in spring. The first generation of wingless females (called stem mothers) are already pregnant…reproducing by parthenogenesis (without fertilization). The offspring are born live, called viviparity…a unique phenomenon in this insect. Stem mothers continue to reproduce throughout the summer, typically giving birth to 5 or 6 nymphs per day. (See bottom female aphid on right birthing a live nymph in photo to the right. Click on photo to enlarge.)

When the host plant becomes overcrowded, or its resources reduced, some of the offspring will develop into adults and grow two pairs of large, clear, membranous wings. Once able to fly, these winged adults, called alates, leave the host plant in search of another, fresh plant. (Alates can be seen among the mass of elder aphids in the photo to the left. Click on photo to enlarge.)

In northern climates, towards the end of the season, the stem mothers produce both male and female offspring. This is timed to dropping temperatures and lowering light levels as the season winds down. After mating, the females lay their eggs on the root collars and roots of the alternate host plants, Rumex and Silene, where the eggs will overwinter. (In warmer climates, there is typically no egg in the aphid life cycle. The stem females reproduce continuously throughout the year.)

Special Notes: Aphids can be found worldwide with the heaviest concentrations found in the temperate climate zones. It is generally thought aphids have been on the planet for roughly 280 million years, placing them in the early Permian period. The oldest aphid fossil was several ten years ago in China…an almost complete insect, minus part of the antennae and part of its legs. It has been determined to be a completely new species of aphid and named Dracaphis angustata. The aphid fossil was dated and found to have actually lived during the Middle Triassic Age…following the Permian period.

To explain some of the body parts on the aphid…the cornicles, or siphunculi, those slightly elevated, slender protrusions on the back of an aphid, are defensive apparatuses which will exude a fluid that hardens when it comes in contact with air as a deterrent to predators. The substance is also thought to contain alarm pheromones.

The shorter cauda tube, located above the anal opening, serves to collect the honeydew excreted from the anus and hold it raised so it does not foul the body.

Aphis sambuci is one of the aphid species which has a symbiotic relationship with ants. (Not all aphid species enjoy this phenomenon.) The ants stroke the aphids with their antennae, enticing them to release a drop of honeydew to feed the ants. In exchange for receiving the honeydew, the ants defend the aphids from predators.

Remedial action: There are several predator insects which hunt aphids…lady beetles, ant-lions (green lacewing larvae), yellow jackets, European paper wasps, and others.

Organically…usually a strong jet of water from the hose, repeated every few days, will dislodge these pests. If possible, and if there are no beneficial insects feasting on the aphids, grasping the affected area of branch between two fingers and sliding them up the branch will squish many of the offenders. Same goes for rubbing fingers over infested leaves.

Another plan of attack is to hit the aphids with a soapy water solution…2 teaspoons (10 ml) of dish soap into 4 cups (1 L) of water, but first check to see if there are any beneficial insects present before you start spraying.

Concentrated, repeat forays against this pest are required in order to eradicate them. With the fast turnaround in their reproduction cycle, their numbers can get out of hand very quickly.

Posted on October 16, 2017

Common name: pear sawfly; pear slug; cherry slug; pear slugworm; cherry slugworm
Family: Tenthredinidae
Host plants: pear, cherry, plum, apricot, quince, apple, hawthorn, cotoneaster, mountain ash, serviceberry
Adult size: 0.1 – 0.25 inch (3.2-6.4 mm) long; wingspan 0.25 – 0.4 inch (6.4-9.5 mm)

Type: Pest     

Life cycle:
            Generations per year: two in the Pacific Northwest, between April and October
            Egg: 10 – 15 days
            Larva: 3 – 4 weeks to grow through five instar stages
            Pupa: about 4 weeks; 2nd generation over-winters
            Adult: unknown

Description & Life Cycle: Adult pear sawflies start emerging from the soil over a few weeks starting in mid-spring. They are non-stinging wasps, shiny brownish-black in colour and have two pairs of transparent wings which they hold folded over their backs when at rest. After mating, the females lay their eggs under the epidermis on the upper surface of a leaf using their saw-like ovipositor.

The oval-shaped eggs are a tan-pale orange colour and roughly 0.04 of an inch (1 mm) long. They look like a small blister on the leaf.

The first generation larvae begin to emerge in May. Early instar stages are grey-green in colour and have no distinct legs. They tend to hold their rear end up slightly. Body shape is wide in the front, narrow in the rear giving them a slug-like appearance, especially as they secrete a slime which completely covers the bodies of the early instar stages. As they progress through the 2nd to 4th instar stages, their body colour darkens to a green-black, then to black caused from a coating of their liquid body waste. They feed on the upper leaf surface, eating through the epidermal layer but stopping before they have eaten all the way down to the lower epidermal layer of the leaf. The removal of the top layers of the leaves produces tan skeletal-like patches…a sure sign there are pests at work on your plant. By the last instar stage, the larvae have developed a more caterpillar appearance…green body with an orange head and 10 pairs of distinct legs. At this stage, they are 0.4 of an inch (9.5 mm) long.

When the first generation of larvae are ready to pupate, they crawl or drop to the ground…digging themselves into the soil. Duration is roughly 3 – 4 weeks with the second generation adults emerging in late-July or early August. Females lay their eggs in the same manner directly after mating. Second generation larvae appear in mid- to late August.

These second generation larvae do the most damage, likely because their numbers are higher and they are preparing to over-winter. Severe feasting damage to the leaves can cause them to drop prematurely, thus weakening the plant. Luckily, they are not known to destroy their host plants. When these larvae reach the fifth and last instar stage, they crawl or drop to the ground and dig themselves 2 to 3 inches (2.5 – 7.5 cm) down into the soil where they spin a cocoon and over-winter.

Special Notes: Caliroa cerasi is native to Europe. It is unknown when this pest was first discovered in North America but speculation puts the timing as far back as colonial times. Today, it is found throughout Europe, Asia, Africa, Australia, Tasmania, New Zealand, parts of South America (Argentina, Chile, Uruguay), the United States, and Canada.

“Pear slug” is the officially recognized common name.

Remedial Actions: Usually, the damage has been done before the gardener notices there is a pest at work. Best line of defense against the pear slug is to hit the affected plant with a jet of water or a dousing of insecticidal soap. However, this may prove difficult if the tree is way above your head.

If the larvae are dropping to the ground to pupate, there is nothing available which will destroy the pupae once they are underground.

In our Zone 7a garden: We have been fortunate up until this year (2017) to have dodged this pest…and we have seven out of the ten host plants I noted above! (Pear tree, plum tree, apple, a flowering quince (Chaenomeles), a serviceberry (Amelanchier), a cotoneaster, and a Sorbus (mountain ash).

This year, my Aronia melanocarpa (black chokeberry) has been hit. I only just realized the damage as I was harvesting the berries this week. Too late to do anything this year but I will definitely be watching for the adult sawflies to appear next April and May…although there is not much one can do to deter the adult females from mating and laying eggs. But I have read Neem oil may be effective in retarding the larvae from molting to the next instar stage. Worth a try. If it does not work, I can always turn a jet of water on them.

Posted on September 20, 2017