San Jose Scale

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Beginner

This pest affects:

Scientific Name
Quadraspidiotus perniciosus

Identification
Crawlers

0.2 mm, oval, orange-yellow
Resemble larval spider mites
6 legs and one pair of antennae
Bristle-like sucking beak that is almost three times the length of its body

Adults:
Females

Bright yellow, nearly round and stationary
Lack appendages
Remain beneath a waxy scale covering (about 1.6 mm in diameter) with a raised nipple in the centre of the covering

Males

Small golden brown winged insects about 1 mm long
Mature beneath elongate scale covers

Injury
Fruit

Small red to purple spots about 3 mm in diameter
Light-colored area in the center of the spot marks the insect's point of attachment to the fruit before the insect was removed
Most abundant around the blossom and stem ends of fruit
Early season severe infestations may result in small, deformed fruit

Trunks and limbs

On young wood a bright red discolouration often shows up, especially on peaches
Reddish discolouration below bark where scales were feeding
With heavy infestations of scale insects – particularly on young trees – decline in vigour, characterized by sparse, yellow foliage and defoliation, cracking and bleeding of the limbs reduced growth and productivity

Severe infestations can kill whole limbs.

Depending on the size of the population, scale can kill a young tree in two to three years
In cherry, leaves of infested trees do not drop in fall, making it easy to detect infested areas of the orchard

Often Confused With
Comstock mealybug - mealy or fuzzy waxed coating; female adults are mobile

Period of Activity
San Jose scale is active from bud break to harvest. Male flight usually occurs during pear bloom, with a series of three overlapping summer flights from mid-summer through fall. Crawler movement begins 4 to 6 weeks after bloom.

Scouting Notes
San Jose scale is most destructive on apple and pear, but it can be a serious pest of sweet cherry, peach, plum and other tree fruits. It also attacks nut trees, berry bushes and many kinds of shade trees and ornamental shrubs. Infestations in backyard or wild trees can spread to nearby orchards.

Monitoring for San Jose scale should be done in orchards with a history of damage from this pest. San Jose scale is seldom distributed uniformly throughout a tree and may infest only a few trees in an orchard block Branches in the tops of trees are usually the first to be injured. The best place to look for scale is in sheltered spots such as the forks of branches, tiny cracks and crevices in the bark, and between the bud and stem on young branches. Confirm San Jose scale injury by cutting away bark to reveal a reddish discolouration.

Wrap black electrical tape (with adhesive side out) around the scaffold limbs of trees, in areas with known infestations, to detect crawler activity. Place bands in trees by mid June for 7-10 days after petal fall and replace every two to three weeks throughout the season. Crawlers’ yellow bodies will be caught on the tape.

Although scale lives primarily on the tree bark, the first indication it is in the orchard may be small red spots on the fruit or leaves. Monitor fruit at harvest for scale.

Table below from
https://ecommons.cornell.edu/handle/1813/43128

	TIMING	WHERE TO LOOK
Adult females	Budbreak through leaf drop.	On trunk and branches prior to fruit set Check beneath loose bark on older trees. Mid-season through harvest, spurs and fruit, especially stem and calyx ends.
Adult males	Bud break through petal fall. Mid-season through leaf drop.	Difficult to detect.
Crawlers and "White-caps"	Approximately 4 to 6 weeks after bloom through leaf drop.	Trunk and branches, often beneath loose bark. On suckers, spurs, and fruit.
"Black-caps''	Dormant and approximately 5 to 7 weeks after bloom, through leaf drop.	On trunk and branches Also on suckers, spurs and fruit.

Thresholds
There are no thresholds for scale insects. In most cases, any fruit injury at harvest warrants corrective measures the following spring. If scale-infested fruit are found after the first generation of crawlers have settled, measures against the second generation are recommended.

Advanced

This pest affects:

Scientific Name
Quadraspidiotus perniciosus

Identification
Crawlers

0.2 mm, oval, orange-yellow
Resemble larval spider mites
6 legs and one pair of antennae
Bristle-like sucking beak that is almost three times the length of its body

Adults:
Females

Bright yellow, nearly round and stationary
Lack appendages
Remain beneath a waxy scale covering (about 1.6 mm in diameter) with a raised nipple in the centre of the covering

Males

Small golden brown winged insects about 1 mm long
Mature beneath elongate scale covers

Injury
Fruit

Small red to purple spots about 3 mm in diameter
Light-colored area in the center of the spot marks the insect's point of attachment to the fruit before the insect was removed
Most abundant around the blossom and stem ends of fruit
Early season severe infestations may result in small, deformed fruit

Trunks and limbs

On young wood a bright red discolouration often shows up, especially on peaches
Reddish discolouration below bark where scales were feeding
With heavy infestations of scale insects – particularly on young trees – decline in vigour, characterized by sparse, yellow foliage and defoliation, cracking and bleeding of the limbs reduced growth and productivity

Severe infestations can kill whole limbs.

Depending on the size of the population, scale can kill a young tree in two to three years
In cherry, leaves of infested trees do not drop in fall, making it easy to detect infested areas of the orchard

Often Confused With
Comstock mealybug - mealy or fuzzy waxed coating; female adults are mobile

Biology
Host plants of San Jose scale include apple, pear, quince, peach, plum, apricot, sweet cherries, currants, gooseberries and numerous woody ornamentals.

San Jose scale overwinters on the tree as immature scales. They remain dormant on the bark until tree sap starts moving in the spring when spring temperatures exceed 10 C and are full grown by late May. Active males emerge from their scales and seek females for mating. Females are immobile and remain under scales throughout their lives. After mating, females begin to produce living young, usually at the rate of 9-10 per day. They reproduce for six weeks and bear from 150-500 offspring (crawlers). Crawlers walk or are air-borne to new sites of infestation on the bark, fruit, and leaves. They can also be spread through orchards by birds’ feet, workers’ clothing and on farm equipment. When they locate a suitable feeding site, they insert their mouthpart and begin to feed on sap. They inject a toxin into the plant as they feed, causing localized discolorations on the bark or fruit Three weeks later they molt and shed their skin. Scales are attached to bark by their sucking mouthparts. As the insects continue to grow, they build a waxy shell around them that protects from desiccation, predators and pesticides. Females develop through two nymphal instars to the adult, while males develop through four instars. The first instar nymph secretes a white waxy covering and is known as the "white-cap" form. The third and final phase of the first instar (the "black-cap") is initiated as peripheral rings of darkened wax are secreted and the "white-cap", except for its center tuft, blackens. The first molt occurs beneath the "black-cap" within 3 weeks following crawler emergence. The scale covering of the immobile second instar females gradually increases in diameter to accommodate the growing insect beneath. A second and final molt to the adult stage female occurs 3 to 4 weeks later. Males become distinguishable from females during the second instar as their scale coverings elongate. Following the second molt, male SJS pass through two non-feeding instars prior to the final molt to adults. Scale populations increase rapidly in hot dry weather, and females produce more than 300 million offspring each year. There are two full generations each year. Natural enemies include parasitic wasps and lady bird beetles, but they do not provide economic control of San Jose scale.

Although scale lives primarily on the tree bark, the first indication it is in the orchard may be small red spots on the fruit or leaves. Monitor fruit at harvest for scale.

Table below from
https://ecommons.cornell.edu/handle/1813/43128

	TIMING	WHERE TO LOOK
Adult females	Budbreak through leaf drop.	On trunk and branches prior to fruit set Check beneath loose bark on older trees. Mid-season through harvest, spurs and fruit, especially stem and calyx ends.
Adult males	Bud break through petal fall. Mid-season through leaf drop.	Difficult to detect
Crawlers and "White-caps"	Approximately 4 to 6 weeks after bloom through leaf drop.	Trunk and branches, often beneath loose bark. On suckers, spurs, and fruit.
"Black-caps''	Dormant and approximately 5 to 7 weeks after bloom, through leaf drop.	On trunk and branches Also on suckers, spurs and fruit.

Management Notes
Carefully examine all nursery trees prior to actual planting. If scale insects are present, discard trees or exchange for clean trees.

Plant new orchards away from hardwood stands and from older plantings where scale has been a problem.

When infestation is severe and dieback is obvious the affected limbs should be pruned and burnt immediately.

For more information on the timing of products for managing scale, see OMAFRA Publication 360, Fruit Crop Protection Guide:

	Chapter 5 Peach Calendar: Recommendations for San Jose scale at Dormant.
	Chapter 5 Plum Calendar: Recommendations for San Jose Scale at Green tip.
	Chapter 5 Pear Calendar: Recommendations for San Jose scale at Dormant

Some information included above excerpted from;

Tender Fruit

San Jose Scale

Beginner

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