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Few things are more satisfying than indulging in food that you grew. That indulgence is made even sweeter, the sweeter the food! So, when approaching your apple tree to harvest and visions of bright, unblemished skin are tainted with views of unsightly brighter red spots, disappointment is likely to be experienced. Indeed, San Jose scale has turned your fruit’s skin into something akin to pubescent acne.
It need not be apple. Preferring members of the rose family, it may be pear, peach, or others damaged by San Jose scale. Scale insects are among the most prevalent pests in Louisiana. Upon hatching, these crawlers, as the nymphs are referred, live up to their name. Within hours, they settle onto bark, leaves, and fruit and insert their bristly mouthparts to feed.
San Jose scale will spend most of its lifetime attached to the location on the plant where the sucking of sap began. Females remain in place, feeding and mating. The winged males take flight following the nymphal stage to mate. Mating can produce hundreds of live young, emerging from under the female’s protective covering over a period of six weeks. The crawlers are oval, yellow, and mobile. The female and male covers are both gray to brown, however, the females’ are circular and males’ are elliptical. Nymph or adult, female or male, viewing them should prove challenging, as they are approximately the size of a pinhead, reaching 2 millimeters in diameter.
There is nothing saintly about these insects. Despite the Saint Joseph namesake, translated from Spanish, San Jose scale will blotch the skin of your fruit. While they should be safe to consume, the cosmetic impact is not easily dismissed. A red to purple halo around each scale insect is visible on the fruit’s skin. In early-season infestations, fruit may be smaller, deformed, and discolored. Severe infestations may result in yield reduction, branch dieback, and plant death.
Quadraspidiotus perniciosus may be easiest to view on fruit, leaves, and year-old wood. Monitor fruit during harvesting and scan limbs during pruning. Scout during dormancy to determine the presence of San Jose scale, being mindful that infestation rarely has even distribution. Sound pruning practices, including the removal of infested limbs and water sprouts, aid in the reduction of scale populations. Should control be necessary, dormant oil may be applied. The oil coats the insects and suffocates them by clogging the pores through which they breath. One application should suffice for less severe infestations and two applications made 7 - 14 days apart should be made for more severe infestations. Always read the product label thoroughly and proceed accordingly.
May your harvest be scale-free!
Article for publication May 13, 2024
