This Rutgers Plant & Pest Advisory blog will review a few of the landscape summer pests specific to mostly oak trees (Quercus). The scarlet oak sawfly will be discussed first, followed by the oak spider mite & finally the oak lace bug. All three pest species have multiple generations during the summer months & therefore can be observed throughout most of the season. None of the pest species are usually considered to be life-threatening to oak hosts but they can cause significant & undesirable aesthetic injuries. However, it could be stated that these pests may have bark, but they have little bite. Therefore, with large oak trees the spraying of many gallons of pesticides would not be justified.

Spraying many gallons of a pesticide against most pests on a large oak as shown above is rarely justified. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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Mimosa webworm early webbing of honeylocust leaflets at outer branches. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Mimosa Webworm (Homadaula anisocentra) = (880-1200 GDD = 1^st generation egg hatch): The overwintering pupal cocoons of this non-native caterpillar emerged as adults last June & eggs have been laid on leaflets or small twigs of honeylocust (Gleditisia tricanthos ) trees in NJ. This caterpillar also feeds on mimosa trees, but since honeylocust plantings in the urban environment are more common, we usually encountered them on these trees. Within many areas of the state, the early, initial 1st generation webbings by 1st instar caterpillars are now becoming noticeable at the outer edges of the leaf canopy.

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Soft Scale Species Controls (June & July): Compared to armored scales, the soft scales are relatively easy to suppress with either contact sprays or systemic treatments. Some of the common landscape soft scale species in NJ include calico, Fletcher, Indian wax, cottony maple, cottony camellia, spruce bud, European fruit lecanium, pine tortoise, striped pine, magnolia, & tulip tree. Although large soft scale adult females are more difficult to control, the immature nymphs are often vulnerable to sprays when good coverage is achieved. However, there are some species that have proven to be more challenging to control. Two good examples include the calico scale & Indian wax scale species. Horticultural oil sprays are often recommended to control immature scale nymphs, but sometimes against the calico & Indian wax species the efficacies are less consistent. This blog will first review soft scale management options & then show photographs & discuss the life cycles of the following soft scale species with crawlers emerging during June & July: (1) Indian wax, (2) calico, (3) cottony camellia, (4) spruce bud, & (5) Fletcher.

Drawing of a soft scale feeding on woody bark. All soft scale species suck sap from phloem vascular tissues. (Drawing Credit: John Davidson, University of Maryland)

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A Large-Scale Dilemma: 

Drawing shows a shrinking female armored scale laying eggs. Waxy covers of each of the 3-instars are pushed above the other. Crawlers emerge from the female cover through the one-way flap. (Drawing Credit: John Davidson, Univ. of MD)

Undoubtedly many arborists, landscapers, nurserymen, and golf course superintendents would agree that effectively controlling scale insects is one of the more frustrating pest management challenges encountered. Of the half-dozen major families of scale insects common in the urban landscape, the armored scales are the most troublesome. With their protective waxy covering, armored scales are considerably less susceptible to various insecticide spray treatments.

Reddish colored crawlers of Pine Needle Scales emerging out from under female waxy covers. (Photo Credit: Ohio State Coop. Ext.)

Historically, many pesticide spray applicators fail to achieve satisfactory controls because they do not have the time or inclination to apply sprays during the scale crawler emergence periods. To complicate matters, the crawler periods for the various armored scale species are quite variable. Furthermore, the improper timing of long residual pyrethroid insecticides can virtually eliminate important parasitoid bio-control activity and hence, often encourage scale infestations. The intention of this blog is to stress the importance of properly timed treatments to achieve better management of scale insects. This is especially true when attempting to control armored scales.

Despite the complications stated above, fortunately some relatively newer insecticides have given improved abilities for scale controls. These newer materials & the life cycles of 5-armored scale species will be covered in this blog. The scales covered include: 1-Euonymus scale; 2-Cryptomeria scale; 3-Japanese maple scale; 4-White Prunicola scale; & 5-Juniper scale.

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Since there are still over 4-weeks before the official start of summer, the accumulation of growing-degree-days (GDD) will continue to accelerate over the next several weeks. Many of our landscape insect pests will be rapidly emerging and be entering their best control windows before they potentially cause feeding symptoms. This writing contains part 2 of 2 parts of only a handful of the many late spring landscape insect pests that require monitoring. Some could more properly be called mid-spring pests, especially in southern NJ. Those included within part 2 of this blog are: Taxus mealybug; Boxwood leaf miner; Aphid species and Bronze birch borer.

The late spring weeks in the landscape means full plant leaf emergence & many flowers plus increasing insect activity. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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Since there are still nearly 5-weeks before the official start of summer, the accumulation of growing-degree-days (GDD) will continue to accelerate over the next several weeks. Many of our landscape insect pests will be rapidly emerging and be entering their best control windows before they potentially cause feeding symptoms. This writing contains part 1 of 2 parts of only a handful of the many late spring landscape insect pests that require monitoring. Some could more properly be called mid-spring pests, especially in southern NJ. Those included within part 1 of this blog are: Four-lined plant bug; Douglas-fir needle midge; Pine needle scale; & Elongate hemlock scale.

The late spring weeks in the landscape means full plant leaf emergence & many flowers plus increasing insect activity. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

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