In most areas of NJ, the application timing of imidacloprid to nursery containers to achieve best efficacy against Oriental beetle grubs (Anomala orientalis) has now expired. The majority of eggs are laid during late June through early July and by the time August arrives, many of the grubs will have begun to molt into the 2nd instar stage. If imidacloprid is not applied until August, then some root feeding damage may have already occurred & furthermore, the larger instars will be more difficult to control. Generally, the preventative applications should be applied from early June to mid-July to achieve best results.

Next year, some nurseries may want to attempt the new Oriental beetle mating disruption pheromone that is discussed in the second half of this article.

Imidacloprid has good efficacy against Oriental beetle 1st instar grubs, but is significantly less effective against the 2nd & especially 3rd instar grubs

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During the past several weeks, significant leafhopper damage has been observed in a few nurseries within central NJ counties. Although there are many species of leafhoppers, the Potato Leafhopper (Empoasca fabae) is probably the most notorious in the northeastern U.S. states. The feeding damage can mimic herbicide injury with distortion & discoloration of foliage. Some of the common deciduous tree hosts include maple, oak, ash, & birch as well as others.  The Potato Leafhopper does not overwinter in NJ, but during the weeks of May is carried-in by upper atmospheric winds from the gulf coast states .

Potato Leafhopper & “hopperburn” symptoms on Acer rubrum  at a Burlington County Nursery   Photo Credit: Steven K. Rettke of RCE

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As would be predicted, observations during the past few weeks within nurseries located in central & southern NJ have shown reduced activities of both the spruce spider mites & southern red spider mites. These common cool season mite pests feed predominately on conifers & broadleaf evergreens, respectfully. During the hot summer months, both of these spider mite species enter into a dormant stage. Alternatively, the two-spotted spider mite & several more host specific shade tree spider mites (e.g., maple spider mites, oak spider mites, honeylocust spider mites & European red mites) are common warm season mite species and are now rapidly laying eggs & building populations.

Spider Mite (0.5 mm), Egg & Pine Needle Stomates         Photo: Cornell University Press

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The common Bagworm Caterpillar (Thyridopteryx ephemeraeformis) has undergone egg hatch throughout much of the state during the past few weeks (GDD = 600-900).  The early instar stages during the month of June can easily be overlooked. For the first few weeks after hatch, the smaller Bagworms do not produce conspicuous feeding symptoms. However, for best control results these early instars should be targeted. Although the potential hosts of the Bagworm are large, they are generally of most concern on evergreen conifers.

Unhatched Bagworm Eggs in Female Sack
Photo by Steven K. Rettke of RCE

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Last week (6-8-13) the first emergence of the adult red-headed flea beetle (Systena frontalis) was observed in a Cumberland County nursery. This insect has been a major pest at numerous NJ nurseries during the past several years. Primarily a concern with container crops in nurseries, it has an extensive host range. The foliage damage to plants from this 0.2-0.25 inch adult beetle can become extreme.

Adult red-headed flea beetle & characteristic feeding symptoms on a leaf. (Photo Credit: Steven K. Rettke, Rutgers Coop. Ext.)

Red-headed flea beetle with prominent reddish head and shiny black thorax and abdomen (4.5-6.5 mm)

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