Monday, June 23, 2014

Pest News Alert for Week of June 23rd


From: Steve Frank, Extension Entomologist

Flea Beetles

Redheaded flea beetles, Systena frontalis, have become a serious pest of nursery stock over the past several years. They are an especially damaging pest because they feed on roots and leaves. They overwinter as eggs in the soil. Larvae hatch in spring and begin feeding on roots. The larvae are elongate and creamy-white. Heavy infestations may reduce root mass or girdle plants. Adult redheaded flea beetles are small, shiny black, beetles with reddish to dark colored head and long antennae. They are about 1/16 of an inch long and, as the name suggests, jump when they are approached. There are at least two generations in Delaware and may be more in North Carolina.

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Redheaded flea beetle on a rose leaf.

Adults and adult feeding damage are present now. The favored hosts are Itea, hydrangea, forsythia, and knockout roses and many perennials like joe-pye weed. Adult management has been frustrating for growers who find that even frequent insecticide applications do not reduce adult abundance and damage to acceptable levels. Part of this has to do with not controlling larvae since even if you kill all the adults present in a crop (which you won’t) more adults are emerging from the soil every day. Research thus far in Delaware and grower reports indicate that Talstar, Sarfari, and Flagship provide good efficacy as foliar applications, but do not have long residual activity.

- One Western NC note-  typically these alerts are earlier than expected emergence here but this pest is very active on Knockout Roses this year and has been for over 10 days. 

Columbine Leafminer

The first round of flowering is about over for my native columbine, Aquilegia canadensis. Columbine is a great early spring flower that flowers profusely and spread easily by seed. Spring bees and humming birds visit columbine flowers particularly in early spring when it is one of the only flowers present.

The columbine leafminer, Phytomyza aquilegivora, overwinters as pupae. Adults emerge in early spring and oviposit in new columbine leaves. Small white maggots mine the leaves creating white or grey serpentine pathways. Often entire leaves are discolored. Larvae pupate after about 10 days on the underside of leaves. Columbine leafminer has at least 4 overlapping generations per year in North Carolina. There are at least 13 species of parasitoids that become more abundant as the summer progresses.

Braman et al. (2005) reported that the native species, A. canadensis, is more resistant to leafminers than many other species of cultivars. Removing and destroying infested leaves before adults emerge may help reduce damage to subsequent leaves. Leafminer control is often best to left the parasitoids become established and just accept some damage. If you are a grower, there are several insecticides available to help reduce leafminer damage.

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New industry articles on spider mite and thrips management for greenhouses.

Periodically I publish articles in industry magazines such as Greenhouse Grower, GrowerTalks, and American Nurseryman. The two most recent articles discuss spider mite and thrips management. You can find these and all industry articles at:

Japanese Beetles

This pest feeds on roses, grapes, flowering plums and other plants during the mid summer and will begin to lay eggs fairly soon after the adults emerge.  Once the eggs are laid we can expect the Juvenile stage; white grubs to hatch within 2 weeks.   Adult beetles are already flying in large numbers in WNC.   Landscapers should consider applying an insect for the adults NOW!.  But turf grass managers need to consider starting applications of insects for the grubs in about 3 weeks.  A couple of very safe products can be considered; Acelepryn (an IGR from Sygenta) and the beneficial nematode- Heterorhabditis 
bacteriophora  can be used.  Both products will need multiple applications from mid July through September.   Mach 2 and Merit are also two very good insecticides however use caution when applying either of these due to potential for damage to pollinators.  

For more information contact your local Cooperative Extension Center and ask for the Commercial Horticulture Agent.