Pest News Update July 8, 2011

ORNAMENTALS AND TURF

From: Steve Frank, Extension Entomologist

Dogwood Twig Borer Oviposition

The last couple of weeks I have noticed flagging branch tips on the red twig dogwoods (Cornus sericea 'Baileyi') in front of my house. The damage was characterized by a cleanly girdled branch with a 1 cm oviposition scar just below. Gradually the tip goes from yellow to brown then falls off. Investigation and help from our excellent diagnostician revealed a large egg within each scar containing a round-headed borer larva. This was the dogwood twig borer. Adults have been active lately laying eggs in twigs. The larvae will overwinter within twigs then continue boring down the twig pith in spring killing the affected branch. This is not likely to be a big nursery pest but should be on the radar. It is much better to identify the flagging branches now and prune out the eggs than wait until spring when a whole branch or small tree will be affected.

If you follow me on Twitter, you know this already! Follow @OrnaPests on Twitter for timely updates on ornamental pest activity.


Western Flower Thrips in Greenhouses

Thrips are a constant problem for growers, not just a problem this week. Western flower thrips, Frankliniella occidentalis, is the most important and damaging thrips of greenhouses and has been called the most damaging greenhouse pest in the world. This is true of greenhouse-grown food and ornamental crops. Nearly all floriculture crops are susceptible to thrips damage.

Western flower thrips reproduce rapidly and are difficult to manage because they live in the cracks and crevices of flower heads and foliage. Thus, they are difficult to contact with insecticides. Western flower thrips also develop insecticide resistance rapidly so it is important to emphasize chemical rotation and to have a resistance management plan.

Sanitation is also very important in managing thrips. Because thrips can feed and reproduce on hundreds of plant species weeds in and around a greenhouse, they have a constant supply even if the crop is sprayed. Western flower thrips pupate in soil, so cleaning up spilled potting soil and other debris can deny them a vital part of their lifecycle.

More information and chemical recommendations can be found in Ornamentals and Turf Insect Information Note at Note 72.


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