My colleague Hannah Mathers just shared with me that the label of the herbicide Marengo® now includes greenhouses floors.  This is good news because of the limited number of herbicides available for greenhouse growers.

Marengo® is a pre-emergent selective liquid herbicide that offers long-term residual control of both grassy and broadleaf weeds on ornamentals.  It controls tough grassy weeds such as crabgrass, annual bluegrass, and annual sedge. Marengo also demonstrates early post-emergence activity against some weeds, including annual bluegrass, crabgrass, and oxalis.  The active ingredient (Mode of Action Group 29) prevents weed seed germination by inhibiting cellulose biosynthesis. Marengo does not move once applied to the soil and does not volatilize.

Users should avoid applications when spray particles may be carried by air currents to areas where sensitive crops and plants are growing. Avoid spraying with winds in excess of 10 mph.

For more information, go to: http://www.ohp.com/Products/marengo.php.

Claudio Pasian

Associate Professor

pasian.1@osu.edu

It’s tempting to stop scouting for insect and disease pests this time of year – there is already so much to do and not enough hours in the day to get it all done.  Remain vigilant and continue to look for signs of insects and diseases lurking in your crops!  Recent greenhouse visits have uncovered two usual suspects – thrips and aphids.  If you aren’t sure what to look for here are a few examples. remember to put out sticky cards and have someone check them weekly – as well as walk through the greenhouse making note of anything out of the ordinary.  The goal is to be proactive in dealing with greenhouse pests, not reactive!

Aphids

Aphids feed on plant sap and can often be detected by the presence of a sticky honeydew.  They are notorious for multiplying quickly on greenhouse crops so thorough scouting and control measures are important to keep populations in check.  Growers might find both winged and non-winged aphids on their crops.  Some control recommendations can be found in a previous post by Dr. Ray Cloyd here:

 Aphids on sweet potato vine.

Thrips

Thrips are tiny, cigar-shaped insects that can often be found in the flower heads of on gerber daisies, osteospermum, dianthus, marigold, petunia, vinca, and countless other bedding and flowering plants.  Thrips feed on leaves and flowers by piercing the plant parts and sucking out its contents.  They not only damage leaves and flowers but can also transmit plant viruses like tomato spotted wilt virus (TSWV).  One good way to detect thrips is to tap or shake a few flowers heads over a white piece of paper.  If thrips are present, a few will generally fall onto the paper and can be easily seen. Dr. ray Cloyd’s recommendations for thrips control can be found here.

 A thrip on Gerbera petal

Thrips damage to osteospermum petals include markings with loss of coloration.

 Thrips damage on foliage due to piercing and sucking of the tissues.