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Horticulture and Home Pest News
Horticulture & Home Pest News is filled with articles on current horticulture, plant care, pest management, and common household pests written by Iowa State University Extension specialists in the Departments of Entomology, Horticulture and Plant Pathology.

Plant and Insect Diagnostic Clinic Update - June 13, 2012

This article was published originally on 6/13/2012

It has been a busy couple of weeks in the Plant & Insect Diagnostic Clinic with a variety of disease and insect samples. Remember you can check the PIDC’s facebook page to ask questions and for updates and more pictures.
 
Disease update
 
Tomatoes are still coming in! Most of them were diagnosed with bacterial canker which causes wilting and in some cases spots on fruit.
 
A tomato sample was diagnosed with leaf mold, a disease that is more commonly seen in greenhouses or high tunnels (see picture). 
 
Garden plants (basil, peas, and lilies) have shown root and stem rot caused by Pythium and Rhizoctonia. To prevent root rot problems avoid overwatering or planting in areas with poor drainage.
 
Septoria leaf spot was also seen on a black-eyed susan (see picture). This fungal disease can be managed by removing infected leaves, increasing plant spacing, and avoiding overhead irrigation.
 
We haven’t received many lawn samples but there were some reports of Ascochyta leaf blight and dollar spot.
 
We’ve also seen maples and oaks which are mostly suffering from some sort of environmental or abiotic issue.
 
Insects
 
Tomatoes have also been having problems with stalk borers (see photo below) tunneling into the stem and causing plants to wilt (look for a small hole in the stem). There are no practical controls for stalk borers on tomato, so be sure to remove tall grass or weeds near tomatoes to reduce stalk borer problems.
 
Picnic beetles (see photo below) are out and about harassing innocent diners. Picnic beetles can be a problem when they feed on soft fruit like raspberries. Be sure to pick and remove overripe or damage fruit to reduce the numbers of beetles attracted to your garden.
 
Fishing spiders are making their presence known. We have received many pictures of this large, yet harmless, spider. When they accidentally get in homes they are often found in sinks and showers where they are seeking moisture and the insects seeking moisture. Think of your shower as your homes watering hole for many creepy crawlies!
 
Variegated cutworms have been numerous in reports from home gardens and landscapes around the state.  Damage appears as large irregular holes in hostas and other plants.  In the garden, tomatoes are a favored host and both leaves and small green fruits will be damaged.  See HHPN from June 1, 2001 for more information and HHPN from May 2, 2011 for photos.
 
Japanese beetles are back!  Reports from central and eastern Iowa indicate the emergence has begun approximately 2 to 2.5 weeks earlier than normal.  For more information see the Clinic online article.
 
Now is the time to expect reports of carpenter bees burrowing into exposed wood rafters and joists.  Learn more from the June 23, 2010 issue of HHPN.
 
 
Leaf mold on a tomato leaf.
 
 Septoria leaf spot on a Black-eyed Susan

Stalk borer.
 
Picnic beetles.