No. 15/September 23, 2014
The hosta is a popular landscaping plant, loved for its beautiful variety of foliage, and ease of cultivation. Around this time, delicate purple or white flowers develop before frost. Ssome of the most prevalent pathogens on hosta in Illinois are listed in this article.
Scoliid wasps, family Scoliidae, feed as parasitoids on the larvae of green June beetles. Where there were high numbers of these beetles, this is followed by large numbers of scoliid wasps. These are one inch long black wasps with the posterior portion of the abdomen being orange with a couple of yellow spots.
White grub infestations continue to be widespread and scattered this year. There appears to be more mammal and bird damage than direct grub damage appearing. With the low number of Japanese beetle and masked chafer adults in most areas of the state, this makes sense. It takes ten to twelve grubs per square foot to cause turf injury.
Oak sawflies are being found on white oak. They are generally most common on pin oak, also occurring on black and scarlet oaks. It is one of the slug sawflies along with pear slug and rose slug that appear as slimy, elongate, slug-like creatures. Oak slug sawfly larvae are yellow and green.