PEST BULLETIN Japanese Beetle Adults June 21, 2002 August 20 Update: Japanese beetle adult activity has finally tailed off, which means it is time to scout for the hungry little 2nd or 3rd instar larvae that may be chomping on your roots. With the huge populations of adults that were observed in some areas this may be a banner year for JB grubs, (if your earlier insecticide application works this year it will probably work regardless of how high the JB population is). July 11 Update: First reports of Japanese beetle activity came in Chicagoland around the end of June, first of July. This pest has reached historic levels in Illinois this year, (some counties catching 300-600 beetles a day per trap!) so expect the situation to get worse before it gets better. This may be a year when more than one insecticide application to your Lindens, crab apples, (which are currently getting devoured at Golf House), or other high value ornamentals may be necessary. Update: On June 24, the first wave of Japanese beetles landed in Danville. Yellow pest alerts for Japanese Beetles in Bloomington, Peoria, and Urbana. Entomologists at Purdue University reported the first sighting of Japanese Beetle adults on June 12 in southern Illinois, near White County (see Japanese Beetles Have Begun to Emerge in Southern Indiana - UIUC Extension). During the next week or so, Central Illinois superintendents should be on the lookout for adult emergence, as last year the beetles began damaging ornamentals around June 27th (see UIUC Home Yard and Garden Pest). The beetle is about 1/2 inch long and is shiny metallic green, with hard bronze-colored wing covers (see Photo 1). These beetles feed voraciously on a variety of host plants,(see Tables below) as well as lay their eggs in turf, so their larvae (annual white grub) can feed and develop on turf roots.   Photo 1 (click on image to enlarge it.) Life Cycle/Predictive Models Prediction models for the life cycle of the Japanese beetle are based on base 50 growing degree days (DD). Japanese beetle adults first start to emerge from the ground at 1050-1180 (DD). Somewhere during the 1590-1925 DD window, 90% of beetle adults will have emerged from the ground, and feeding activity on ornamentals and trees can become a significant problem. Ten to fourteen days after the 1590 DD mark, Japanese beetle eggs will have hatched in the turf, and annual white grub feeding begins. The following table provides the IT pest alert descriptions and recommendations for Japanese beetle adults and annual white grubs. IT Prediction Model for Japanese beetle/grubs Life Stage Event DD - base 50 Alert color Recommendation Adults 1st adults emerge 1050-1180 Yellow Scout for beetles on ornamentals/trees 90% adults emerged 1590-1925 Orange Treat ornamentals if necessary Grubs Hatch - actively feeding 10-14 days after 1590 DD Red Treat in this window period for actively feeding grubs Photo #1.   Japanese beetle adult.   Table 1. Ornamental plants highly susceptible to feeding by Japanese beetle adults. Japanese maple Norway maple Gray birch Horsechestnut Black walnut Sassafras American elm Althea London planetree Rose Black cherry Crab apple American mountain ash Lombardy poplar Pussy willow Lindens Table 2. Ornamental plants less susceptible to feeding by Japanese beetle adults. Red maple Silver maple American holly Boxwood Snowberry Winged euonymus Flowering dogwood White cedar Yellow poplar Saucer magnolia White/Green ash Lilac Norway spruce Scotch pine Douglas fir Canadian hemlock Mock orange Hydrangea Yew Forsythia UIUC Home Yard and Garden Pest