Indiana Department of Natural Resources sent this bulletin at 07/01/2020 09:31 AM EDT
Weekly Review for July 1, 2020
This informal report by the Division of Entomology and Plant Pathology is designed to update the Nursery and Greenhouse industry of insect and disease pests the Division has been encountering on a week to week basis and as a way to give a “heads up” of things to be on the lookout for. Comments and questions about this report are welcome and can be sent to your respective Inspector.
Bagworm has emerged throughout the state and in evergreen plants. Last year’s damage is evident, as can be seen on this picture taken in a field, but what might not be as noticeable from a distance is all the tiny little bags on all of the surrounding trees, which will slowly begin to cause more visible damage. Now is the time to do something. If you wait until the bags get too large, the only real option to treat them will be to manually remove bags from trees and by that time, the damage will be done for this year.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week I was doing an inspection at a greenhouse grower and found Impatiens Necrotic Spot Virus (INSV) on several fancy varieties of coleus. I also found this virus on coleus last year at a different, unrelated greenhouse. INSV can be spread through cuttings from infected mother plants as well as by an insect vector, the western flower thrips, which picks up the virus as it feeds on infected plants and spreads it to other plants. The virus can affect hundreds of different species of plants, many of which are commonly found in greenhouses (which are also perfect environments for thrips to thrive). PPDL confirmed the diagnosis of INSV using virus test strips and confirmed the thrips I found as western flower thrips. To eliminate the virus from the greenhouse, a combination of sanitation, destroying infected plants, and monitoring and controlling the insect vector will have to occur or this will continue to be a problem.
I also found suspected crown gall on pieris at a box store in Tippecanoe County. Crown gall is caused by a soil bacterium (Agrobacterium tumefaciens) and has hundreds of known host species. It can be spread through soil, gardening tools, and can enter the plant through wounds. This is a regulated pest in Indiana, so symptomatic material is stop-saled and destroyed.
Last, I found this fuzzy white mass on some lilies in my garden. On closer inspection, there were several fuzzy little planthopper nymphs. I’ve seen adult planthoppers feeding on these lilies in the past.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
We finally got some rain in Bloomington. 0.95 inches so far this week. Some areas of the state got over 4 inches on Saturday alone. I saw one Japanese beetle in my garden last week and had verbal reports of Japanese beetles in Sullivan County. However, I have not encountered any damaging populations yet. Fall webworm was found in Brown County last week, but this was an isolated case. Look for webbing at the ends of branches. This pest often becomes more apparent toward late summer. Small, infested branches can be pruned out of trees. There are insecticide labeled for control of this pest if you are getting objectionable damage.
Interestingly, I am finding damage from four-lined plant bug in my yard on big leaf hydrangea and Shasta daisies. This pest is active in early summer and can cause damage quickly, but it usually does not last long. Look for small, round areas of necrotic tissue that have separation from each other. If you are lucky you will be able to find a small yellow and black striped bug. I rarely see damage from this pest, and in this situation I was not able to find any adults. I am also seeing more lace bug damage during the past week. Look for that coarse stippling, colonies and fecal spots on the undersides of leaves. Azalea lace bug was found in Vigo County at a nursery and Oak lace bug was found in a forested area of Brown County. Two spotted spider mites continue to be a problem on butterfly bush, but I have not seen them on burning bush yet.
Powdery mildew was found on flowering dogwood, susceptible phlox varieties and columbine during the last week. I have only encountered one case of fire blight so far this year. I would have thought I would have seen more symptoms of fire blight occurring due to the fact that we had multiple spring freezes. This is what happened in 2012, but it is not the case this year. There are numerous leaf spot disease starting to appear on many ornamentals. Septoria leaf spot is become wide spread on red twig dogwoods. I am also seeing leaf spots develop on strawberry plants.
There are a lot of varieties of strawberries available in the market, and I would highly recommend finding a resistant varieties. Multiple years of leaf spot on my strawberry patch weakened the plants over time. The heavy rain in areas this week should bring on some more disease issues. So far I am able to control the leaf spot on my tomatoes this year. That has been one good thing about the dry June. However, this week will put my cultural practices and fungicide treatments to the test. Viral symptoms were found on one hosta plant in Brown County. There are several viruses that can occur on hostas, but the most important one is Hosta Virus X. I do not encounter this disease as frequently as I have in the past. Laboratory testing is necessary to determine the type of virus that infect hostas. Plants with viral symptoms should be discarded.
Gypsy moth mating disruption treatments were done last week in Huntington and Marshall counties. That concludes our treatments for this year.
I found my first Japanese beetle of the year in my own backyard, just a few days earlier than last year.
I’m starting to see a lot of the rust diseases on hawthorn, apples, and serviceberry. Other finds in nurseries include cottony maple scale on newly arrived “Eskimo Sunset” maples, powdery mildew just starting on dogwoods, and apple scab hitting some of the older apple and crabapple varieties pretty hard.
