Indiana Department of Natural Resources sent this bulletin at 05/01/2019 07:41 AM EDT
Weekly Review for May 1, 2019
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.
In my one greenhouse inspection this week, I found heavy aphid populations in the nooks of the leaves on daylilies and some minor spider mite on the miniature roses.
A homeowner called about suspected boxwood blight. They had a lot of boxwoods scattered across the landscape. Various clusters of plants were displaying cold damage, old spider mite damage, and most seriously, really heavy boxwood leaf miner. While it might be getting late to use soil drenches on the leaf miner, there is still plenty of time to prepare for foliar treatments.
Finally, we are starting to find some traces of Gypsy Moth egg hatch. Vince found some hatch in Fort Wayne and I found a few in Wakarusa. I have also heard from homeowners who noticed hatch in Elkhart. Last year, they all popped at once. This year, with the variable temperatures in the forecast, I expect egg hatch to be drawn out over a week or so.
Ken Cote (Nursery Inspector & Compliance Officer) - KCote@dnr.IN.gov
Things get really busy at this time of year but it is important to take a moment and look at the beauty around you while working. Remember to take time in life to smell the Viburnums. Yes, the Viburnums and not the roses this week. I found several issues on roses this past week. During the past week I found early infections of black spot on Queen Elizabeth rose. It is fairly early for this pathogen, but my experience with the diseases is that once it is above 60F at night with rain, it will start to get established. I also found one case of rose mosaic virus. This viral disease appears as bright, yellow mosaic patterns on infected leaves. There is not any cure for the disease and infected plants should be destroyed. It seems that there is always a trade off when it comes to disease resistant plants. I have William Baffin rose in my yard which is resistant to blackspot and powdery mildew, but I already see early stages of rose anthracnose starting to develop before the plant has bloomed. The same is true for Knock Out Roses. They are black spot resistant however, we are starting to find more cases of downy mildew on the plants. This is a more serious disease than powdery mildew. Downy mildew becomes established on leaves but can also overwinter in stem tissue of the plant which makes control very difficult or nearly impossible in heavy infestations. Roses heavily infested with downy mildew should be destroyed.
Botrytis has been found on many annual plants with the recent streak of cool wet weather. Look for fuzzy, grayish spores on infected areas. During the past week I found this problem on New Guinea impatiens, geraniums, periwinkle and begonias. Avoid overwatering and let plants dry out a bit when we have long periods of cloudy cool weather. I know this is sometimes difficult, especially when it is 80F the day before and the greenhouse needs to be watered. Then, the next day it is 50F with rain. I also found cankers on willow and yellow twig dogwoods. This disease cause blackening of the stem tissue and canker formation that can lead to branch dieback. Other canker type disease could cause similar symptoms and a laboratory diagnosis is needed to 100% confirm which pathogen is causing observed cankers.
I have seen a few pest related problems during the past week. Eastern tent caterpillar was found on crabapples. I also found two spotted spider mites on butterfly bush. Two spotted spider mites are often a problem on butterfly bush, especially in a nursery setting. Treat infestations early because you can have several generation during the growing season which can lead to serious plant injury. Also, two spotted spider mite feeds on many types of plants including burning bush, tomatoes and sweet potato vine. This is a warm season mite and has primarily been found on greenhouse grown plants.
Ren Hall (Nursery Inspector & Compliance Officer) - RHall@dnr.IN.gov
Last week I finished up the last of my greenhouse inspections. I had two notable finds, the first of which was one of the worst infestations of spider mites I have ever seen. There were a few tables of different cultivars of sweet potato vine, and they were just swarming with mites so badly that you could see them crawling around with the naked eye. There were even little chains of the mites hanging down from the plants and crawling all over each other, almost swinging from the movement. I have never seen anything like that before. From my pictures, you can see why they call them spider mites.
The other problem I found was on a few different cultivars of Japanese maple that had just come in from a wholesale nursery the day before. The newer growth was blackened and dying back. No insects were present so I didn’t think it was sooty mold, and I initially suspected Pseudomonas (a bacterial infection) which can cause blackened twigs and dieback. However, I sent a sample of the ‘Waterfall’ cultivar which had the worst damage to Purdue’s Plant and Pest Diagnostic Lab and they confirmed it was in fact sooty mold with the short twig dieback caused by Phyllosticta sp or Phoma sp. The lab report states that the dieback may be pruned out and the plants should grow out of the problem eventually.
Eastern Tent Caterpillar Ken reported ETC last week in Brown County. I have not seen any tents in Washington County or around Vallonia Nursery in Jackson County. Over the years, Monroe, Brown, Lawrence County intersection have been the area of ETC populations causing defoliation to Black Cherry in the forests. So I consider that area to be a focal point of periodic ETC epidemic defoliation to Black Cherry and then also moving onto fruit trees and even oaks.
Sycamore Anthracnose Has not shown up at this time in the southern third of the state. However, weather conditions are favorable for noticeable defoliation of sycamore from now through May/June. Over time I have found the last week of April and first week of May with temperatures averaging 50F and weekly rainfall averaging 1 inch will result in sycamore anthracnose. Following with heavy sycamore anthracnose, you can expect to see oak anthracnose and Ash anthracnose if you have Ash which would be southwestern Indiana which still has big trees. Other areas of state will have seedling/sapling and small ash unless they have protected ash with insecticides that could show anthracnose. Depending on where in middle and northern Indiana, you could also see sycamore anthracnose. Also, expect to see fire blight as that disease seems to be more prevalent when you have heavy sycamore anthracnose.
Red Bark Sycamore Last fall early winter, I received report from a County Extension Agent and the Purdue Diagnostic Lab of a landowner east of Madison in Jefferson County with the bark showing a red color. The red color could also appear orange or rust red in color occurring on the smooth bark area in the mid and upper bole of the trees. Trees with the red color bark occurred in drainages. With the district forester, we examined the trees and took bark samples sending them to PPDL. Gail Ruhl at PPDL identified the red color as algae and found a reference to this from Connecticut. The red color algae does not cause any damage to bark. That is, under the bark tissue is alive and healthy and no canker formation. Examining the trees in leaf off, I did not see any twig dieback in the canopy. The landowner reported seeing the red color bark in 2017. Recently, I talked with Joe Boggs in Ohio who also has received reports of red bark on sycamore. So, if you see red color bark on sycamore where it should be white color, please share that location and extent of occurrence to Phil Marshall Forest Health Specialist by phone text or email – 812-595-2740 or pmarshall@dnr.in.gov.
EAB adult emergence EAB adults will be emerging shortly in southern Indiana with emergence lasting through June as you move north through the state.
Too much rain to do live inspections. I did look at dead hives in 2 different apiaries. One apiary was varroa mite and virus problems. The other is a beekeeping management problem- not enough food for the bees to make it through the winter and poor condition of some of the frames. Once this rain lets up there will bound to be some swarms from strong hives out there. Beekeepers have reported finding queen cells in hives. I did hear this weekend of reports of swarms in Jeffersonville area.
The Bedford beekeepers had their bee intensive Saturday the 27th. We were able to go through hives before the rain came in. Some of the hives are under a roof so could still go through the hives in the afternoon. During one session I was doing, we found a new queen and she was pipping. That was a great experience for new beekeepers to hear. The queen will make a “pipping” sound when there are other new queens in the hive. This hive had several other queen cells in it.
Once I watched a queen do the pipping sound. She stops moving and through body movement she is able to make this sound. This queen was right next to a queen cell. A queen was about to come out of the cell. Workers bees were paying attention to the cell, kind of help chewing away the capping for the queen. A queen within a cell can communicate with bees letting them know she is about to come out. Worker bees will feed a queen larvae, but once capped they will not pay attention to the cell until the queen is ready to emerge.
We maintain a list of beekeepers willing to remove and recover bee swarms on our website Swarm season for Indiana can be mid-April through end of June. Beekeepers should still go to collect any later swarms. These later swarms can be put in a double nuc to make it through the winter. The swarm could also be combined with another hive.
