Indiana Department of Natural Resources sent this bulletin at 07/03/2018 01:40 PM EDT
Weekly Review for July 3, 2018
Indiana Department of Natural Resources Division of Entomology & Plant Pathology Phone: (317) 232-4120 Our Website Inspector Territories
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.
Links can be found at the bottom of the page to manage your subscription to this list. Comments and questions about this report are welcome and can be sent to Eric Biddinger or to your respective
Inspector.
Inspection
Reports
With vacations and scheduling conflicts, we were planning on
taking this week off.However, Jared brought
up an idea that was too good to pass up.This report was written up a couple weeks ago, but gives a unique look
into what you can find if you just look! We’ll be back with the regular reports next
week.– Eric Biddinger
I am beginning to think that the fruit of an English oak is Oak Lecanium scale because I always find the two together. I paid a visit to a site with 24 English oak planted in the landscape and I was surprised at what I found. I had located these trees a couple years ago and I was looking to get some photos of crawler emergence. At my first visit this year, I found that there had been quite a population explosion of the scale but the crawlers were not out yet. On the second visit, I hit the jackpot and then some.
Adult Oak Lecanium scale (the scales are actually dead and the female bodies are protecting the unhatched eggs). Photo taken on May 30 and according to the nearest weather station the GDD would be in the High 800’s.
Oak Lecanium scale crawlers after emergence crawling across the adults. Photo taken June 12 and according the nearest weather station the GDD would be about 1150.
Once hatched the crawlers move out onto the leaves and settle down to feed for the summer. Prior to leaf drop they will move back to the twigs and small branches to spend the winter.
With this many scale, you are bound to find natural predators like this Asian lady bird beetle. Generally, lecanium scale doesn’t reach this kind of severity because of natural predators but these trees are isolated out away from any other habitat, so I suspect the predators are having a harder time finding them.
The pupae of an Asian lady bird beetle.
An egg from a lacewing, there were many of these that I found but despite my best efforts I was unable to locate and an adult lacewing or lacewing larvae.
Looking over the scale, I also find some scale that had been apparently parasitized. You can see the exit holes in the scale coving indicated by the red arrows.
While looking at the scales I also found some katydid eggs which had hatched (Green Arrows). Scale are Red Arrows.
Early instar bagworm feeding.
I found some gouty oak gall. This gall is formed by a wasp in the Cynipidae family which causes a stem gall. There are two generations of this wasp on two different portions of the tree similar to horned oak gall (its cooler cousin). The first generation of wasps emerges from the stem gall but is all female. These females are parthenogenetic and lay eggs in the leaves of the oak. Galls are formed in the leaves and in a few months the second generation of wasps emerges which contains both male and female. After mating the females return to the young branches and lay eggs forming new stem galls which will then take several years to develop.
I believe this is a Gouty oak leaf gall from the second generation but I haven’t been able to confirm it yet (i.e. I haven’t asked the folks with the PhD after their name). I’ll correct myself if I’m wrong.
This is a photo of the leaf gall with the majority of the leaf peeled off.
This is the leaf gall cracked open.
Solitary Oak Leaf Miner is the larvae of a moth. I’ve seen quite a bit of this so far this year. This leaf miner leaves a somewhat circular window pane mine as opposed to the serpentine pattern many miners make.
If you hold a leaf miner up to the light the frass becomes very apparent regardless of what type of host or leaf miner you are dealing with.
An oak leaf with the top membrane of the leaf mine peeled away to reveal the solitary oak leaf miner larvae.
The ever present aphid colony. Although there numbers weren’t all that impressive. I would assume that a lacewing or lady bug would choose an aphid over a scale crawler.
I found this odd blistering on a couple leaves.
After flipping the leaf over I noticed what looked like exit holes.
I started to try and peel apart the leaf to see if anything was inside. After a couple of failed attempts I found a little black spot which was alive and wiggling. I managed to extract what I think was a wasp but it didn’t hang around long enough to get a good look at it.
I later found this little guy wandering the surface of another leaf but I do not have an ID on it.
Do you think spiderman will get mad if we use the term “web crawlers” to describe this situation? Yes, these are lecanium scale crawlers caught in a spider web.
I guess the tree is going to have the last laugh. Apparently, lecanium scale are not the fruit of English oak as they do, in fact, produce acorns.
