Greenhouse Scout School 2026

1.Last week, I added a few more sticky cards to my propagation house. I did not notice any new insects, however, there were significantly more fungus gnats on the pots that house geraniums compared to the coleus plants. This week I added 2 more sticky cards to a spider plant and an additional geranium to see if something similar will happen next week.  

2. I am unsure if it is due to the warmer weather we have been having or the longer day lengths, but I am slowly discovering that my plants are needing more water. More geraniums at Allegany State Park are showing the leaf purpling that I found last week. Next watering, I am planning on giving all the geraniums some fertilizer.

3. Since I am the head grower, I will list some information I would like an employee to give me if I gave them the task of scouting.

I would like to see the date, location, plant species, pest presence/density, and plant health on a weekly basis. If any corrective action was taken (for instance watering a plant that looks wilted) that should be documented as well. If new pests were found or if it seems like pest pressure is increasing, I would like to know immediately.

 At the end of the season, it would be helpful to see a graph of what pests were located during the different times of the season. Markers on the graph showing when different treatment methods took place would also be helpful. This could show which methods of control were effective or not. This helps to make informed decisions for the following growing season.  

Part 2 diseases (and other problems) on new plants that came in

The greenhouse received a huge shipment of tropicals since my last scouting visit.  The grower said they are often short on staff and time, and have to rush the new stock out onto the floor without being able to completely inspect anything first.

Since my last visit, they have made a couple of spot sprays on specific, target plants for mites.  Unfortunately, they did not realize that the grower had also sent some bio-control predatory mites with the foliage plant shipment, so the spray that was used killed the beneficials and the pests.  (We just read about this warning in the course work, and then I got to hear their story of how it actually happened in real life.)

The greenhouse has been getting warmer with the sunny days:  low 68℉ - high 86℉

There is no gauge for humidity in the houses.

Ceiling/peak vents are manually operated, but have not yet been opened this winter.  

A couple of fans placed above-the-head create air flow.

I was able to examine several plants and found:

Aglaonema ‘Etta Rose’ (with green and pink variegation)... I found several small, perfectly round holes in the leaf tissue.

Aglaonema ‘Silverado’ (with green and white variegation)... 

There is some color-break or fading of color on the leaves, though maybe not apparent to people not familiar with the species.  

There is also thin yellow streaking.

And, there are some leaf spots that look brown and dried up.

And, there was one spot (half the size of a nickel) that looked black and water-soaked.  It had a yellow margin ring around the black area.  I tried mimicking a method we read about in the course materials to see if the spot was bacterial:  I cut through the damaged spot and placed the leaf tissue in a flat tray with some fresh, clear water to see if any grey clouds of bacterial spores oozed out, but I did not see any.

The thin, yellow streak might suggest color-break and therefore a virus or viroid.  

There were also bumps and curled distortion at the leaf tip on one Aglaonema leaf, which might suggest edema or viral distortion.

I examined it with the hand-held microscope.

More from Part 2 of this assignment in a separate post.

Part 2, continued

Dicksonia (Australian Tree Fern)... This is the same plant where I had placed a sticky card.  The manager thought he had seen a mealy bug on it a couple of days earlier, so we both examined it and found three possible mealybug indicators.  I examined them under the hand-held microscope and found two living, long-tailed mealy bugs, and one that was not moving.  They were all on separate leaves, but all on the mid-ribs of each.

One of the active ones ran off of the leaf tissue and onto the table.  They look really fast when you are trying to hold the tiny microscope lens over their body to get a still picture.  I also took two video of them moving, but I can't get them to upload because they are too big.

Part 2, continued

Algae on the brick stairs and connector space from Greenhouse #1 to #2.  No pictures.

Alocasia gigantea ‘Aurea’, newly arrived, 3-4” pots… It took the entire course, but I finally got something really cool… and creepy… and cool.  During my talk with the two managers, one mentioned that they had seen mites on the Alocasia a couple of days ago, so they had done a diluted alcohol bath on the foliage and returned the plants to the sales floor.  They had forgotten to tell me that during our initial talk about treatments done during the last week.  That made me realize that I have to ask questions the way I do when working with landscape clients:  ask multiple questions about the same basic thing, but from many different angles to make sure we cover everything.

I examined the Alocasia  and found… wait for it… two-spotted mites running around and tending their eggs!!!  We were all very excited, and then one manager said that viewing the mite with her egg almost made him feel sorry for her.  The mites themselves were not on mid-ribs or side-veins, but I think I found some cast skins on the mid-rib.  You can hear me gasp on the video when I actually look at my computer screen to see what the microscope is capturing.

I then ran the hand-held microscope all the way along the mid-rib and found, what I think are, mite cast-skins or maybe egg casings opened, or maybe just damage from mite activity. ??  They were in a long row and clinging to the vein.

I am bummed that I could not get the videos to load because of their size.  I had mites crawling and mealy bugs running.  I appreciate any advice to get the videos to load.  Thank you, everyone.

1. When I moved my cards to another growing house I got a lot of the same pests. 

2. With the beginning of spring we moved a lot of the houseplants from the outdoor greenhouses back inside to the main houseplant greenhouse and I was able to see a lot of mealy that had gone unchecked in some of the taller dracaenas. The owner decided to toss those plants. There was as a lot of spider mite on the alocasia. That has since been sprayed and so far there have been no more indications of a further problem. 

3. Since I work at the greenhouse I’m scouting in I talk to the grower/owner everyday. We have a system in place at work that allows any worker to make a note of a pest found on a chart up front. We have a column for what type of pest, the plant it was found on, and the greenhouse that plant is located in. If there is a really pressing infestation on a plant I will also talk to him directly about the problem instead of relying on the chart to know that a plant will be treated.