2019 Cornell Floriculture Field Day: Pest and Pathogen Walk

Cornell University hosted their annual Floriculture Field Day on July 30, 2019. The trial gardens have traditionally been housed at Bluegrass Lane, but were moved to the Bonatic Gardens on campus this year.  As part of the trials (you can read more specifics about the annual trials on their blog), the gardens are not treated for pathogens or pests (except for deer). The NYS IPM ornamentals team led a group through the Botanic Gardens to point out some common signs and symptoms to be aware of.

Symptoms: There are a couple symptoms that were quickly pointed out on this pepper plant, leaf discoloration (yellowing/chlorosis) and leaf distortion.


Both symptoms are indicative of a couple different issues. They suspected INSV since there was a thrips issue in the greenhouse before planting, but a grower pointed out they also saw those symptoms when broad mites were present.

What did we find?

Broad mites were the culprit! However, we would still recommend testing for INSV to be sure that’s not a contributing factor.

In the video, there’s one larger adult and a couple small immatures (one moves off screen quickly). These are difficult to spot, and you’ll need at least a hand lens to find them. I used a handheld digital microscope to capture this video.

Symptom: White spots on the upper surface of zinnia leaves.

Earlier in the day, Margery Daughtrey from the Long Island Horticultural Research & Extension Center spoke about how to identify some common diseases, so we were all able to correctly identify this as Powder Mildew (PM). The major clues: The clusters of white spots on the upper surface of the leaf (PM can show up under the leaf, but it’s not common), and the high humidity created the perfect conditions for this fungus to thrive. Zinnia isn’t one of the most common hosts, but it is still susceptible to it.

And although you may not have to deal with this next problem in your own operations, I know some of you occasionally get pest questions from customers, and this one might come up.


We found a growing tulip-tree aphid colony (Illinoia liriodendri)  on a tulip tree (Liriodendra tulipifera). They can reach damaging levels if the population grows large enough to cover the leaves in honey dew, but I haven’t heard of that happening in New York.

You can differentiate these aphids from other species by the long black cornicles and antennae and the long cauda (the tail). These are quite small in comparison to foxglove aphids that we’ve been seeing a lot of this year, so you may need a hand lens to spot the differences.

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