The past year brought a variety of challenges to operations across the country, including insects and diseases that may have threatened your crops. Learn about the top pests we encountered in 2021 from three industry researchers.

• Fulya Baysal-Gurel
  Interim Associate Dean for Research, Department of Agricultural and Environmental Sciences, Tennessee State University
• Margery Daughtrey
  Senior Extension Associate, School of Integrative Plant Science, Plant Pathology and Plant-Microbe Biology Section, Cornell University
• Dan Gilrein
  Extension Entomologist/Associate Agricultural Program Director, Cornell Cooperative Extension of Suffolk County

What diseases had the greatest impact on greenhouse crops in your area?

Margery Daughtrey: Botrytis blight caused by Botrytis cinerea was problematic on rosemary, lavender, Bells of Ireland, poinsettia and lemon cypress. Black root rot (Thielaviopsis) affected calibrachoa crops, and some unrooted poinsettia cuttings came in from offshore with soft rot bacteria. Basil was affected by the bacterium Pseudomonas cichorii and by downy mildew (Peronospora sp.). Downy mildew also occurred on Phlox divaricata. Losses in Echeveria production were associated with Fusarium and Pestalotia spp. Leaf spots caused by Cercospora and Myrothecium spp. were seen on New Guinea impatiens. Xanthomonas leaf spot was a problem on English ivy and Asclepias in production this season. Impatiens necrotic spot virus (INSV) was seen on coleus, basil, lobelia and impatiens.

What were some of the main insects greenhouse growers faced this year?

Dan Gilrein: Broad mite, western flower thrips, and several species of aphids continue to be among some of the pest issues we saw on bedding and pot crops. There were also some issues with European pepper moth and tarnished plant bug damage in mums.

What diseases did growers encounter in nurseries?

Margery Daughtrey: In nurseries in the Northeast, there were noticeably more problems with Phytophthora diseases than usual, in both nursery and production, likely due to the unusually frequent rains during the summer. P. cinnamomi and P. nicotianae were seen on rhododendrons, stachys, roses and rudbeckias. Not surprisingly, Pythium root rot was also seen on container-grown privet and cimicifuga. Ilex glabra, dianthus and phlox were troubled by black root rot (Berkeleyomyces basicola). Leaf and needle infections also thrived with the wet conditions this season. Both Seiridium and Phyllosticta needle blight were seen on arborvitae in nursery and landscape. Boxwood blight (Calonectria pseudonaviculata) was primarily detected in the landscape while Volutella blight (Pseudonectria sp.) and Macrophoma leaf spot (Dothiorella candollei) were seen on boxwood in production. Fusarium wilt was observed on lavender and mums this year. Leaf spot diseases were also problematic this year. Alternaria leaf spot was severe on California privet, Cercospora leaf spot and anthracnose were problematic on hydrangea, and Septoria leaf spot was disfiguring to Cornus sanguinea in production.

What insects had the greatest impact on nursery crops this year?

Dan Gilrein: Some of the things we saw included lace bugs on Pieris and rhododendron, fungus gnats and shore flies in propagation houses, rust mite and white prunicola scale on privet, spruce spider mite on conifers and boxwood leafminer on some varieties. The redheaded flea beetle continues to be an issue in container production of some shrubs. Some areas with gypsy moth outbreaks saw damage in nursery crops as well.

What diseases had the greatest impact on crops in the Southeast region?

Fulya Baysal-Gurel: We encountered root rot issues caused by Phytophthora species such as P. cinnamomi, P. nicotinanae, Phytopythium vexans and Rhizoctonia solani on different woody ornamental plants. We also noticed foliar diseases such as powdery mildew, Cercospora leaf spot on several ornamental species, Volutella blight (Pseudonectria buxi and P. foliicola) and Macrophoma leaf spot (Neofusicoccum buxi) on Boxwood, downy mildew and black spot on roses.

Early cercospora leaf spot on pansy
Nancy Rechcigl, Syngenta photo.

Which pests were you surprised to see this year and which ones did you not find?

Dan Gilrein: There have been a few inquiries about whiteflies, mostly sweetpotato, various species of mealybugs, and Lewis mite on poinsettia in greenhouses – we have not seen much of the latter for several years. Brood X cicadas were almost non-existent in the Northeast, so we haven’t seen the flagging or dieback affecting trees in the Mid-Atlantic. Jumping bush cricket damage appears to be increasing somewhat in Long Island including some minor leaf damage on nursery plants.

Margery Daughtrey: We saw a bacterial leaf spot (Pseudomonas cichorii) on Brunnera for the first time. The new Beech Leaf Disease, caused by the nematode Litylenchus crenatae subspecies mccannii, was also found in a few nurseries on American and European beech. Cercospora leaf spot and Xanthomonas leaf spot were seen on hydrangea and Cercospora leaf spot was also a significant problem on hiemalis begonias. Cases of Xanthomonas leaf spot on zinnia seen in the landscape may have originated from production problems associated with seed contamination. At least we didn’t see any powdery mildew on poinsettia this year!

Take Preventive Action in 2022

Whether you encountered these pests, or others in your operation, proper cultural practices and chemical tools are the best ways to combat them. View our comprehensive portfolio of fungicides and insecticides to help control pests you may see in the new year.

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