In response to the increased air temperature highs and averages, accumulating growing degree-days, increasing soil temperatures, and expected rainfall and overcasts days the following pest alerts have been generated for boxwood blight, ambrosia beetle, white pine weevil, and clearwing borers. Oomycete/Phytophthora treatment considerations are also listed at the bottom of the posting.

Stay informed:

• Sign up for the 2026 – Rutgers Ornamental IPM Program – click here to sign up
• Program is free, but registration is required – Registration includes:
  • Site visit to your ornamental nursery/farm from Rutgers agents
  • Delivered printed IPM resources (Guides, factsheets, bulletins)
  • Free pheromone & sticky trap kit + guidance on setup/monitoring (for commercial nursery/greenhouse and Christmas tree farms)
  • Access to live bi-weekly webinars (Zoom)
  • (First session TUESDAY 4/14 @ 12PM)
  • Every Second and Fourth, Tuesday, April through September

Boxwood Blight: high potential for new /spreading infections this week in Southern NJ

[pictorial tri-fold] Common Boxwood Pests and Diseases (click-here). This includes Box Tree Moth images. Print the PDF out double-sided, then fold.

If you suspect Boxwood Blight and would like to have this verified – please contact the Rutgers Plant Diagnostic Laboratory (click here) for sample submission instructions

• It is time to begin protective fungicide applications in boxwoods throughout the state if you have not already done so. 

• If BWB is important to your business – Use the USPEST – PUSH Alerts – (click here) – to setup weekly email alerts.
• Please visit the USPEST.ORG Boxwood Blight Risk Model – CLICK HERE TO CHECK YOUR LOCAL PREDICTIONS)

Fungicides; 

1. You very well may have these materials already applied as ‘cover-sprays’ – But – be mindful that protectant fungicides loose efficacy the more rain (or overhead irrigation) they are subjected to, and reapplication may be warranted.
2. ROTATE between Fungicide Resistance Action Committee (FRAC codes) to avoid this pathogen becoming resistant to specific chemicals

Format: [FRAC code]: Chemical name (Trade names * no endorsement implied, other options exist)  

• [M05]: Chlorothalonil (Daconil WS)
• [M05 + 1] Chlorothalonil + Thiophanate methyl (Spectro 90WDG)
• [11] Trifloxystrobin + [7] Fluopyram  (Broadform)
• [11] Trifloxystrobin + [3] Triadimefon (Armada 50WDG)
• [M03] Mancozeb
• [12] Fludioxonil (Medallion WDG)
• [3] Tebuconazole (Torque)BW

Approaching boxwood blight season – 2026 (threat this week in Central and Southern NJ)

Ambrosia beetle adult flight will VERY LIKELY occur this week throughout most of NJ. 

The last few seasons we have seen an upswing in ambrosia beetle activity in nursery production, principally in field grown nursery stock of thin barked trees (commonly – dogwood, honey locust, magnolia, maple, redbud, zelkova, styrax, Prunus spp.). Based on evidence from multiple lines of trap collection data throughout the United States, adult female flights appear to be correlated to consecutive days (2-3) of 70F temperatures (highs) with daily average air temps around 65F (max+min/2), i.e. THIS WEEK IN NJ.

Consider using pyrethroids in your production areas if this pest has been a regular problem OR there are water stressed (typically flooded / slow draining) plants.

Contact insecticides: 

• Pyrethroids [3A]: –thrins (bifenthrin, permethrin, etc.) – Pyrethroids longer lasting residual activity is why these materials are so effective against ambrosia beetles. 
• Systemic insecticides DO NOT WORK

Ambrosia Beetle Borers of Nursery Plants

White Pine Weevil (WPW) may have already emerged during the last heat wave, but if not, it will very likely occur this week throughout NJ.

Factors leading to this post include increased air temperatures and climbing growing degree-days (WPW adult movement and egg laying is around 7-58 growing degree-days (GDD50)), and most importantly rising soil temperatures as this pest typically begins movement with soils hovering around 50F. All of these factors lead to WPW movement this week and growers may wish to utilize a preventative, long lasting residual spray (pyrethroids) to target adults before they begin egg laying in the upper canopy.

So we have: 

• Within the GDD window for adult movement and egg laying (~58 GDD50)
• Soil temperatures in NJ are at or above 50F.
• Increased air temperatures and insect mobility

Chemical Controls for WPW at this stage of the season:

Chemical insecticides against white pine weevils during the spring period are only effective when adults are feeding & before females lay eggs. Arial sprays only need to be applied to cover the terminal leaders at the tops of trees. Pyrethroids sprayed on the bark can have an effective residual of up to 3-weeks. Included within this group of insecticides include bifenthrin (e.g., Onyx), permethrin (e.g., Astro) & cyfluthrin (e.g., Tempo). Since an extended egg-laying duration occurs with this pest, a second application may be recommended.

White Pine Weevil: Overwintering Adults Become Active in March & April

Clearwing borers: Be prepared to manage these pests in the coming weeks.

If you are a commercial grower signed up for the 2026 Rutgers Ornamental IPM program (click here to register), please contact twaller@njaes.rutgers.edu for clearwing pheromone trap kits.

• CLICK HERE – Please visit the Rutgers Ornamental IPM program website for more information on this group of pests

Identifying Clearwing Moth Borers in Pheromone Traps

Early season management of Phytophthora, Pythium, Phytopythium should be initiated throughout NJ in sensitive plant species, areas with known histories of disease, and in Christmas tree plantations.  

PESTICIDE USE DISCLAIMER. THE LABEL IS THE LAW . The Rutgers Plant and Pest Advisory is not intended for homeowners. Recommendations and considerations given herein are designed to be specific to the state of New Jersey, even though it may be broadly applicable across multiple geographic areas. A pesticide applicator is legally bound by the labeling found on and with the pesticide container in their possession. Before using a pesticide, check and always follow the labeling distributed with the product at the point of sale for legally enforceable rates and restrictions. New Jersey notes. 1. Private and commercial applicators must be certified AND possess a valid applicator license to make applications or supervise the use of ANY* EPA-registered pesticide (*as required NJAC 7:30; limited exemptions exist). 2. Only certified applicators possessing a valid New Jersey applicator license may purchase restricted use pesticides (RUPs). 3. Pursuant to NJ S1016, neonicotinoids can only be applied in agricultural settings. Commercial applications in outdoor, non-agricultural settings (i.e. landscapes) is prohibited, with no pest-specific exceptions, as of the printing of this document. In addition to the pesticide chemistries and Mode of Action (MoA) listed in this document, others may be commercially available. It is understood that no discrimination is intended and no endorsement by Rutgers Cooperative Extension is implied. THE LABEL IS THE LAW. Cooperating Agencies: Rutgers, The State University of New Jersey, U.S. Department of Agriculture, and Boards of County Commissioners, Rutgers Cooperative Extension, a unit of the Rutgers New Jersey Agricultural Experiment Station, is an equal opportunity program provider and employer.