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

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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

Boxwood Blight Risk Assessment as of 3/30/2026
Region	Location	CODE	MON	TUE	WED	THU	FRI	SAT
			30-Mar	31-Mar	1-Apr	2-Apr	3-Apr	4-Apr
Southern	Upper Deerfield	NJ50	Very Low	Low	Very Low	Infection Risk	Very Low	Infection Risk
Southern	Vineland	NJ73	Very Low	Low	Very Low	Infection Risk	Low	Infection Risk
Southern	Millville	KMIV	Very Low	Very Low	Low	Infection Risk	Very Low	Infection Risk
Southern	Bridgeton	D4116	Very Low	Low	Very Low	Infection Risk	Very Low	Infection Risk
Southern	Mays Landing	G4661	Very Low	Very Low	Very Low	Low	Very Low	Infection Risk
Central	Howell / Freehold	NJ10	Very Low	Low	Very Low	Low	Very Low	Low
Central	Princeton	F0303	Very Low	Low	Very Low	Low	Very Low	Low
Central	Somerville	F6261	Very Low	Low	Very Low	Low	Very Low	Low
Northern	High Point	NJ59	Very Low	Low	Very Low	Very Low	Very Low	Very Low
Northern	Randolph	AU137	Very Low	Low	Very Low	Very Low	Very Low	Very Low
Northern	Belvidere	E7133	Very Low	Low	Very Low	Low	Very Low	Low
Please check your local boxwood blight risk at (https://uspest.org/risk/boxwood_app)

• 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)

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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.

(generic) Ambrosia Beetle Flight Predictions – as of 3/30/2026
Region	Location	Metric	MON	TUE	WED	THU	FRI	SAT	SUN	MON	TUE	WED
			30-Mar	31-Mar	1-Apr	2-Apr	3-Apr	4-Apr	5-Apr	6-Apr	7-Apr	8-Apr
Southern	Millville	High Temp [ºF]	69	78	82	55	71	77	75	59	59	58
		Low Temp [ºF]	57	62	50	45	58	57	47	40	41	43
		Average [ºF]	63	70	66	50	64.5	67	61	49.5	50	50.5
		High at/above 70ºF	FALSE	TRUE	TRUE	FALSE	TRUE	TRUE	TRUE	FALSE	FALSE	FALSE
		Avg at/above 65ºF	FALSE	TRUE	TRUE	FALSE	FALSE	TRUE	FALSE	FALSE	FALSE	FALSE
		Adult flight risk	Probable flight				Potential flight
Central	Freehold	High Temp [ºF]	71	80	83	48	67	75	75	59	58	58
		Low Temp [ºF]	57	63	45	42	58	52	46	40	41	42
		Average [ºF]	64	71.5	64	45	62.5	63.5	60.5	49.5	49.5	50
		High at/above 70ºF	TRUE	TRUE	TRUE	FALSE	FALSE	TRUE	TRUE	FALSE	FALSE	FALSE
		Avg at/above 65ºF	FALSE	TRUE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE
		Adult flight risk	Probable flight				Potential flight
Northern	Hackettstown	High Temp [ºF]	70	77	75	47	65	75	69	57	58	57
		Low Temp [ºF]	55	60	45	39	54	49	42	36	38	39
		Average [ºF]	62.5	68.5	60	43	59.5	62	55.5	46.5	48	48
		High at/above 70ºF	TRUE	TRUE	TRUE	FALSE	FALSE	TRUE	FALSE	FALSE	FALSE	FALSE
		Avg at/above 65ºF	FALSE	TRUE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE	FALSE
		Adult flight risk	Potential flight				Minor risk
Air temperatures: Weather Underground (https://www.wunderground.com/) and NEWA: (https://newa.cornell.edu/)
Compiled by Waller. T. 3/30/2026 [twaller@njaes.rutgers.edu]

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

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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

White Pine Weevil (Pissodes strobi) – as of 3/30/2026
Region	Location	CODE	METRIC	MON	TUE	WED	THU	FRI	SAT
				30-Mar	31-Mar	1-Apr	2-Apr	3-Apr	4-Apr
Southern	Upper Deerfield	NJ50	GDD50	81	98	117	117	117	118
			High Temp [ºF]  (Average)	69 (63)	78 (70)	82 (66)	55 (50)	71 (64.5)	77 (65)
			24hr Average –       Soil TEMP [ºF]	54	<- (This will change over time / no prediction available)
Central	Freehold / Howell	NJ10	GDD50	68	83	100	100	100	100
			High Temp [ºF]  (Average)	70 (64)	80 (71.5)	83 (64)	48 (45)	67 (62.5)	75 (63.5)
			24hr Average –       Soil TEMP [ºF]	55	<- (This will change over time / no prediction available)
Northern	HACKETTSTOWN	G5633	GDD50	59	72	89	89	89	89
			High Temp [ºF]  (Average)	69 (62)	77 (68.5)	75 (60)	47 (43)	65 (59.5)	75 (62)
			24hr Average –       Soil TEMP [ºF]	54	<- (This will change over time / no prediction available)
USPEST.ORG – Model: simple average/growing degree-day, Min: 50F – Max: 95F, NMME forecast
GDD Forecast:  7-month NMME based seasonal climate forecast (USPEST.ORG) – Subject to change regularly = Check Often
Air temperatures: Weather Underground (https://www.wunderground.com/) and NEWA: (https://newa.cornell.edu/)
Soil temperatures (10cm): https://www.greencastonline.com/tools/soil-temperature
Compiled by Waller. T. 3/30/2026 [twaller@njaes.rutgers.edu]

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

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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.

Clearwing Borer Flight (GDD model) as of 3/30/2026
Events / Pests	Southern NJ		Central NJ		Northern NJ
	UPPER DEERFIELD (NJ50)		HOWELL (NJ10)		RANDOLPH (AU137)
	Date	DDs	Date	DDs	Date	DDs
* START *	1-Jan	0	1-Jan	0	1-Jan	0
* NOW *	29-Mar	76	29-Mar	64	29-Mar	71
Lilac / Ash Borer (Podosesia syringae)	18-Apr	149	30-Apr	151	5-May	153
Dogwood Borer (Synanthedon scitula)	19-Apr	154	1-May	158	6-May	161
Lesser peach tree borer (Synanthedon pictipes)	12-May	362	21-May	352	25-May	352
Rhododendron borer (Synanthedon rhododendri)	23-May	516	1-Jun	515	5-Jun	513
Greater peach tree borer (Synanthedon exitiosa)	27-May	583	5-Jun	584	9-Jun	578
USPEST.ORG – Model: simple average/growing degree-day, Min: 50F – Max: 95F, NMME forecast
Forecast:  7-month NMME based seasonal climate forecast (USPEST.ORG) – Subject to change regularly = Check Often
Compiled by Waller. T. 3/30/2026 [twaller@njaes.rutgers.edu]

• 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

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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.  

Oomycide Considerations in Ornamentals – (Phytophthora, Pythium, Phytopythium)
Prepared by T. Waller – Rutgers Cooperative Extension – 2026 for use in New Jersey
FRAC	Risk of pathogen resistance	Active ingredient	Tradename examples*	(Review each specific label) Notes	Translocation Movement in plant
P07	Low	Phosphonates. Aluminum tris (O-ethyl phosphonate)	Areca, Aliette, generic fosetyl-Al	See label. Foliar and drench/soil reapplication interval is 30d or greater. Do not apply group P07 and copper-based fungicides within 14d of one another	Fully systemic – xylem and phloem mobile (amphimobile)
P07	Low	Phosphonates. Mono-and di- potassium salts of phosphorus acid	Alude, Reliant, Rampart, K-Phite 7LP	See label. Generally, soil drench minimum reapplication interval is 30d and foliar applications, less than. Do not apply group P07 and copper-based fungicides within 14d of one another	Fully systemic – xylem and phloem mobile (amphimobile)
40	Low to Medium	Dimethomorph, Mandipropamid	Stature SC, Micora	See label. Foliar, drench, soil directed, and chemigation applications.	Translaminar systemic – local translocation
40 + 45*	Medium + High*	Dimethomorph + ametoctradin*	Orvego	See label. Foliar, drench, soil directed, and chemigation applications.	Translaminar systemic – local translocation
49	Medium to High	Oxathiapiprolin	Segovis	See label for use restrictions and tank-mix compatibility.	Xylem mobile systemic – translocation upwards (acropetal)
11	High	Fenamidone	Fenstop	See label: Now labeled for outdoor nurseries. Reapplication interval is 28d	Xylem mobile systemic – translocation upwards (acropetal)
43	Medium	Fluopicolide	Adorn	See label. Foliar, drench, and chemigation applications. No more than 2 applications per crop cycle. Minimum reapplication interval – 14d.	Xylem mobile systemic – translocation upwards (acropetal)
4	High	Mefenoxam	Subdue Maxx, Subdue GR, generic Mefenoxam	See label. Typically, spring and fall drench applications with total allowable of 6lb/A/year (Subdue Maxx). Foliar, drench, soil directed, soilless media incorporation, and chemigation applications. See label for minimum reapplication intervals for drench applications (ranging from 3 weeks to 4 months). Mefenoxam resistance has been detected in the USA.	Xylem mobile systemic – translocation upwards (acropetal)
21	Medium to High	Cyazofamid	Segway-O, Celoxid SC	See label. Minimum reapplication interval 14 – 21d. No more than 2 applications per crop cycle. Applied as drench or soil directed.	Protectant – no systemic activity
BM02	Unknown (likely low)	Biologicals	Rhapsody (bacteria), Root Sheild Plus (fungi)	See label. Reapplication interval typically very rapid at 3-10d.	Antagonistic – hinders pathogen colonization of host tissues
–	–	Quaternary ammoniums	KleenGrow, Uptake, Physan 20, Green Shield	See label. Typically used in sanitation efforts, irrigation maintenance (biofilms), and some labels allow for application to plant surfaces. Phytotoxicity concerns are rate and label specific. Generally considered broad spectrum fungi/bacteria/oomycete pesticides.	Direct contact – varying residual activity, no systemic activity
–	–	Hydrogen dioxides	Zerotol, Oxidate

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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.