Nursery Pest and Disease Update 6/15/2023

In this edition:

  • Insects:
    • MORE Scale crawlers emerging
    • Borers
    • Beetles
  • Diseases:
    • Oomycete root diseases (Phytophthora, Pythium, Phytopythium)
    • Leaf spots / foliage diseases
    • Boxwood Blight – reminder
    • Virus observations
  • Nutrient Management 
    • Managing Soluble Salts by monitoring EC
    • Plant Tissue analysis
  • Plant Spotlight:
    • American Holly (Ilex opaca)
  • Cumberland Nursery / NJNLA – Twilight: tonight (6/15) for NURSERYMEN ONLY (contact twaller@njaes.rutgers.edu or 856-451-2800 Ext. 1. for details)

Please click “read more” below to get updates on pests, diseases, and other important resources for the week of 6/15/2023.

Insect Pests

Projected GDD50 accumulation as of 6/15/2023
Region Location 16-June 23-June 30-June 7-July 14-Jul
Southern Upper Deerfield (NJ50) 860 1012 1190 1376 1568
Central Howell / Freehold (NJ10) 633 775 939 1112 1290
Northern High Point (NJ59) 585 695 825 964 1107
Forecast: 7-month NMME based seasonal climate forecast  (USPEST.ORG)

Please download and print the Rutgers Nursery and Landscape Pest Scouting Guide  or  Conifer and Christmas Tree Pest Scouting Guide and refer to this post “Obtaining your local growing degree-days (GDD)” for additional information.  (See pest scouting guides for complete list of references – cited within lists below) 

Please SHARE what you SEE!! If you see a pest, disease, otherwise interesting or troublesome issue please report it to the Working Group by following the QR Code on the front of the Pest Scouting Guides or by filling out this reporting form.

PESTS ON THE RADAR

Scale insects – Crawler EMERGENCE:           MORE SCALE CRAWLERS COMING!

  • About: If you have areas with known scale insect problems, please keep a very keen eye on them. Typically, scale crawlers (mobile juvenile phase) have a cream to red to orange appearance and are by far the easiest stage to target for successful management of scale insects. Once the crawlers settle, treatment becomes exponentially more difficult. Crawlers can be observed with double sided tape, hand lens / loupes, and microscopes. If scale population is extreme, one may be able to see the coloration with the naked eye.
Group Common Name Scientific Name GDD Min (50F) GDD Max (95F) Ref.  Developmental / Target Stage / Notes Favored Host Plants
Scale Sprucebud scale Physokermes hemicryphus 700 1150 4 Crawlers (1st generation) Conifer
Scale White prunicola scale Psedaulacaspis prunicola 707 1151 1 Crawlers (1st generation) Many
Scale Juniper scale Carulaspis juniperi 707 1260 1 Crawlers (1st generation) Conifer
Scale Calico scale Eulecanium cerasorum 714 6 Crawlers (1st generation) Many
Scale Striped pine scale Toumeyella pini 750 800 4 Egg hatch Conifer
Scale Oak leacanium scale Parthenolecanium quercifex 789 6 Crawlers (1st generation) Oak, hickory, birch, many
Scale Cottony maple leaf scale Pulvinaria acericola 802 1265 5 Crawlers (1st generation) Acer
Scale Cottony maple scale Pulvinaria innumerabilis 802 1265 1 Crawlers (1st generation) – control target Many, shade trees
Scale Golden oak scale Asterolecanium variolosum 802 1266 5 Egg hatch Oaks
Scale Japanese maple scale Lopholeucaspis japonica 829 6 Crawlers (1st generation) Maples
Scale European elm scale Gossyparia spuria 831 1388 6,2 Crawlers (1st generation) Elm
Scale European fruit lecanium scale Parthenolecanium corni 932 1645 6,1 Crawlers  – control target Shade trees
Scale Pine tortoise scale Toumeyella parvicornis 1000 1200 4 Egg hatch ends, last of crawlers Conifer
Scale Fletcher Scale (Yew) Parthenolecanium fletcheri 1029 1388 1 Crawlers (1st generation) – control target Yew, many conifers
Scale Indian wax scale Ceroplastes ceriferus 1145 6 Crawlers (1st generation) Many
Scale Euonymus Scale Unaspis euonymil 1150 1388 5 2nd generation targeted treatments Euonymus
  • Cultural management: Remove scale infested trees and shrubs prior to crawler emergence if at all possible. In many cases scale crawlers (once hatched) can be dislodged when moving and destroying infested trees. Application of treatments prior to moving these infested materials, may prove beneficial in high valued and trafficked areas. Additionally, monitoring for crawler activity or lack thereof may help reduce unneeded pesticide use. Also note, many scale insects can be killed, yet carcasses remain affixed to the bark layer, and may require physical removal.
  • Material considerations for crawlers: “Distance (pyriproxyfen) & Talus (buprofezin) are both insect growth regulators. Distance is a juvenile hormone mimic & Talus is a chitin synthesis inhibitor. Both materials will give best efficacy against crawler emergence stages” – quoted from this post by Steven Rettke (RU IPM) outlining additional materials and considerations for armored scales in the nursery and landscape. Also see – this post referencing soft scales.

Borers: Borers attack stressed plantsIf you recently dug then heeled-in trees, transplanted seedlings, or otherwise seriously stressed a tree, please consider taking immediate action to protect them from both adult flights (contact trunk sprays) and future infestations (systemics).

Group Common Name Scientific Name GDD Min (50F) GDD Max (95F) Ref.  Developmental / Target Stage / Notes Favored Host Plants
Borer – Clearwing moth Dogwood borer Synanthedon scitula 350 850 4 adults, eggs, caterpillars Dogwood, apple, pecan, elm, hickory, willow
Borer – Flathead / Metalic beetle Bronze Birch Borer Agrilus anxius 440 880 1 Adults (egg laying) Birch
Borer – Clearwing moth Rhododendron borer Synanthedon rhododendri 509 696 1 Adults emerge Rhododendron
Borer – Clearwing moth Greater peach tree borer Synanthedon exitiosa 575 710 4 Adult emergence Malus, Prunus, many

If borer insects are a common problem for your operation there are specific degree-day models made for Bronze birch borer and Emerald ash borer. You can set up these emailed alerts through the USPEST – PUSH Alerts for a multitude of pests and diseases. Contact twaller@njaes.rutgers.edu for assistance.

Based on these specific USPEST.org models:

Beetles: Beetles that mature underground or within growing substrate are more difficult to predict with GDD models, however they should be on your radar.

Group Common Name Scientific Name GDD Min (50F) GDD Max (95F) Ref.  Developmental / Target Stage / Notes
Beetle N. masked chafer beetle Cyclocephala borealis 898 905 1 1st adults
Beetle Japanese beetle Popillia japonica 950 2150 5 Adults emerge and feed
Beetle Redheaded flea beetle Systena frontalis 1028 1570 8 2nd generation of un-hatched eggs
Beetle Oriental Beetle Anomala orientalis 1147 6 Adult emergence

NOTES:

DISEASES ON THE RADAR

Phytophthora, Pythium, Phytopythium root diseases 

  • Compounds used to control Oomycetes (Phytophthora, Pythium, Phytopythium) are called Oomycides and are fundamentally different than those used for fungal and bacterial diseases. Therefor, proper identification is required, as a plant with a fungal root rot (black root rot or rhizoctonia) would require completely different materials. Contact the Rutgers Plant Diagnostic Lab for diagnostic services.  Within available materials there are three main groups, which describe where they will work on the plant given the application technique. Cultural practices are always more important than materials, especially in this case. 
  • Management focuses around treating the roots, or providing materials that reach the roots.
    • Protectants – are non-mobile, meaning they stay exactly where applied, must be root / drench / watered-in, applied.
    • Xylem mobile systemics – move upwards, and the roots must be treated.
    • Translaminar systemics – move very short distances into tissues, again meaning the roots must be targeted.
    • Amphimobile/Fully systemics (P07 / phosphonate group)– can move upwards to needles (xylem) and down to the roots (phloem) meaning foliage or roots can be targeted.

Refer to each label for treatment intervals as they vary greatly, however it is valuable to get ahead of this pathogen as very few materials can “cure” plants. Additionally, more than one material should be in your tool kit as Mefenoxam-resistance has been identified in the Mid-Atlantic region.

Do not apply group P07 and copper-based fungicides within 14d of one another, as phytotoxicity is likely to occur!

**Fenstop (Group 11) – NOW APPROVED  FOR OUTDOOR NURSERIES! – ( click here for updated specimen label)

Leaf spot / foliage disease management – ( CLICK FOR NEW POST FROM DIAGNOSTIC LAB – “Got Leaves?”)

  • About: Most leaf spots are caused by several different genera of fungi, including but not limited to Alternaria, Colletotrichum, Cercospora, Diplocarpon, Phoma, Phyllosticta, and Septoria. There are also bacteria that can cause leaf spot (Psuedomonas and Xanthamonas) and even foliar nematodes (Aphelenchoides). Some common ornamental species that are regularly affected by leaf spot / foliage pathogens include maple, hydrangea, cherry, crape myrtle, redbud, viburnum, oak, Virginia sweetspire, and rose, though there are many other plants that can also be infected.
  • Cultural management: While the symptoms may not appear until later in the season, the infection period starts in the spring. Reducing the leaf wetness period by limiting overhead irrigation and increasing airflow can help to prevent these diseases, as well as proper sanitation by removing any diseased leaves from the area.
  • Material considerations: Protective fungicides and/or bactericides can also be effective if applied early in the season before the symptoms develop. Materials include copper hydroxide, mancozeb, propiconazole, chlorothalonil, myclobutanil, azoxystrobin, or thiophanate-methyl.

Boxwood Blight (BWB)

Recent VIRUS observations: 

  • Lilac Ring Mottle Virus – *tentatively* identified in multiple varieties of Syringa vulgaris in southern NJ. This would be a first-report in our state. Please closely inspect your Syringa for any viral symptoms. This virus is reported to spread mechanically (pruning, propagating, equipment). Please see this informative webpage about Lilac Ring Mottle Virus (PNW Pest Management Handbook)
    • If you suspect this virus in your Syringa PLEASE CONTACT – twaller@njaes.rutgers.edu– we would like to compile data to help reporting this in NJ – which will help our growers manage this virus.
  • Tobacco Rattle Virus – is suspected to be present in multiple hosts, especially Peony. Please be aware this virus has a huge list of host plants and is highly transmissible by plant sap (through pruning, damage, handling, root feeding (nematodes), etc.). Please see this informative webpage about Tobacco Rattle Virus (TRV) (Iowa State)
Tobacco Rattle Virus

Tobacco Rattle Virus (*tentative ID) – Tim Waller – Cumberland RCE

Lilac Ring Mottle

Lilac Ring Mottle Virus (*tentative ID) –  Tim Waller – Cumberland RCE

 

NUTRIENT MANAGEMENT 

Managing Soluble Salts by Monitoring EC

  • It is important to monitor fertilizer and salt concentrations in ornamental plants to ensure that the plants are receiving adequate nutrients, while not allowing salts to build up and cause damage. There are various methods to monitor salt concentrations by measuring electroconductivity (EC) and seeing if that reading is within the optimum range for a particular plant species. Two common procedures for measuring EC include the saturated media or paste extract (SME) and the pour through (PT) method. Many university and commercial labs will use the SME method, as it has shown to be reliable and there have been numerous research studies and fertility trials used to develop general interpretation guidelines based on this procedure. However, the process can be somewhat challenging to accurately execute outside of a laboratory setting. The PT method was developed as simplified and practical way to reliably measure EC for container grown crops. Each method has its advantages in helping to maintain acceptable levels of soluble salts. Strategies to keep salt levels low include: (a) keep adequate moisture in the growing medium, (b) avoid applications of dry fertilizer or highly concentrated nutrient solutions to a dry growing medium, (c) avoid fertilizers that give a high salt stress for a given amount of nutrient (high salt index), and (d) be alert to changes in environmental conditions (like temperature and humidity) that affect plant transpiration, soil water evaporation, and nutrient release from slow or controlled-release fertilizers. For more information, see the fact sheet: Monitoring and Managing Soluble Salts in Ornamental Plant Production by Johnson and Cabrera
  • Rutgers Soil Testing Laboratory – click here

Plant Tissue Analysis

  • Plant tissue analysis can provide you with valuable information about the current nutrient levels of your plants. It will let you know if your fertilizer applications are optimized, and it can help to identify any nutrient deficiencies or toxicities that may be present. A plant tissue analysis is a good way to check in on the fertility levels of your plants mid-season, especially if something just doesn’t seem right and you want to accurately diagnose the problem. When collecting your sample, it is important to collect leaves from multiple representative plants of the same species. This will help to improve the accuracy of the analysis. You will need approximately one pint of leaf material to send to the lab. The Agricultural Analytical Services Lab at Penn State University offers plant tissue analysis services that include 10 elements: nitrogen, phosphorus, potassium, calcium, magnesium, manganese, iron, copper, boron, and zinc. They also provide a report with fertility recommendations for the specific crop that was tested. The cost is approximately $24 per sample (plus shipping) depending on which type of tissue analysis you are looking for. Click here for more information on the Ag. Analytical Services Lab at Penn State University

NATIVE PLANT SPOTLIGHT

Homer Edward Price – Creative Commons

American Holly (Ilex opaca) is a native tree species that is important in our coastal maritime forests. In the landscape, it can be used to create evergreen hedges with high deer resistance. It is moderately salt and drought tolerant, with blooms from May through June that attract bees and butterflies. American holly’s red berries persist through the winter months to feed birds and other wildlife. American holly branches can also be cut and harvested for holiday wreaths and other decorations.

 

 

 

Please SHARE what you SEE!! If you see a pest, disease, otherwise interesting or troublesome issue please report it to the Working Group by following the QR Code on the front of the Pest Scouting Guides or by filling out this reporting form.

Please note: The Rutgers Nursery and Green Industry Working Group is working to deliver regular pest and disease updates throughout the season. These will be in addition to important alerts, critical topics, and pesticide credit opportunities. This tool is made for you, the commercial agriculture business, so please let us know if there are particular topics you would like to see included in the regular update. Email:  twaller@njaes.rutgers.edu Phone: 856-451-2800 Ext. 1.

DISCLAIMER: The label is the law, always refer to it for allowable host crops, use-restrictions, application rates, reapplication intervals, re-entry intervals (REI), application timing, and mix compatibility information. Production and pesticide information on this site are for private/commercial pesticide applicators and landscape professionals only, and are NOT for home gardener use. Provided materials represent examples and do not cover all possible control scenarios. Trade-names listed do not imply endorsement and are used as examples only. Please contact your local agent or chemical sales representative for more information or to discuss additional pest management options.