NYS IPM Weekly Field Crops Pest Report, May 2, 2019

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Volume 17: Number 1

View from the Field

Welcome back to the NYS IPM Weekly Field Crops Pest Report. For the next 20 weeks or so we will be providing you with current and up-to-date pest information on field crops and livestock pests. Extension educators, crop consultants and farmers all provide pest information on a weekly basis throughout the growing season. Again Welcome Back!

Indiana and Pennsylvania are reporting captures of black cutworm and true armyworm moths the last few weeks and are expecting a possible problem with them as spring continues. Black cutworm have been caught in NYS. We now have a small network of extension educators with 27 traps statewide that are monitoring for black cutworm and true armyworm moths migration into NYS this spring. We have caught low numbers of black cutworm moths. For more information see articles below.

Weather Outlook – May 2, 2019

Jessica Spaccio

NOAA Northeast Regional Climate Center, Cornell University

Last week temperatures 2-8 degrees below normal. Precipitation has ranged from ¼” – 2”. Base 50 growing degree-days ranged from were under 20.

An unsettled week ahead with mild temperatures but many days with rain possible. a cold front brings rain and isolated thunderstorms on Friday.

Today temperatures will range widely from upper 40’s to low 70s with scattered showers. Overnight lows will be in the 40’s to mid 50s, rain possible for some areas.

Friday will be in the mid 50s to 60s with, a cold front will bring rain and isolated thunderstorms, heavy rain is possible in some areas. Overnight temperatures will be in the low 40s to low 50s.

Saturday temperatures will be in the 60s to near 70 with rain moving in later in the day. Overnight temperatures will be in the 40s.

Sunday highs will be in the 50s and lower 60s with rain possible in southern areas. Overnight temperatures will be in the 40s.

Monday temperatures will be in the 60s with rain possible as another system moves through. Overnight temperatures will be in the 40s.

Tuesday highs will be in the 60s with rain possible from a cold front. Overnight temperatures will be in the 40s.

Wednesday highs will be in the upper 50s and lower 60s with rain possible. Overnight temperatures will be in the 50s and 50s.

The seven-day precipitation amounts will range from ¾” to 1.50”.

The 8-14 day outlook (May 9-15) favors below-normal temperatures and above-normal precipitation for the state.

Maps of 8-14 day outlooks:

http://www.cpc.ncep.noaa.gov/products/predictions/814day/index.php

National Weather Service watch/warnings map:

http://www.weather.gov/erh/

US Drought Monitor

http://droughtmonitor.unl.edu/Home.aspx

Drought Impact Reporter:

droughtreporter.unl.edu/map 

CLIMOD2 (NRCC data interface):

http://climodtest.nrcc.cornell.edu

Be on the Lookout for Early Season Diseases of Small Grains

SG1

By Jaime Cummings and Ken Wise, NYS IPM

Winter wheat forming tillers on April 25th in Aurora, NY (photo by Jaime Cummings, NYS IPM)

With spring underway, our fall planted wheat, barley, rye and triticale crops have woken up and are in early developmental stages, and some spring planted barley, oats and rye are emerging.  By now, you’ve already assessed plant stands for winterkill or other weather-related damage and weed pressure.  But did you look for signs of diseases?

Fungicidal seed treatments protect our small grains crops from soilborne pathogens that cause damping-off, and foliar fungicides may be warranted for many of our common early-season foliar diseases.  Early epidemics from these pathogens may spread throughout the canopy as the season progresses, given favorable weather conditions, resulting in potential yield reductions.  An integrated approach for managing these diseases involves crop rotation, residue management, planting pathogen-free seed of resistant varieties, proper fertility and canopy management, and foliar fungicide applications where necessary.  Susceptible cultivars benefit most from fungicide applications for reduction of diseases.  While scouting, keep an eye out for some of our most common early season diseases:

Powdery Mildew can be commonly found lower in the canopy of all small grain crops, and is easily identifiable by its white, fuzzy fungal growth on both the upper and lower leaf surfaces (Fig. 1).  This pathogen overwinters on straw residues which provide inoculum in the spring to blow into growing wheat stands.  Cultivars vary in their levels of resistance to powdery mildew, and resistance is the most cost-effective method of defense.  Should you find high levels of powdery mildew in your field, you may consider a triazole foliar fungicide application at flag leaf emergence.

Powdery Mildew triticale

Figure 1.  Powdery mildew of wheat (photo by Ken Wise, NYS IPM).

Septoria and Stagonospora Leaf Blotches are two other very common foliar diseases you may encounter in NY wheat fields.  Though caused by two different pathogens, the leaf spot symptoms can be somewhat similar and difficult to differentiate for scouts (Fig. 2).  Both fungal pathogens overwinter on crop residues, and initial infection often occurs on seedlings emerging in the fall, but may also occur in the spring.  Many commercially available cultivars are available with varying levels of resistance to these pathogens.  But if you notice high levels of leaf blotches in your field, you may consider a foliar application of a strobilurin or triazole fungicide at flag leaf emergence to protect yield.

Stagonospora leaf blotch of wheat

Figure 2.  Stagonospora leaf blotch of wheat (photo by Ken Wise, NYS IPM).

Leaf Rust, or brown rust, can occasionally be found early in the season, though it often appears later as the spores migrate on winds from the south.  Leaf rust is easily identified as bright orange pustules on the upper leaf surfaces throughout the canopy of all small grain crops (Fig. 3).  Rust fungi are obligate pathogens, which require a living host, and therefore must either over-winter on alternate hosts, or arrive on wind currents from the south.  Planting resistant cultivars is the most cost-effective management tool, and a flag leaf application of a strobilurin or triazole fungicide also offers effective control of leaf rust on susceptible cultivars.

Rust on wheat

Figure 3.  Wheat leaf rust (photo by Ken Wise, NYS IPM).

Scald is another fungal leaf spot that easily identified on winter malting barley by its distinctive lesions that can be found on any above-ground plant tissue (Fig. 4).  The fungal pathogen can over-winter on residues or can be seed-transmitted.  On susceptible cultivars and under favorable environmental conditions, scald can spread quickly throughout the canopy and field, resulting in significant yield loss.  Pay attention to scald resistance ratings when selecting malting barley cultivars to plant, as they vary drastically in susceptibility.  Susceptible cultivars will benefit from a triazole fungicide application at flag leaf, or even earlier to protect yields.

Scald on malting barley

Scald on malting barley

Figure 4.  Scald on malting barley (photo by Jenn Thomas-Murphy, Cornell University).

When deciding whether or not to spray a fungicide, there are many points to consider.  Not least of all, cost.  Use the following information as a guide from the Cornell Integrated Guide for Field Crop Management for making fungicide decisions in small grains:

Activity Worksheet: Economical Analysis of Thresholds in Wheat:

Does the crop have a reasonable yield potential?

Assess the crop in early May (stem elongation stages) for adequate stand (density of approximately 30 strong stems per foot of row for 7-inch rows on good soils) and plant vigor. If the stand is sparse or plants are not vigorous or show widespread virus symptoms, fungicide application should not be considered further.  ____ Yes    ___ No

Have foliar diseases been observed before flag (last) leaf emergence?

Assess upper three leaves for symptoms and signs of powdery mildew, leaf spots, or leaf rust in early to mid-May, before flag leaf emergence. If disease (any amount) is observed on approximately 50 percent of main tillers, averaged across the field, a spray should be considered now. This threshold is exceeded in less than 50 percent of location/year situations in New York, so there is a significant risk of making an unnecessary fungicide application.   ____ Yes   ___ No

Have foliar diseases been observed during head emergence?

Assess upper two leaves for foliar diseases in late May to early June; if disease (any amount) is observed on approximately 50 percent of main tillers, a spray should be considered now. Fungicide applications made after early June may control some diseases but are unlikely to produce significant yield benefits.  ___ Yes  ___ No

Are climatic predictions conducive for further disease development?

Powdery mildew development is reduced dramatically once the average daily temperature rises above 70˚F; this disease often disappears by June. Severe leaf spot development is favored by extended periods of wet weather; it may be insignificant if dry weather persists in May and June. Listen for regional advisories on the threat from leaf rust; rust inoculum often builds up in areas to the south and west of New York and is deposited here by thunderstorms in June or July. In addition to disease observations, use long-range local weather forecasts in making your spray decision.  What is your short to medium term weather conditions?

Have I selected fungicides appropriate for the disease spectrum and have I read the label carefully?

Be sure that the materials you spray will be effective against the range of diseases found in your field; e.g., some products effective against powdery mildew are ineffective against leaf spots or vice versa. Check in the Cornell University Guide for Integrated Crop Management.

Is the spray decision consistent with my perception of risk?

A simple formula for evaluating the relative economics of a fungicide spray is: Relative Profit = (Grain Yield Increase x Grain Price) – (Cost of Fungicide + Application Costs). If ground spray rigs are used, the yield lost to wheel traffic should also be factored in. Each of these variables influences the relative economics of fungicide application. At a grain price of $4, producers will need to see approximately a 5 bu/A yield increase to break even on the added costs of fungicide application. Because disease occurrence is erratic over years and locations, fungicide application cannot be expected to result in a 5-bushel or greater yield increase every year. Spray decisions should be tied closely to disease scouting information. When considering your economic risk, also be aware that foliar fungicides will not protect potential yield components that may be diminished by scab disease (fungus that infects heads at or following flowering), viral diseases (wheat spindle streak mosaic and yellow dwarf), soilborne diseases, or several other environmental factors.

 

Relative Profit = (Grain Yield Increase x Grain Price) – (Cost of Fungicide + Application Costs)

Spring malting barley planted on April 4th in Aurora, NY – photo taken on April 25th (photo by Jaime Cummings, NYS IPM)

Black Cutworm in Field Corn

Ken Wise-NYS IPM

 Black Cutworm is an early season pest of corn. Adult Black Cutworm moths migrate on storms from southern regions to the northeast each year in mid-May and June. As these moths migrate in the spring on weather fronts they are looking for attractive locations to lay their eggs. Black cutworm is a generalist feeder and has a large list of host plants including small grains, corn and some vegetables as well as weeds such as bluegrass, curled dock, chickweed, lambsquarters, yellow rocket, and redroot pigweed. Corn fields with grassy weeds and other weeds problems are prime locations for the moths to lay eggs. No-till fields are at particular risk to black cutworm if grassy weeds are not controlled early enough.

What happens is after the eggs hatch the larvae start to feed on the grassy weeds. Once the weeds are sprayed and eliminated, their food source vanishes. What is left in the field to eat? “CORN!” If you happen to know when moths arrive with you can predict what stage of local black cutworm larval development by using growing degree day calculations and a base temperature of 500F degrees. Many states have trapping networks that you can get the date for your area. The way it is calculated is from the first catch date take the high and low temperatures and add them. Then divide that by 2 and subtract 50 degrees. This will give you the growing degree days. You can do this for each day after that catch date. Many states give weekly reports on the development of this pest in your area. NEWA Degree Day Calculator

Black Cutworm Degree Days

Degree Days                     Stage                           Feeding Activity

0                Moth Capture              Egg Laying

90              Eggs Hatch

91-311       1st to 3rd Instar           Leaf Feeding

312-364     4th Instar                     Cutting Begins

365-430     5th Instar                     Cutting Begins

431-640     6th Instar                     Cutting Slows

641-989     Pupa                            No feeding

Source: University of Minnesota Black Cutworm Trapping Network

Black Cutworm larvae are grey to black. They have a brown to black head. Larvae have a greasy appearance with coarse granules present over their body.  The larvae range from ½ inch to 2 inches depending on the instar. The chart present here can help you determine what developmental instar. This is a nocturnal pest and feeds mostly at night. During the day larvae burrow into the soil next to the corn plant. These larvae curl into a C shape when disturbed.

Black Cutworm Larvae

Symptoms of damage are leaf feeding, irregular holes in the stem, notched and cut plants which could be wilting, and/or death of plants. The classic symptom are plant cut at the base near the soil surface. One way to better manage this pest is to control grassy weeds early to reduce the attractiveness of the fields to adult egg laying moths.  Once the corn plant reaches the V-6 stage of growth it becomes resistant to feeding.

Scout fields to find black cutworm larvae when they are less than 1/2 inch long. If there are sufficient numbers and damage present, an insecticide could be justified. Treat only the affected area and a 20 to 40-foot border around the infestation. Rarely does a whole field need to be treated for cutworm. Larger cutworm larvae are somewhat more difficult to control. These large larvae are also more tolerant of insecticides, reducing the effectiveness and economic viability of this option.

The use of insecticide seed treatments is one management tool for BCW. Much of the corn seed comes pretreated with a neonicotinoid insecticide. There are several transgenic corn hybrids with certain Bt. genes that have resistance for black cutworm. You can check to see which hybrids have this resistance by checking out the Handy BT trait publication online.

http://msuent.com/assets/pdf/28BtTraitTable2016.pdf

Reference

https://extension.entm.purdue.edu/fieldcropsipm/insects/black-cutworms.php

Black Cutworm Moth Captures

      The week of  
County Town May 1 May 12 May 19
         
Dutchess Amenia 0  
Oneida Kirkland 4  
Washington Easton 1  
Seneca Waterloo 12  
Wayne Ontario 1  
Tompkins Ulysses 4  
TOTAL 22  

 

 Alfalfa Weevil and Growing Degree Days

Ken Wise-NYS IPM

Alfalfa weevils overwinter as an adult. When the weather gets warmer in the spring they start to move back into the alfalfa fields. If you do not know what they look like they are light brown weevils that are 3/16” long. They have a band of darker brown down the center of their back with a long snout as seen in the photo below:

Alfalfa Weevil Adult

The adults will feed on alfalfa leaflets and lay eggs into new stem tissue in the plant. The eggs are hard to find. Look for tiny pinholes in the stem. These are where the female weevil has chewed a small hole and lay her eggs in the hollow stem cavity. These eggs are bright yellow but very small. As the eggs mature they start to darken. Each female can lay up to 25 eggs/stem and as many as 500 to 2000 eggs per season.  Depending on the temperature the eggs generally hatch in one to two weeks.

Calculating alfalfa weevil activity. By calculating the number of alfalfa weevil heat units you can predict the different life stages of the weevil.

Things you will have to know are the maximum and minimum temperature data from March 1 through the current day. Take the high and low temperature of each day and divide it by 2 and subtract 48 degrees F. This will give you the number of heat units for an individual day. If it is a negative number then there were no heat units that day for alfalfa weevil to develop.

(High Temperature + Low Temperature / 2) – 48 F = AW heat units.

Keep a running tally of the accumulated heat units from day to day. Compare the total GDD’s and compare this number against the expected alfalfa weevil growth stage from the following table.

Growing degree Days for peak (50%) Occurrence of Alfalfa Weevil growth stage:

 

Stage

Degree Days

(Base 48)

Egg 280
Instar 1 351
Instar 2 395
Instar3 470
Instar 4 550
Cocooning 600
Pupa 725
Adult Emergence 815

 (Note: for alfalfa weevil predictions use Base Temp of 48F)

Source: NYS IPM Growing Alfalfa the IPM Way

Instead of doing all those long drawn out calculations let NEWA do it for you! NEWA is short for Network for Environment and Weather Applications. This website has a function that will calculate the alfalfa weevil heat units for your region or area of the state. This is at http://newa.cornell.edu/index.php?page=alfalfa

 

2019 Degree Day Models for Field Crops Pests across New York (May 1, 2019)

 

Station Location

Alfalfa Weevil

(Base 48)

March 1

GDDs (Base 50 F)

March 1

Black Cutworm (Base 50)

May 1

Ceres 108 74 7
Chazy 41 28 0
Geneva 91 58 2
Highland 168 126 0
Ithaca 123 83 3
Massena 45 26 0
Northport (Richters) 188 130 6
Valatie 141 100 0
Versailles 124 83 14
Watertown 43 25 0

NEWA Growing Degree Days

Clipboard Checklist

General

*Walk fields to check tile flow, check and clear drainage outlets. Look for line breaks
*Note and record location of wet areas on field maps or aerial photo for future tiling considerations and crop decisions, check for areas of soil erosion
*Pre-plant weed evaluation, timing cultivation and/or pre-plant weed management
*Watch for early season weeds: winter annuals, chickweed, henbit, field penny cress, shepherd’s purse, giant and common ragweed, purple deadnettle, lambsquarters, redroot pigweed, velvet leaf, Pennsylvania smartweed, common sunflower, quackgrass, foxtail

Alfalfa:
*Evaluate established legume stands for winter damage (thinning stand, frost heave, brown root rot), determine average alfalfa stand count adjust crop plans if necessary
*Monitor for alfalfa weevil
*Monitor new seedings for Pythium blight and Phytopthora Root Rot.
*Monitor for Alfalfa Snout Beetle (In Oswego, Jefferson, Cayuga, Wayne, Lewis, St. Lawrence, Clinton, Essex, and Franklin counties)

Small Grains:
*Monitor winter grain fields for over wintering survival (snow mold and other cold injury issues), weed issues (such as winter annuals, corn chamomile and chickweed), growth stage, number of tillers
*Check stands for soilborne virus diseases, Wheat spindle streak mosaic and Soilborne wheat mosaic, check for signs of powdery mildew or other maladies, cereal leaf beetle, weed escapes, goose damage

Corn:
*Prepare land and plant corn as conditions allow
*Pre-plant weed evaluation, timing cultivation and/or pre-plant weed management

Soybeans:
*Prepare land and plant soybeans as conditions allow
*Pre-plant weed evaluation, timing cultivation and/or pre-plant weed management

Pastures:
*
Check and mend fences as needed.
*Check crop growth
*Monitor fields for invasive species, plants harmful to livestock
*Review/Plan rotation system

Equipment:
*Remove / clean soil and crop debris from equipment
*
Arrange for custom weed control or check your own application or cultivator equipment for repairs.
*Carry appropriate / necessary NYS DEC and EPA required documents: (pesticide applicators license, pesticide labels, MSDS sheets, etc.) with application equipment
*Calibrate:

-planting equipment – maintain records on planting rate per field

-manure spreaders – maintain records on amount spread per field

-pesticide application equipment – Check nozzles, pumps, etc., recalibrate pesticide application equipment before use.

Storage:
* Check stored grain bins for temperature, moisture and signs of mold and insects. Aerate, core, transfer grain or treat as necessary
*
Check forage allocation and anticipate feed program adjustments as forages from previous year are used up
*Plan where forages should be stored for optimum allocation next feeding season

Dairy Cattle:

*Clean around feeding rings, feed bunks and water sources removing spilled feed and undisturbed organic matter that is favorable fly breeding habitat.