Volume 16 Number 15
View from the Field
Western Bean Cutworm
This week we caught over 10,288 Western Bean Cutworm (Striacosta albicosta) moths in 44 traps reporting. This is the most moths we have ever caught in a week. There are reports by Mike Hunter (CCE Northern NY) that several fields have reached threshold for eggs masses and small larvae. These fields are going to be sprayed with an insecticide. See more on the Western Bean Cutworm Report below.
Common Rust on Corn
There have been a lot of reports of common rust (Puccinia sorghi) on corn across New York. This fungus is brought on storms from the southern US. The spores become airborne and are blown here on fronts that move north. Since we have had several storm fronts this year we have received the inoculum. The disease proliferates at 60 – 70◦ F and wet weather. The best way to combat this disease is to select resistant hybrids.
The symptoms are small, round to elongate brown pustules form on both leaf surfaces and other above ground parts of the plant. As the pustules mature they become brown to black. If disease is severe, the leaves may yellow and die early. Common rust generally does not require a fungicide application and is not economical in field corn.
Soybean aphids (Glycine max) are starting to rise in populations. There have been some reports of them over the 250 aphids/plant economic threshold between the R1 and R5 stage of soybean growth. See article below on how to scout for soybean aphid.
Downy Mildew on Soybeans
Dr. Gary Bergstrom (Cornell Extension Field Crops Plant Pathologist) indicates that many soybean fields in New York are showing signs of downy mildew. Downy mildew is a common disease of soybeans and only occasionally can cause yield losses. This disease proliferates under high humidity and cool temperatures. The fungus can overwinter on last season crop residue and can the transmitted by seed. Fungal spores are transmitted to the plant by wind and rain. When conditions are right the disease can spread quickly through a field. If the seed was infected with downy mildew the seeding will also be infected. Downy mildew is a biotrophic organism. This means that the disease can only grow and reproduce in associated with soybeans. The disease can have rapid genetic changes in response to the genetic changes to the soybean plant because of this close relationship. There are many different races of this disease and it is monitored closely when new cultivars are being breed. The first sign of the disease are pale green or light yellow spots on the upper leaves. As the disease progresses the spots will enlarge into varying shapes and sizes. Next, lesions show on lower leaf surfaces, particularly in moist weather. The leaves will yellow and become dusted with gray or purplish mildew. Severely infected leaves may curl turn brown, and drop off prematurely. The pods can be infected without obvious external symptoms. Infected seed appear dull white and partly or completely covered with a pale coating of fungal spores.
- Use certified disease-free seed. If you use seed that is not certified are saved seed from your previous harvests many contain the pathogens we discussed earlier.
- Use resistant cultivars; ask your dealer how cultivars compare for disease susceptibility or resistance and productivity. Make sure the cultivar is suitable for your specific region of the state.
- Use a fungicide seed treatment at planting. This will kill pathogens that might infect the seed at planting. If you are organic make sure the soil temperature is over 500F. This will allow the soybean to grow quickly and avoid pathogens in the soil.
- Plow infected residue under the soil surface. This will help reduce the amount of disease laying on the surface that can infect the next crop.
- Foliar fungicides are seldom warranted in New York, but sometimes despite our best efforts a fungicide is needed. If you need to select a fungicide please consult the Cornell Guide for Integrated Field Crop Management
Weather Outlook – August 10, 2017
NOAA Northeast Regional Climate Center, Cornell University
Last week temperatures ranged within 2 degrees of normal. Precipitation ranged from less than a quarter inch to over 4 inches in isolated ares. Base 50 growing degree-days ranged from 70 to 150.
A weak cold front will bring scattered showers and thunderstorm Thursday evening through Saturday. Sunday through Wednesday carry a chance for isolated showers but will be mostly dry.
Friday temperatures will be in the mid 70’s to low 80’s, with scattered showers and thunderstorms possible. Overnight temperatures will be in the 60’s.
Saturday’s highs will be in the mid to upper 70’s with showers and thunderstorms possible and increasingly humid. Overnight temperatures will be in the low to mid 60’s.
Sunday highs will be in the mid 70’s to low 80’s with isolated scattered showers. Overnight temperatures will be in the mid 50’s to low 60’s.
Monday’s highs will be in the 70’s to low 80’s with isolated scattered showers. Lows will be in the mid 50’s to low 60’s.
Tuesday will have temperatures in the mid 70’s to low 80’s with isolated scattered showers. Lows will be in the mid 50’s to low 60’s.
Wednesday, temperatures will be in the mid 70’s to low 80’s with isolated scattered showers. Lows will be in the mid 50’s to low 60’s.
The seven-day precipitation amounts will range from ¼” to near 1”.
The 8-14 day outlook (Aug 17-23) slightly favors above-normal temperatures in far northern NY and slightly favors below-normal temperatures in southeast N, other areas can expect near-normal temperatures. The precipitation outlook slightly favors below-normal precipitation amounts for southeast NY and favors near-normal amounts for the rest of the state.
Scouting Soybean Aphid
Keith Waldron-Cornell University, NYS IPM
Soybean aphid (SBA) appeared this week in central NY. The economic threshold is 250 SBA’s/ PLANT. It is the time to begin checking soybean fields for soybean aphid.
What to look for:
Check the under surface of leaves for presence of very small aphids. If present, the aphids are usually seen in small clusters near the leaf veins. They are tiny, 1/16″ long at their largest, with distinctive black cornicles (tail pipes). Soybean aphids are the only aphids to successfully colonize soybean plants. These aphids may or may not have wings.
Infested fields may also be stunted, have areas leaf curling and the sticky “honey dew” residue associated with a high aphid population and relatively low numbers of natural enemies. A large colony of soybean aphids often includes white, shed skins and brownish carcasses killed by fungal pathogens. Plants with very high SBA populations can also attract ants that can be seen on and in the plant canopy.
SBA threshold guideline is 250 soybean aphids per plant if populations are actively increasing on 80% or more of the plants prior to early pod fill (R4). The 250 SBA / plant action threshold is based on an average of aphids per plant over 20-30 plants sampled throughout the field. This threshold incorporates an approximate 7-day lead time between scouting and treatment to make spray arrangements and handle weather delays. Midwestern research has found that treating earlier than this threshold in most cases does not pay for itself. When scouting the early vegetative stages of soybeans for soybean aphid, it is just as important to watch for the aphid’s natural enemies, including ladybugs, syrphid fly larvae, parasitic wasps, and fungal pathogens.
If fields are approaching threshold, a follow up field visit is recommended within a week, particularly following rain storms, to determine if SBA populations are increasing, assess potential impact of natural enemies and re-assess if rains have affected aphid numbers on plants.
Insecticides labeled in NY for treatment of SBA’s are shown in Cornell Guide for Integrated Field Crop Management. If fields are treated, re-evaluate fields for SBA numbers at least 7-10 days following treatment. Information from any treat / no treat side-by-side comparisons is always appreciated.
Western Bean Cutworm Report
Western bean cutworm trap catches nearly doubled last week’s record numbers. This is the most moths we have ever caught over one week. We have already caught more moths than we did all of last year.
Highest moth captures were recorded in several locations in western and northern counties. Several fields have reached the economic threshold for western bean cutworm egg masses and small larvae. These fields will be sprayed with an insecticide.
The Mid-Hudson Valley and Delaware County has seen an increase in the number of moths caught from all past years of monitoring. This week’s high counts hopefully signal peak flights have occurred. WBC eggs laid this week will hatch in 5 – 7 days with larvae heading towards corn ears in the next 10 days. Individual trap catches can vary, even with in a township, based on such factors as local overwintering success and attractiveness of corn stage of development. As trap accumulations approach 100 moths per traps risk of WBC infestation increases and field monitoring for egg masses and young larvae is recommended.
Growing Degree Days in New York State
Keith Waldron, NYS IPM
*Walk fields to check general field condition, weed, vertebrate and other issues
*Watch for crop maturity, stand assessments, weed escapes, nutrient deficiencies, lodging issues
*Evaluate established legume stands for approximate days until harvest
*Monitor potato leafhopper, foliar, systemic and crown rot diseases.
*Monitor new seedings for potato leafhopper, pythium blight, phytopthora root rot.
*Monitor grain fields for growth stage, disease and lodging issues, grain maturity, harvest timing
*Record diseases present, location and types of weed escapes
*Monitor for mid-season corn pests including European corn borer, corn rootworm, western bean cutworm, slugs, foliar diseases such as northern corn leaf blight and gray leaf spot, weed issues, nutrient deficiencies, vertebrate damage.
*Monitor for soybean aphid, defoliators, foliar diseases, white mold, weed issues, vertebrate damage
*Check water sources, mend fences as needed.
*Check crop growth, clip pastures between grazing as needed
*Monitor for invasive species, plants harmful to livestock
* Check stored grain bins for temperature, moisture and signs of mold and insects. Aerate, core, transfer grain or treat as necessary
* Clean and disinfect empty storage bins in preparation for grain harvest
*Check forage allocation and anticipate feed program adjustments as forages from previous year are used up
*Mow around storage bins and facility to minimize pest hiding places
Dairy Cattle Barn Fly Management:
*Monitor animals and barn area for house fly, stable fly and other pest management needs including presence of rodents and birds.
*Check facilities for favorable fly breeding conditions: (organic matter + moisture): leaks in watering systems, roof gutters for leaks and potential overspill, drainage,
*Sanitation, sanitation, sanitation – clean animal resting areas, feed troughs, minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal loafing yard
* Continue fly monitoring: install “3X5″ index card fly speck monitoring cards throughout barn
*Use, replenish, replace fly management materials: sticky fly tapes/ribbons, insecticide baits, natural enemies (parasitoids), fly population monitoring (3 x 5) spot cards
*Consider purchase and release of Muscidifurax raptor and/or M. raptorellus natural enemies of house and stable fly pupae.
Dairy Cattle on Pasture:
*Monitor animals for presence of face flies, horn flies and stable flies. Action guidelines: face flies (average 10 per animal face), horn flies (average 50 / dairy per animal side, 200 / beef cattle per animal side), stable flies average 10 per animal (all four legs)
*Check feed bunk / water source locations for signs of stable fly breeding (moist undisturbed organic matter – spilled feed, round bales, etc.), minimize source of moist organic matter i.e. fly breeding areas in barn and in adjacent animal exercise yard.
*Check pasture for forage quality / quantity, rotate as appropriate
*Check pasture for vegetation poisonous to livestock
*Consider use of pasture fly traps to help reduce deer, horse and stable fly populations