Volume 16 Number 13
View from the Field
NOTE: The western bean cutworm report will be added to the blog on Monday when we have a complete data set to present.
While potato leafhopper remains at high infestation levels there are some reports that they have declined in alfalfa fields. I found that alfalfa that had been cut were below threshold. Alfalfa that was tall (7 inches or taller) had PLH over threshold.
Aaron Gabriel (CCE Capital District) during a field meeting found gray leaf spot on the lower leaves of corn. For more information on gray leaf spot see article below. Be on the watch for other diseases like northern corn leaf blight as corn reaches pollination.
Jeff Miller (CCE Oneida County) reports finding soybean aphids on soybeans at low infestation levels. As the summer continues aphid populations could rise. I found a few soybean aphids on soybeans in Columbia County this week.
Since there is more conventional corn being grown this year be on the lookout for corn rootworm. Corn is approaching pollination in some fields and this is when you find the beetles in the field feeding. See article below on identification and how to scout for them.
Weather Outlook – July 27, 2017
NOAA Northeast Regional Climate Center, Cornell University
Last week temperatures ranged from 4 degrees below-normal to 2 degrees above-normal. Precipitation ranged from a quarter inch to over 4 inches (over 7” in Hammond!). Base 50 growing degree-days ranged from 80 to 160.
Showers & thunderstorms today then mostly dry for the week!
Today temperatures will be in the mid 70’s to low 80’s. Scattered showers and thunderstorms are likely as a frontal system moves through. Severs storm are possible for central to eastern NY, with heavy rain and damaging winds. Overnight lows will be in the 60’s.
Friday temperatures will be in the 70’s, with some leftover showers possible in southern areas of the state. Overnight temperatures will be in the mid 50’s to low 60’s.
Saturday’s highs will be in the 70’s with clearing skies and mostly dry conditions. Overnight temperatures will be in the 50’s.
Sunday, highs will be in the mid 70’s to low 80’s and mostly sunny. Overnight temperatures will be in the mid 50’s to low 60’s.
Monday’s highs will be in the upper 70’s to low 80’s with sunny and dry conditions. Lows will be in the low to mid 60’s.
Tuesday will have temperatures in the upper 70’s to low 80’s with isolated showers and thunderstorms possible. Lows will be in the upper 50’s to mid 60’s.
Wednesday, temperatures will be in the upper 70’s to low 80’s with isolated showers and thunderstorms possible. Lows will be in the upper 50’s to mid 60’s.
The seven-day precipitation amounts will range from a trace to ½ ”.
The 8-14 day outlook (Aug 3-9) favors above-normal temperatures for southeast NY, and near-normal temperatures for the rest of the state; the outlook slightly favors above-normal precipitation.
2017 Corn Diseases and Plant Health in a Wet Growing Season
Ken Wise, NYS IPM-Cornell University
Joe Lawrence, PRO-DAIRY-Cornell University
The current 2017 wet/rainy weather and high humidity can create a situation where diseases can become an issue in corn. While there are several foliar diseases that can occur on corn under these conditions, gray leaf spot and northern corn leaf blight have been especially problematic over the last several years. Gray leaf spot and northern corn leaf blight can cause yield losses and the risk of infection may be an issue this year. What should a grower do about it? While applying protective fungicides is an option, there are several things to consider before spaying. Here are a few steps to follow when making a decision.
- Scout fields for the gray leaf spot and northern corn leaf blight at tasseling. If there are lesions on leaves at or above the corn ear exceeding 5% of the plant leaf area consider a fungicide. If lesions develop later after tasseling, then economic benefits from using a fungicide will be less.
- Does your hybrid have at least moderate resistance? This can make a big difference in yield and likely will not require a fungicide application. Disease symptoms may be present in resistant corn, but a fungicide most likely will not increase yield.
- Crop rotation and tillage is an effective method to control the fungi. The longer the rotation the less inoculum will be on the surface. If you maintain no-tillage, zone-tillage or reduced tillage rotating away from corn for 2 years can help reduce pathogen populations.
- Fungicides can be very effective when disease exists above the economic threshold. However, fungicides are protective not curative, so applications need to be made before the full extent of disease damage is known. It is generally not economical to spray fungicide on silage corn.
-Gray Leaf Spot (Cercospora zeae-maydis)
Early symptoms are yellow to tan lesions with a faint watery halo. As the lesion progresses, it turns brown and is rectangular in shape, between the veins. When fully developed the lesion can be 3 to 4 inches long and a 1/6 to 1/8 inch wide. The fungus can overwinter on corn debris left on the soil surface. Sporulation occurs during warm and humid weather in late spring. The spores can be transmitted by both wind and rain. In some cases gray leaf spot can reduce corn yields from 5 to 40 bushels per acre.
-Northern Corn Leaf Blight (Exserohilum turcicum)
The symptoms are long, cigar-shaped lesions that are about a 1/8 to ¼ inch wide. The lesions can be many inches long. Lesions are grayish-tan and have a pigmented border. There are numerous races of the pathogen, some of which overcome resistance genes deployed in many of the corn varieties grown in NY. The fungus overwinters on corn crop residue from previous years.
Other foliar diseases of corn to look out for this season
- Northern Corn Leaf Spot (Cochliobolus carbonum)
- Eyespot (Aureobasidium zeae)
- Common Rust (Puccinia sorghi)
- Anthracnose (Colletotrichum graminicola)
Certain fungicides now carry a label for plant health benefits when used at the V4-5 stage and, if warranted, again at tasseling. Product labels suggest potential yield and quality benefits from their use. Cornell University is conducting field evaluations to better understand the economic returns of using fungicides in this manner.
There are numerous factors affecting the forage quality of corn silage. Major factors on overall quality include whole plant maturity at harvest, ear to stover ratio and seasonal weather patterns. A healthy plant with minimal damage to plant tissue is able to mature to desired corn silage dry matter content in a more efficient and timely manner.
It is extremely difficult to predict the chances of mycotoxin issues in silage. It is important to recognize that mycotoxins only develop on living plant tissue and therefore the necrotic tissue resulting from leaf diseases are not an indicator of potential mycotoxin risk.
Plant injury to living tissue, where mycotoxins can develop, such as feeding damage on the ears and stalk do offer a pathway for disease organisms and moisture to get into the plant and wet conditions late in the growing season can increase the chances of mold development. Again it is very important to understand there is not a clear causal relationship, even when an ear or stalk mold is present it is not a sure indication that mycotoxins will develop. It is important to work with your nutrition consultant at harvest to test for potential mycotoxin issues.
We have videos on Northern Corn Leaf Blight and Gray Leaf Spot on Field Corn
Know your corn rootworms
Ken Wise-NYS IPM
Western corn rootworm (WCRW) adults are black and yellow beetles that are approximately 1/4 inch long. The female is yellowish with 3 black stripes on its back, while the male is solid black with a pale yellow area at the tip of its abdomen.
Northern corn rootworm is slightly smaller than the western, and it is bright green in color (see photo). The northern corn rootworm (NCRW) used to be the predominant species in New York State, but since the arrival of the western in the 1980’s, the western has become the dominant species.
Scouting for Corn Rootworm
Ken Wise-NYS IPM
You will need to scout all corn fields that will be kept in corn next year from emergence of the tassel until pollination is complete. Pollination occurs for three weeks and monitoring takes about 20 minutes per field. You will need to monitor each field once a week until you reach a threshold or until pollination is over. Look for gravid, (i.e. mature, egg laying) corn rootworm female beetles–the ones that, when you squeeze their bodies, release white eggs from their posteriors.
Here’s how you scout:
- Are female beetles present? Mature and capable of egg laying? Conduct the squeeze test (see above) to determine if they are ready to lay eggs.
- Approach a corn plant carefully because the beetles will fly off if they disturbed too much.
- Grasp the silk with one hand.
- Count the beetles on the entire plant.
- Start counting at the top working down.
- Gently pull leaves away from the stalk so you count any beetles that may be hiding in the whorls.
- For each corn plant monitored, record the total number of beetles observed. See the sequential sampling chart below. Since western corn rootworms are potentially more damaging than their northern cousins, count each western (yellow striped) beetle observed as “one” and each northern (green type) as “1/2”.
- Check several plants at random (not next to each other!) in several parts of the field.
- Continue sampling at seven-day intervals until the ear silks are brown, approximately 3 weeks after tassels are first visible, pollination is complete or an above threshold number of beetles are found.
Using the Sequential Sampling Card for Corn Rootworm
- Keep a running total (RT) of the number of corn rootworm beetles you have counted on each plant. Each northern corn rootworm has half the value of each western corn rootworm. The western corn rootworm does twice the damage to corn than does the northern. So if you count 3 westerns and 4 northern (2 western equivalent) on a plant you would have a total of 5 beetles.
- If the number of corn rootworm beetles observed is smaller than the “N” (“Not at threshold”) number stop and scout 7 days later.
- If the number of corn rootworm beetles observed is larger than the “T” (“At threshold” or “Treat”) number then you need to manage rootworms next year.
- If the number of corn rootworm beetles observed fall between “N” and “T”, continue sampling additional plants until you finally go over or under.
- In a very low or very high rootworm population a sampling decision can be made in sampling as few as 3 to 8 plants. For moderate populations more samples may be necessary to insure accuracy.
We also have a video on how to scout for corn rootworm in field corn:
Western Bean Cutworm Update 7.31.17
Western bean cutworm trap catches took this past week was 5X as many moths caught this week than last. Higher moth captures more often found in western and northern county than southern locations. This year we are seeing an increase in the numbers of moths caught in traps in the Hudson Valley and Catskills. See summary table below.
Monitoring fields for WBC egg masses:
As trap accumulations approach 100 moths per traps risk of WBC infestation increases and field monitoring for egg masses and young larvae is recommended. Pre-tassel corn is the preferred host for egg laying WBC moths. Egg masses will be laid on the upper surface of leaves close to emerging tassels including leaves in the whorl. Check 10 – 20 consecutive plants in at least 5 random locations in the field. Threshold for field corn is 5% of plants with WBC egg masses. Egg masses are typically laid on upright leaves or those just beginning to lay over. I usually check top 4 leaves.
If leaves are oriented towards the sun you can see the egg masses better on the top side of leaf or if looking at the bottom surface of leaves look for a shadow of an egg mass on the upper surface of the leaf. WBC eggs take ~5 – 7 days to hatch turning purple 1 – 2 days prior to hatch. Newly hatched larvae initially feed on their egg case and then make their way to silks or ears. If suitable food sources are not found the larvae will starve.
Several video’s are available on-line on how to monitor for WBC egg masses in corn. https://www.youtube.com/watch?v=cH-yVeDuUM0
Pictures of WBC larvae and moths including look-a-like moths and larvae can be found at: http://www.msuent.com/assets/pdf/07WBCID.pdf and
Degree Day Models for Field Crops across New York
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