Lebanon Crop Management Video


23 August 2016

Brown Stem Rot- Case Study

Del Voight Penn State Extension
Street View of problem area

Visible Leaf Disease narrowing diagnosis down to Brown Stem and or Sudden Death

Initial Walk in view of problem area

Root area to pull infected plants and begin to cut stems in two to differentiate between BSR and SDS

Cut Stems with the initial browning of the stem will check field in a week to see if more distinct stem browning occurs. No presence of the bluish fuiting bodies of SDS at this point leaning to BSR

Update Checked field 2 weeks after initial call and found fruiting bodies on roots and the stem remained water soaked in appearance.  This now confirms SDS and management for future soybean crops should consider this disease.

Note the bluish fruiting bodies

Note the absence of brown stem more water soaked appearance with SDS.

02 August 2016

Foliar Applications of Fungicides on Corn.

The continuing wet humid weather has many growers asking questions about foliar applications of a fungicide on tasseling corn.  Most labels dictate that applications be made between VT and R1 stages.  The labels I reviewed also require that adjuvants NOT be used after corn has reached the V8 stage. However some offer this option on fully tasseled corn.   Recent Agronomy Journal Publications have shown the formation of beer can ears as a result of adjuvants applied near VT.  The wet weather has aloud for ideal uniform emergence of silk and tassel applications between VT and R2(blister) are the key times to apply the fungicides. Below are some considerations to better make a decision to treat or not.  Many growers may be tempted to add additional products to the tank while going over the field.  Most labels allow for the inclusion of insecticides but caution that growers only apply approved tank mixes and observe the most restrictive labeling.
Finally on some products there is a 30 day harvest restriction for forage and grain so bare this in mind early forage harvest might need to be delayed should an application be made. This is not a straight forward recommendation on corn and growers should look at each field and best determine its needs. We have a bumper crop in the making right now and this application on many fields would really make the most difference in preserving potential yield!!
Fungicide Selection- There are numerous options to select to manage foliar diseases. In 2014(figure 1), Dr Collins and I conducted a test of 5 different fungicides on corn and applied product at the V6 and Tassel stage as well as two applications one at V5 and followed by a R2 stage  of  various fungicides. In 6 out of the 10 treatments, there was a significant response exceeding 11bu/acre overall to the application of a fungicide. In all cases there was a response but not all due to the treatment. The decision is not as much which product to use but rather whether the hybrid will respond to an application. The hybrid in our trial last year was susceptible to leaf diseases.  This data supports some Mid Western data showing the response of hybrids over several fields.  This link will take the reader to an article and chart for the various options and what disease different products control and their PHI. I recommend one print this off as a reference.  Fungicide Efficacy Comparisons

Figure 1 Penn State SEAREC- 2014 Corn Response to Fungicide Applications- D.G. Voight and A. Collins
Questions to ask?
Ask some simple questions to determine the benefit that might come through a foliar application of a fungicide to VT-R1 Corn. We cannot make a decision for you but if you ask some simple questions of yourself to address your fields and also to address your seed representative and seed guides to determine the benefit of an application.

A. Disease history: Low lying fields with a history of disease are more likely to respond to a fungicide.                                                                            
1. No
2. Yes

B. High yield history:  High yield fields are more likely to show an economic response. 
1. Poor
2. Average
3. High yielding

C. Hybrid resistance: The lower the genetic resistance to gray leaf spot, northern corn leaf blight and anthracnose, the more potential for an economic response.
1. Highly resistant
2. Average
3. Poor resistance

D. Crop rotation: Corn following corn tends to harbor more disease inoculum.
1. Following other crops
2. Following corn

E. IPM: Corn diseases are just starting to appear, especially in no-till corn on corn fields. The more presence of disease on the leaf the higher the risk of further development.
1. Less than 5% visible disease
2. 5-10% visible disease
3. 10% or greater disease

F. Fertility: Low K levels and compacted soils could exacerbate disease effects on lodging and yield.    If the field has poor fertility the likelyhood of increased disease invasion is higher.                                                              
1. High fertility
2. Average
3. Poor fertility

If you go through these simple questions and more than one meets lends the field to infection spraying might be a profitable venture. 

Corn Ear Molds

Del Voight – Penn State Extension
Two Items to be reviewing as the corn season progresses. Ears are rapidly forming and growers are applying fungicides presently to fields that the hybrid may be susceptible to leaf diseases.. Knowing the characteristics of the molds are helpful in management. Also many fields of corn were planted late and are showing some leaf diseases. This is important also in determine early harvest prior to complete infection of the plants.
Here are some pictures of ear molds and a description of their mycotoxin potential as well as some management ideas.  As in other cases just because there is the mold does not mean that a mycotoxin will result.  There is still a lot that needs to be learned regarding these molds and there relationship to the toxin formation.  Both fusariums can be an issue and have been researched the most intensively mainly in the silage portion for dairy.  As you get out on farms in the coming weeks it might be wise to have this or some other reference in your truck to use as a discussion.  Also keep an eye on the nitrate situation(silage after rains return) and stalk lodging due to stalk rot. Many times with a drought the plant robs leaves, stalk and roots to feed the ear and during this time stalk rots invade since the plant is weakened.  A squeeze test of the lower stalk can reveal the management of the field for early harvest. 
I have viewed mostly corn smut. at differing stages of development.  This is not a fungus that can cause any harm to livestock contrary many folks will consume it as a delicacy.

Gibberella Ear Rot

The most common and important ear mold in Ontario is Gibberella zeae which is the sexual reproductive stage of Fusarium graminearium. This fungus not only infects corn but also small grains such as wheat and can survive on soybean roots. Although, the fungus can produce a white colour mold which makes it difficult to tell apart from Fusarium Ear Rot, the two can be distinguished easily when Gibberella produces its characteristic red or pink colour mold.
Scout fields which have a susceptible hybrid planted. If you are not sure how your hybrid rates for Gibberella contact your seed supplier.
Gibberella Ear Rot is economically important not only because of the potential yield and quality losses but because Gibberella zeae and Fusarium graminearum produce two very important mycotoxins that occur in Ontario, deoxynivalenol (vomitoxin or DON) and zearalenone. These mycotoxins are especially important to swine and other livestock producers since they can have a detrimental affect on their animals. Feed containing low levels of vomitoxin (1ppm) can result in poor weight gain and feed refusal in swine. Zealalenone is an estrogen and cause reproductive problems such as infertility and abortion in livestock, especially swine. If you have Gibberella ear rot (5 % or more) and are planning to feed the grain, you should have the grain tested for these toxins.
Figure 2 - Gibberella Ear Rot

Fusarium Ear Rot
Unlike Gibberella, Fusarium infected kernels are often scattered around the cob amongst healthy looking kernels or on kernels that have been damaged for example by corn borer or bird feeding. Fusarium infection produces a white to pink or salmon-coloured mold. A "white streaking" or "star-bursting" can be seen on the infected kernel surface. Although many Fusarium species may be responsible for these symptoms, the primary species we are concerned about in Ontario is Fusarium verticillioides (formerly Fusarium moniliforme). The significance of this fungus is that it produces a toxin called fumonisin.
Figure 3. Fusarium Ear Rot

Diplodia Ear Rot
The characteristic ear symptom of Diplodia maydis infection is a white mold that begins at the base of the ear and will eventually cover and rot the entire ear. Mold growth can also occur on the outer husk which has small black bumps (pycnidia) embedded in the mold. These reproductive structures are where new spores are produced. Unlike Gibberella and Fusarium, Diplodia does not produce any known toxins.
Figure 4. Diplodia Ear Rot

Penicillium Ear Rot
Penicillium rot (Penicillium oxalicum) produces a light blue-green powdery mold which grows between the kernels and cob/husk surface. Infected kernels could become bleached or streaked. Can be a serious problem if corn is stored at high moisture levels (greater 18%). Although other Penicillium species have been shown to produce Ochratoxins, Penicillium oxalicum dos not and this toxin does not occur in Ontario.
Figure 5. Penicillium Ear Rot

Table 1 – Common Ear Rots and Molds That Occur in Pa and The Primary Mycotoxins They Produce
Corn Ear Rot
(Gibberella zeae also called Fusarium graminearum (asexual stage)
  • Red/pink mold
  • Begins on ear tip
  • Bird, insect injury increases damage
  • Deoxynivalenol (Vomitoxin or DON)
  • Zearalenone
  • T-2 toxin
(Fusarium verticillioides)
  • White, pink or salmon coloured
  • Can occur anywhere on ear
  • Often begins at the sites of insect damage
  • Fumonisins
(Stenocarpella maydis)
  • White mold
  • Begins at base of ear but often entire ear covered
  • Black pycnidia (bumps) on husks and kernels
  • · None
(Penicillium oxalicum)
  • Blue-green mold
  • Mold between kernels and on cobs/husk
  • Ochratoxins (other Penicillium species)
  • P. oxalicum does not produce ochratoxin; not detected in Ontario
Management – Iowa State University.
The best option for moldy grain is to feed it or sell it instead of storing it. However, it should be tested for toxins before feeding. Testing for mycotoxins can be done before putting the grain in storage. The best sampling method is to take a composite sample of at least 10 pounds from a moving grain stream, or to take multiple probes in a grain cart or truck for a composite 10-pound sample. If toxins are present, it is possible that the grain can be fed to a less sensitive livestock species, such as beef cattle, depending on the specific toxin and its concentration. A veterinarian or extension specialist can help with these decisions. If the grain is sold, there may be a reduced price due to mold damage.
Cleaning the grain removes fine particles that are usually the moldiest and most susceptible to further mold development. Good storage conditions (for example, proper temperature and moisture content, aeration, insect control, and clean bins) and regular inspection are essential in preventing mold and toxin development in any stored corn. For additional information on sampling and other aspects of ear rots and mycotoxins, see Iowa State University Extension publications PM 1800, LEAF DISEASESAflatoxins in Corn (free), and PM 1698, Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health ($1.50 plus shipping).

Two Spotted Spider Mites in Soybeans

Del Voight - Penn State Extension
Credits: Minnesota Extension

Growers should be inspecting the edges of the soybean fields now.  Here is what you are looking for:
Plant Symptoms; stippling on the leaves

Mite Presence

Observe under the leaves. you will note very small spider like insects in small colonies with some webbing. There are two variations of the two spotted spider mites. Only a trained entomologist can tell the difference. One variant is susceptible to insecticides and the other is resistant. This may have changed since Dr. Ron Ochloa USDA first identified the differences in 2008.

Thresholds for treatment:

Insecticide Treatment Options:

Important Notes regarding two spotted spider mite control:
  1. Edge treatment does not always work since many times the mites are already within the field.
  2. The use of pyrethroids other than Bifenthrin prior to a drought and this application can spike the two spotted spider mites. Check fields within 14 days of treatment to see if mite populations have exploded.
  3. Mites are on the underside of leaf be sure to apply in excess water more than 20 gallons per acre to ensure coverage.
  4. None of the insecticides control eggs so repeat applications may be necessary. In 2009 near Hershey three applications were made with little success due to egg hatch as well as low carrier rates.
  5. If rains return this does not translate into mite control. They build in droughts due to the absence of a disease and it takes time for hte disease to build after rains to assist in managing the populations.  Heavy rains may wash some off but rarely lead to control of the pest.

For more reading go to Penn State Extension - Two Spotted Spider Mite Fact Sheet


Corn Leaf Disease beginning to show in numerous hybrids.

Del Voight – Penn State Extension
Corn Leaf Diseases – Adapted from Purdue University Plan Pathology.
Many of my colleagues are reported that they viewed numerous hybrids exhibiting gray leaf spot infections.     However it is wise to determine the hybrids performance in resisting plant diseases.  The major rule in managing leaf diseases is similar to wheat in that one strives to keep the leaf that feeds the ear clean of disease.  Infections below that point typically have less of an impact on corn yields.  Most if not all recommendations particularly for no till corn will stem in hybrid selection to manage diseases.  Applications during tasseling are also an option.   Data from across the east and Midwest is variable and the key to determine the need to treat is related to specific field conditions.  In some studies completed with industry and Extension involvement it appears that fields that have observable disease infecting the lower leaves, fields with hybrids that are prone to disease infection, and reduced tilled fields that are showing signs of infection are fields that may prove to return a profit. In some industry hybrids 60% of hybrids showed a response above the economic return.  Universities found that a fourfold response occurred in fields showing disease infection.  Most of the studies suggested an average of 8 bu/acre resulted in fields where a disease is present in the east.  In the southern climates responses to a fungicide treatment of 15 bu/acre, were observed by Universities.  The thresholds developed are based on typical crop markets.  Current markets may certainly have changed but the key to the best response is the infield observation of what diseases exist and to what extent.  From a practical stand point with the number of fields that were converted to no till this season growers that utilized the same hybrid in two consecutive years should take a serious look at fungicide applications on corn.  In Pennsylvania research is underway looking at the affects of fungicides on grain and also the silage impact as well.  If one does choose to apply a fungicide read and follow label directions and be sure the application equipment can get high enough above the canopy to provide proper coverage.

Disease Name: Gray Leaf Spot

Pathogen: Fungus. Cercospora zeae-maydis

Symptoms: Initial lesions appear as greenish black water soaked circular areas with chlorotic halos, expanding into oval and then the diagnostic parallel sided rectangular brownish gray lesions.

Conditions: Infection is favored by extended warm, wet, humid weather.

Inoculum Survival: Infected crop residue (leaves and leaf sheaths).

Inoculum Dispersal: Airborne spores.

Management: Select hybrids with resistance (tolerance based on risk), two year crop rotation, cleanly plow under infected residue.
Click on an image to display it in larger detail.
Disease Name: Anthracnose Leaf Blight

Pathogen: Fungus. Colletotrichum graminicola

Symptoms: Small, oval to elongated water-soaked lesions enlarge to become brown, spindle shaped spots with yellow to reddish-brown borders. Lesions may coalesce and blight entire leaves. Older lesions will turn gray in the center with small black specks (acervuli with sterile black hairs). Leaf blight may be followed by top kill and stalk rot. Leaf blight rarely causes large yield losses. Stalk rot phase is most important (see Anthracnose Stalk Rot).

Conditions: Favored by cool to warm, wet, humid weather, continuous corn with reduced tillage.

Inoculum Survival: Infected crop residue (leaves, leaf sheaths and stalks), seed (endosperm).

Inoculum Dispersal: Airborne spores.

Management: Resistant hybrids, rotate corn with nongrass crops. Cleanly plow under infected residue.
Click on an image to display it in larger detail.
Disease Name: Common Corn Rust

Pathogen: Fungus. Puccinia sorghi

Symptoms: Initial symptoms are chlorotic flecks on leaf surfaces. Flecks develop into oval to elongate reddish brown powdery pustules on upper and lower leaf surfaces. Reddish brown spores break through the leaf epidermis. Pustules become brownish-black as they mature. Usually not a serious disease in hybrids.

Conditions: Disease favored by cool (66 F optimum) humid weather.

Inoculum Survival: Spores blown into the Midwest from the South. Does not survive winter in Indiana, except possibly in rare years along the Ohio River.

Inoculum Dispersal: Airborne spores.

Management: Resistant hybrids. Foliar fungicides may be useful in seed production fields.
Click on an image to display it in larger detail.
Disease Name: Southern Corn Rust

Pathogen: Fungus. Puccinia polysora

Symptoms: Similar to common rust except pustules occur almost exclusively on the upper leaf surface, rarely on lower. Pustules are more orange than brick-red and slower to break through epidermis of leaf than common rust pustules.

Conditions: Favored by high humidity and temperatures around 80 F.

Inoculum Survival: Spores blown into the Midwest from the South. Does not survive winter in Indiana, except possibly in rare years along the Ohio River.

Inoculum Dispersal: Airborne spores.

Management: Resistant hybrids. Foliar fungicides may be useful in seed production fields.
Click on an image to display it in larger detail.
Disease Name: Northern Corn Leaf Blight

Pathogen: Fungus. Exserohilum turcicum

Symptoms: Long cigar-shaped gray-green or tan lesions.

Conditions: Favored by extended wet, cool, humid weather, minimum tillage, continuous corn. Usually occurs during or after pollination.

Inoculum Survival: Infected crop residue (leaves, husks, stalks).

Inoculum Dispersal: Airborne spores.

Management: Resistant hybrids. Foliar fungicides may be useful in seed production fields. Cleanly plow under infected residue.
Click on an image to display it in larger detail.
Disease Name: Northern Leaf Spot

Pathogen: Fungus. Helminthosporium carbonum (Race 3)

Symptoms: Narrow, small, linear to oval shaped leaf lesions. Lesion type may vary with the genotype of host and isolate. Lesions are grayish tan and surrounded by a light to darkly pigmented (usually purple) border. Chain-like leaf lesions are often produced.

Conditions: Favored by moderate temperatures and high relative humidity, minimum tillage, continuous corn.

Inoculum Survival: Infected crop residue (leaves, husks, stalks, seed).

Inoculum Dispersal: Airborne spores.

Management: Resistant hybrids. Disease is primarily a problem in seed production fields with certain highly susceptible inbreds. Foliar fungicides may be useful in seed production fields. Cleanly plow under infected residue.

Delbert G. Voight, Jr. -M.S, CCA Penn State Extension - Crop Management Team
2120 Cornwall Road
Lebanon, Pa 17042