Hail Damage and Fungicide Use in Field Crops

Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu; @Delmarplantdoc

With recent hail in the region, some growers may be wondering about the use of certain fungicides (specifically some containing strobilurin active ingredients (QoI FRAC group 11) for the mitigation of plant stress or to protect the plant against wounded plant tissues. Some people consider fungicides for hail-damaged crops because it is believed that hail can either increase infection of fungal pathogens or increase plant stress and therefore disease. Furthermore it is believed that the potential physiological effects of strobilurins allow for plants to recover from hail damage and limit potential yield losses. It is important to note that the fungi that infect field crops do not require wounds to infect and cause disease. It is also important to note that bacterial diseases, which potentially could increase with wounding of plant tissues, will not be controlled by these fungicides.

What does the research say? Researchers from the University of Illinois conducted a two year field study using simulated hail damage (via string mowers) at the V12 stage followed by foliar fungicides containing either pyraclostrobin or azoxystrobin (both strobilurins). Overall, the study showed that the fungicides did not provide any yield benefit to hail-damaged corn. A link to the study can be found here: http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-94-1-0083.

A study at the University of Wisconsin examined different corn hybids and fungicides for their reaction to anthracnose. During the course of the study hail naturally damaged the corn in the trial. Although the hail did reduce yields, fungicides did not improve plant health or result in improved yields. A soybean trial that was conducted at the same time and also damaged by hail showed no differences between fungicide treated plots vs. untreated controls. A write-up of these studies can be found here: http://www.apsnet.org/meetings/Documents/2010_Meeting_Abstracts/a10ma201.htm

Other research looking at timing of hail damage to corn and soybean and various pesticides was conducted by researchers at Iowa State. Results of their studies indicate that hail damage to soybean at R4 caused less yield loss than hail damage at R1. In corn, hail damage at R2 caused more yield loss than hail damage at VT.  Fungicide application, either immediately following injury or applied several days afterwards, did not have an effect on yield.  These studies were recently published in Plant Health Progress- located when you search under the keyword “hail” www.plantmanagementnetwork.org/

Fungicides are effective at controlling fungal diseases and their benefits are realized when used in situations where fungal diseases are likely to limit crop productivity. They will not help with bacterial diseases, such as Goss’ wilt, bacterial stalk rot, or bacterial leaf streak. The current studies indicate that the application of fungicides for mitigation of hail damage does not appear to significantly improve yields over untreated controls. If you do choose to apply a fungicide to hail damaged crops this year, it would be a good idea to leave an untreated strip in the field to allow for a comparison of treatment effectiveness at the end of the growing season.

Hail Damage Showing Up in Scattered Vegetable Fields

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

This has been a strange spring weather pattern we have been having. It has been cloudy and wet for the last 10 days or so and on top of all that we have had isolated down pours with hail. In some fields growers were not aware of the hail that had passed through and wonder now what could have caused the type of damage they are seeing in their crop. The damage on tomatoes and onions that I saw was from pea-size hail (Figures 1 and 2). The damage to tomatoes was always one-sided or even a quarter of a side of the tomato that was not covered by foliage. There was some tomato foliar damage, but not much. The noticeable and important damage was to the developing fruit. Developing vegetable fruit is often more sensitive to damage from hail than the stems and even leaves which are more durable and can take some small hail damage. Onion leaves were more beat up, but the bulbs all looked good in the fields I visited. In cucurbit fields the damage again was usually on only one side of the fruit with much lighter damage to stems and leaves (Fig. 3). If you have not had a chance to check out your vegetables or fruit, be sure to do so in the next few days to get an idea of how much, if any, damage occurred.

If you do have hail damage be sure your fungicide spray coverage is thorough and that plants are at least sufficient if not better in nutrient levels. This may be a good time to try some biostimulants that are purported to help plants overcome stressful conditions. Be sure to treat only some or half of your damaged plants to see if the biostimulant worked or not. Damaged fruit should be removed from plants as it will be unmarketable, but will continue to drain the plant’s resources until it is removed.


Figure 1. Hail damage to tomato on only one side of fruit by pea-size hail


Figure 2. Hail damage to onions


Figure 3. Hail damage to zucchini on only one side of fruit and light damage to stems

Hail Damage to Vegetables

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

It was not too much of a surprise to see some hail damage to vegetables after the storms that rolled through our area on Tuesday. The damage on tomatoes and onions that I saw was very characteristic of damage from pea-size hail (Figures 1 and 2). The damage to tomatoes was always one-sided or even a quarter of a side of the tomato that was not covered by foliage. There was some tomato damage to tomato foliage, but not much as the noticeable and important damage to the developing fruit. Onion leaves were more beat up, but the bulbs all looked good in the fields I visited. If you have not had a chance to check out your vegetables or fruit be sure to do so in the next few days to get an idea of how much if any damage occurred.

HailDamageTomato

Figure 1. Hail damage to tomato fruit, only one side of fruit damaged by pea-size hail

HailDamageOnion

Figure 2. Hail damage to onions

Fungicides for Hail Damage?

Nathan Kleczewski, Extension Specialist – Plant Pathology; nkleczew@udel.edu

With recent hail, some growers may be wondering about the use of certain fungicides (specifically some containing strobilurin active ingredients) for the mitigation of plant stress such as hail damage. Some people consider fungicides for hail damaged crops because it is believed that hail can either increase infection of fungal pathogens or increase plant stress and therefore disease. Furthermore it is believed that the potential physiological effects of strobilurins allow for plants to recover from hail damage and limit potential yield losses. It is important to note that the fungi that infect field crops do not require wounds to infect and cause disease.

Researchers from the University of Illinois conducted a two year field study using simulated hail damage (via string mowers) at the V12 stage followed by foliar fungicides containing either pyraclostrobin or azoxystrobin (both strobilurins). Overall, the study showed that the fungicides did not provide any yield benefit to hail damaged corn. A link to the study can be found here: http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-94-1-0083.

A study at the University of Wisconsin examined different corn hybids and fungicides for their reaction to anthracnose. During the course of the study hail naturally damaged the corn in the trial. Although the hail did reduce yields, fungicides did not improve plant health or result in improved yields. A soybean trial that was conducted at the same time and also damaged by hail showed no differences between fungicide treated plots vs. untreated controls. A write-up of these studies can be found here: http://www.soils.wisc.edu/extension/wcmc/2010/pap/Conley_hail.pdf.

Other research looking at timing of hail damage to corn and soybean and various pesticides is being conducted by researchers at Iowa State. Preliminary results of their research from 2012 indicate that hail damage (using a special ice launcher) to soybean at R4 caused less yield loss than hail damage at R1. In corn, hail damage at R2 caused more yield loss than hail damage at VT. This study is still underway and final results from multiple years should be published in the near future. Some of the preliminary data has been summarized and can be found here: http://www.extension.iastate.edu/CropNews/2013/0717sissonmueller.htm.

Fungicides are effective at controlling fungal diseases and their benefits are realized when used in situations where fungal diseases are likely to limit crop productivity. The current studies indicate that the application of fungicides for mitigation ofhail damage does not appear to significantly improve yields over untreated controls. If you do choose to apply a fungicide to hail damaged crops this year, it would be a good idea to leave an untreated strip in the field to allow for a comparison of treatment effectiveness at the end of the growing season

Storm Damaged Vegetables – Wind and Hail

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Several areas throughout Delmarva have been hit with violent storms producing heavy winds and/or hail. Damage to vegetable crops by severe wind and hail includes leaf defoliation, leaf tearing and shredding, stem breakage, stem bruising and wounding, loss of flowers and small fruit, and fruit bruising and wounding.

Effects of storm damage on vegetable crops and recovery of crops will depend on a number of factors including the type of vegetable, stage of growth, weather conditions immediately after storms, and prevalence of disease organisms. Continued hot, wet conditions after storm events pose the most risk by increasing disease incidence, particularly bacterial diseases.

Defoliation reduces leaf area and plants will need to grow new leaves from buds (for vegetables such as vine crops where this is possible). It will take several weeks to replace the leaf area lost. This will cause delays in maturity. If crops are more advanced, loss of leaf area can reduce fruit or storage organ quality (reduced sugars). Fruit or storage organ size may or may not be affected. Leaf area recovery (growing new leaves) will be aided by additional nitrogen applications after the storm event.

In crops such as sweet corn that cannot grow new leaves, research has shown that hail damage will reduce marketable ears and overall tonnage if leaf damage occurs in vegetative stages or at silking. Leaf loss near harvest will have minimal effects.

Fruit bruising or wounding often causes the most severe losses in crops such as tomatoes. Fruits may be rendered unmarketable or of reduced grade. Wounds can also increase the incidence of some fruit diseases and storage rots. In particular, bacterial rots that normally are minimal may be increased in damaged fruits. In plants such as tomatoes, it is advised to remove damaged fruits from plants. These fruits are likely to be unmarketable and will just be a drain on food resources produced by the plant. By removing damaged fruits, remaining uninjured fruits will have access to more photosynthates being produced by the plant.

Stem breakage or injury can lead to major losses in some fruiting crops such as peppers by loss of fruiting area as well as increased sunburn as plants are opened up. Many vining crops will recover significantly from stem breakage by producing new branches, although production will be delayed.

Losses of flowers or small fruit may limit yield potential and delay crop harvest in many vegetable crops. Beans that are flowering are particularly susceptible and flower loss due to storms may lead to split sets.

Damaged plant tissue also can affect healthy surrounding tissue. As cell contents leak, enzymes, oxidative compounds, and other reactive chemicals are released that can injury surrounding cells.

Age and stage of development of plants will also be a factor in the overall impact of storm damage. A good example is with bean plants. In the case of hail, the bean plant is considered dead if it is in the cotyledon stage and is cut off below the cotyledons, or if the cotyledon is damaged by hail to such a degree that they have no green leaf tissue or re-growth. The reason is that nutrients and food reserves in the cotyledons supply the needs of the young plant during emergence and for about seven to 10 days after emergence, or until there is one fully-developed trifoliolate leaf. Cotyledons are the first photosynthetic organs of the bean seedling and are also major contributors for seedling growth. Unlike corn, whose growing point is below ground until it reaches V5-V6, the growing point for beans is between the cotyledons and moves above the soil surface at emergence. This makes beans particularly susceptible to damage from hail, or anything that cuts the plant off below the cotyledons early in its life. Stand reductions are likely to follow hailstorms. If the first trifoliate leaf is formed, photosynthesis by the developing leaves is adequate for the plant to sustain itself.

Of immediate concern after storms will be bacterial diseases on susceptible crops. Bacterial diseases have been shown to be more severe after storm damage as they can readily enter through wounds. Including copper products in spray programs after storm injury is recommended to limit bacterial diseases. In North Carolina research, peppers were shown to have increased bacterial spot after hail. Use of copper fungicides with maneb limited the effect of bacterial spot in these hail damaged peppers.

There has been some recommendation to use peroxide based fungicide/bacteriacide products after storm events. These products kill what they contact and have no residual. There may be some reduction in the numbers of disease organisms on plant surfaces; however, there is little research to show major benefits after storm damage.

General recommendations for storm damaged vegetables are to first evaluate the extent of the damage. According to the stage of the crop and extent of damage, determine if the crop can be salvaged. Crop insurance adjusters are trained to evaluate storm damage in many crops and should be contacted immediately for insured vegetable crops. For crops that will be salvaged or kept, consider applying additional nitrogen to encourage new growth where appropriate. Apply fungicides and include copper compounds where bacterial diseases are of concern.

haildamagedcabbage

Hail damage to cabbage

Hail Damage to Agronomic Crops

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

There was heavy hail damage in the northwest area of Kent County on June 9. Of course, small grains will have large yield losses. Corn that is 10 leaf stage or younger may have limited yield losses.

 hailwheat1Hail damage to wheat

hailwheat2 Hail damage to wheat.

hailbarley1Hail damage to barley.

 hailbarley2Hail damage to barley.

hailcorn1 Hail damage to corn.

hailcorn2Hail damage to corn.

hailcorn3Hail damage to corn.

The following is information from the National Corn Handbook (http://www.extension.iastate.edu/Publications/NCH1.pdf) on assessing losses due to hail in corn.

1) Assess stand losses. Wait about a week and then go out into the field and check for plants that have died or where the growing point is dead. Split suspect plants open and check to see if the growing point is light in color (still alive) or dark in color (is dead or dying).

2) Assess the loss of leaf area.

The following tables from the National Corn Handbook are used to estimate yield losses to stand loss and leaf loss. (Click picture to see larger version.)

haildamage12


haildamage2

 The following information is from Iowa State University on hail damage in corn:
http://www.ipm.iastate.edu/ipm/icm/2004/5-31-2004/hail.html
http://www.extension.iastate.edu/CropNews/2008/0607LoriAbendrothRogerElmore.htm

In contrast to soybean, corn has an advantage early season when hail damages the aboveground plant, because its growing point remains below ground until approximately the sixth-leaf stage. The sixth-leaf stage of the ISU leaf-collar system correlates to the seventh-leaf stage used by hail adjusters. Several fields that received hail damage are beyond this point, with the growing point at soil level or above.

Two different methods exist for assessing damaged fields based on the developmental stage of the crop when it incurred the damage:

In fields where the corn was at the fifth leaf or smaller, regrowth is expected and yield impacted negligibly. This is true regardless of the amount of defoliation.

In fields where corn was near or beyond the sixth leaf stage, evaluate injured plants to determine whether the growing point is viable. Make assessments of plant survival three to five days after the storm so that surviving plants have a chance to recover. If weather is not conducive for plant growth for a prolonged period after the storm, assessing the remaining stand may require waiting up to a week. It may take that long before it is clear which plants will survive and which will not.

Assessing a damaged field requires that the growing point is located and evaluated. Use a sharp knife and cut lengthwise down the stem in order to cross-section the stem. Assess the viability of the growing point; it should have a white to cream color. Plants with a healthy growing point should survive, especially if the growing point lies below the soil surface.

If most of the corn has not reached the V5-V6 growth stage yet this is good news because the growing point is still below ground and even if the leaves have been destroyed or the plant has been cut off, re-growth from the growing point below ground will occur. The loss of those early leaves will reduce growth rate following the damage but will not affect the overall yield significantly. Corn that had reached the V6 or more advanced growth stages may not be viable due to the growing point having moved above ground. At these growth stages, the plant will continue to grow if only the leaves have been knocked off or shredded and the stem has not snapped. When the stems have snapped at the base of the plant, the plant should not be considered viable. Leaves on the plant may have been shredded, but as long as they are connected to the stem they will continue to be an energy source for the plant and plant growth will therefore continue. Defoliation should not be considered a problem until later growth stages, approximately V7 or greater.

Unlike soybean, corn can do little to change its growth pattern to take advantage of increased space in reduced plant populations. A low plant population of corn will mean fewer ears on an area basis, resulting in a yield reduction. Therefore, stand loss is more of a problem in corn, making estimation of viable plants very important.

See the following for how insurance adjusters evaluate hail damage:
http://www.rma.usda.gov/handbooks/25000/2007/07_25080.pdf

Soybeans were also damaged in the recent storms. The following is information from the Integrated Crop Management Newsletter from Iowa State University

Soybean differs from corn in that as soon as the plant emerges the growing point is above ground and is extremely sensitive to adverse weather events such as hail or frost. In the case of hail, the plant is considered dead if it is in the cotyledon stage and is cut off below the cotyledons, or if it is damaged by hail to such a degree that they have no green leaf tissue or re-growth. The reason is that nutrients and food reserves in the cotyledons supply the needs of the young plant during emergence and for about seven to 10 days after emergence, or until about the V1 stage (one fully-developed trifoliolate leaf). Cotyledons are the first photosynthetic organs of the soybean seedling and are also major contributors for seedling growth. Unlike corn, whose growing point is below ground until it reaches V5-V6, the growing point for soybean is between the cotyledons and moves above the soil surface at emergence. This makes soybean particularly susceptible to damage from hail, frost, insects like bean leaf beetles, or anything that cuts the plant off below the cotyledons early in its life. Stand reductions are likely to follow hailstorms. After V1, photosynthesis by the developing leaves is adequate for the plant to sustain itself. It is important to remember that defoliation during the vegetative stages will seldom have a large impact on yield. However, it is a whole other story during the reproductive stages.