Agronomic Recommendations

Wayne County IPM Notes from the Week of June 1- June 4

Agronomic Crops

Emerging soybeans in a no-till field.

Corn and soybeans are emerging and beginning to progress through early vegetative stages. Within the next week or so we will begin doing stand counts and encourage you to do the same. We will also keep an eye out for early season insect and pest problems such as slug damage and bean leaf beetle feeding in soybeans as well as slug feeding, cut worm damage and flea beetle activity in field corn.

In alfalfa most of the fields we are scouting are now in regrowth after first cutting. These second cutting fields have very limited pressure from weevil larvae and overall are relatively problem free. In the coming weeks, we need to be alert with regard to the potato leaf hopper. According to the most recent C.O.R.N. newsletter, potato leaf hoppers are now being found in Ohio alfalfa fields. We plan on starting with sweep net counts this week to determine current populations of PLH in our area fields.

Vegetable Crops

Cucumber beetle feeding on the foliage of a summer squash plant.

Insects continue to be the main headline in the vegetable crops in our area. Of greatest concern is the cucumber beetle. The populations continue to increase in number and the efficacy of seed treatments or in-furrow applied insecticide starts to decline 4-6 weeks after the seed germinates or after the insecticide is applied. This means that more of the beetles are feeding without being affected by the insecticide. Be sure to scout cucurbit crops frequently and carefully to get accurate counts of the beetles. The thresholds for cucumber beetles are as follows: Cotyledon stage – .5 beetles per plant, 2-4 leaf stage – 1 beetle per plant, greater than 4 leaves – 3 beetles per plant. Limiting the amount of feeding that cucumber beetles do will also limit the amount of bacterial wilt occurring in these plantings. Do be cognizant of the plants that are in bloom and limit your spraying to a time when it will be least impactful on the pollinators.

 

Colorado potato beetle larva feeding on a potato plant. Tommy Becker photo.

Other insects that were spotted this week include Colorado Potato Beetle larvae and imported cabbage worms. Both of these pests can cause significant damage in their respective crops when left unchecked. Flea beetles also continue to feed on plantings of cole crops, preferring young transplants versus older, more established plantings, although both should be inspected for beetles.

Sweet corn plantings are growing quickly and some plantings that were done into plastic mulch and covered this spring already have a few tassels poking out. Overall, there has been no major concerns in the sweet corn plantings so far, however, do your best to keep up on weed control. Weeds such as bindweed, thistle, and ragweed can not only compete for resources, but can also make harvest difficult and may serve as refuge locations for insect pests to retreat to.

Small Fruit and Orchards

We are beginning to enter a critical period for managing diseases in grapes. This period, which extends from immediate pre-bloom through four to five weeks post bloom, is a critical time to control fruit infections by the pathogens which cause black rot, powdery mildew, and downy mildew. According to the 2021-2022 Midwest Fruit Pest Management Guide, the fruit of the most commonly planted varieties becomes resistant to infection by these diseases by four to five weeks after bloom.

In strawberry plantings we are seeing a lot of green fruit and in some locations, harvest is beginning to ramp up. Overall, there have been very few concerns in the

Blueberries starting to enter the “fruit coloring” stage.

strawberries to this point, with just a few slugs here and there and a spotting of powdery mildew on a few plants. Powdery mildew is managed by spraying either pre-bloom or during the early bloom through bloom stage.

Other small fruit like blueberries and brambles look to have a heavy fruit set this year. Blueberries are beginning to get some color to them, and the blackberry and raspberries are either in bloom or in fruit development.

In apple and peach orchards, the fruit are noticeably starting to increase in size. We are finding some aphids in apple trees, feeding on the leaves and new shoots. In peaches, we did find a few instances of powdery mildew affecting the fruit. Trap counts for OFM and CM were under threshold in all of our traps this week. The counts are down after last week with several orchards above threshold for CM and OFM counts.

Wayne County IPM Notes from the Week of May 17th – May 21st, 2021

Agronomic Crops

Cut alfalfa field in Wayne County.

The weather was very cooperative this week and a lot of forages were cut, and field conditions were right to either get fields ready to plant or start to get seeds in the ground.

In the interest of alfalfa growers, we have been paying close attention to the alfalfa weevil larvae and their development. The weevil larvae are forming cocoons and pupating.  Typically, we only experience a single generation of alfalfa weevil per season, however, given the early development and continuation of above average temperature, there is the chance of seeing a fairly substantial 2nd generation. This is problematic for a few reasons. First off, if we continue to see hot and dry conditions, that in itself will stunt regrowth on cut alfalfa. Additional feeding by young 2nd gen weevil larvae on stressed alfalfa regrowth can either severely delay 2nd cutting or if the infestation is significant enough, total loss of 2nd cutting.  Typically, by this point in the year, we begin to move on from alfalfa weevil scouting and turn our attention to the Potato Leaf Hopper, however, this year we may be dealing with both at the same time.

We are not yet scouting any corn or soybeans; however, we expect that we will begin to see more of those acres planted and have relatively rapid germination due to increasing soil temperatures. A few timely rains can help to push these crops germination as well. Soil temperature and GDD Accumulation

Vegetable Crops

             As we move into warmer temperatures, it would be best to remove row covers from field planted crops in the interest of pollination and reducing heat stress. In crops that do not need pollinated such as cole crops, the row cover can serve as an insect barrier and prevent early infestation from the Imported Cabbageworm. Crops such as summer squash, cucumbers and tomatoes

Flea beetles feeding on a recently transplanted brassica plant.

all need to be uncovered sooner than later to avoid poor pollination and subsequently, poor fruit set.

Hot weather can also be problematic when transplanting into black plastic. The black plastic can become very hot and planting a young, tender transplant into the plastic on a hot, sunny day can cause a significant amount of stress, burns on the leaves and stems and in some cases, death of the transplant. Try to plant in the evenings, as temperatures cool down or on cloudy, cooler days.

Colorado Potato Beetle adults on a potato plant.

In the last week we have seen an explosion of flea beetle in cole crops, and the Colorado potato beetles have begun to make their way into potato plantings. Frequent scouting and monitoring of these insect pests is extremely important. Large populations on young plants can stunt their growth and reduce yields. Conditions have been ideal for rapid population increases, hence the need for frequent scouting. An interesting insect problem we observed was a planting of cole crops where the roots of some plants were being destroyed by ants. In most cases, as you turn on your irrigation lines under plastic, it will drive the ants elsewhere.

Generally speaking, disease pressure has been very low in vegetable crops to this point. We have observed some early blight in a tomato high tunnel, as well as blossom end rot in high tunnel tomatoes.

Small Fruit and Orchards

            Apples and peaches are both reaching fruit development. There was significant growth and change in the size of the fruit over the past week. Out of all of

Strawberry blooms with black centers, damaged by freezing temperatures, alongside healthy blooms.

the orchard traps that we have out, we caught 1 OFM and 1 CM. We began to find aphids in apple orchards. The feeding was evident by curling leaves and shoots.

Blueberries are in petal fall and are setting fruit. Raspberries are getting ready to bloom and overall seem to be coming along just fine.

 

Grape bud that had been damaged due to freezing temperatures now showing secondary growth. Tommy Becker photo.

Strawberry varieties that were early to bloom, and left uncovered, likely suffered heavy bloom loss due to the freezing temperatures that we experienced. Some early blooming varieties had very few, if any, healthy looking blooms. Many plants have put on new blooms, which are very easy to distinguish from the frosted blooms. Early varieties of plasticulutre strawberries that were covered and protected from the cold are setting fruit and beginning to ripen and may even be in harvest. We are not finding any thrips at this time. Unfortunately, we are finding a lot of slugs in strawberry plants and on the berries.

Currently, grapes are now past the bud burst stage, as most are at the 4-8” shoot stage.  We are beginning to see where grape buds that had been damaged due to freezing temperatures are putting out secondary buds and shoot growth, which is very promising.

Wayne County IPM Notes, May 3-7, 2021

Agronomic Crops

Mycelial growth on the crown of an alfalfa plant due to infection by Sclerotinia Crown Rot.

Generally speaking, the crop that we are most interested in at this point of the year is alfalfa. The corn and soybeans may have been planted, and in some areas, may be starting to emerge. The main concern in alfalfa in terms of insect pests is the alfalfa weevil. This year, it is especially problematic due to increased GDD accumulation. The early warm temperatures pushed us to about two weeks ahead of where we were last year in terms of our accumulated heat units. This is reflected in the progression of the alfalfa weevil, not only in size, but in number. Most fields were not over threshold, but certainly showed weevil damage and the weevils that were feeding ranged from 1st to 3rd instar.

While scouting alfalfa fields, its important to inspect the entire plant. The prolonged cool and wet weather that we have been experiencing has been perfect for development of Sclerotinia crown and stem rot in alfalfa and clover fields. It can be easy to confuse this disease as winter kill, but further inspection of the plant, especially near the crown can reveal white, mycelial, cotton like growth. You may also find sclerotia in or on the stems and crown. Once the weather warms up and fields dry out, this disease will likely stop progressing, and some infected stands may recover and produce sufficient yields in subsequent years. Keep in mind that those sclerotia will remain in the soil for many years waiting for perfect conditions to start the disease cycle again.

Vegetable Crops

            With the cold temperatures extending into our early growing season many growers with high tunnels are using heat sources such as wood burners and gas stoves to keep their high tunnels warm. If you are doing this, please make sure your vents are clear and that all of the exhaust, fumes and smoke are making their way out of the tunnel. Double check to make sure chimney pipes are snug and the joints are not loose. Plants, especially tomatoes, are very sensitive to ethylene gas, a by-product of burning and when the smoke or fumes from the stoves are making it back into the tunnel, the plants are exposed to the ethylene for prolonged periods of time. Plants exposed to ethylene will show signs of epinasty, or a downward spiral of shoots and curling leaves, as well as blossom abortion.

Epinasty in tomato due to ethylene exposure.

Other than vegetables in high tunnels, some cole crops and lettuce are planted. Onions and fall planted garlic are also handling this cool wet weather with relative ease. As a word of caution, wet soils and cold temperatures do not equate to great growing conditions for both transplants and direct seeded crops. Some crops handle it much better than others. For crops like summer squash, peppers, and tomatoes, it would be wise to hold off for a bit longer be fore attempting to get them in the ground.

Small Fruit and Orchards

            Apples are at petal fall. Peaches are at petal fall and, in some cases, shuck split. No CM or OFM concerns at this point in the orchards. We did observe some frost or freeze damage on some apple blossoms, but there are more than enough healthy blossoms to cover any loss from the freeze that occurred.

Blueberries are in full bloom and have no concerns at this time.

 

Strawberry bloom with a dark center. The dark center is the dead part of the bloom that would grow into the berry.

Strawberry varieties that were early to bloom, and left uncovered, likely suffered heavy bloom loss due to the freezing temperatures that we experienced. Some early blooming varieties had very few, if any, healthy looking blooms. They will still put on new blooms, but do not expect large yields from early season strawberries.

Grapes also experienced some damage due to the cold temperatures. Currently, grapes are around the bud burst stage. Some buds that were exposed to the cold have died; others look damaged. In another week or so, we will be better able to tell the extent of the damage that occurred to the grapes.

Winter Injury to Forages, Wheat and Rye

Ohio is no stranger to a wide range of fluctuating winter conditions. After the recent spell of cold and snow in Ohio, we are now looking ahead to rain and warmer temperatures. While this relief from the winter elements may be appreciated by many, this flip of conditions can result in some challenges with our over wintering grain and forage crops.

Dennis Pennington, a wheat system specialist from Michigan State University shares some of the details on why crops such as wheat need the cold weather and why the break in cold temperatures can cause problems.

Pennington, on wheat states, “Winter wheat goes through a vernalization period where the plant hardens and adjusts to the colder winter temperatures. The hardening off period begins in the fall once temperatures at the crown (growing point, generally placed about 1-2 inches below ground surface level) drop below 48 F and continues as the temperature decreases. The hardening process causes a reduction in moisture content in the cells of the crown which slows growth processes and the accumulation of soluble carbohydrates, all of which help the plant to resist frost damage.”

Dennis goes on to discuss the hardening process, as he states, “The hardening process takes place over four to eight weeks and the level of hardiness is directly related to the soil temperature at the crown depth. Daylength also impacts hardiness, as shortening days in the fall induce wheat winter hardiness. Conversely, longer days in spring bring wheat out of hardiness. Cold tolerance is dynamic and can be lost if soil temperatures rise above the previous temperature that the plant hardened to. According to a study by D.B. Fowler from the University of Saskatchewan in 1982, if the crowns of the plants are exposed to warmer temperatures for as little as 50 hours, the cold hardiness can be decreased substantially. The loss of cold tolerance has several major implications.”

Winter wheat greening up in the spring. Some tip die-back is visible in this photo.

The two major implications that Pennington describes in his article are the following: First, if soil temperature decreases below the current level of winter hardiness, injury will occur. Secondly, once a crop loses winter hardiness, it will never reach the original level of hardiness and it will de-harden more quickly each time the soil temperature rises above the minimum survival temperature.

As pointed out by Pennington in his article, what you want to see is a steady line in the temperature, without large spikes in either direction. Whenever the temperature spikes up followed by a spike down below the original temperature, injury can occur.

Generally speaking, when looking at the crops that are over-wintering in the fields, snow melt can be a concern. Obviously, warm weather causes the snow to melt. Snow, however, serves as an insulator and can protect the crowns of plants against major swings in air temperature. Snow melting can also result in ponding in the fields. In cases where drainage is adequate, there should be little to no concerns, but where water persists, evident by ponding or high levels of field saturation, waterlogging may occur. Additionally, if the water persists, the crowns may absorb more water, which could be problematic should conditions become cold again as it would result in cell rupture when the water in the plant freezes and expands. Ice damage can also occur in areas where standing water freezes over dormant plants for an extended period of time, essentially suffocating them. There is really a wide range of problems that can occur when we have a significant amount of snow the melts off before we are safely out of reach of winters grasp.

An example of how far an alfalfa plant can be heaved out of the ground via several rounds of freeze/thaw cycles.

Another concern, especially in forages, is heaving. Now that the ground is exposed, should we get back into a freeze/thaw pattern, heaving could occur. Heaving occurrence can increase significantly in areas of fields where there is a lot of moisture, and with the recent snow melt, there are a lot of fields with excess moisture.

Getting closer to spring, these issues may not be anything to worry about, but certainly something to be aware of. Worrying about temperatures will do nothing to change them, and this area of crop production is unfortunately out of our hands but being aware of these concerns can help you assess damages should any occur. Getting out to scout alfalfa, wheat and rye fields in the spring is recommended, not only this year, but every year. Evaluating your fields as early as you can in the spring can help you make efficient and impactful management decisions and consequently, take action if warranted.

Snow and Freezing Temperatures Bring Harvest Challenges in Agronomic Crops

Although it is not necessarily a common issue that we tend to worry about in this area, it does happen; that issue being snow accumulation occurring before crops are harvested. Obviously, this is not a new issue for those who may be dealing with snow covered crops but let this serve as a reminder of some considerations for harvesting crops this time of year.

One of the most important drawbacks of harvesting a crop this far past prime harvest season is that there will be a yield reduction. A study was done by the University of Wisconsin on the average yield loss in corn, when left in the field through winter. The study was reported on a monthly basis and showed that corn that was left in the field until January or February averaged a yield loss of 35%, per month. Now there are a few factors to consider for yield loss. One of the major factors is lodging. Lodging, or breakage of the stalk below the ear or pod, results in harvesting difficulties, pest, and disease problems, as well as grain loss due to ear or pod drop. Another factor resulting in yield reduction is the grain getting wet and then freezing. Repeated freezing and thawing can be problematic, especially in soybeans. Soybeans are prone to pod split and seed shatter. In corn, the wet husks can stick to the ear, leading to mold concerns and difficulty cleaning the grain properly. Additionally, leaving the grain out in the field leaves it open to wildlife feeding. Wildlife feeding, along with the other mentioned yield reducing factors compounded together can lead to significant yield losses.

Asides from yield loss, another issue that comes up when harvesting grain this time of year is the stress it can put on the equipment. It is important to get the combine settings right when harvesting frozen grain. It is also important to take care of preventative maintenance, as well as fixing appropriate repairs before running the combine through a frozen field. Combines can run in those conditions but running through a frozen and snowy field is not the easiest on them when looking at wear and tear.

Another important factor to consider is the soil. When you run a combine and a grain cart over wet, cold soil, compaction and rutting will happen. It is best to be patient and wait for a time when either the soil is frozen enough to be on, or the soil is dry enough to reduce compaction chances. The more likely of those situations is the soil freezing, as rarely do we have dry soils in the winter. Compacting and rutting the soil will result in problems for many years down the road. Out of all of the other impacts of winter grain harvest, the impact on the soil should be the one that you give the most consideration to. Severe compaction of your soil, as a result of attempts to harvest a corn or soybean field, likely with large yield losses already, can really hurt the productivity of the soil.

There is a choice to be made: try to salvage what yield you can this year by getting out in rough field conditions or wait for the ground to freeze and then harvest the crop, with minimal impact on the soil. Be patient and be willing to wait for the right conditions to get grain harvested and be willing to accept the hit on yield. Yes, a hit on yield is never easy to take, but a hit on long term field productivity is an even harder hit. Obviously, the situation calls for you to choose between the lesser of the evils, so while it may be something you have to deal with this year, have it in mind to do what you need to do to avoid the situation in the future.

Field Management Considerations Post-Harvest

As crops are being harvested, and fields are being prepped for the winter, there are several field management decisions that need to be considered. It is important to note that there is no singular correct management plan. Different approaches to field management will fit some farms better than others, it all depends on the goals you have set for your farm based on your management strategies.

Dealing with residue in the fall will help to avoid issues in the spring. Some issues that are encountered in spring while planting include attaining good seed-soil contact or disease issues due to a field not drying out. Another issue that can arise from improperly managed residue is large populations of slugs that can decimate young seedlings. Sanitation of the field and intensive management of residue can help to break up insect pest life cycles as well as disease cycles.

Residue management is a major aspect of post-harvest field treatment. The residue that we are concerned with is the chaff and stalks that are left after grain harvest. There are two ways to look at this residue. On one hand, the residue can act as a mulch that lessens the impact of rain falling on the soil, lessen the amount of erosion, help to retain soil moisture, and add organic matter and nutrients back into the soil. On the other hand, residue can help to over winter problematic insects, act as inoculum for diseases and slow soils from warming up and drying out in the spring.

The decision on how to manage residue comes out of your tillage and field management plans. In a no till or conservation tillage system, residue is considered more of a benefit to the field and left mostly as is. In a more intensive tillage system, residue is incorporated and broken up to influence a more rapid breakdown. There are benefits, as well as drawbacks, to both of these systems.

In an approach focused on conserving the residue, as previously stated, there are several benefits when looking at soil health and soil management. Conversely, the risk for insects to over winter and for diseases to carry over is also greatly increased. If there are fields on your farm with histories of diseases or insect problems, consider looking at how you have been managing the crop residue. If you would like to maintain your current conservation tillage systems, but reduce the risk of disease and insect infestations, using different tillage tools, such as vertical tillage, may be of interest to you. Using a vertical tillage tool serves several purposes. One is that it helps to chop up and spread out the crop residue. These tillage implements also often kick the soil up in a way that covers up a considerable percentage of the residue. This is important because covering the residue with soil will help to increase the rate at which decomposition occurs.

This approach, aimed more towards conservation tillage, may be of interest to those who have been involved with more intensive tillage. Intensive tillage and turning of the soil certainly results in a faster breakdown of crop residue. However, this tillage system leaves more soil exposed and can result in more wind and water erosion. Finding a system that can appropriately manage the crop residue while also maintaining some form of soil structure and improving soil health, will not only help the crops from year to year, but will also increase the sustainability and productivity of your soil.

Integrated Pest Management Considerations for Stored Grain Crops

Integrated pest management of a crop should not stop after it has left the field. The last thing that you want to have happen is for a crop, that you worked hard all summer to get to harvest, to be lost due to poor management while it is being stored in the bin. It is important to realize that storage of grains will not improve the quality of the grain. The quality of the grain will be at its best immediately after harvest. The goal of bin storage is to protect and maintain that quality.

Before putting grain in the bin, there are several steps that you should take to prepare the bin for new grain. One of the most important steps to take is to thoroughly clean the bin to remove any old, previously stored material from all components of the grain bin system. This includes the augers, fans, and the bins themselves. If you can tell what grain was last stored in the bin, it still is not clean enough.

While cleaning the bin, take time to make sure that the bin is sealed correctly and that the seals are not failing. A common area for a seal failure to cause damage is at the base of the bin where the bin rests on its cement base. This area is just one spot where moisture can enter the bin and cause significant spoilage. Also make sure to check the seals around doors and hatches. Screens should also be in place on roof vents to prevent larger animals from entering the bins. Aside from keeping a grain bin dry, keeping it sealed appropriately will also prevent the entry of insects, birds, and rodents.

Grain bin sanitation should also extend to the areas around the outside of the bin. At a minimum, at least 10-15 feet around the outside of the bin should be kept clean. This includes keeping it mowed and cleaning up spilled grain. Leaving favorable habitat and a food source intact that close to the bin is essentially creating a refuge for many of these pests. Not doing anything to prevent this is asking for trouble. Keeping this area cleaned up and maintained will prevent pest populations from building up within such a close proximity to your bin.

Some common insect pests that are found in grain bins include: flat grain beetles, saw-toothed grain beetles, red flour beetles, and Indian meal moths, just to name a few. The challenge with these insects is that they, as well as their eggs and larva can be harbored in old debris and grain remnants, hence why bin sanitation is so important. There are several preventative insecticides that can be added to the grain while putting it in the bin, as well as preventative products that can be added as a top dress after the bin is full. Fumigation, although not used as frequently as it once was, is also an option for insect management. As with any pesticide, the label is the law. Make sure to read and follow the label and use as directed.

Management of the bin while there is grain being stored is also important when considering pest management and grain quality control. Aeration will help to keep grain dry as well as disturb insects that may have made their way into the bin. Temperature monitoring is another way to manage grain quality, both from moisture and insect management perspectives. Keeping the grain bin at the appropriate temperature will prevent moisture from being drawn into the bin. It can also slow down or altogether prevent insect life cycles from repeating. Insects typically require certain amounts of heat units to progress from one life stage to the next, and if that can be slowed down or prevented, this lessens the need for chemical treatments.

It is important to realize that relying only on chemical options for insect management can be ineffective and costly. Without implementation of other integrated pest management strategies, chemical treatments are going to hurt your bottom line. It is essential to work strongly on the prevention aspects of grain bin pest management, rather than focus all your time, money, and effort on the reactive treatments. An ounce of prevention is worth its weight in gold by the time you are ready to move the grain out of the bin. Employing integrated pest management strategies into your grain storage systems can result in cost savings, from less reliance on chemical treatment, and better overall product quality.

Potato Leaf Hopper in Alfalfa

Alfalfa growers should be keeping an eye on the populations of Potato Leaf Hoppers in their fields. On the most recent C.O.R.N. (Crop Observation and Recommendation Network) call, it was shared that around the state there are very active populations of PLH. In several cases it was shared that PLH levels were reaching more than double the action threshold. The threshold for 20+ inch alfalfa is 20 PLH and levels were seen as high as 50-60 PLH per 10 sweeps. Even for alfalfa with a high tolerance to stress from PLH feeding, these elevated PLH population levels will almost certainly result in a yield reduction. This yield reduction can not only impact the current stand, but the stress of heavy PLH feeding may result in a yield loss in subsequent cuttings. Management of the PLH can be broken down into three strategies: growing PLH resistant or tolerant varieties, harvesting at an appropriate time to limit population growth, and if warranted, a rescue insecticide treatment.

In the PLH Fact Sheet written by Ron Hammond, Andy Michel, James Eisley and Mark Sulc, attention is brought to considering the economics of deciding whether a treatment would be justified. “The economic value of an alfalfa stand is also a key factor in a treatment decision. Treatment of a 1st or 2nd year stand of alfalfa may be justified, whereas treatment of an older, thinner alfalfa stand may not be warranted unless the PLH infestation is very heavy. In the case of a new alfalfa seeding, treatment may be warranted for marginal infestations of PLH to insure stand establishment.”

Action threshold table from the PLH Factsheet

 

-Frank Becker, IPM Program Coordinator, OSU Extension Wayne County