Agronomic Crop Insects – May 17, 2013

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Field Corn
Depending on the location in the state, we can find both cutworm and slug damage, mainly in no-till corn fields. Although we do not have pheromone traps out to monitor black cutworm moth populations, higher than normal populations are being reported in some areas of the Midwest as well as Pennsylvania. In past years, when populations were higher in the Midwest we have also seen a spike in damage. It is important to check all fields for cutworms, even where at planting treatments were used. The treatment threshold is 3% cut plants in spike to 3-leaf stage corn. In some cases you will need to check fields twice a week to be sure you do not miss an economic population. In addition to cut plants, be sure to watch for leaf feeding which can be an indication of the potential for significant cutting damage and yield loss.
http://www.ent.iastate.edu/imagegal/plantpath/corn/bcutworm/1287bwcholes.html

Small Grains
We continue to find armyworms and cereal leaf beetles in barley and wheat fields that were not treated. Population levels remain variable throughout the state, so scouting fields will be the only way to determine if an economic level is present. In addition, with the cooler spring we are seeing extended egg laying and hatch for both insects. Although armyworm can attack both wheat and barley, they can quickly cause significant losses in barley. Heavy defoliation of the flag leaf can result in significant economic loss. Armyworms generally begin head clipping when all vegetation is consumed and the last succulent part of the plant is the stem just below the grain head. Larvae can feed on the kernel tips of the wheat, resulting in premature ripening and lower test weight.

Soybeans
Seed corn maggot will be a potential problem in no-till soybeans, especially if the weather remains cool and wet. It could also be a problem in conventional soybeans where a cover crop is plowed under immediately before planting or where manure was applied. All of these situations are attractive to egg laying flies. Control options are limited to commercial applied seed treatments containing an insecticide and one hopper box material containing permethrin (Kernel Guard Supreme). Labels state early season protection against injury by seed corn maggot. No rescue treatments are available for this insect pest.

As the earliest beans emerge, be sure to watch carefully for slug damage. Remember, if you had a problem in past years, the slugs will still be present in fields and can quickly damage soybeans if they are feeding as plants emerge. You should also watch fields carefully for bean leaf beetles and grasshoppers.

Effect of Cereal Cover Crop Species on Full Season Soybean Performance

Robert Kratochvil, Extension Specialist – Grain and Oil Crops, University of Maryland; rkratoch@umd.edu

Does choice of cereal cover crop species affect full season soybean? Does cereal cover crop kill date matter? These are questions that soybean farmers are asking as Maryland cover crop acreage continues to increase.

To address these questions, three years of research was conducted by planting three cereal species (barley, wheat, and rye) as cover crops at the Wye Research and Education Center (fall 2009 and 2010) and Central Maryland R&E Center-Beltsville (fall 2010 and 2011). A no cover crop treatment (only fall-winter weed growth) also was included. Three (Wye) and two(Beltsville) cover crop spring kill dates that supported varying amounts of cover crop biomass production were used. The kill dates at Wye are defined as 1) extra early kill for only the rye and the no cover treatments (mid-late March during the two study years); and at both Wye and Beltsville 2) early kill date for all treatments (ranged from 13 April to 23 April); and 3) late kill date for all treatments (ranged from 2 May to 16 May). Soybean varieties Asgrow brand3539RR2 (mid-MG 3) and Asgrow brand 4630RR2 (mid-MG 4) were planted into all cover crop treatments between 2 and 3 weeks after the last kill date. Soybean harvest dates were considered normal ranging from 17 October to 3 November during the three years.

Approximately three weeks post-planting, stand emergence was assessed to see if the cover crop species or kill date treatments impacted stand establishment. Over the three year period, no emergence differences were observed indicating that neither choice of cereal cover crop nor spring kill date had a detrimental effect on soybean germination and emergence. The most important criterion when planting full season soybean into a cereal cover crop is attainment of good seed-soil contact.

Starting approximately mid-June each year, a weekly measurement of growth stage progression was done by randomly selecting 5 plants in each plot, determining the growth stage according to Fehr and Caviness (1971), and averaging the growth stage. The primary growth differences observed were associated with the two varieties. Both varieties progressed through vegetative growth similarly. The onset of reproductive growth always was observed for the earlier of the two varieties, as expected. The weekly readings continued until early-mid September. Occasionally, only very minor differences in growth stage progression for the soybeans were observed for either the cover crop species or the kill date treatments. These differences were inconsistent across the assessment dates and are considered to have no influence on soybean growth and performance.

Soybean yield (72 bu/acre average) was excellent during the three years. The most consistent yield difference observed was associated with variety, however there was no consistent trend favoring one over the other. At Wye, the MG 3 variety produced better than the 6 MG 4 variety during 2009-2010 and the opposite occurred during 2010-2011. During 2010-2011 at Beltsville, the MG 4 variety was best and during 2011-2012, there was no yield difference between the two.

Response of soybean yield performance to cover crop species and kill date varied by location. During the two years at the Wye, a cover crop species × (by) kill date interaction was observed. For the March kill date (extra early), soybeans planted into the no cover crop treatment produced 10% (2009-2010) and 4% (2010-2011) better than soybeans following rye.

For the 2010 April kill date (early), soybeans planted following any of the three cover crop species produced the same (62 bu/acre) but soybeans following the no cover treatment yielded nearly 10% more (68 bu/acre). In 2011, the April kill date produced no yield differences (~67.5 bu/acre average) among the four cover treatments.

For the two years the study was conducted at Beltsville, there was no cover crop species × kill date interaction during 2010-2011 but in 2011-2012 this interaction was significant. At Beltsville in 2010-2011, soybeans planted where cover crops were killed during April produced over 6% greater than soybeans following the May kill date. However during this study year, there were no differences in soybean yield associated with any of the cover crop treatments.

During 2011-2012, soybeans following either barley or wheat cover crop produced the same for the two kill dates. However, soybeans that followed either rye or the no cover crop treatment, produced approximately 12% greater following the May kill date. Based on three years of data collected in this study, answers to the two primary questions about soybean performance following cereal cover crops are:

1. Does choice of cereal cover crop species affect the performance of full season soybean?
The performance of full season soybean following a cereal cover crop cannot be predicted by the cereal species grown. Differences may occur but they will be associated with location and kill date.

2. Does cereal cover crop kill date influence soybean performance?
The optimum kill date for cereal cover crops followed by full season soybean is difficult to predict. Factors that can affect soybean performance for any particular kill date are location, year, weather, and variety.

Wheat Head Blight Update for Delaware

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

Updated on May 13, 2013

Disease models at http://www.wheatscab.psu.edu/ currently are listing much of Kent County and portions of Sussex County as being at high risk for FHB (See photo below).  Growers in these regions should consider applying appropriate fungicides (Prosaro, Caramba, Proline) if wheat is at early flowering (Feekes 10.5.1).  All growers should continue to monitor the growth stage of your wheat and the wheat scab modeling website to determine if and when fungicide applications may be needed.  See last week the article below for more information on FHB management.  

FHB13May2013

Original Article:
We are entering the period where outbreaks of Fusarium head blight are possible on winter wheat. This disease is caused by a fungus (predominantly Fusarium graminearum) that resides in crop residue (corn stalks, wheat straw, and other host plants). The fungus produces spores on this residue, which are dispersed by rain or wind to the flowering wheat. Once wheat is infected, wheat heads may become bleached (Figure 1) and pink to orange fungal growth may be seen at the base of diseased spikelets. The fungus also produces mycotoxins such as vomitoxin (aka: DON), which are toxic to humans and animals and can be present in infected wheat grain. In this article I will go over some important factors that impact head blight severity and discuss fungicide use to help suppress this disease.

Growers should consider applying fungicides to wheat if the environment favors disease and plants are in a susceptible growth stage. Over the past two weeks Delaware has experienced wet weather associated with persistent cool temperatures. The cool temperatures likely have slowed the development of Fusarium spores and the risk for severe head blight outbreaks. However, the risk for head blight will rise if moisture remains high (>90% RH) and temperatures increase. Optimal temperatures for head blight infection are between 59 and 86°F. I encourage all growers to visit the FHB Risk assessment tool at http://www.wheatscab.psu.edu to keep abreast of the blight risk in their area. As of May 7th, the forecasting model shows a small section of southeast Sussex County with moderate to high levels of head blight risk.

The severity of Fusarium head blight is not only impacted by weather, but also by the growth stage of the plant. Fusarium infections are most severe at flowering; consequently, this is when you should apply a fungicide. Fungicide treatments will be most effective if applied preventively at early flowering. A link to identifying this stage in wheat can be found at http://www.youtube.com/watch?v=7NJNE1wbVaU. Fungicides applied earlier or later will be ineffective at controlling this disease. In addition, fungicides applied before heading or at the flag leaf stage will not provide scab control. Even if timed properly and applied preventively, a fungicide may only result in approximately 50% disease control. However, the goal of a fungicide application is to reduce the impact of this disease on yield and to reduce mycotoxin levels in grain. Therefore, it is important that you choose the correct fungicides to maximize the benefit of the fungicide treatment.

headbleachingFigure 1. An example of head bleaching that may occur from infection by the Fusarium head blight/scab fungus.

What fungicides should you apply? The best fungicides for control of head scab belong to the triazole class of fungicides (Group 3), but they vary greatly in their level of activity. The two best products for wheat head scab control are Caramba™ (active ingredient: metaconazole) and Prosaro™ (active ingredients: prothioconazole+tebuconazole). Proline™ (active ingredient: prothioconazole) provides some control but often is not as effective as Prosaro™. Products containing only tebuconazole (e.g. Folicur™) have been used in the past to control head blight. However, research from The Ohio State University indicates that Caramba™ and Prosaro™ provide between 10 and 15% greater control of blight, and between 20 to 25% greater control of DON than Folicur™. The nice thing about Caramba™ and Prosaro™ is that they will also give you some control of Septoria/Stagonospora glume blotch, rust, and tan spot. Fungicides containing a strobilurin (group 11) should not be applied to heads or flowers because strobilurins may increase DON levels in grain. Examples of these products include Quadris™ Headline™ Stratego™ and Quilt™.

In closing, remember that fungicides are only one part of Fusarium blight management and work best when combined with other practices. There are several options that you have to proactively reduce the risk of head blight. These include using resistant wheat varieties, tilling, removing crop debris from the field, and spreading risk by planting several varieties at different dates. Even if these management practices are followed, head scab outbreaks are possible given the right environmental conditions. Visit the FHB risk assessment tool often and monitor the growth stage of your wheat to determine if and when a fungicide treatment is needed. I encourage growers to contact University of Delaware Extension personnel to assist with your wheat disease management needs. Additional information on Fusarium head blight management can be found at http://www.scabsmart.org/ and http://www.apsnet.org/edcenter/intropp/lessons/fungi/ascomycetes/Pages/Fusarium.aspx.

Agronomic Crop Insects – May 10, 2013

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Alfalfa
In general, alfalfa weevil populations have been higher in many fields this spring. For alfalfa over 16 inches tall, the threshold increases to 2.5 larvae per stem. Early harvest is often the best option once fields are greater than 16 inches tall and populations exceed 4 larvae per stem; however, there must be enough “stubble heat” after harvest for this technique to provide control. If populations were above threshold before cutting, be sure to check for alfalfa weevil adults and larvae within a week of cutting. Feeding from both stages can hold back re-growth. A stubble treatment will be needed if you find 2 or more weevils per stem and the population levels remain steady.

Field Corn
At this time, we can find both cutworms and slugs feeding in newly emerged corn fields. In addition to black cutworm, which generally attacks later planted corn, we can find a number of other cutworm species present in corn fields at planting time. They include the dingy cutworm, claybacked cutworm and variegated cutworm. Information from the Midwest indicates that the claybacked cutworms can cause economic loss in corn. They overwinter as half-grown larvae in the soil so they can get a “jump” on black cutworms when it comes to cutting each spring. Since they are larger in size, this species can damage very young corn plants. Scouting fields at plant emergence is important, even if at planting materials were used, to catch any potential problems. In addition, a higher rate of an insecticide will be needed to control larger cutworms. As a general guideline, a treatment is recommended if you find 10% leaf feeding or 3% cut plants. If cutworms are feeding below the soil surface, it will be important to treat as late in the day as possible, direct sprays to the base of the plants and use at least 30 gallons of water per acre. For cutworms, fields should be sampled through the 5-leaf stage for damage.

With the continued wet weather, we have seen an increase in slug damage on recently emerged corn. If slugs are damaging plants, you will be able to see “slime trails” on the leaves. Since corn was planted later this year and in many cases fields are just emerging, we could see more injury from slugs that have been hatching and beginning to grow. As indicated in previous newsletters, Deadline M-Ps is available for slug management this year in field corn. This is the only product that we have local experience with in regards to slug management in field corn. We continue to see very good control with Deadline MPs when applied at the 10 lb/A rate as long as you get good distribution of the product (5 pellets per square foot). The best control with the Deadline M-Ps has also been observed when applications were made and there was at least one day of sunny weather after an application. There are also a couple of other products available for slug management in field corn: Sluggo (iron phosphate) and IronFist (sodium ferric FDTA). At this point, we do not have local experience with these two products so will be evaluating them in replicated plots. We hope to get our first applications out today so we should have more information on their efficacy by next week. Please see the following link for comments from Ohio regarding slug management in field crops this season (http://corn.osu.edu/c.o.r.n.-newsletter#2).

Small Grains
Grass sawflies and true armyworms have been found in fields in Kent and Sussex counties. In addition, cereal leaf beetle adults have been found laying eggs and we are seeing the first larvae. Population levels remain variable throughout the state so scouting fields will be the only way to determine if an economic level is present. Depending on the temperature, cereal leaf beetle larvae will feed for up to 3 weeks. Research from Virginia and North Carolina indicates that the greatest damage can occur between flowering and the soft dough stage. Although armyworm can attack both wheat and barley, they can quickly cause significant losses in barley.

You will also need to watch for aphids feeding in the heads of small grains. With the continued cool wet weather and projection for cool weather again next week, populations could continue to increase and beneficial insects will have a hard time keeping up with populations. The treatment threshold is 20-25 aphids per head with low beneficial insect activity.

Black Light and Pheromone Trapping Program Has Begun for the Season

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Our black light and CEW pheromone traps are now up and running for the season. The traps are generally checked on Monday and Thursday and counts are posted by early Tuesday and Friday morning. This season we will be trapping for corn earworm, European corn borer and 3 stink bug species. Please use the following link to access all trap information: http://agdev.anr.udel.edu/trap/trap.php. In addition to the new look to the page; you will also see that we have added a new feature — historical information in both a tabular and graph format. Please try out the new feature and provide feedback to me on its usefulness. I will also begin the Crop Pest Hotline in mid-May (instate: 800- 345-7544; out of state: 302- 831-8851).

Agronomic Crop Insects – April 26, 2013

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Field Corn
As the first plants emerge, we often can see both cutworm and bird damage in the same field. In general, small cutworms feed on leaves before cutting plants. You can distinguish bird damage from cutworm damage by the pattern in the field. With bird damage, you generally see longer strips of damaged plants, plants pulled out of the ground, and/or plants cut high that are compressed at the base of the stems. Although birds can cut plants off at the soil surface, they tend to pull plants out of the ground. In addition, if you look closely you will see “bird prints” near the missing plants or holes where birds have pulled plants out of the ground. As a reminder, we do still have the 24(c) Special Local Needs Registration for Avipel Hopper Box (dry) Corn Seed Treatment for bird management on field corn in Delaware. The 24 (c) label should be on the pesticide canisters. If you need a copy of the label, please contact Dave Pyne at the Delaware Department of Agriculture.

Small Grains
In general, insect activity has been very low in barley and wheat. We have found a few barley fields with aphids moving in to the grain heads. With the current cooler weather, beneficial activity will lag behind increases in aphid populations. Once grain heads emerge, the treatment threshold for aphids is 20-25 per head. We continue to get questions about stink bugs and the damage potential in small grains. We can find low levels of native brown stink bug populations (not brown marmorated stink bugs) in barley and wheat. As indicated in last week’s newsletter, information from southern states indicates that wheat may be susceptible to native stink bug feeding at the milk and soft dough stages. They also state that it takes extremely high numbers to cause damage to heading wheat. Thresholds in the south for native stink bugs range from one per head to one per 5 to 10 heads. In addition, they find the highest populations of stink bugs along field edges, which has also been our experience.

Agronomic Crop Insects – April 19, 2013

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Alfalfa
As alfalfa approaches harvest, the decision to cut instead of treat should be considered as a management option for alfalfa weevil. However, this option should only be used if you plan to cut shortly after you find an economic threshold level of weevils, since damage can occur quickly. Cutting should only be considered as a management option if you can cut within 3- 5 days of finding an economic level. As you get close to harvest, be sure to check labels carefully for time between application and harvest.

Field Corn
Since corn has been planted in some locations for about a week now, be sure to check for cutworm feeding as soon as plants emerge, even if an at-planting insecticide or a Bt corn was used for cutworm control. Although conditions have not been extremely favorable for slugs, we are starting to see an increase in the number of slugs encountered under shingle traps in New Castle County. Once corn emerges, we generally see more problems when conditions remain cooler and soil remains wet. However, it is the generally during the warmer days of April to early May when we start to see significant egg hatch. Although no thresholds are available, past experience in the Mid-Atlantic has indicated that levels of five or more grey garden slugs per square foot have indicated the potential for a problem. As a reminder, Deadline MPs are still available for use in corn and soybeans in 2013.

Small Grains
In barley fields where the heads have emerged, be sure to sample for grass sawfly and armyworm larvae. As indicated last week, we generally see significant outbreaks in years when armyworm larvae are a result of populations coming from a combination of local overwintering populations and migrating moths. Looking at this week’s report from Kentucky, their traps have only caught a few moths but the current year’s capture is in line with the outbreak year of 2008. It is still too early to tell what will happen but it is important to be aware of trap catches in southern states. We will be putting out our traps next week and the first counts will be available by April 30. Remember, armyworm larvae are nocturnal so look for larvae at the base of the plants during the day. As a general guideline, a treatment should be considered if you find one armyworm per foot of row for barley and 1-2 per foot of row for wheat. Since sawflies feed on the plants during the day, small sawfly larvae can often be detected early using a sweep net. However, there is no threshold for sweep net samples. Once sawfly larvae are detected, sample for larvae in 5 foot of row innerspace in 5-10 locations in a field to make a treatment decision. You will need to shake the plants to dislodge sawfly larvae that feed on the plants during the day. As a guideline, a treatment should be applied when you find 2 larvae per 5 foot of row innerspace or 0.4 larvae per foot of row. If armyworms and sawflies are present in the same field, the threshold for each should be reduced by one-half. The higher rates of insecticides are needed for grass sawfly control.

We have started to hear reports of an increase in brown stink bugs in states to our south and each year we get questions about the potential for damage to small grains in our area. In past years, the only species we have seen is the native brown stink bug, very few brown marmorated stink bugs have been encountered. Although information from the south indicates that stink bugs can damage wheat, they also indicated that it only occurs when you find very high numbers. Thresholds used for treatment in some southern states are as high as two stink bugs per ten grain heads. The threshold used in North Carolina is one per ten grain heads. Stink bugs feed on the developing tissue and will damage wheat as the grain is filling. The milk and dough stages are known to be especially susceptible to damage resulting in yield loss.

Besiege – (Syngenta) – It was recently announced that Besiege received a label for use in soybeans. It is a combination of two active ingredients (lambda-cyhalothrin and chlorantraniliprole). Here is a link to the new label: http://www.cdms.net/LDat/ldA7G011.pdf.

Agronomic Crop Insects – April 12, 2013

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Alfalfa
Continue to scout fields for both alfalfa weevil and pea aphids. Under dry weather conditions, you may need to reduce the following thresholds, especially when both insects are present in a field. As a general guideline, you should consider a treatment in alfalfa less than 10 inches tall if you find 40-50 aphids per stem. The treatment threshold for alfalfa 10 inches or taller in height is 75- 100 per stem. Beneficial insects can help to crash aphid populations and as a general rule, you need one beneficial insect per every 50-100 aphids to help crash populations. For alfalfa weevil, the following thresholds, based on the height of the alfalfa, should be used as a guideline when making a treatment decision: up to 11 inches tall – 0.7 per stem; 12 inches tall – 1.0 per stem; 13 – 15 inches tall – 1.5 per stem; 16 inches tall – 2.0 per stem; 17 – 18 inches tall – 2.5 per stem.

Small Grains
It appears that we could see head emergence in some barley fields by next week. Once grain heads have emerged, you should begin sampling for grass sawfly and armyworm larvae. Although we can see economic damage from local overwintering armyworm populations, we often see significant outbreaks in years when moths coming from the south migrate to our area. You can look at the following link from Kentucky that compares their moth flights this year compared to 2006 & 2008 – which they consider outbreak years. (http://www.uky.edu/Ag/IPMPrinceton/counts/taw/tawgraph.htm ). Currently moth populations are low in their traps but this week of warm weather could cause a significant increase in moth activity. Armyworm larvae are nocturnal so look for larvae at the base of the plants during the day. As a general guideline, a treatment should be considered if you find one armyworm per foot of row for barley and 1-2 per foot of row for wheat. Although armyworms initially feed in lower canopy on the leaves, under drought conditions we could see them quickly moving to the heads. In addition, barley is more susceptible to damage and early head clipping so be sure to scout carefully for armyworm. Since sawflies feed on the plants during the day, small sawfly larvae can often be detected early using a sweep net. However, there is no threshold for sweep net samples. Once sawfly larvae are detected, sample for larvae in 5 foot of row inner space in 5-10 locations in a field to make a treatment decision. You will need to shake the plants to dislodge sawfly larvae that feed on the plants during the day. As a guideline, a treatment should be applied when you find 2 larvae per 5 foot of row inner space or 0.4 larvae per foot of row. If armyworms and sawflies are present in the same field, the threshold for each should be reduced by one-half. The higher rates of insecticides are needed for grass sawfly control.

Continue to watch for winter grain mite activity in no-till wheat fields, especially in fields planted into corn stubble. Although the current summer-like conditions are not favorable for this mite, the predicted cooler temperatures this weekend are favorable for increases in populations. Remember that these mites do not cause the yellowing characteristic of spider mite feeding. Heavily infested fields appear grayish or silvery, a result of the removal of plant chlorophyll by mite feeding. When high infestations feed on the plants for several days, the tips of the leaves exhibit a scorched appearance and then turn brown. Many of the infested plants do not die, but become stunted and produce little forage or grain; damage on young plants, however, is more severe than on large, healthy ones. Damage may also be greater in plants stressed by nutrient deficiencies or drought conditions. Heavy spring infestation can result in reduced yields, so be sure to check for mites if fields appear off color.

Timothy
Cereal rust mites remain active in fields so if you have not checked for this pest, be sure to sample all fields. Symptoms can appear as retarded growth, leaf curling, stunting, and plant discoloration. Injured plants appear to be drought stressed even when adequate moisture is available for plant growth. There are no established economic thresholds for the pest; however, treatment is recommended in fields with a previous history of cereal rust mites and/or when 25% of the plant tillers exhibit curled tips of the new leaf blades within several weeks following green-up. The use of a 20x-magnifying lens is often necessary to find mites on leaves. The only effective and labeled material on timothy is Sevin XLR Plus. Be sure to read the label for information on the number of applications per season as well as the days to harvest. For effective rust mite control, the use of the higher labeled rate and at least 25 gal/acre of carrier to get good coverage of leaf surfaces generally results in better control.

Agronomic Crop Insects – April 5, 2013

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Alfalfa
Be sure to watch for an increase in pea aphid and alfalfa weevil populations. When sampling for aphids and weevils, collect a minimum of 30 random stems throughout a field and place them top first in a white bucket. For aphids, you want to count the number present per plant as well as any that have dislodged from the stem into the bucket. As a general guideline, you should consider a treatment in alfalfa less than 10 inches tall if you find 40-50 aphids per stem. The treatment threshold for alfalfa 10 inches or taller in height is 75-100 per stem. Although beneficial insects can help to crash aphid populations, the recent cool temperatures has slowed their activity. As a general rule, you need one beneficial insect per every 50-100 aphids to help crash populations. For alfalfa weevil, you will want to record the number of weevil larvae per stem. The following thresholds, based on the height of the alfalfa, should be used as a guideline when making a treatment decision: up to 11 inches tall – 0.7 per stem; 12 inches tall – 1.0 per stem; 13–15 inches tall – 1.5 per stem; 16 inches tall – 2.0 per stem and 17–18 inches tall – 2.5 per stem.

Field Corn
As a result of the cool spring temperatures, we have not seen the early slug egg hatch that we saw in 2012. However, with the predicted warm weather next week we will start to see an increase in egg hatch. Two new videos on slug management in field corn and soybean were posted in Plant Management Network News. These videos provide a good review of slug biology and management and can be accessed at

http://www.plantmanagementnetwork.org/edcenter/seminars/soybean/SlugManagementSoybean/
and http://www.plantmanagementnetwork.org/edcenter/seminars/corn/slugmanagementcorn/

Small Grains
We have had a few reports of winter grain mites being found in no-till small grains fields. The second generation develops from eggs laid by the first generation, and populations peak in March and April. Adult and immature mites feed on the plant’s chlorophyll giving plants silver or frosted appearance. Severe feeding may result in dead or stunted plants, and it has the potential to significantly reduce yield. Young plants are more susceptible to the feeding damage than older, more robust plants. Plants that are either drought stressed or nutrient deficient also exhibit more severe feeding damage than unstressed plants. More information on identification, sampling and management can be found at the following link: http://extension.udel.edu/factsheet/winter-grain-mite-management-in-small-grains/

Timothy
Be sure to watch for an increase in cereal rust mites which are favored by cool temperatures. Symptoms can appear as retarded growth, leaf curling, stunting, and plant discoloration. Injured plants appear to be drought stressed even when adequate moisture is available for plant growth. There are no established economic thresholds for the pest; however, treatment is recommended in fields with a previous history of cereal rust mites and/or when 25% of the plant tillers exhibit curled tips of the new leaf blades within several weeks following green-up. The use of a 20x-magnifying lens is often necessary to find mites on leaves. The only effective and labeled material on timothy is Sevin XLR Plus. Be sure to read the label for information on the number of applications per season as well as the days to harvest. For effective rust mite control, the use of the higher labeled rate and at least 25 gal/acre of carrier to get good coverage of leaf surfaces generally results in better control.

http://extension.udel.edu/factsheet/cereal-rust-mite-in-timothy/