Posts Tagged ‘Hessian fly’

Thoughts on Planting Soft Red Winter Wheat Early

Friday, September 14th, 2012

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

With corn harvest proceeding much earlier than in ‘normal’ years, many growers could be considering whether to go ahead and plant their wheat or barley crop in the next few weeks. The recommended or suggested planting date varies from county to county based on the Hessian fly-free date. (For more information on Hessian fly see the article by Joanne Whalen “Agronomic Crop Insects – September 7, 2012” in issue 20:25 of the Weekly Crop Update) The fly free dates are Oct. 3 for New Castle County, Oct. 8 for Kent County, and Oct. 10 for Sussex County.

For barley, we have conducted planting date studies in Sussex County comparing early-planted (September 26) barley with a close to suggested planting date (October 7). Our results indicated a fairly consistent 5 percent reduction in yield with September planted barley as compared with the October 7 planting date. Winter weather in the years the study was conducted did not result in significant visual winter injury to the barley so the impact appeared to be more of a general nature. Barley planting was dramatically affected by late planting unlike wheat. Delaying barley planting by just one week to October 15 resulted in a (four year average) yield reduction of over 15 percent and delaying two weeks to October 25 resulted in an over 20 percent yield reduction. Delaying planting barley until November increased the yield potential reduction to over 40 percent.

For winter wheat, experience has to be our guide with respect to planting date. We have evaluated the ideal planting date versus later planting dates but not against a September planting date for wheat. However, we can use both past experiences and basic agronomic knowledge to evaluate the risk involved with early planting wheat.

Since September planting dates are before the Hessian fly-free date for all our counties, we can surmise that the risk of lodging during grain fill will be increased versus planting after the fly-free date. You do need to keep in mind that the fly-free date is based on temperature averages and during warmer than normal falls fly emergence and egg-laying activity can extend past the listed dates. Larval activity can cause lodging, stunting, and yield loss since wheat tillers can be severely injured. In past variety trials, we have seen significant injury and yield reductions on susceptible varieties. Early planting of wheat can increase your risk of an infestation especially if wheat is planted in fields with wheat stubble or in fields next to one with wheat stubble.

For wheat that is planted following dryland corn, the greatest risk this year likely is due to excessive soil residual nitrogen (N); or, if the fall weather is warm and moist, to fall N mineralization from the high levels of nitrate in the dryland corn residue. High fall N availability can lead to excessive growth that will be more susceptible to winter kill or injury if we have a cold, open winter. In past years, we have had many growers asking what they could do about all the excessive top growth that occurs when wheat is planted in September and fertility levels are high. In some areas of the country, the extra foliage is used to graze cattle or sheep but most Delaware farmers do not have this option. The option tried has been to mow off and sometimes remove the excessive top growth. This has at least in part been successful in reducing winter injury but there are significant costs associated with the practice.

Another concern that again depends on fall weather conditions as well as insect populations and a residue of disease inoculum is the development in September planted wheat of disease or insect problems. In particular, barley yellow dwarf virus, which is transmitted in the fall by aphids feeding on the lush growth, can cause more severe injury than spring infections. The lush growth of early planted wheat could be more of an attractant for aphids but certainly will have a longer exposure to the risk of infestation.

All these cautions are not to say that you should never plant wheat or barley before the fly-free date only that you should be aware of the possible consequences and make a decision on when to plant and how many acres to plant from a position of knowledge.

Agronomic Crop Insects – September 7, 2012

Friday, September 7th, 2012

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

Soybeans
We continue to find corn earworms in soybeans. If you have not checked your fields, be sure to sample fields so you do not miss a late hatch of larvae. Although trap catches appeared to be declining on September 3, we will need to watch trap catches at the end of this week to see if this trend continues. In addition, we need to watch what happens in states to our south.

A number of defoliators are still present in double crop beans. The threshold for defoliation will need to be reduced if a mixed population is present. Although soybean looper populations remain low, there are reports from the southern states of building populations.

In New Castle and Kent Counties, we are a finding a few more fields with high levels of Brown Marmorated Stink Bugs on field edges of full season soybeans. Although we do not have a threshold for BMSB, we are also finding levels that we use as a threshold for native stinkbugs (2.5 per 15 sweeps) along the edges of double crop fields in New Castle County. Native stink bugs populations continue to be at threshold levels in fields throughout the state.

Small Grains
As you make plans to plant small grains, you need to remember that Hessian fly can still be a problem. Since the fly survives as puparia (“flax seeds”) in wheat stubble through the summer, you should still consider this pest as you make plans to plant small grains. In our area, damage has generally been the result of spring infestations. Plants attacked in the spring have shortened and weakened stems that may eventually break just above the first or second node, causing plants to lodge near harvest. Warm fall weather conditions can extend fly emergence and egg-laying beyond the fly-free dates, but these dates should still be used as a guideline for planting. Plants attacked in the fall at the one-leaf stage may be killed outright. Wheat attacked later in the fall will be severely stunted, with the first tillers killed and plant growth delayed. Plants infested in the fall can easily be recognized by their darker than normal bluish coloration and leaves with unusually broad blades. Combinations of strategies are needed to reduce problems from Hessian fly:

● Be sure to completely plow under infested wheat stubble to prevent flies from emerging.

● Avoid planting wheat into last season’s wheat stubble, especially if it was infested with Hessian fly.

● Avoid planting wheat next to last season’s wheat fields – the most serious infestations can occur when wheat is early planted into wheat stubble or into fields next to wheat stubble.

● Eliminate volunteer wheat before planting to prevent early egg-laying.

● Do not use wheat as a fall cover crop near fields with infestations.

● Plant after the fly-free date. (Oct 3 – New Castle County; Oct 8 – Kent County; Oct 10 – Sussex County).

● Plant resistant varieties. You should look for varieties that have resistance to Biotype L. You will need to check with your seed dealers to identify varieties that our adapted our area.

The following link from Alabama provides additional information on Hessian Fly Management (http://www.aces.edu/dept/grain/HessianFly.php

Agronomic Crop Insects – September 11, 2009

Friday, September 11th, 2009

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

Soybeans
We continue to hear reports of newly hatched corn earworm larvae in fields that were not treated in some areas of Sussex County and on the lower eastern shore of Maryland. If you have not checked your fields, be sure to check them for corn earworm.

With the continued cool temperatures, soybean aphids are still a problem in a number of double crop fields, especially in the western areas of the state and in a number of counties in Maryland. With the continued cool weather, populations are increasing in some fields and populations are well above the threshold of 250 aphids per plant. After talking to a few entomologists in the Midwest about soybean aphids, they still emphasize that treatment is needed through the R-5 stage (seed is 1/8 inch long in the pod of one of the four uppermost nodes on the main stem) of soybean development if economic levels are present. As far as spraying through R-6 stage (pods containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem) – their recent data continues to vary as to the benefit of spraying once plants reach the R-6 but in some years and some situations there has been an economic return. Spraying after R-6 stage has not been documented to increase yield in the Midwest. The suggested treatment threshold from the Midwest is still 250 aphids per plant with an increasing population. The following link from Wisconsin provides additional information on aphid management (http://www.plantpath.wisc.edu/soyhealth/aphids/aphid_management.htm). Information from the Midwest indicates that if the majority of aphids are winged or developing wings, it is an indication that the aphids will soon leave the field.

There are also a number of other insects still present in double crop fields including stinkbugs, bean leaf beetles, grasshoppers, and green cloverworms. The threshold of all may need to be reduced if a mixed population is present. As a reminder, both bean leaf beetles and grasshoppers will also feed on pods.

Small Grains
As you make plans to plant small grains, you need to remember that Hessian fly can still be a problem. Although we have not seen major infestations for the last few years, we did see fields with isolated infestations this spring. Since the fly survives as puparia (“flax seeds”) in wheat stubble through the summer, you should still consider this pest as you make plans to plant small grains. In our area, damage has been the result of spring infestations. Plants attacked in the spring have shortened and weakened stems that may eventually break just above the first or second node, causing plants to lodge near harvest. Warm fall weather conditions can extend fly emergence and egg-laying beyond the fly-free dates, but these dates should still be used as a guideline for planting. Since we rarely see plants stunted in the fall, we still feel that most of the damage we see is occurring from spring infestations. Plants attacked in the fall at the one-leaf stage may be killed outright. Wheat attacked later in the fall will be severely stunted, with the first tillers killed and plant growth delayed. Plants infested in the fall can easily be recognized by their darker than normal bluish coloration and leaves with unusually broad blades. Combinations of strategies are needed to reduce problems from Hessian fly:

● Be sure to completely plow under infested wheat stubble to prevent flies from emerging.

● Avoid planting wheat into last season’s wheat stubble, especially if it was infested with Hessian fly.

● Avoid planting wheat next to last season’s wheat fields – the most serious infestations can occur when wheat is early planted into wheat stubble or into fields next to wheat stubble.

● Eliminate volunteer wheat before planting to prevent early egg-laying.

● Do not use wheat as a fall cover crop near fields with infestations.

● When possible, plant after the fly-free date. (Oct 3 – New Castle County; Oct 8 – Kent County; Oct 10 – Sussex County).

● Plant resistant varieties. You should look for varieties that have resistance to Biotype L. You will need to check with your seed dealers to identify varieties that are adapted our area.

Several Pest Management Issues to Think About if You are Saving Cover Crop Wheat or Barley for Grain Production

Friday, March 28th, 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu and Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

With the high prices of wheat and barley some cover crops may be kept for grain instead of plowing them under. As long as the stand is sufficient for economical yield the fields can be managed for grain production. There are several pest management issues that could be a problem if you have decided to do this. Loose smut is a systemic fungus disease that is transmitted in infected seed. Infected seed looks healthy and germinates as if it were not infected. When the seed germinates the fungus is activated and systemically grows within the young seedlings. The fungus remains in the plant over the winter and when growth resumes the fungus grows with the plants and eventually to the head where the fungus spores replace the wheat or barley kernel and other flower parts. The only window to control this disease, if the seed is contaminated, is with a seed treatment for loose smut at planting. If the cover crop seed was certified and/or treated with Baytan, Raxil, Vitavax, or Dividend at rates for loose smut control, the crop is protected. Currently there is no labeled foliar fungicide for wheat or barley that will control loose smut if the plants are infected. There is no way to tell if the crop is infected until heading, so if you planted untreated, saved seed or untreated seed from an unknown source there is a risk of loose smut at heading.

Since cover crops are often planted before production fields, Hessian fly could be a potential problem. Fields planted well before the “fly free” dates (New Castle County -Oct 3; Kent County – Oct 8 and Sussex County- Oct 10) could have been exposed for a longer time to egg laying by Hessian fly adults. Any eggs laid in the cover crop wheat hatched into maggots which fed on that wheat and then changed into pupae (called flax seeds) to survive the winter. When the Hessian fly adults emerge from the flaxseed this spring, they will seek a host upon which to lay their eggs. Since wheat is the principal host plant of the Hessian fly and they are not strong flyers, these fields may be susceptible to spring infestations. Please refer to the article “Management of Hessian Fly in the Spring” in WCU Volume 16, Issue 1 for sampling and possible control options.

Management of Hessian Fly in the Spring

Wednesday, March 26th, 2008

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu and Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

Last fall, we received a number of calls regarding the need to control Hessian fly in wheat. Although we have not seen or heard of any significant damage from fall infestations, we continue to receive questions about the possibility of problems from the spring population. If stands appear thin and you are checking fields for a reason, you should consider Hessian fly as one of the possible culprits. Volunteer wheat could also be a source of spring infestations. Although the adult fly is not a strong flyer, production fields near volunteer fields that were heavily infested last fall could be at risk for a spring infestation. When the Hessian fly adults emerge from the flaxseed this spring they will seek a host upon which to lay their eggs. Wheat is the principal host plant of the Hessian fly but it may also be found on rye, barley and other wheat-related species.

Although we have not had experience controlling spring infestations with a foliar insecticide, information from North Carolina and Georgia indicated that it can be done but it will not be easy to time applications. Information from North Carolina indicates that if applied timely, Warrior® will provide control. (See link to North Carolina publication). (more…)