Pest Alert: Kudzu Bug Detected in Delaware

A new insect pest has been detected in Delaware.  Below is more information from Joanne Whalen, Extension IPM Specialist, UD:

Identification of the first find of the Kudzu bug in Delaware was recently confirmed as the result of a collaborative effort between the University of Delaware Cooperative Extension and consultants (who found the first bugs), the Delaware Department of Agriculture’s Plant Industries Section who submitted the bug found by the University of Delaware to the USDA identifier and the USDA folks who responded quickly to the request to provide a positive confirmation. The first find came from a pole lima bean field in Sussex County. Entomologists at the Un of DE and DDA who looked at the specimen were fairly confident of the ID but we needed to hear back from the USDA identifier to officially confirm the identification and establish this find as a new state record. We also received another specimen from a soybean field in Sussex County last Friday.

So, be sure to carefully sample all beans crops (soybeans and all succulent beans) for this new insect pest. If you have suspect specimens you can contact Joanne Whalen at or call 302-831-1303.

Entomologists in the south have done a great job of developing sound management strategies for Kudzu bug in soybeans that should apply to management of this bug in soybeans in Delaware. In addition, they have evaluated a number of insecticides labeled in soybeans for control of this insect and there are a number of effective labeled options.

Information on the identification and management of Kudzu bug can be found at the following link — You should also follow Virginia’s Plant Pest Advisory since my colleague Ames Herbert does a great job of updating what is occurring in Virginia – including documenting the range of spread in Virginia and management options —

Here is a brief summary of information on management from the south on soybeans:

(a) A threshold of one immature nymph (big enough to see) per sweep should be used in fields that are flowering or developing pods. Information on the kudzu website also indicates that if adult populations are extremely high and beans are stressed for some other reason, a control should be considered. However, this is a judgment call since they do not have a threshold for adults at this stage of crop development.

(b) Since many fields will be planted late this year and you may see bugs on small plants, there is new research from Georgia regarding management on seedling and vegetative plants. They recommended treating at V2-V3 stage soybeans if you find an average of 5 bugs (adults and/or nymphs) per plant. The threshold increases to 10 bugs per plant for plants from 1-2 feet tall. The established threshold of one nymph per sweep should be used for plants above 2 feet tall. It should also be noted that you do not want to treat too early for adults and you will want to sample the entire field – not just field edges. In other areas, treating too early has resulted in the need to make multiple applications for this insect pest.

Most of the management work on Kudzu bugs has been done with soybeans regarding treatment timing and yield impacts. However there is current work being done in Georgia looking at host plant preference, including succulent beans. Initial findings are that they do not prefer non-soybean beans, but will occur on them. They will be continuing this work this summer and have more information by the fall. In the meantime, you will want to watch succulent beans to see if this trend is true in our area. We may have to use the information developed for soybeans this season to help us make management decisions in succulent beans if the need arises. We will keep you posted of any new finds as well as new management information as it is developed.

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Fall Lima Bean Harvest

Lima bean harvest continues in the county through the month of October.  It has been a tough year for lima beans in Kent County as the early planted crop went through extreme heat and drought causing abscission of flowers and pods.  Many of the June planted lima beans had split sets.  Growing conditions have been more favorable for July planted lima beans, though Hurricane Irene dumped up to eleven inches of rain causing some damage.  September’s wet and cool weather provided optimum conditions for downy mildew development, pressuring growers to make several fungicide application.  While early planted lima beans suffered and resulted in very low yields, the late planted lima beans are finishing with better yields.  

Pod-stripping Combines harvest lima beans from a field near Felton, Delaware.  Photo by Phillip Sylvester.

As a side note to the harvest, lima bean growers still have an opportunity to plant a cover crop.  Cereal cover crops such as wheat or rye will help to stabilize the soil, add organic matter, take up excess nitrogen in the fall and carry through to next spring, and provide some weed suppression.  Rye in particular is likely to do best late planted.  Plan to seed before the end of the month so adequate fall growth can take place. 

Phillip Sylvester, Extension Agriculture Agent, Kent County, UD

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Hot Weather and Lima Beans

Recent weather conditions have been very warm and dry with some scattered thundershowers.  Daytime temperatures have been topping out in the 90’s (18 days over 90 in Dover area in the month of July).  Below is information on how lima beans respond to high temperatures and low soil moisture:

Many factors influence lima bean yields, but weather conditions that affect flower bud development, pollination, and pod maturation have the most impact on yields in Delaware. Low lima bean yields are associated with profuse abscission of flowers and developing pods. Research conducted at the University of Delaware in the 1970s revealed that high temperatures, low relative humidity, and low soil moisture lead to reduced pod set and retention. Temperatures of 90 degrees Fahrenheit or above reduce pollination and pod set. Prolonged drought (7 days or more with less than 1 inch of water) also negatively affects yield. High humidity favors pollination and pod set and is one reason lima beans have been grown successfully in Delaware. Fogs, heavy dews, and their moderating effects on temperature are helpful to pollination and pod set. High night temperatures also adversely affect yields, because energy is consumed through respiration, thereby limiting the plants physiological ability to set and retain pods.

Lima bean flower are produced on an indeterminate raceme; three flowers appear at each node along the raceme. Recent research conducted at The University of Delaware identified important phenomena related to flowering. The two outer flowers at each node begin to develop simultaneously, while the middle structure lagged in development. If one or both of the outer structures abscised, the middle structure continued to develop, but at a greater rate than when the outer two flowers continued to develop into fruit. In Delaware, this “reflowering” contributed very little to final yield, while concurrent studies in California found that re-flowering accounted for up to 75 percent of the final pod set.

This helps explain the consistently higher yields in California (4,000 pounds/acre versus a state average of 1,800 in Delaware). Cool nights in California also play a role in allowing the plant to perform at higher levels of efficiency. Interestingly, Delaware yields generally increase with later planting dates, which correspond to both higher rainfall, cooler day temperatures, and cooler night temperatures in September and October, at a time when later plantings are flowering and setting pod.

Depending on variety, first flowering generally occurs at 35 days from planting, and peak flowering at 60 days; harvest occurs from 80 to 90 days for baby varieties, and 90 to 100 days for Fordhook varieties. However, a wide range of factors can influence maturity, including temperature, drought, and any environmental conditions that cause a prolonged flowering period (split-set).

From Successful Lima Bean Production in Delaware.  Ed Kee, James Glancey, and Tracy Wooten.  VF-6. University of Delaware Cooperative Extension. 

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Lima Bean Planting Time

Baby lima bean planting has begun in the county.  Plantings will continue into small grain harvest and will end sometime in July.  Lima beans are planted in 30 to 36 inch rows and growers should shoot to have 3 to 4 plants per foot.  A yard stick can be used at planting to count the seeds in 36 inches and divide by 3. Plant 50 lbs per acre, 1.5 inches deep, unless the soil is dry which warrants deeper planting.  For irrigated fields, row spacing should be 18 to 30 inches apart with 4 to 5 inches between plants.  Plant between 76 pounds per acre at wider spacing and 96 pounds per acre at close spacing.  For growers planting the Fordhook Type this year, rows should be 30-36 inches apart with 2 plants per foot.  Plant 85 pounds per acre, 1.5 inches deep.
Lima beans require between 60-80 pounds of nitrogen.  If lima beans are planted after peas, nitrogen rates should be reduced.  Growers should consider splitting nitrogen applications, 30-40 pounds at planting and another 30-40 lbs 3-5 weeks after emergence.  This can be especially beneficial if heavy rainfall occurs after planting which can leach the nitrogen applied at-planting.

Phillip Sylvester, Extension Agricultural Agent, UD, Kent County.  Information from 2011 Delaware Commercial Vegetable Production Recommendations.

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Pythium Pod Rot in Lima Beans

Pythium pod rot has been found on lima beans in Kent County. The following is more information on this disease.

Pythium pod rot can be a problem when we have wet, warm weather that occurred last week and the week before. Pythium is soil born and moves into pods that are touching the soil and then can spread to other plant parts under ideal conditions. It can be more of a problem in snapbeans but does occur sporadically in lima beans as well. It is extremely hard to predict when and where it will occur unless the field has a history of Pythium problems. Ridomil Gold/Copper has a 24c label for use on snapbeans in DE, MD and VA. Application should be made before the pods develop and touch the soil surface. The phosphorus acid fungicides that are labeded on beans such as Prophyt and would be another product to try if the situation warranted it.

Pythium Pod Rot in Lima Bean

Infomation from Bob Mulrooney, Extension Plant Pathologist, UD

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Summer Lima Bean Pod Diseases

The following is information three common lima bean pod diseases that we see in the summer in Delaware.

Remember that lima beans can get downy mildew (Phytophthora phaseoli), white mold (Sclerotinia sclerotiorum), and Phytophthora capsici (lima bean pod rot). White mold tends to be very fluffy and white when active. It will infect flowers first, then infected flowers fall onto branches leaves and stems and further infections can take place on those plant parts. White mold will produce the black sclerotia that are imbedded in the white fluffy fungus growth. P. capsici only infects the pods and is very grainy looking almost like granular sugar. Downy mildew infects the pods and flower spikes (racemes) sometimes infecting petioles as well. Downy is downy looking not as fluffy as white mold most of the time, and often there is a reddish border between healthy and infected pod tissue.

White mold on snap bean. The disease looks very similar on lima beans.

Information and photos by Bob Mulrooney, Extension Plant Pathologist, UD

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Nitrogen Deficiency in Lima Beans

I recently looked at several plantings of processing lima beans as well as pole lima beans showing nitrogen deficiency. The following is more information.

Both early planted processing baby lima beans and market garden pole lima beans are showing signs of nitrogen deficiency now across the state, even with adequate N being applied. This is likely a result of excessive N leaching during the wet spring periods in May and early June in many fields, especially on very sandy soils. Pole lima beans commonly show N deficiencies later in mid-summer as pod set and development progresses; however this year, yellow plants are being seen much earlier.

Severe N deficiency in lima beans will be seen as an overall yellowing of plants with lower leaves often dropping off as N is mobilized from the oldest leaves to support the new growth at growing tips. Less severe N deficiency will be seen as a lighter green color than normal with lowest leaves most affected. Tissue tests can be used to confirm N deficiencies. Take the uppermost fully expanded leaves to send off for analysis. There are other potential causes for yellowing in lima beans including low pH leading to magnesium deficiencies and excessively high pH leading to micronutrient deficiencies, most commonly manganese.

It is important to apply additional N as soon as possible in N deficient lima beans. General recommendations are to sidedress 30-40 lbs of N, 3-5 weeks after emergence in baby lima beans and at early pod set in pole lima beans. In fields that have suffered heavy leaching losses, this may need to be increased slightly. However, remember that too much N can lead to excessive vine growth and delay flowering and pod set. Deficient pole lima beans will need an early sidedress application now and will likely need an additional sidedressing of N in August during pod development.

Gordon Johnson, Extension Agriculture Agent, UD

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Early Processing Lima Beans

The following is information on early processing lima beans.

The earliest processing lima beans will be planted starting in the next 10 days. May planted lima beans often have a lower yield potential than June and early July plantings due to a number of factors. Soil conditions may be cold and this delays germination and reduces stands. Minimum soil temperature for best germination is 65°F. Soil borne diseases such as Rhizoctonia and Fusarium can become established on plant roots, especially when they are growing slowly in cold soils, limiting later yield potential of these early planted lima beans. Heavy infestations of seed corn maggot can overwhelm seed treatments in cold, wet soils reducing stands.

The major limiting factor for early lima beans is the fact that they flower and set pods during summer conditions when day and night temperatures are high. Low lima bean yields in early plantings are associated with high levels of flower and pod drop. Hot, dry weather in July and August will lead to reduced pod set and retention. Day temperatures of 90°F or above reduces pollination and pod set and night temperatures in the 70’s or higher will also adversely affect yields because higher levels of carbohydrates are consumed in night respiration, limiting the plants ability to set and retain pods. Plants may reflower when cooler conditions recur leading to split sets.

The following are some considerations for early lima bean plantings:

• Plant in fields with light soils that heat up quickly and where emergence will not be delayed. Conventional tillage is required for early plantings to speed this warming.
• Plant on a warming trend when soils are 65°F or higher.
• Consider using an additional fungicide treatment for Rhizoctonia control (Ridomil Gold PC or Quadris).
• Choose fields carefully. Fields closer to water bodies were temperatures are moderated by fog, heavy dew, high humidity, and cooling breezes during summer are good candidates.
• Irrigate early planted fields paying particular attention to the flowering and early pod set period. Daytime irrigation can also help to moderate high temperature effects during hot summer periods. It is critical to keep early planted lima bean plants from being water stressed during this period. Do not plant early lima beans dryland.

Although success in early lima bean plantings can be improved by following these suggestions, if there are extended periods with day temperatures in the 90’s and night temperatures in the high 70’s, yields will still be limited.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

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Split Sets in Dryland Lima Beans

We are seeing some severe split sets in dryland lima beans this year. Those dryland limas planted in late June and early July produced a poor set in August when plants were essentially shut down by the drought. This was most evident in plantings on lighter soils. When rains came in early September, vine growth resumed but re-flowering did not occur immediately. With additional rainfall from the recent Nor’easter, plants are now reflowering. The following are some pictures I took from a field this past Friday that has this problem – split set with delayed re-flowering.

Gordon Johnson, Extension Agricultural Agent, UD, Kent County

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Late Summer Vegetable Notes

The following are late summer notes on vegetables for mid-State.

Early processing baby lima beans have been harvested over the last two weeks. Dry-land lima yields are ranging in the 900-1100 lbs/acre range. Cooler weather in August has contributed to decent pod set but drought conditions have reduced seed fill and increased pod abortion in later planted dry-land baby limas. With extended drought, dry land lima bean yields will continue to go down. We also risk split sets if we do get rain soon in dry land limas. In August there were only 3 days in the high 80s or low 90s and nighttime temperatures have dropped to the 50s or 60s. As a result, irrigated mid to late season lima beans should have excellent yields. Pigweed escapes continue to be a major issue in lima beans and wiper bars were used in many fields this year for control once pigweeds were over top of the beans.

Nematodes can be an issue in heavy vegetable rotations. It would be wise to take soil and root samples while there are still live roots in fields if you are seeing reduction in growth, extra stress, or reduced yields in vegetable fields. Sampling instructions and sample bags can be obtained at any Delaware Extension Office.

It is common to find low pH to be a problem in vegetable fields where there is poor growth. Mark any areas that are showing poor vegetable performance and once summer vegetables are finished, plan to take soil samples in these areas and field wide. Low pH spots will need additional lime this fall.

I encourage more vegetable growers to try some acreage using cover crops that can be no-tilled into next spring. In particular, hairy vetch has proven to be an excellent cover crop for late spring, direct-seeded and transplanted vegetables. The key is to plant as early in September as practical and make sure there is irrigation to get the hairy vetch out of the ground and growing this fall if there is no rain. Pumpkins no-tilled into hairy vetch are becoming the standard in much of the region, but we have limited acreage in Delaware.

A common question is when to stop spraying pumpkins for disease and insect control. Unless pumpkins will be harvested in the next two weeks, plan on additional sprays. The best place for a pumpkin is on a healthy vine. Late season powdery mildew will greatly reduce handle (stem) quality and reduce marketability. We have several growers that plant pumpkins into rye cover crops. The rye mulch has greatly improved quality by eliminating fruit rots and greatly reducing dirt where the pumpkin sits on the ground.

Vegetables for Fall harvest have been planted throughout the summer and we have significant acreage of late green beens, late lima beans, cabbage, spinach, other cole crops (broccoli, cauliflower) and greens. At this stage, insect control is a priority in these crops as this is one of the most active insect periods of the year with corn earworm, fall armyworm, cabbage worms, loopers, diamondback moth larvae, harlequin bugs, webworms, and many more attacking vegetables. Check the weekly crop update for scouting guidelines, thresholds, and control recommendations.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County.

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