- Agronomic: sunflower
- Vegetables: peppers, sweet corn
- Crop Production: intercropping
- Education and Training: on-farm/ranch research
- Pest Management: biorational pesticides, row covers (for pests), trap crops
- Production Systems: organic agriculture
The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), a native of eastern Asia was accidently introduced into Pennsylvania in the late 1990’s (Hamilton 2009). Since its introduction into the United States, BMSB has spread into more than 30 states as well as Canada (Leskey and Hamilton 2010, Jacobs 2011). Current research and observations in the mid-Atlantic states have shown that BMSB has tremendous potential to reduce yields in numerous agricultural commodities. Stink bug feeding injury on fruit may result in a white spongy area on the surface of the fruit and catfacing damage, which render the fruit unmarketable for fresh market use (McPherson and McPherson 2000). In addition, feeding damage can cause fruit drop which impacts fruit yield (McPherson and McPherson 2000). Since the first indications of economic injury (Nielson et al. 2008), up to 80% yield loss has been reported in fruit tree orchards due to BMSB feeding injury (Leskey and Hamilton 2010). In 2010, disruption of IPM tree fruit programs occurred and record losses were reported in both field and vegetable crops due to BMSB damage (Leskey and Hamilton 2010). Frequent applications of broad-spectrum insecticides have increased in an attempt to control BMSB. Even with increased spray programs, apple growers suffered economic losses of 37 million dollars in the Mid-Atlantic states in 2010 (U.S. Apple Grower 2011). In addition, losses averaging about 20% were estimated for certain vegetable crops including sweet corn, peppers, and tomatoes. The economic injury caused by this insect can be devastating. Conventional IPM programs are ineffective and this pest will pose an even greater challenge to organic systems. Currently available organic pesticides are generally not effective at reducing stink bug populations in field situations (Kamminga et al. 2009). As a new invasive insect, researchers are still attempting to determine the most appropriate and sustainable methods for management. Moreover, relatively little information has been reported on the biology of BMSB including the number of generations expressed per year. Although it is considered to be univoltine in the northern states (Nielson et al. 2008), multiple generations may occur as it moves southward creating more pest pressure and challenges for southern growers. Compared to native stink bug populations, BMSB can occur at unusually high numbers in agricultural systems. These tremendous numbers may be possible in part because there are few natural enemies of BMSB in North America. For instance, about 50% of native stink bug eggs are parasitized (Koppel et al. 2009); while recent reports by Dr. Kim Hoelmer, of the USDA-ARS, indicate that egg parasitism of BMSB may only be around 5%. Additionally, Dr. Hoelmer states that a common obligate parasitoid of native stink bugs, tachinids, are not able to complete development in BMSB (Holtz and Kamminga 2010). In addition to high population numbers, BMSB also reportedly has more than 300 host plants (Hoebeck and Carter 2003, Nielsen et al. 2008), which contribute to the difficulty in controlling BMSB populations. Statement of Proposed Solution In 2010, more than 54 thousand acres of bell peppers were planted in the United States with a value greater than 637 million dollars (NASS Quick Stat, 2010). In addition, bell peppers are a high value crop for many diversified smaller growers in the mid-Atlantic and southern states. Data collected in 2010 and 2011 indicate that bell peppers are a preferred host of BMSB causing significant economic damage from feeding injury (Leskey and Hamilton 2010). Current control options include older broad-spectrum insecticides such as organophosphate, carbamates and pyrethroids that are disruptive and hazardous to the environment. We plan to test cultural and mechanical control methods that may offer alternative methods of control for BMSB. These methods are part of IPM programs and safer for humans and non-target species. Native stink bugs typically move into an agricultural field from nearby wild hosts; therefore, causing greater injury and crop loss along the perimeter of a field. This edge effect has also been documented as a common characteristic expressed by invading BMSB (Leskey and Hamilton 2010). A potential management method to decrease crop loss is planting a trap crop. Trap crops have been successfully used to reduce stink bugs in soybean by planting more attractive soybeans along the field perimeter (Todd and Schumann 1988, Bundy et al. 1998, Smith et al. 2009). The stink bugs prefer the early maturing bean pods confining them to an easily treatable area for the grower. Trap crop implementation may reduce chemical sprays since treatment would only be applied to the trap crop instead of the entire field. The reduction in insecticide application saves money for the grower, is safer for the environment, and serves as a refuge for natural enemies. Our preliminary data from 2010 indicate that BMSB is strongly attracted to sweet corn and sunflower (Fig. 1) when present on a farm. Thus, sunflower or sweet corn could potentially serve as a trap crop for bell pepper and other high value crops. A successful trap crop will reduce stink bugs in the primary crop and consequently reduce feeding damage. Furthermore, the use of a trap crop offers a habitat for beneficial insects to thrive. Adult egg parasitoids feed on flower nectar. Thus, a trap crop such as sunflower will not only be a refuge, but also a food source for beneficial insects. A mechanical control strategy that has received very little attention in an agricultural system is a physical barrier to prevent insects from feeding on high value plants. A screen barrier such as mosquito netting could eliminate the need for insecticide application. Placed over crop plants, it will protect the high value vegetables from stink bugs as well as other flying pests.
Project objectives from proposal:
Objective 1: Evaluate the potential of a trap crop of sweet corn and sunflower trap crops to reduce the numbers of BMSB in the primary crop, bell peppers.
During the first year of the study we will determine if stink bug populations can be maintained below economically damaging levels in the primary crop through implementation of a trap crop. To test our trap crop strategy, we will plant three large spatially-isolated blocks (75 ft X 75 ft) (Figs. 2 and 3) at Mr. Hill’s farm. The first block will not have a trap crop and will be planted as 25 rows of bell peppers only. The next two blocks will implement trap crops: one with sunflowers and one with sweet corn. For these treatments, the middle 15 rows of each block will consist of bell peppers, while the outer 5 rows on each side will be comprised of the trap crop (Fig. 2). In order to sustain the attractiveness of the trap crops to stink bugs, seeds of the two trap crops will be sewn within the trap crop rows every two weeks throughout the growing season. With this approach, the reproductive plants will remain attractive to stink bugs throughout the pepper-growing season.
Stink bugs will be sampled weekly using a beat sheet in both the trap crops and the peppers beginning once the peppers flower. Sampling will consist of ten random 6 ft beats per block; four samples will be taken from the perimeter and six from the interior of the block.
If there is a reduction in stink bug damaged peppers in the blocks with a trap crop for the first year, the second year will consist of repeating the design as a randomized complete block. Four blocks of each treatment will be planted and sampled using the same protocol as the first year. Analysis of variance (ANOVA) will be conducted to analyze the data between treatments using SAS software JMP version 9.0 (JMP 2010).
Objective 2. Evaluate if a trap cropping system increases egg parasitisim of the BMSB.
Beginning at flowering, five random plants per row (trap crop and peppers) will be sampled weekly for stink bug egg masses. All egg masses discovered will be removed. The eggs will be returned to the laboratory and placed in a labeled Petri dish with a moistened cotton paper and kept in a growth chamber at 24°C, 85% RH and 14:10 [L:D] (Koppel et al. 2009). The dishes will be checked daily for either parasitoid or stink bug emergence. All emerged parasitoids will be moved to vials containing 95% alcohol and identified to species using taxonomic keys (Johnson 1984a, b, 1985). Analysis of variance (ANOVA) will be conducted to analyze differences between treatments using SAS software JMP version 9.0 (JMP 2010)
Objective 3. Evaluating the potential of new technology to reduce stink bug damage on high value vegetables.
A separate pepper block from Objective 1 will be planted to evaluate a new technology to reduce stink bug injury to bell peppers. This plot will also consist of 25 rows (75 ft by 75 ft). specialized mosquito screening (6 ft X 20 ft) obtained from Vestergaard-Frandsen Inc. (Sweden) will be placed over one row by 20 row feet of pepper. Screened plots (treatment) will be replicated four times within the pepper plots. Four non-screened plots will be marked as the untreated control of 20 row feet of pepper. Stink bug damage will be assessed three times throughout the season on both the screened and control plots. To assess damage, fifty marketable sized peppers will be picked per plot and assessed for stink bug damage. A t-test will be conducted to analyze differences between screened and unscreened plots.
Project Relevance to Sustainable Agriculture
The BMSB is a significant economically damaging insect pest. The disruption of IPM programs across the mid-Atlantic has had a detrimental impact on sustainable agriculture. Organic and conventional growers alike are having difficulty controlling this new invasive insect. Even with increased use of broad-spectrum insecticides, BMSB has still resulted in severe economic crop loss for some growers. In addition, the use of broad-spectrum insecticides has or will undoubtedly lead to secondary pest outbreaks from the destruction of natural enemies. For vegetables such as peppers in Virginia for example, secondary pests could include beet armyworm, western flower thrips, spider mites, and green peach aphids as demonstrated by Chapman et al. (2009). All of the aforementioned pests are resistant to pyrethroid insecticides, which would be the primary insecticide class used for BMSB control.
Regardless of the occurrence of secondary pest outbreaks, the repeated use of broad-spectrum insecticides in vegetable production is not sustainable and certainly not environmentally sound. Nonetheless, the BMSB has led to a dramatic increase in the use of these insecticides in tree fruits, row crops and field crops (Leskey and Hamilton 2010). As BMSB spreads south and west throughout the United States, more specialty crops will be affected. Alternative and more sustainable approaches to BMSB management are desperately needed. It is imperative that we begin conducting research in this area.
Trap cropping is a cultural method that has successfully been used to manage other stink bugs in soybean (Todd and Schumann 1988, Bundy et al. 1998, Smith et al. 2009). It provides a more attractive food source to the stink bug than the primary protected crop. Moreover, it may also increase the egg parasitisim rate by providing a food source to the adult parasitoids, and may also enhance the natural enemy population through reduction in broad-spectrum insecticides.
The outcomes obtained from our research may lead to documentation of new and sustainable cultural and biological management possibilities for this insect. If our trap crop studies with bell pepper are successful, these techniques may be expanded to other high value crops. All three objectives will reduce the use of broad-spectrum insecticide spray that will benefit the environment and conserve natural enemies in the ecosystem. Our third objective not only supports organic agriculture, but also provides a new alternative technology for stink bug control. This methodology is easily assembled and applied and may offer an alternative control method for growers. Like our trap cropping objective, this too could lead to a reduction in broadcast insecticide applications.