EFFECTIVE CONTROL OF COLORADO POTATO BEETLES ON POTATO USING PREDATORS AND PREDATOR CHEMICAL CUES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1014313
• Project Start Date: Oct 12, 2017
• Project End Date: Sep 30, 2019
• Program Code: [(N/A)]- (N/A)

Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853

Performing Department
Entomology

Non Technical Summary
Across ecosystems, an average of 50% of the effect of predators on prey and plant damage is through changes in prey behavior when they perceive the presence of predators (without being eaten!). We will investigate manipulating native predators along with their chemical cues to maximize the control of an important pest on potato, Colorado potato beetle.

Animal Health Component

(N/A)

Research Effort Categories

Basic

100%

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
212	1310	1130	100%

Knowledge Area
212 - Pathogens and Nematodes Affecting Plants;

Subject Of Investigation
1310 - Potato;

Field Of Science
1130 - Entomology and acarology;

Keywords

potato

colorado potato beetle

native stink bug predator

biological control

Goals / Objectives
The Colorado potato beetle is one of the most economically devastating pests of potato crops and other Solanaceous crops in NY and worldwide. While many techniques have been used to control the beetle, they are very resilient. Many biological control agents are targeted at beetle larvae which can cause heavy defoliation of potato plants, including the commercially available, native, generalist predator Podisus maculiventris. However, one of our strongest findings from previous federal capacity funded research is that adult Colorado potato beetles also strongly reduce feeding and oviposition in the presence of stink bug predators. This is surprising given that the stink bugs do not frequently consume adult beetles. But, adults may alter their behavior in order to provide a safe environment for their offspring both when they emerge from overwintering in the spring and when the second generation emerges in the summer. These findings give us a new opportunity for manipulating the behavior of a key life stage and new avenues for controlling this important pest.The combined use of biological control with behavior modifying volatiles may lead to more effective pest management. Our federal capacity funded preliminary results show that beetle adults detect stink bug predators using the predator aggregation pheromone odor. Therefore, we will test strategies that combine the adult responses to odors from predators with living predators. We have two specific objectives.How do adult CPB movement and oviposition decisions vary with predation risk?We will test this with the first generation of adults emerging from overwintering in the spring and with the second generation adults that emerge in the summer. Both of these generations of beetles are two important sources of damage for potato plants but, they have different movement patterns and may use predator information differently.We will test whether predator odors combined with lethal predators can provide cost-effective pest control.Combining predator odor cues with low densities of lethal predators may allow economically viable densities of predators to provide effective control. We will combine releases of the odor of the predator with lethal predators in field plots and measure the effects on herbivore abundance and plant yield. We will do this in two summers to see if the results are repeatable across seasons.

Project Methods
Objective 1: How do adult CPB movement and oviposition patterns vary with predation risk?We will put out patches of four potted Yukon Gold potato plants and ten Colorado potato beetle adults without cages. Potato plants will be grown in the greenhouse until they are 1 month old and then used for experiments.Each patch will be either a control or predation risk treatment. We will establish 30 replicates of each treatment in a plowed field at the Freeville Experimental Farm. To provide a predator odor source in the predation risk treatments, patches will have either a mesh cage used to contain ten male stink bug or an empty bag, hung in the middle of the patch. Control patches will have only the empty bag hung in the center. Adult wild-collected Colorado potato beetles (5 male and 5 female) will be released into the center of each plot. Before putting the beetles out, we'll mark them by poking holes in elytra with an insect pin so we can separate colonists from beetles that we have put out. We will check all plants in each replicate every day for four days and measure beetle abundance and egg density including the number of clutches and the number of eggs per clutch. On the fourth and last day, we will measure the amount of beetle herbivory the plants in each replicate receive. Leaf area will be measured on all leaves using a 1 x 1 mm acetate grid. Colorado potato beetles are the major leaf chewers on potato plants and so most damage can be attributed to the beetles.These experiments will be conducted twice during the season. First, in June using the overwintering generation of beetles collected from the field. Second, in July using the summer generation of beetles. We will compare the cumulative number of adult beetles and egg clutches in the control and predation risk treatment using Chi-Square analyses. We will compare the cumulative total number of eggs and leaf damage between the treatments using ANOVA. This experiments will be conducted in Year 1.Objective 2: We will test whether predator odors combined with lethal predators can provide cost-effective pest control.We will conduct this experiment in a potato field at Cornell's Freeville Experimental Farm. The Yukon Gold potatoes will be planted in double rows with plants within rows spaced approximately 0.3 m from each other and with 1 m between rows. We will use 2m wide x 3m long lumite mesh cages to enclose the plots. We will begin the experiment on young potato plants, one week after they have emerged from the ground. We will establish three treatments: control, lethal predator, and lethal predator + pheromone aggregation cue. Six adult stink bugs (3 male + 3 female) will be added to the appropriate plots each week. The 5 component predator aggregation pheromone identified by Jeff Aldrich will be released in two rubber septa per appropriate plot with dispensers replenished weekly. Fifteen cages (replicates) per treatment will be established.We will measure beetle abundance, oviposition and larval density once per week throughout the season. We will count the number of adult beetles present on the plants in each treatment. The number of egg clutches and the number of eggs per clutch will be measured every four days throughout the experiment. When larvae begin to hatch, we will measure the number of larvae present on every plant per cage every 4 days. We will measure plant damage using 1 mm acetate grids one week after the experiment has begun. We will randomly select two plants in each cage for the damage measurements. Three weeks after the experiment has begun, we will measure plant damage again. Since the plants will be larger, we will again randomly select two plants per cage for damage assessment. On each plant, we will measure leaf area damaged on the 4th leaf from the top of the tallest stem and the 8th leaf from the top of the tallest stem. Yield will be measured at the end of the season by harvesting and weighing all of the potatoes produced in each replicate. We will use ANOVAs to compare the effect of the three treatments on beetle abundance, egg number, damage and yield.We will compare the effect of lethal predators and lethal predators + pheromone to the control treatment to test our prediction that adding pheromone increases the effectiveness of the lethal predator. Our expectation is that the lethal predator treatment in combination with aggregation pheromone will provide greater control than the predator treatment alone. We will conduct this comparison for each of our measures, adult presence on plants, egg and larval numbers, plant damage and yield to see if different components that contribute to yield and yield itself are affected by the predator treatments. This experiment will be conducted in Year 1 and Year 2 to test for consistency across years.

Progress 10/12/17 to 09/30/19

Outputs
Target Audience:This year, we worked to publish the work from this project submitting papers to both basic and applied ecological journals. We presented this research at predator-prey Gordon Research Conference. This year, the project provided research opportunities to 3 undergraduate students (Abigail Dittmar and Sheyla Lugay) and one graduate student (Nick Aflitto). Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?In total five undergraduates (Ari Grele, Fiona Goggin, Shiela Lugay, Abigail Dittmar, Emma Weissburg), 3 graduate students (Julie Davis, Nicholas Aflitto, Sara Hermann), and 1 postdoc (Will Wetzel) conducted research on this project. These students received substantial one on one mentoring from me on experimental design and analysis, chemical analysis and scientific writing. The graduate students and postdocs presented their findings at the Plant-Insect Discussion group and international meetings for feedback. Two of the undergraduates involved with this project (Ari Grele and Fiona Goggin) are currently in PhD programs and one is completing her Honor's thesis research in our lab on a related project. Sara Hermann is now an Assistant Professor at Pennsylvania State University and Will Wetzel is an Assistant Professor at Michigan State University. How have the results been disseminated to communities of interest?We have presented these results in undergraduate classes and multiple scientific meetings. University of Montana, Missoula, Montana. Tritrophic Interactions and the Ecology of Fear. University of Kentucky, Lexington, Kentucky, Tritrophic Interactions and the Ecology of Fear, Student Invited Speaker. Gordon Research Conference. Plant-Herbivore Interactions. Tritrophic Interactions and the Ecology of Fear. University of Wisconsin, Madison, Wisconsin, Keynote Speaker, Ecology Fall Symposium Max Plank for Chemical Ecology, Tritrophic Interactions and the Ecology of Fear, Jena, Germany What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Objective 1: Goal 1 was completed and the last paper submitted (Aflitto and Thaler, in review). Overall, this project demonstrates that Colorado potato beetle damage is reduced when beetles are exposed to predator odors in the field. Multiple beetle life stages are affected by predator odors. The last piece of this, was showing that feeding damage by early colonists was initially reduced by 49% in predator odor treated plots. Driven by the early season effect, overall damage was reduced by 22%. Three mechanisms were investigated to better understand why prey response to the predator odor treatment weakened over the first season and interannually including changes in predator odor cue, prey habituation, and abiotic factors. Predator cue strength appeared to best explain the prey response pattern, as dispensers, which released synthetic predator odors over the entire season, provided a greater reduction in damage and more consistent prey response. These results suggest that temporal patterns of predator cue release and strength may drive the beetle response across the season, underscoring the importance of cue release-rate and consistency in both species interactions and for the future use of applying non-consumptive effects in agricultural systems. Goal 2: Because Colorado potato beetles (Leptinotarsa decemlineata) detect their predators using volatile cues, we tested how these cues work in conjunction with lethal predators to control beetles. We found that predators can still detect their prey, even when the synthetic odor is present. These experiments are complete and will be coupled with other concurrent research for publication.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Wetzel, W.C., N. Aflitto, J.S. Thaler. 2018. Plant genotypic diversity interacts with predation risk to influence an insect herbivore across its ontogeny. Ecology, https://doi.org/10.1002/ecy.2472
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Hermann, S.L. and J.S. Thaler. 2018. The effect of predator presence on the behavioral sequence from host selection to reproduction in an invulnerable stage of insect prey. Oecologia 188: 945-952. 10.1007/s00442-018-4202-7.
• Type: Journal Articles Status: Submitted Year Published: 2020 Citation: Aflitto, N and Thaler, J.S. Predator Odors Elicit a Temporally Dependent Non-Consumptive Effect in Prey, Journal of Applied Ecology, in review.

Progress 10/12/17 to 09/30/18

Outputs
Target Audience:This year, the project provided research opportunities to 3 undergraduate students (including 2 students conducting Honors Theses: Ari Grele, Fiona MacNeil and Abby Ditmar who assisted with experiments, one graduate student (Nick Aflitto), and one postdoc (Will Wetzel). Notably, one of the undergraduates Ari Grele, attended the Entomological Society of America and presented a poster on his research. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?In total three undergraduates, 2 graduate students (Julie Davis, Nicholas Aflitto), and 1 postdoc (Will Wetzel) conducted research on this project. These students received substantial one on one mentoring from me on experimental design and analysis and scientific writing. The graduate students and postdocs presented their findings at the Plant-Insect Discussion group and international meetings for feedback. Will Wetzel got a faculty job at Michigan State University. Notably, one of the undergraduates Ari Grele, attended the Entomological Society of America and presented a poster on his research. How have the results been disseminated to communities of interest?We have presented these results in undergraduate classes and multiple scientific meetings. What do you plan to do during the next reporting period to accomplish the goals?We will publish the final paper with the last results from Goal 1 about seasonal variation in prey responses to predators. We will complete Goal 2 which investigates how lethal predators and predator odors interact to affect beetle growth and survival.

Impacts
What was accomplished under these goals? Objective 1: Goal 1 was nearly completed. We found that adult beetle plot choice was not affected by the presence of predators but that adult feeding and oviposition was reduced (Wetzel et al 2018, Herman and Thaler 2018). Initial work conducted this summer indicates that both overwintering and summer beetle generations are responsive in the field. Our results indicate that predation risk drives adult herbivores to adjust behaviors that not only affect themselves (feeding) but also impact their offspring (oviposition).In addition, detection of predator cues is unlikely to have a large spatial range since initial colonization is unaffected. Yet, smaller scale cues are likely playing a role, evidenced by behavioral changes post-colonization. In our study, beetles choose to colonize patches with predators present even when safe patches were available which suggests that predation risk could alter herbivore population growth in habitats with heterogeneous risk by affecting host-plant utilization behaviors that occur post-colonization. Goal 2: Because Colorado potato beetles (Leptinotarsa decemlineata) detect their predators using volatile cues, we tested how these cues work in conjunction with lethal predators to control beetles. We began addressing this goal this year by establishing a greenhouse experiment with 5 3rd instar beetle larvae in bagged plants. The three treatments included: live predators, live predators with odor dispensers, and an empty odor dispenser control. The assay ran for 48hrs and was repeated three times. Over a 48h period, we did not find a difference in the number of beetles killed by adding the dispenser (average alive: predator only = 1.58 (±0.26), predator + dispenser = 1.56 (±0.25), control = 4.83 (±0.36)) (Fig. 5). We did however document a difference in larval position on the plant dependent on treatment. In the control and predator + dispenser groups, larvae were found on the top third of the plant 100% and 92% of the time, respectively. In the predator only treatment, the larvae were found on the top third of the plant 78% of the time, suggesting that the synthetic odor might be affecting the beetle's ability to detect the location of a predator, but not the predator's ability to find a beetle. This goal will be completed in the coming year.

Publications

• Type: Journal Articles Status: Published Year Published: 2018 Citation: Wetzel, W.C., N. Aflitto, J.S. Thaler. 2018. Plant genotypic diversity interacts with predation risk to influence an insect herbivore across its ontogeny. Ecology, https://doi.org/10.1002/ecy.2472
• Type: Journal Articles Status: Published Year Published: 2018 Citation: Hermann, S.L. and J.S. Thaler. 2018. The effect of predator presence on the behavioral sequence from host selection to reproduction in an invulnerable stage of insect prey. Oecologia 188: 945-952. 10.1007/s00442-018-4202-7.