Final Report for LNC08-296
Project Information
After low MALB populations in 2011, we continued the study one more year into 2012 via an extension to attempt and collect further data on the efficacy of the push-pull strategy. However, 2012 proved to be an even lower density year than 2011. In addition, the first detection of a new invasive pest in MN grapes was made and confirmed as the spotted winged drosophila (SWD), Drosophila suzukii. Based on the new pest identification, insecticide sprays were applied to the entire vineyard to protect the grape clusters from infestation. In an early ripening variety, Leon Milot, levels of grape cluster infestation with maggots reached 80%. Our study had just commenced prior to the discovery of SWD and with a very low MALB catch on sticky cards, despite the usual high level of fresh splitting damage in Leon Milot, and the insecticide sprays, we decided to end the MALB trial as we would not be able to collect data for the push-pull strategy against MALB.
Overall we believe that the data collected over the course of these studies demonstrate the concept of the push-pull strategy has potential to be successful. Critical aspects of the strategy that must be in place to achieve a successful design include an effective trap coupled with an effective lure and a repellent that can aid in moving the insects toward the traps and the perimeter of the cropping area. In addition, the timing of deployment of the strategy is critical to influence insect populations, and for MALB specifically, both prior to infesting the crop and prior to harvest of the crop.
Introduction:
The focus of this project will be the development of a sustainable management plan to manipulate populations of H. axyridis to simultaneously repel beetles (push) from grape clusters within a vineyard, and also attract, trap and kill beetles (pull) at the perimeter of the vineyard. This approach builds on previous and ongoing research at the University of Minnesota, in cooperation with several grape and wine producers in Minnesota and Wisconsin. Moreover, this approach, recently referred to as a “push-pull” strategy is gaining acceptance worldwide as an effective pest management strategy in many cropping systems. For grapes, and particularly those grown for the increasingly popular Midwest wine industry, most growers prefer to avoid, or use less pesticide. With H. axyridis this is a major challenge, as this beetle has the potential to build up to very high levels near the end of the growing season, usually within 7-14 days before harvest. Although new insecticides have been approved for use near harvest, growers are reluctant to spray this close to harvest, due to the possibility of detectable residues on grapes, negative effects on farm workers who usually hand-harvest grapes, or potential impacts on final juice and wine product.
Harmonia axyridis has emerged as an economic, contaminant pest of wine throughout the eastern U.S., because it produces a foul defensive substance when they are crushed or disturbed; the process is known as “reflex bleeding”. Chemicals found in this liquid (methoxypyrazines) give the wine an unpleasant flavor and odor, often referred to as “burnt-peanut butter” affect. Recent work in our lab, in cooperation with the UofM Enology lab, and the Dept. of Food Science and Nutrition’s Sensory lab, has confirmed that the detection threshold (odor and taste) suggests that in-field infestations of just 3-5% of the clusters, infested with1 or more beetles/cluster, is sufficient to contaminate the wine and cause losses of entire lots of wine. Our previous field work, has confirmed that inexpensive yellow sticky cards can be used to monitor MALB in the field, to verify when populations migrate to the vineyard, typically late-August in Minnesota and Wisconsin. We have also developed rapid, reliable methods for sampling MALB in grape clusters.
The proposed research will benefit growers of wine grapes and grapes for juice. MALB has easily caused million dollar losses throughout the eastern U.S. in recent years in both industries, wine and juice grapes. We believe our approach is appropriate for this audience given their need for non-insecticidal alternatives. More important, we believe this technology is particularly suited to many of the relatively small grape growers in the NC Region, who currently only produce 1-4 acres each. The placement of repellents and traps in vineyards, is initially labor-intensive, but can be completed in ca. 2 hrs/acre and thus is feasible for smaller operations.
- 1)— Four-arm olfactometer to complete identification of most active attractants and repellents to H. axyridis under laboratory conditions (preliminary data for 6 compounds complete).
2)— Determine retention times (i.e., half-life) of candidate semiochemicals used for attractants and repellants placed on sticky traps under field conditions.
3)— Field assessment and efficacy of candidate “pull”-attractants (based on those found to be most efficacious from laboratory studies), using sticky cards (e.g. Galvan et al. 2006). This will be done at the Rosemount, UofM Agric. Experiment Station (UMORE Park), near soybean fields.
4)— In-field “push”-repellent studies to assess if volatiles can effectively repel H. axyridis.
5)— Combine the best push-pull compounds into a complete IPM program in vineyards.
Cooperators
Research
Objective 1. Four-arm olfactometer to complete identification of most active attractants and repellents to H. axyridis under laboratory conditions.
Methods.
Synthetic standards will be diluted in diethyl ether (e.g., 10-6 g / ?L), applied to a filter paper strip, and placed in one of the four arms of the olfactometer. The air will be delivered by an air delivery system (ARS, Gainesville, FL) at 200 ml / min. The air flow in each arm will be checked daily by a flowmeter before the beginning of the tests. The air movement inside the olfactometer chamber will be calibrated by making “white smoke” from dry ice and hot water. The chosen flow, 200 ml / min, should produce four separated air fields in the chamber. Before the air reached the olfactometer chamber, it was humidified by passing through individual containers with distilled water.
One male or female (10 to 30 days old, and starved for 24 hours) will be placed in the center of the olfactometer through the entrance located below the central chamber. During the introduction of each beetle into the chamber, the hose connecting the vacuum pump to the olfactometer will be disconnected. After the insect reached the chamber, the vacuum pump hose will be quickly connected to the olfactometer, and the bioassay will start. The position of the beetle will be recorded at 2-min interval for 20 min. If the beetle do not move for 3 consecutive observations (i.e., 6 min), the test will be halted, and the beetle will be discarded. Between runs, the olfactometer chamber will be swabbed with ethanol and pentane, and let dry for 5 minutes. At the end of each day, the olfactometer will be disassembled, washed with soapy water, and rinsed with distilled water, alcohol, and pentane.
Fifteen adult males or females will be used per each treatment-dose combination. The tests will be run between 10:00am and 3:00pm, at room temperature (23 ± 2°C). On each day, one treatment-dose-gender combination will be run. A treatment will be a single compound or a combination of compounds. Treatments with potential attractants are the conspecific compounds 2-isopropyl-3-methoxypyrazine (IPMP), 2-sec-butyl-3-methoxypyrazine (SBMP), and 2-isobutyl-3-methoxypyrazine (IBMP), the aphid alarm pheromone (E)-?-farnesene, the plant volatiles ?-terpineol, 2-phenylethanol, methyl salicylate, cis-jasmone, cis,trans-nepetalactone, cis,trans-nepetalactol, neomatatabiol, and dihydronepetalactone. The potential attractants will be placed in one arm of the olfactometer, and the other three arms will be left as blank. However, treatments with potential repellents (i.e., aphid alarm inhibitor (-)-?-caryophyllene, and plant volatiles camphor, and menthol) will be placed in three arms of the olfactometer, and one will be left as blank. Ten ?L of each treatment (compound diluted in hexane) will be applied to filter paper (1 cm x 1 cm), and placed in one of the four arms (attractants), or in three of the four arms (repellents). New arms to receive the treatments will be randomly selected each day. The observed data will be compared with expected frequency using chi-squared statistics. The relative stay of beetles in each arm will be compared by contrast using residual mean square from ANOVA.
Objective 2. Determine retention times (i.e., half-life) of candidate semiochemicals used for attractants and repellants placed on sticky traps under field conditions. Results from this objective will establish the number of days, or weeks, a bait should be left in the field.
The compounds evaluated in this experiment will be the ones that showed either attraction or repellence to H. axyridis under laboratory conditions from Objective 1. Compounds will be placed on rubber septa and attached to stakes with yellow sticky cards along the field edge of a soybean crop in mid-August to assess the attraction or repellence of H. axyridis over time. Yellow sticky cards will be attached to wooden stakes, approximately 3 ft above the ground, within the first rows of the edge of a soybean field. Rubber septa will be attached to the wooden stake directly below the sticky card. Data will be recorded daily for the presence and number of H. axyridis until at least 7 days have passed. Each treatment will be replicated 4 times.
Objective 3. To assess the efficacy of candidate “pull”-attractants (based on those found to be most efficacious from laboratory studies) under field conditions using sticky cards. This trial will be done at the Rosemount, UofM Agric. Experiment Station (UMORE Park), near soybean fields, so as not to confound or interfere with H. axyridis movement studies in the vineyards.
Over a 1-2-week period a study in soybean fields will be done to evaluate the effects of compound concentration, and compound ratio in a mix of compounds on the attraction or repellence to H. axyridis. For each location, 4 replicates (i.e., traps) of each compound concentration-ratio combination will be used. The number of concentration and ratio levels will depend on the number of compounds that showed attraction effects in the 4-arm olfactometer. Traps will be checked daily for lady beetles. A single compound will be applied to red rubber septa. Each rubber septa will be attached on a wooden stake at about 3 ft high from the ground. Each trap (i.e., one yellow sticky card and rubber seta with one compound) will be replicate four times in each field. Four traps with no compound on it will be used as control. The traps will be placed 50 ft apart on the edge of the soybean field.
Objective 4. In-field “push”-repellent studies to assess if volatiles can effectively repel H. axyridis.
Methods will be the same as in Obj. 3 and over a 1-2-week period a study in soybean fields will be done to evaluate the effects of compound concentration, and compound ratio in a mix of compounds on the attraction or repellence to H. axyridis. For each location, 4 replicates (i.e., traps) of each compound concentration-ratio combination will be used. The number of concentration and ratio levels will depend on the number of compounds that showed repellence effects in the 4-arm olfactometer. Traps will be checked daily for lady beetles. A single compound will be applied to red rubber septa. Each rubber septa will be attached on a wooden stake at about 3 ft high from the ground. Each trap (i.e., one yellow sticky card and rubber seta with one compound) will be replicate four times in each field. Four traps with no compound on it will be used as control. The traps will be placed 50 ft apart on the edge of the soybean field.
Objective 5. Combine the best push-pull compounds from objectives 3 and 4 (Year 1) into a complete IPM program to be evaluated in vineyards in 2010 and 2011 seasons (Years 2 and 3).
This study will be conducted in one treated and one untreated block per vineyard-variety combination. Three vineyards, each containing Frontenac, Foch, or both varieties of wine grapes will be used in this trial. In each vineyard, a block containing only one variety (i.e., either Frontenac or Foch) will be divided in two. In one of these sub-blocks, rubber septa baited with a repellent will be placed across the center of the sub-block. The repellent bait will contain one or more repellents from the field study in soybean fields. Yellow sticky traps containing a rubber septum baited with attractants will be placed around the edge of the same block. The attractant bait will contain one or more repellents from the field study in soybean fields. The untreated sub-block will not contain any repellent or attractant. Each vineyard-variety combination (i.e., n = 3) will be used as a replicate. Paired t-test will be used to compare the frequency of H. axyridis adults in the yellow sticky traps as well as the infestation level of H. axyridis in grape clusters in treated and untreated sub-blocks.
1)— Four-arm olfactometer to complete identification of most active attractants and repellents to H. axyridis under laboratory conditions (preliminary data for 6 compounds complete).
In the fall of 2008, odds ratio and its confidence limits identified cis-jasmone (1 ?L/10 ml), ?-caryophyllene, and dihydronepetalactone as attractants (Table 1), and cis-jasmone (100 ?L/10 ml), and ?-terpineol as repellents to H. axyridis adults (Table 2). Two combinations of compounds, one containing E-?-farnesene, ?-terpineol, 2-phenylethanol, methyl salicylate, and cis-jasmone, and another containing cis-trans-nepetalactone and cis-trans-nepetalactol (3:1) also attracted H. axyridis adults (Table 1). In addition, four combinations of compounds containing i) camphor and menthol; ii) E-?-farnesene, ?-terpineol, 2-phenylethanol, methyl salicylate, cis-jasmone, and ?-caryophyllene; iii) dihydronepetalactone and neomatatabiol; and iv) cis-trans-nepetalactone and cis-trans-nepetalactol (1:1), all significantly repelled H. axyridis adults (Table 2).
Since the odds ratios were estimated from coefficients of log-linear models that held the treated arm as the reference cell, the odds ratio for each of the non-treated arms was compared to the reference cell. For example, when cis-jasmone (1 ?L/10 ml) was used for H. axyridis females reared in the laboratory, the odds (CL) of these beetles to move or stay in the first non-tread arm was 0.2 (0.1 – 0.4) times compared to the odds of these beetles to move or stay in the treated arm (Tables 1 and 2). That is, the females were statistically less likely to move or stay in a non-treated arm than in the treated one since the confidence limit did not include 1. In this case, when the 3 non-treated arms showed odds ratio and confidence limits lower than 1 compared to the treated arm, we concluded that cis-jasmone (1 ?L/10 ml) was an attractant to H. axyridis females reared in the laboratory. Similar conclusions were made for other treatments that attracted H. axyridis adults except for the treatment that combining camphor and menthol. In this combination, 3 arms were treated, and when the odds (CL) of these beetles to move or stay in the 3 tread arm was lower than 1, we concluded that the combination of camphor and menthol was a repellent to H. axyridis adults (Table 2). On the other hand, cis-jasmone (100 ?L/10 ml) and ?-terpineol (100 ?L/10 ml) among other treatments increased the odds of H. axyridis adults to move or stay in the 3 non-treated arms (Table 2). Therefore, these treatments showed a repellence effect to H. axyridis adults.
With additional field testing, one or more of these compounds could offer potential for use as attractants or repellents in the field, and may be promising for use in push-pull systems for high value fruit crops, such as grapes, that are grown in small areas. However, prior to implementation of these compounds in a push-pull system for H. axyridis, candidate compounds must first be tested in the field using sticky traps or other devices to collect beetles with attractants, or to show the potential for repellency. For example, the attractants could be field tested by attaching each compound (e.g., via rubber septa) to yellow or color-neutral sticky traps. Yellow sticky traps alone are known to be attractive to H. axyridis adults, and the use of an attractant should be expected to enhance trap catch.
2)— Determine retention times (i.e., half-life) of candidate semiochemicals used for attractants and repellants placed on sticky traps under field conditions.
Retention time in the field was assessed by recording trap catches on a daily basis. Over the duration of the study it would appear that the candidate lure compounds did demonstrate positive results compared with the untreated check treatment. How well the lures performed over time appeared to be dependent on the density of MALB in the field. With high population levels as in 2009, there appears to be an indication that the b-Caryophyllene 500µl lure shows promise out to 7 days of field exposure. However, over the next 3 years, typically with lower population levels, there were few statistical differences between the lures and the untreated check over time. A trend was present for the b-Caryophyllene 500µl treatment to catch MALB at a higher rate than the untreated check but with lower densities the variability of the data is too great to show statistical differences.
3)— Field assessment and efficacy of candidate “pull”-attractants (based on those found to be most efficacious from laboratory studies), using sticky cards (e.g. Galvan et al. 2006). This will be done at the Rosemount, UofM Agric. Experiment Station (UMORE Park), near soybean fields.
Field assessments were conducted in 2008 - 2012 at the U of MN Experiment Station in Rosemount, MN. Yellow sticky cards were placed in the edge of soybean fields on 3 ft high wooden stakes and the candidate attractant compound was placed on a rubber septa and attached to the wooden stake just below the yellow sticky card. In 2009, b-Caryophyllene lures appeared to provide the best activity for MALB. The high rate of 500µl was selected to move forward with field testing in the following years of the study. In the remaining years of the study, except 2011, the b-Caryophyllene 500µl lure did not catch significantly higher numbers of MALB than the untreated check. This may be attributable to the drop in MALB population levels.
4)— In-field “push”-repellent studies to assess if volatiles can effectively repel H. axyridis.
Candidate compounds for repellents were tested in 2008 - 2012, (see objective 3) alongside candidate compounds for attractants at the U of MN Experiment Station in Rosemount, MN. The repellent compounds tested were Cis-Jasmone, 2 proprietary repellents with a slow and fast release carrier, Predalure®, and Catnip oil. None of the repellent compounds showed any significant differences in trap catch compared with the untreated check except Catnip oil in 2011 where it actually caught significantly more MALB than the untreated check. However, the Catnip oil did not have a significantly higher MALB catch than the b-Caryophyllene lures. In general, the repellents did show numerically lower trap catch than the untreated check and the b-Caryophyllene treatments (Tables 3-13).
5)— Combine the best push-pull compounds into a complete IPM program in vineyards.
In 2009 - 2012, based on data from field tests of repellents and attractants (see objs. 1 and 2) we implemented a push-pull strategy in 5 test vineyards in MN and WI. Slow release repellents were placed across the middle of an area of the vineyard. Around the perimeter of the vineyard, yellow sticky cards with b-Caryophyllene 500µl lures were placed every 20 ft. In an area adjacent to the where the sticky cards and lure/repellents were setup, no cards or lures were placed and this served as the untreated check. Fifty grape clusters were sampled in each area and the number of MALB per cluster and the presence of fresh damage on the grapes were recorded. On each sample date, the number of MALB present on sticky cards was also recorded. In 2009, while no significant differences were found in the number of MALB between the untreated and treated area, numeric trends in both Hastings, MN sites suggest the lure/trap/repellent combination may be reducing infestation levels with a reduction in the number of MALB per cluster. However, in the remaining years of the study MALB populations were extremely low in the vineyards despite some vineyards having higher levels of fresh damage on the clusters of grapes. Low MALB density did not allow us to fully evaluate the push-pull strategy in those years. Data for 2012 is not shown because of the detection of the invasive insect pest Drosophila suzukii, the spotted winged drosophila (SWD), after the 1st vineyard sample. Insecticide sprays were applied after the detection of SWD was confirmed.
We feel that results from the field trials were encouraging and suggest that a push-pull strategy or a trapping strategy for managing MALB in grape vineyards has merit. Results re-emphasize that managing physiological damage to the grape berry from environmental factors that lead to splitting or from vertebrates such as birds are critical to minimizing potential cluster infestations from MALB. Because the presence of MALB in the vineyards was variable, it is difficult to measure the potential efficacy of the push-pull strategy and may require this management tactic to be used in coordination with other grape management options such as variety selection, water management, and fertility management to minimize physiological splitting. Being aware of local population levels of MALB in the surrounding area (e.g., in soybean fields) can also be helpful in gaining an overall understanding of the potential for MALB infestations in the vineyard but likely is not indicative of if MALB will be present on clusters. With high MALB population levels and high proportion of clusters with fresh berry damage, there still may be a need to use insecticides to manage MALB even with an effective push-pull strategy in place. It is encouraging to see that when MALB populations decline that the risk for infestations in vineyards declines as well, even when high levels of fresh berry damage are present in the vineyard.
Economic Analysis
Economic evaluations were not feasible given the low densities of MALB in the vineyards during the majority of the study.
Farmer Adoption
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Educational & Outreach Activities
Participation Summary:
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Project Outcomes
Areas needing additional study
Based on the continual arrival of new invasive species into the United States and the North Central Region, there is a need to consider how the management of multiple pests in fruit crops, specifically grapes, will be affected. Minnesota grapes are currently either experiencing pest infestation or infestation is anticipated by spotted winged drosophila, japanese beetle, brown marmorated stink bug, and multicolored Asian lady beetle. Management of these pests individually or as a pest complex, will need to be addressed when viewing grape production and pest managment as a whole.