Behavior Manipulation of the Multicolored Asian Lady Beetle in Midwest Vineyards: Novel Repellants and Attractants for a Sustainable IPM "Push-pull" Strategy

Behavior Manipulation of the Multicolored Asian Lady Beetle in Midwest Vineyards: Novel Repellants and Attractants for a Sustainable IPM "Push-pull" Strategy

Summary

Field trials were conducted in 2010 to evaluate attractants and a push-pull management strategy in MN and WI vineyards. Trials in vineyards used b-Caryophyllene lures attached to yellow sticky cards and catnip oil repellents were placed in the center of the trapping area. Low MALB population levels in the vineyards (>1.05 per sticky card) led to grape clusters that were infested at a level of 0.04 MALB per cluster or less. This low level infestation occurred despite having relatively high levels (~50%) of clusters with fresh damage in most test vineyards. Because of this low level of infestation, no significant differences were found.

Objectives/Performance Targets

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.

Accomplishments/Milestones

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).

Completed in 2008 and 2009. See 2009 annual report.

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 (Table 1). We saw very little difference in trap catch over the 9 day time period that the trial was conducted. This may be a reflection of the relatively low levels of adult MALB as compared to previous years and this may suggest that there could be some relationship between population level and efficacy of the lure. In addition, soybean aphid populations were lower in 2010 than in 2009 which may influence the movement of MALB by affecting the time spent searching for food sources. Despite the lower levels of MALB in the overall study, there was still significantly higher trap catch with b-Caryophyllene single lure and Agbio b-Caryophyllene lure at 7DAT. Again, this data may also reflect the inherent variability associated with trapping MALB adults.

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 2010 at the U of MN Experiment Station in Rosemount, MN. As in 2008 and 2009, yellow sticky cards were placed on the edge of soybean fields on 3 ft high wooden stakes and lures were placed on a rubber septum and attached to the wooden stake just below the yellow sticky card. In 2010, 2 new lure delivery systems were tested, both from Agbio Inc (Table 2). The new lure delivery systems were supposed to provide a more controlled and consistent release of the attractant compounds. In addition, we continued to test compounds on rubber septa and these were treated one week prior to testing and stored in a sealed vial until the day the septa were put in the field. Traps were checked daily and adult MALB were removed from the sticky trap with forceps. Cards were not changed unless the trial lasted longer than 7 days at which time new sticky cards were placed on the wooden stakes. No significant differences were found between the treatments and the untreated check (Table 2). As mentioned in Objective 2, this may be influenced by the relatively low MALB populations that were present in soybean during the trial. In 2010, we were also able to conduct an additional trial where the lures were 10 days old and MALB numbers had increased dramatically in soybean (Table 3). Again, there were no significant differences between any treatments and the untreated check. However, the b-Caryophyllene lures caught a much higher number of beetles than the untreated check (Table 3). Unfortunately, with the higher populations, higher variability in trap catch occurred masking any potential treatment effects.

4) In-field “push”-repellent studies to assess if volatiles can effectively repel H. axyridis.

A new repellent was used in the test vineyards in 2010 (see objective 5.) Based on information from Agbio Inc., catnip oil was used as a repellent compound in the test vineyards.

5) Combine the best push-pull compounds into a complete IPM program in vineyards.

In 2010, we redesigned the setup of the push-pull study in the test vineyards. The trials were implemented in 4 test vineyards in MN and WI. Yellow sticky cards and lures with b-Caryophyllene at 500 ul were attached to 3ft high wooden stakes, placed every 20ft, on all four sides (on the perimeter) of one half of each test vineyard. In 2 of the test vineyards, 20 repellents each were placed in the center of the area where the sticky cards had been placed and the repellents were attached to the trellis wires. On the other half of the test vineyard, there were no cards, lures, or repellents and this area served as the untreated check. Fifty grape clusters were sampled in the untreated check area, in the area where the repellents were located (for 2 test vineyards) and in the area between the lures and repellents (for 2 test vineyards). In vineyards with no repellents 50 clusters were sampled in both the area with cards and lures and the untreated check area. 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 (Table 4). No significant differences were found in the number of MALB between the untreated, treated, or repellent areas for any test vineyard. There were no differences in the proportion of freshly damage grapes between the two treatments in any of the test vineyards (Table 4). Despite having moderate levels of fresh damage on grape clusters, we did not see significant infestations of the clusters by MALB. This supports previous findings that suggest if MALB populations are low, infestation will be low regardless of the proportion of clusters with fresh damage. Conversely, if fresh damage is low, infestations of MALB will be low regardless of MALB population levels.

• Obj. 2: Table 1
• Obj. 3: Tables 2 and 3
• Obj. 5: Table 4

Impacts and Contributions/Outcomes

Based on 2010 results and low MALB populations, we are unable to establish the effectiveness of the push-pull strategy in the test vineyards. We feel that results from the field trials suggest that a push-pull strategy or a trapping strategy for managing MALB in grape vineyards still has merit. As in 2009, results demonstrate that there is a close relationship between MALB population levels and the levels of fresh damage in grape clusters. If high levels of fresh grape damage are present, high MALB infestations are likely given moderate MALB population levels. However, in the absence of fresh damage in the grape clusters, infestations with MALB will be low regardless of MALB population levels. This highlights the importance of managing grape berry damage caused by environmental factors that lead to splitting (fresh damage) or from vertebrates such as birds. Because MALB populations appear to be variable from year to year and location to location, measuring the potential efficacy of the push-pull strategy is difficult and may suggest a complimentary approach is more appropriate. This may include management tactics being used in coordination with other grape management options such as variety selection and water and fertility management to minimize splitting. In addition to these management tactics it still may be necessary to use insecticides to mange MALB, if MALB population levels are high while a high proportion of clusters with fresh berry damage are present in the vineyard.

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