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

In 2011, we continued field trials to evaluate attractants and a push-pull management strategy in MN and WI vineyards. As in previous years, trials in the vineyards used b-Caryophyllene lures attached to a yellow sticky card and in one location catnip oil repellents were placed in the center of the trapping area. In 2011, very low MALB population levels in the vineyards (< 0.30 per sticky card) led to grape clusters that were not infested. Despite the low level of MALB in the vineyards, some locations still had high levels of clusters with fresh damage (> 80%). Because of the lack of MALB in the vineyards, no significant differences were found for the level of clusters infested. However, this does indicate that high levels of damage can be present in the vineyards in the absence of MALB and that MALB is not a primary source of damage to the grapes. Because of the low levels of MALB in 2011 a no-cost extension was applied for and approved, and as a result, trials to evaluate the efficacy of the push-pull strategy will be repeated in 2012.

Objectives/Performance Targets

1. 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 repellents 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 repellants 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 repellents placed on sticky traps under field conditions.

Retention time in the field was assessed through the use of yellow sticky cards and by recording trap catches on a daily basis (Table 1). We saw very little difference in trap catch over the 7 day time period that the trial was conducted. There were some numeric differences early in the trial but variability was too high for differences to be significant. This may be a reflection of the low levels of adult MALB. Soybean aphid populations were low again in 2011 which also may be affecting the time spent in and around soybean. For all dates of the study, and despite lower levels of MALB, there was still higher trap catch with b-Caryophyllene single and double lure than in the untreated check treatment for most dates of the study, suggesting the potential of b-Caryophyllene as a lure and that lures could be used for at least 7 days without a significant drop in efficacy.

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 2011 at the U of MN Experiment Station in Rosemount, MN. As in 2008-2010, 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. 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 but all treatments had significantly higher trap catch than 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 2011, we were able to test the catnip oil repellent and found that under these field conditions the repellent actually caught just as many MALB as the attractants. This may indicate the catnip oil has no repellency or that at these low levels and under field conditions that the repellent may act as an attractant. This could also indicate that the amount of catnip oil in the repellent may need to be adjusted for greater efficacy as a repellent.

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

A catnip oil repellent was used in the test vineyards in 2011. However, based on field test results from Rosemount, MN in 2011, the catnip oil repellent may need to have a rate or composition modification made to improve repellency.

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

In 2011, trials were conducted in 3 test vineyards in MN and WI. Yellow sticky cards and lures with b-Caryophyllene at 500 µl 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 one of the test vineyards, 15 repellents 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 the vineyard with repellents) and in the area between the lures and repellents. In vineyards with no repellents, 50 clusters were sampled in both the area with cards and lures and the untreated check area. Numbers 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. 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 treatments in any of the test vineyards (Table 3). Despite having high levels of fresh damage on grape clusters at the Hastings vineyard and low levels of fresh damage on grape clusters in the Stillwater and Somerset vineyards, we did not see any infestation 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.

• Table 2
• Table 1
• Table 3

Impacts and Contributions/Outcomes

Results for 2011, with extremely low MALB populations, do not allow us to establish the effectiveness of the push-pull strategy in the test vineyards. We feel that based on previous results from the field trials that a push-pull strategy or a trapping strategy for managing MALB in grape vineyards still has potential. Previous 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), disease, or from vertebrates such as birds. Because MALB populations are 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. If high MALB populations coincide with a high percentage of clusters with fresh berry damage, it still may be necessary to use insecticides to mange MALB, even with an effective push pull strategy in place.

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