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

Using a 4-arm olfactometer, several compounds were identified as attractants for MALB. Field trials were conducted in 2008 and 2009 to evaluate attractants, and b-Caryophyllene at a rate of 500ul was identified as the best performing attractant / rate combination. Trials in vineyards using b-Caryophyllene lures attached to yellow sticky cards and a proprietary repellent placed in the center of the trellis area were conducted in 2009. Even though MALB per grape cluster in the area with the traps and lures was numerically lower than the untreated check in two of five vineyards, there were no statistically significant differences.

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).

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. We see the first two days of trap catch, 1DAT and 2DAT (Table 3) show that b-Caryophyllene has a significantly higher trap catch than the untreated check, while all other treatments are not significantly different from the untreated check. At 3DAT and 4DAT, we no longer see statistically significant differences but we continue to see numerically higher catches in b-Caryophyllene treatments. This may suggest that the variability is increasing and the lures may not be functioning as effectively as they were earlier in the study or it may reflect the inherent variability involved with trapping adult MALB. We see b-Caryophyllene again with significantly higher catches on 7DAT. This may suggest that lures would need to be changed frequently or an improved delivery device is necessary to provide a longer more controlled release of the compound.

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 and 2009 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 2008, 3 main attractant compounds were tested (Table 4). Rubber septa 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. In 2008, no significant differences were found among the candidate compounds when compared to the untreated check. However, numerical differences suggested that some attraction may be occurring. Thus, in 2009, the same compounds were used and at various rates above those used in 2008 (Tables 5 and 6). In addition, the trial was conducted in 2 separate soybean fields. In 2009, we see that b-Caryophyllene at 100 and 500 ul provided significant higher trap catch compared to the untreated check (Table 5). In the 2nd field trial (Table 6) there were no significant differences for any compound / rate combination when compared to the check; however, the b-Caryophyllene treatments were numerically the highest treatments in the test.

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

Candidate compounds for repellents were tested in 2008 and 2009 (see objective 3) alongside candidate compounds for attractants at the U of MN Experiment Station in Rosemount, MN (Tables 5 and 6). The repellent compounds, specifically Cis-Jasmone, and 2 proprietary repellents with a slow and fast release carrier did not show any significant differences in trap catch compared with the untreated check. In general, the repellents did show numerically lower trap catch than the untreated check and the b-Caryophyllene treatments (Tables 4-6).

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

In 2009, based on data from field tests of repellents and attractants in 2008 and 2009, we implemented a push-pull strategy in 5 test vineyards in MN and WI. Slow release repellents were placed across the middle of the vineyard. Around the perimeter of the vineyard, on one side of the repellents, yellow sticky cards with b-Caryophyllene 500 ul lures were placed every 20 ft. On the other side of the repellents, 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 (Table 7). 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. There were no differences in the proportion of freshly damage grapes between the two treatments in any of the test vineyards so that variable should not have been influencing the results (Table 7). In fact, at the Stillwater, MN and 2 Somerset, WI test vineyards the relatively low level of freshly damaged grapes likely led to the lack of infestation with MALB in the clusters as the sticky cards did indicate MALB was present in the vineyards, albeit at low levels.

• Obj. 1: Tables 1 and 2
• Obj. 2: Table 3
• Obj. 3: Tables 4-5-6
• Obj. 5: Table 7

Impacts and Contributions/Outcomes

We feel that results from the field trials to date are encouraging and suggest that a push-pull strategy or a trapping strategy for managing MALB in grape vineyards has merit. Results emphasize that managing grape berry damage based on 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 and around a vineyard is 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 soybean fields nearby can also be helpful in gaining an overall idea of potential MALB levels in the area but likely is not indicative of MALB presence on clusters in the vineyard. 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.

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