The title of the project: From Beneficial Insect to Economic Pest: a Sustainable Management to the Asian Lady Beetle in Midwestern Grapes

The title of the project: From Beneficial Insect to Economic Pest: a Sustainable Management to the Asian Lady Beetle in Midwestern Grapes

Summary

This research provided significant contributions to our knowledge of the Harmonia axyridis-wine grape system. Adult beetles feeding on wine grapes appeared to increase their overwintering survival. Also, yellow jackets and beetles were not able to break the skins of grape berries directly. For growers, we developed practical sampling plans based on six potential action thresholds. We also examined the efficacy of biorational and conventional insecticides for managing H. axyridis. The combination of a sampling plan and the use of effective insecticides proved useful to growers in 2005; both will be essential components of sustainable management plans for this new pest.

Objectives/Performance Targets

1 – Evaluate floating row cover barriers to exclude H. axyridis from grapes near ripening.

This objective will compare the efficacy of row cover in protecting grapes from H. axyridis with the efficacy of insecticides and an untreated check. To be a practical management tactic, the mesh must not alter the quality of grapes for wine production. Potential negative effects from shade induced by the row cover will be evaluated through measuring sugar, pH and time to ripening of grapes.

2 – Spatial distribution of H. axyridis infestations in vineyards.

This objective will evaluate the spatial distribution of H. axyridis in vineyards, and develop a sampling plan for H. axyridis in wine grapes.

3 – Biological impetus and mechanisms for H. axyridis feeding on fall ripening grapes.

This objective will determine how H. axyridis utilizes simple sugars obtained from grapes. Sub-objective 3A evaluate the survival of males and females of H. axyridis adults after feed on a 25% sucrose solution, fresh squeezed grape juice, or water alone for 48 h. Sub-objective 3B will determine the amounts of body sugars and lipids of males and females of H. axyridis adults after feed on the aforementioned diets.

4 – Interaction among H. axyridis, wasps, and grapes: source of initial fruit damage?

This objective will determine if wasps cause direct damage that subsequently allows H. axyridis feeding.

Accomplishments/Milestones

1 – Evaluate floating row cover barriers to exclude H. axyridis from grapes near ripening.

In 2005, the density of H. axyridis adults and the proportion of clusters infested with H. axyridis adults at harvest in plots treated with bifenthrin 7 DBH, bifenthrin 30 DBH, zeta-cypermethrin 7 DBH, and imidacloprid 1 DBH was statistically lower than untreated plots.

In 2005, levels of sugar, titratable acidity, and pH in the grape juice did not differ statistically across the treatments.

In 2005, levels of alcohol, titratable acidity, and pH in the wine did not differ statistically across the treatments.

2 – Spatial distribution of H. axyridis infestations in vineyards.

Taylor’s power law parameters a = 3.28 and b = 1.24 were determined by a regression analysis of the log-mean and log-variance of 34 data sets (slope = 1.24 ± 0.04 (SE), intercept = 0.52 ± 0.06, and R2 = 0.96). The b value greater than 1 suggests that an aggregated dispersion for H. axyridis in the vineyards. In addition, we did not notice any edge effect of H. axyridis distribution, suggesting that a trap cropping would not be a feasible control tactic.

We developed eight sampling plans to assess adult density or infestation level. The sampling plans were developed using 49 data sets collected from commercial vineyards sampled in 2005. The two enumerative plans covered two precision levels (0.10 and 0.25), and the six binomial plans covered six action thresholds (3, 7, 12, 18, 22, and 31 % of cluster samples infested with at least one H. axyridis). The average sample number (ASN) for each sampling plan was determined through analyses using resampling software. For research purposes, with a precision level of 0.10 (SE/ ), the enumerative plan resulted in an ASN of 552 clusters. For IPM applications, the enumerative plan with a precision level of 0.25, resulted in an ASN of 184 clusters. By contrast, the binomial plans resulted in much lower ASNs, and should be more practical for IPM purposes. At a tally threshold of 1 adult per cluster, the operating characteristic curve, and the six action thresholds provided binomial plans where the ASN ranged from only 19 to 26 clusters (Fig. 1). We also develop decision stop lines for each action threshold (Fig. 2). In addition, the percentage of correct decisions ranged from 83 to 96, and the percentage of incorrect decision to not treat was always smaller than incorrect decision to treat.

3 – Biological impetus and mechanisms for H. axyridis feeding on fall ripening grapes.

Sub-objective 3A in 2005: Survival of H. axyridis males in all diets (83.24 ± 6.59 to 92.45 ± 1.18) was significantly higher than in the untreated check (39.39 ± 10.73) (Fig. 3A; Table 10). Survival of H. axyridis males fed on a solution of sucrose 25 % was the highest, and it was followed by H. axyridis males fed on water, and on grape juice (Fig. 3A; Table 10). Survival of H. axyridis females was significantly higher than males (F = 14.47, P = 0.0003, and df = 1, 96). Survival of H. axyridis females fed on grape juice (92.05 ± 1.49) was significantly higher than in the untreated check (75.46 ± 3.18) (Fig. 3B; Table 10).

4 – Interaction among H. axyridis, wasps, and grapes: source of initial fruit damage?

Three treatments were used in this trial: i) grape berries with intact skin and yellow jackets; ii) grape berries with intact skin and H. axyridis adults; and iii) grape berries with intact skin alone. For each treatment, 3-4 grape berries of ‘Frontenac’ with intact skin were set in a 150 x 80 mm Petri dish with one yellow jacket (i), one H. axyridis adult (ii), or nothing (iii). The treatment with yellow jackets was replicated 21 times, and the other two treatments were replicated 10 times. After 24 h, insects were removed from the Petri dishes, and each berry was carefully inspected for injury. All berries, for all treatments, did not have any injury. These results showed that neither yellow jackets, nor H. axyridis adults can cut off the grape berry skin under laboratory conditions.

Impacts and Contributions/Outcomes

Outcomes from this research have improved the basic knowledge of the wine grape-H. axyridis system and contributed to a more sustainable approach for managing H. axyridis in wine grapes. Regarding basic knowledge, we found that feeding on wine grapes (i.e., uptake of sugar) during the fall (Sept.), may increase the survival of H. axyridis through the winter. We also found that survival rate of males is more dependent on sugar uptake before overwintering than the survival rate of females. In addition, we observed that yellow jackets and H. axyridis adults are not able to directly break grape berry skins. This result indicates that control of yellow jackets in vineyards may not affect H. axyridis feeding, and that H. axyridis feeding on wine grapes depends on previous injury in grape berries (e.g., injury caused by birds of physiological splitting). For pest management, we developed six practical binomial sampling plans based on six potential action thresholds for H. axyridis in wine grapes. The use of sampling has prevented growers to spray their vineyards with insecticide. For example, in 2005, only one out of five vineyards that were sampled required insecticide spray. This represents less environmental contamination, lower insecticide exposure to farmers, and more consistent economic returns for wine grape production. In addition to sampling, we also examined the efficacy of possible insecticides to be used in wine grapes to manage H. axyridis. Based on insecticide efficacy, pre-harvest intervals for currently labeled insecticides, and the late-season influx of H. axyridis infestations, chemical control is presently limited to carbaryl at 7 days before harvest (DBH), malathion at 3 DBH, or imidacloprid 1 at DBH. The combination of a sampling plan and the use of effective insecticides are new, essential components for the sustainable management of this exotic beetle pest.

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