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Applying Landscape The lack of effective con- trol measures for straw- Ecology to Improve berry sap beetle is a problem at many farms. Strawberry Sap Beetle The beetles appear in strawberry fi elds as the Management berries ripen. The adult beetle feeds on the un- Rebecca Loughner and Gregory Loeb derside of berries creat- Department of Entomology ing holes, and the larvae Cornell University, NYSAES, Geneva, NY contaminate harvestable he strawberry sap beetle (SSB), fi eld sanitation, and renovating promptly fruit leading to consumer Stelidota geminata, is a significant after harvest. Keeping fi elds suffi ciently complaints and the need T insect pest in strawberry in much of clean of ripe and overripe fruit is nearly the Northeast. The small, brown adults impossible, especially for U-pick op- to prematurely close (Figure 1) are approximately 1/16 inch in erations, and the effectiveness of the two length and appear in strawberry fi elds as labeled pyrethroids in the fi eld is highly fi elds at great cost to the the berries ripen. The adult beetle feeds variable. Both Brigade [bifenthrin] and grower. Our research has on the underside of berries creating holes. Danitol [fenpropathrin] have not provided Beetles prefer to feed on over-ripe fruit but suffi cient control in New York and since shown that the beetles do will also damage marketable berries. Of they are broad spectrum insecticides they not overwinter in straw- more signifi cant concern, larvae contami- can potentially disrupt predatory mite nate harvestable fruit leading to consumer populations that provide spider mite con- berry fi elds. This may complaints and the need to prematurely trol. The beetles are not resistant to pyre- lead to a bait and trap close fi elds at great cost to the grower. The throids but rather tend to feed underneath beetles are widespread and present at all fruit where they are unlikely to come in control strategy. of 14 New York farms sampled in 2002 contact with insecticide. The use of large (Figure 2), but seem to be a signifi cant quantities of water (200 gallons/A) only problem only in certain locations. Concern marginally improves control. colonize strawberry plantings in the late regarding SSB centers on the lack of effec- It is not atypical to fi nd strawberries, spring, causing economic damage. tive control measures if the beetles become raspberries, cherries, apples, melons, and Some possibilities for reducing SSB a problem at a farm. Understanding why sweet corn, all potential food sources for damage include: 1) altering management SSB reaches high densities on some farms SSB, growing on the same farm to sup- practices to lower susceptibility of fruit to and not others is a key goal of our current port direct marketing of produce through SSB, 2) planting strawberries at a suffi cient research since it should provide insights roadside stands, U-Pick operations, and distance from alternate food sources and into new management strategies. farmer’s markets. These alternate food overwintering sites to minimize access Current recommendations for control sources potentially help promote large to resources that contribute to a larger include applying pyrethroids, improving overwintering populations of SSB that overwintering SSB population, and 3) Figure 1. Strawberrry Sap Beetle (SSB) Figure 2. Agricultural region classifi cations used to group New York strawberry farms. Approximate locations of sampling sites are indicated by black circles. Strawberry sap beetles were found at varying levels at all 14 sites during a survey conducted in 2002. NEW YORK FRUIT QUARTERLY • VOLUME 14 NUMBER 4 • 2006 27 developing traps that would attract and Table 1 kill adults before they enter strawberry fi elds in the late spring/early summer. Mean total ± standard error and range for adult SSB collected in wooded areas and In this article we summarize the crops before and during fruiting in 2005. results of three years of research that examines how cultural practices (plant structure and time of renovation) and habitat surrounding strawberry fields (wooded areas and alternate food sources) infl uence the size of the SSB population. This work has led to some initial progress in understanding SSB biology needed to develop alternative management tactics. Overwintering habitat ries held off the ground in 2005 during contact with the ground even when fruit A total of fi ve adult SSB were found in one time period when all cultivars had at is ripe fits with anecdotal reports that the 220 soil cores collected from wooded least some ripe fruit (Figure 3). Although the cultivar tends to hold fruit off the areas in the spring of 2004, while no SSB there was a signifi cant positive correlation ground and thus is less damaged by SSB in were present in the 480 samples taken between fruit being ripe and in contact the fi eld. from fi elds of other crops during the same with the ground, certain cultivars did The hypothesis that plant structure time period. All beetles in the samples not fi t this trend. The cultivar ‘Serenity’ may be useful in developing control tactics came from wooded areas at one farm had a high proportion of fruit touching is based on the assumption that berries in known to have high densities of SSB. More the ground before most of the fruit had contact with the ground are more likely beetles were found in 2005 after increasing ripened, while ‘Evangeline’ had a low pro- to be damaged by SSB. To test this as- the area sampled from 0.16 m2 (wooded portion of fruit in contact with the ground sumption, we conducted an experiment area) or 0.26 m2 (crops) in 2004 to 2.03 m2 in at peak ripeness. The fi nding that berries at NYSAES where we assigned three-foot 2005. Beetles were found in both of the two on ‘Evangeline’ are less likely to come in sections of a three-year-old strawberry wooded areas sampled, in blueberry, and in raspberry for samples collected before fruiting occurred in the late winter/early Figure 3 spring and after fruit residue was present Mean ± standard error of the mean for A) Proportion of ripe fruit touching the during the fi eld season (Table 1). No SSB ground and B) Proportion of total fruit ripe for 14 strawberry cultivars in a trial were found in any of the three strawberry garden planting at NYSAES. fi elds for the overwintering sample, but beetles were found in samples collected when fruit began to ripen in the fi eld. The absence of SSB from early season samples in strawberry confi rms that most, if not all, beetles move into berry fi elds as fruit ripens. This has important management implications. First, it makes no sense to apply insecticides for controlling SSB before fruit ripening. Second, we may be able to exploit this colonization pattern by intercepting the beetles before they enter the fi eld using traps baited with an attrac- tive lure and an insecticide (see below). Strawberry plant structure Sampling and manipulative experi- ments were designed to better under- stand how variation in plant structure of strawberry cultivars could impact fruit resources available to the SSB population. Specifi cally, since SSB adults and larvae are generally found on fruit touching the ground, cultivars that tend to hold their fruit off the ground may experience less damage. To address this hypothesis, we sampled 14 strawberry cultivars planted out at NYSAES for the proportion of ber- 28 NEW YORK STATE HORTICULTURAL SOCIETY ground. The beetles may preferentially Figure 4 feed on fruit touching the ground and only damage fruit in the canopy when Mean ± standard error of the mean for the proportion of berries damaged in cages densities of SSB are high. Damage to fruit assigned to treatment combinations of strawberry clusters pinned down or staked in the plant canopy has been reported in up and inoculated with strawberry sap beetle or not. Non-inoculated plots were such situations at commercial farms. Even included to control for slug damage, which can appear similar to feeding damage a comparatively low proportion of fruit in caused by adult SSB. contact with the ground may provide SSB with a greater food resource than needed. In such a case, we would expect a similar density of beetles across all cultivars as was found in a sampling of 28 cultivars in a strawberry cultivar trial monitored at Penn State University by Kathy Dem- chak, Senior Extension Associate for small fruit. Although the population of SSB in the planting was low, beetles were found in almost all plots. Overall, the potential appears limited for directly impacting the SSB population by choosing a strawberry cultivar with a particular growth habit. Time of strawberry plot renovation A manipulative experiment was used to investigate the effect of time of renova- tion on the number of SSB emerging from planting to four treatments: 1) all clusters direct contact with the ground are more strawberry with the idea that rototilling of fruit pinned to the ground, no SSB, 2) likely to be damaged by SSB than ber- may kill or wound SSB larvae and pu- all clusters pinned down to the ground, ries in the canopy, although the results pae before they have time to complete SSB added, 3) all clusters staked up off the also clearly show that SSB was willing development and leave the fi eld. Plots ground, no SSB added, and 4) all clusters to feed on fruit not touching the ground within a strawberry planting at NYSAES staked up, SSB added. Plots were covered (Figure 4). were randomly assigned to either rototill- with a cage, and fruit was evaluated for While proportion of fruit touching ing immediately after mowing (prompt damage two days later.

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