Final Report. Cooperator: Dr. Amanda Hodges, Assistant Extension Scientist, Univ. of Florida

Transcription

1 Final Report Project Directors: Dr. Oscar E. Liburd and Dr. Gurpreet Brar Cooperator: Dr. Amanda Hodges, Assistant Extension Scientist, Univ. of Florida Project Title: Developing spotted wing drosophila (Drosophila suzukii) integrated pest management program in blueberry and strawberry crops: Monitoring, management and outreach Objectives 1: To initiate an SWD surveys in strawberry fields and expand on the current SWD survey in blueberry plantings A: Monitoring for Spotted Winged Drosophila in Florida Strawberry and Blueberry Fields Spotted winged drosophila (SWD) was monitored in the field using apple cider vinegar (ACV) baited traps. Each trap was made from a 1-liter clear plastic container that had 1-12 small holes near the rim of the container. Each trap was baited with ~15 ml of the ACV and placed under shaded areas near the host crops (blueberries and strawberries). SWD monitoring in strawberries: Traps were deployed on 16 farms in Plant City, Florida (the principal strawberry growing area), 6 farms in Bradford County, Florida, and 4 farms in the Alachua County area. Sampling in Plant City area was conducted between January 22 and March 24, 214 (peak harvest times for strawberries). Farm size ranged from about 15 to 1 acres, where one of the small fields produced organic strawberries. Depending on field size, each site had from 3 to 5 traps. Sampling was conducted 4 times during the period on February 9-1 (Time 1), February (Time 2), March 9-1 (Time 3), and March (Time 4). To determine if SWD were emigrating from the neighboring wooded areas near strawberry fields, traps were set up in the field (within or near strawberry plants) and others were set up on the perimeter of the fields. Bradford and Alachua Counties are in the northeastern and north central part of the state, consequently, the strawberry season is a few weeks behind Plant City. Sampling was conducted between February 25 th and May 6 th 214. The farms in this region are also much smaller ranging from.25 acres to 5 acres and therefore all traps were set within the field. In all locations, the baiting liquid was changed every two weeks. Trap collections were brought back to the Small Fruit and Vegetable IPM Laboratory where SWD males and females were identified under a dissecting microscope. Numbers of other Drosophilidae species were recorded including those from another invasive species, Zaprionus indianus or African Fig fruit fly. SWD monitoring in blueberries: Monitoring in blueberries was conducted between April 1 st and May 3 th 214. Sampling was conducted at 7 and 14 days intervals between sampling dates. Sampling was conducted on 13 farms in 8 counties. Traps numbers varied between 2 and 5 depending on the size of the farm. Results and Discussion: Plant City Farms (strawberries) 1

2 Table 1 shows the mean number of SWD counted per farm on each sampling time and the overall mean for the season in Plant City area. Out of the 16 farms sampled, SWD was found on 8 of the farms. On our 3 rd sampling date (March 9-1) no SWD was found which may be due to insecticide applications. After discussing the pest status (presence of SWD) on their farms with several growers embarked on a rotational spray program. Additionally traps were set in the perimeter of the field on the 3 rd sampling date and the results showed an increase in the number of SWD trapped in perimeter traps. This may indicate that SWD populations might be emigrating from the wooded areas adjacent to the strawberry fields. An attractant more favorable than apple cider vinegar may help to increase detection of SWD in the field. The number of SWD in perimeter and field traps were also compared separately for period 1 and period 4 (Tables 2). For period 1, none of the traps in the field attracted SWD, but 7 of the perimeter traps (26.92%) did have SWD. For period 4 after data normalization, only 1 field trap (.6%) had SWD, but there were 6 perimeter traps (37.5%) with SWD. SWD population appears to be more predominant in the perimeter than within the strawberry fields. Only two SWD were found in the organic field. Results and Discussion: Bradford and Alachua County Farms (strawberries): Figure 1 shows the total number of SWD adults counted per each farm per sampling time Bradford County. At least one SWD adult (either a male or a female) was recorded on each farm at one particular time during the sampling period (Feb to May). Farm 6_T had up to 8 adults (7 females and 1 male) captured in the four traps early on March 12 th. The SWD population on this farm reduced to zero during the following sampling period. SWD adult/s was recorded on all farms except Farm 4_K all the on March 12 th. Since growers were notified of the results, most of them ended up spraying either Malathion or a synthetic pyrethroid except Farm 1_F who delayed management actions until after April 8th. On all the sampling dates except May 6 th, an SWD adult was recorded on Farm 5_N. It was particularly noted that a trap behind their Fruit Stand selling fresh fruits and vegetables always had an adult on each sampling date. We hypothesize that flies could be originating from the Fruit Stand or the rotting and disposed-off fruits. In Alachua County, monitoring on strawberry farms was coordinated between the growers and the extension agent. Fruit monitoring was done by randomly collecting berries from the field and subsequently dissecting the fruit or allowing maggots to exit the fruit in the small fruit and vegetable IPM laboratory. Approximately 3% of the fruit sampled from all 4 farms were infested with SWD. After fruits were found to be infested this information was relayed to the growers who employed management actions (routine spray program) traps were then deployed to monitor adults in these fields until the end of the season. Results and Discussion: Blueberry Farms: Spotted wing drosophila was reported in all 13 farms surveyed (Table 3). The highest number of SWD was recorded during the sampling period April 16-3 th which coincides with the blueberry ripening period on southern higbush blueberries. On all the farms the population of SWD dropped significantly later in the season due to insecticide applications after the growers were notified of the SWD status on their farms. The most common products used included Delegate (spinetoram), Mustang (zeta-cypermethrin), Malathion and Danitol (fenpropathrin). 2

3 Table 1: Mean number of spotted wing drosophila (SWD) collected per strawberry farm (A-P) on each sampling time noted as collection 1-4 alongside the means for the entire season. All the farms were within Plant City, Florida (principal strawberry growing area. Field Number of SWD per trap Time 1 Time 2 Time 3 Time 4 Average A B C.5.1 D E F G H.7.2 I J K L.3.1 M N O.5.1 P Table 2. Comparison of the number of SWD in strawberry fields versus the perimeter for trap samples collected on February 9-1 (Time 1) and March (Time 2). Sampling date Feb 9-1 March Trap Placement Mean # of SWD % of traps with SWD Field.% Perimeter % Field.6% Perimeter % 3

4 Total # of SWD per Farm Per Sampling Time Farm 1_F Farm 2_C Farm 3_P Farm 4_K Farm 5_N Farm 6_T 2 Figure 1: Total number of SWD adults captured in each of the six farms in Bradford County Table 3: Total number of spotted wing drosophila collected per blueberry farm (1-13) for the periods between April 1 st and May 3 th in various counties. County Farm # April 1-15 April 16-3 May 1 15 May 15 3 Marion Marion Alachua Alachua Alachua Putnum 6 5 Citrus Sumter Polk Lake Lake 11 1 Citrus Polk

5 Objective 2: To provide additional tools that growers can use for management of SWD by evaluating reduced-risk and conventional insecticides with short PHI s from various classes The purpose of this study was to evaluate the effectiveness of various insecticides on killing SWD adults after exposure to insecticide-treated strawberries. The first part of this objective was conducted in a laboratory setting and the second part as a field-based bioassay. a) Laboratory insecticide efficacy trial Procedures / Materials and Methods: Spotted wing drosophila colony: Adult flies were obtained from a laboratory colony that is being maintained at the University of Florida s Small Fruit and Vegetable IPM Laboratory at 23 o C, 65 ± 2% RH and 16:8 day and night photoperiod. All the flies used for the experiment were 5-7 days old after hatching. Before the start of the experiment berries were collected from the field and examined for presence of SWD maggots. The products evaluated were as follows 1) Mustang zeta-cypermethrin (FMC Corporation, Philadelphia, PA), 2) Hero - zeta-cypermethrin + bifenthrin (FMC Corporation, Philadelphia, PA), 3) Exirel - Cyazypyr (E. I. du Pont de Nemours and Company, Wilmington, DE), 4) Pyganic - permethrin (McLaughlin Gormley King Co., Minneapolis, MN) 5) Radiant spinetoram, 6) Entrust -spinosad, Dow AgroSciennces 7) Apta - tolfenpyrad, Nichino America Inc, 8) Untreated control. Each insecticide compounds were applied according to the manufacturer s recommended rate for the product mixed with water equivalent to 5 gal (189 L) per acre. Insecticides were used within 1 h of mixing and deionized water was used as the control. Berries were submerged in each chemical solution for 3 s and allowed to air dry for 4-5 h before introducing flies. Insecticide-treated berries were placed in 1 liter clear plastic containers with lids that had insect proofing net for aeration. Berries were placed such that they were not rolling over to knock each other. Sugar solution in a 5 ml eppendorf fitted with a dental s wick was placed in the container as a source of food for the flies. In each container 1 adults (5 males and 5 females) were introduced into each bioassay chamber and placed on the laboratory bench for 24 h under 16:8 day and night photoperiod. Temperature in the laboratory is ~ 22 o C and RH around 5%. Each treatment was replicated 1 times. The first five replicates were assessed only one time at 24 h while other 5 replicate were assessed at 24 h and 48 h after it was determined that 24 h may not have been sufficient for some compounds. Each treatment was replicated 1 times. The first five replicates were assessed only one time at 48 h while other 5 replicates were assessed at 24 h and 48 h after treatment. All the flies were removed from the bioassay chambers after 48 h and berries incubated to observe for larval incidence in the berries. On day five, the berries were gently mashed by hands and the liquid passed through a sieve to observe for maggots. 5

6 Percent Mortality 48h AT Results & Discussion: Lab Efficacy Trial Figure 1 shows the results for the first replicates after 48 hours of exposure to treatments. Almost all the insecticides tested in the laboratory bioassay were very effective except Pyganic that performed similarly to control. Entrust (spinosad), Radiant (spinetoram), Mustang (zetacypermethrin), Hero (zeta-cypermethrin + bifenthrin) and Exirel (Cyazypyr) resulted in > 9% SWD mortality after 48 hours of exposure (Figure 1 & 2). Apta (tolefenpyrad) performed very well in the first experiment (>9%) but in the second experiment only 6% of the flies were killed after 48 h exposure. Mustang and Hero resulted in 1% mortality in both experiments but the two products are not registered for use on strawberries. Entrust and Radiant are registered for use and performed equally well. No SWD larvae were recorded in most of the effective compounds after exposing flies to berry-treated insecticide for 48 h. The control had the highest number of larvae per berry (19.9) followed by Pyganic (9.4). Mustang and Hero treated berries (Figure 3) Entrust Apta Radiant Pyganic Control Mustang Hero Exirel Figure 1: Percent number of dead SWD counted after 24 h exposure to insecticide treated strawberries 6

7 # of larvae / 5 berries Percent Mortality hr 48 hr Entrust Apta Radiant Pyganic Control Mustang Hero Exirel Figure 2: Percent number of dead SWD counted after 24 and 48 h exposure to insecticide treated strawberries Entrust Apta Radiant Pyganic Control Mustang Hero Exirel Figure 3: Total number of SWD larvae in 5 berries after four days incubation after exposure to insecticide-treated berries 7

8 Percent Mortality One DAT b) Field-based efficacy trial Procedures / Materials and Methods: This study was an extension of the laboratory efficacy trial and only selected insecticides were evaluated in the field trial. These products were Radiant (spinetoram), Entrust (spinosad), Malathion, Pyganic and soon to be registered new insecticide, Exirel (cyazypyr). Insecticides were applied at the recommended rates per acre. Each treatment was replicated four times and experimental plots were 6 meter long consisting of three strawberry beds. Leaves and fruits from the treated plants were collected at 1, 3 and 7 days after treatment and brought back to the laboratory where 1 SWD adults (5females and 5 males) were exposed to the insecticide-treated leaves and fruits. Experimental set up consisted of 3 leaves or 1 strawberry fruits per bioassay chamber. Flies were provided with sugar-water solution during the exposure and their mortality recorded at 24, 48 and 72 hours. Results & Discussion: Figure 4 & 5 shows SWD mortality after being placed on fruits and leaves collected from treated strawberry plants in the field. The results show that Cyazypyr, Entrust, Radiant and Malathion were very effective in killing SWD adults one and three days after treatment. There was a slight decrease in chemical residues on the plant leaves between day 1 and day 3. Residual effects of these products were significantly reduced after 7 days of treatment when all products had less than 2% mortality (data not shown). However, on day 5 there was a heavy downpour which probably could have washed off some chemical residues on the leaves. Overall, the four products were effective in killing SWD under field and laboratory conditions DAT Leaf 1 DAT Fruit Pyganic Apta Control Cyazypyr Entrust Radiant Malathion Figure 4. Mortality of adult SWD after being placed on fruit and leaves collected from treated strawberry plants in the field. Samples were collected one day after treatment (DAT) 8

9 Percent Mortality Three DAT DAT Leaf 3 DAT Fruit Pyganic Apta Control Cyazypyr Entrust Radiant Malathion Figure 5. Mortality of adult SWD after being placed on fruit and leaves collected from treated strawberry plants in the field. Samples were collected three day after treatment (DAT) Objective 3: To educate extension faculty, crop consultants and growers on monitoring and correct identification of SWD. Several extension related activities took place over the past year that was directly related to this project. We participated in a Fall Blueberry Short Course on September 19 th 213 in Plant City, Florida and a presentation was given to about 15 growers (primarily blueberry but approximately 2% of these growers plant strawberries). The presentation was entitled Management of spotted wing drosophila in berry crops. Several extension agents, crop consultants and other agricultural personnel attended this fall blueberry short course. In the Spring, March 8 th in Alachua County we co-hosted (with horticultural extension agents) an SWD training session for small fruit growers. During this hands-on extension activity, we distributed a handout summarizing pest management strategies for SWD to each grower, we also had illustrations of SWD identification characters on a training sheet and utilized 25 portable microscopes that growers had access to visualize the characters of adult and larval SWD. Approximately 11 growers attended this meeting and training session. On March 27, we met with two of the largest berry producers in the state to discuss how to address SWD issues on their farms for the up-coming blueberry season. An extension publication on management of SWD in blueberries was also published during the summer of 213 (see below). This publication can be accessed at Publication. Liburd, O. E. and L. E. Iglesias Spotted wing drosophila: Pest management recommendations for southeastern blueberries. Publication #ENY-869. EDIS UF/IFAS Extension, Gainesville, FL