Teresia W. Nyoike

Effect of Trap Design, Bait Type, and Age on Captures of Drosophila suzukii (Diptera: Drosophilidae) in Berry Crops

ABSTRACT Field experiments were conducted in commercial southern highbush blueberries and wild blackberries to evaluate the attractiveness of different trap designs, bait types, and bait age on captures of the spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). During the 2012 trap design study, the five treatments evaluated were four 1-liter clear plastic cup traps (with and without a yellow visual stimulus or odorless dish detergent) and the fifth treatment was a Pherocon AM yellow sticky card trap. Cup traps were baited with 150 ml of apple cider vinegar (ACV) and the Pherocon AM trap had a 7.4-ml glass vial containing ACV. In 2013, the Pherocon AM yellow sticky card was omitted because of low spotted wing drosophila captures in 2012. The four treatments evaluated were four 1-liter cup traps with and without a yellow visual stimulus. One cup trap (with a yellow stimulus) was baited with yeast + sugar in place of ACV and the other cup traps were baited with ACV. In both years, there were no differences in spotted wing drosophila captures among cup traps baited with ACV with and without yellow visual stimulus. However, the cup trap baited with yeast + sugar and yellow visual stimulus captured more spotted wing drosophila than the ACV-baited cup traps irrespective of visual stimulus or detergent. In another study, four baits including 1) ACV, 2) yeast + sugar mixture, 3) yeast + flour mixture (yeast, sugar, water, whole wheat flour, and ACV), and 4) wine + vinegar mixture (rice vinegar and merlot wine) were evaluated in a commercial blueberry planting using 1-liter clear plastic cup traps (as described above). The experiment was repeated in wild blackberries but the yeast + flour bait was replaced with ACV + merlot wine + sugar. Results indicated that the two yeast baits captured significantly more spotted wing drosophila and more nontarget organisms than the vinegar baits. In the final study, although we found that the attraction of ACV and yeast + sugar to spotted wing drosophila did not change with bait age, the attraction to other Drosophilidae flies decreased with age. The ease of implementing a trap-and-lure system for spotted wing drosophila is discussed.

Suppression of Whiteflies, Bemisia tabaci (Hemiptera: Aleyrodidae) and Incidence of Cucurbit Leaf Crumple Virus, a Whitefly-transmitted Virus of Zucchini Squash New to Florida, with Mulches and Imidacloprid

Abstract The sweetpotato whitefly, Bemisia tabaci B biotype (Gennadius) (Homoptera: Aleyrodidae) also known as Bemisia argentifolii (Bellows and Perring) is a key pest in zucchini squash (Cucurbita pepo L.) causing both direct and indirect damage. A field experiment was conducted in the fall of 2005 and repeated in the fall of 2006 to investigate the effect of mulches alone or in combination with a reduced-risk insecticide, imidacloprid (Admire® 2F) on whiteflies and related problems in zucchini squash. UV-reflective mulch and the living mulch, buckwheat (Fagopyrum esculentum Moench), with and without imidacloprid, were evaluated in a randomized complete block design with 4 replications. White mulch (standard) was included as a control in the experiment. Mulches in combination with imidacloprid resulted in fewer whiteflies per leaf than those without imidacloprid in 2005 and 2006. More whiteflies were recorded on zucchini plants growing on white synthetic mulch than all other treatments in both years. In the 2006 growing season, these plants also showed the first symptoms of viral infection caused by Cucurbit leaf crumple virus (CuLCrV), a whitefly-transmitted geminivirus. Both living and reflective mulches were more effective than white mulch in reducing the densities of whiteflies and the incidence of CuLCrV on zucchini plants.

Effect of Tetranychus urticae (Acari: Tetranychidae), on Marketable Yields of Field-Grown Strawberries in North-Central Florida

ABSTRACT Understanding the impact of a pest species on a particular crop is critical for the success of a pest management program. Field studies were conducted to determine the effect of the twospotted spider mite, Tetranychus urticae Koch, on marketable yield of strawberries during the 2008/2009 and 2009/2010 growing seasons. Low, medium, and high mite infestation levels were established by initial inoculations of 5, 10, and 20 twospotted spider mites per strawberry leaf, respectively. A control treatment maintained at near zero mites through applications of an acaricide, bifenazate (Acramite 50 WP), was also included. Weekly records of motile twospotted spider mites were obtained over 13 and 16 wk during the 2008/2009 and 2009/2010 growing seasons, respectively. Degree-days and weather parameters were monitored to determine their effect on mite population. In addition, mite-days were calculated for each year from weekly mite counts to determine the effect of mites on marketable yield of strawberries. In both years, twospotted spider mite population increased throughout the growing seasons. More degree-days were accumulated during the 2008/2009 growing season, and mite population was higher in 2008/2009 than in 2009/2010. Mite population density per leaf increased up to 278 motiles per leaf in 2008/2009 growing season as compared with 137 in 2009/2010 within the high-infestation-level treatment. The divergence in mite population between the two growing seasons was attributed mainly to temperature differences between the two seasons that affected mite population development and establishment. During both growing seasons, the high mite infestation level had lowest marketable yield. A negative correlation between cumulative mite-days and harvested marketable yields was detected in both seasons, but it was only significant during the 2008/2009 growing season. Strawberry yield reduction was detected when plants attained 80 mites per leaf in 2008/2009 and 50 mites per leaf in 2009/2010 within the high mite infestation treatment. Factors that affect mite population establishment and management for twospotted spider mites on strawberries are discussed.

Detection of Cucurbit leaf crumple virus in Florida Cucurbits.

In October of 2006, yellow straightneck and zucchini squash plants (Cucurbita pepo L.) with crumpled, curled, thickened leaves were found in St. Johns and Marion counties in central Florida, respectively. Both locations had high populations of the whitefly, Bemisia tabaci. Incidences of symptomatic plants were greater than 95% in three squash fields (33 ha total) in St. Johns County and 35% in an experimental plot in Marion County. Twenty-three samples were collected from symptomatic plants (two from St. Johns County and 21 from Marion County). DNA was extracted for PCR and tested for the presence of begomoviruses using the following pairs of degenerate primers: AC1048/AV494, which amplifies a conserved region of the coat protein gene (2), PAR1c496/PAL1v1978, which amplifies a region of the begomovirus A component, and PBL1v2040/PCRc154, which amplifies a hypervariable region of the begomovirus B component (1). All squash samples yielded amplicons of sizes expected for a bipartite begomovirus: 1,159 nt with PAR1c496/PAL1v1978, 550 nt with AC1048/AV494, and 493 nt with PBL1v2040/PCRc154. The 1,159- and 493-nt amplicons obtained from two squash plants were cloned and sequenced. The 1,159 nt sequences from both plants shared 98% sequence identity with each other and 97% identity with equivalent regions of the A component of Cucurbit leaf crumple virus (CuLCrV) from Arizona and California (GenBank Accession Nos. AF256200 and AF224760, respectively). The 493-nt sequences amplified with PBL1v2040/PCRc154 were identical and shared a 96% identity with CuLCrV sequence (GenBank Accession No. AF327559) from Arizona and 97% identity with CuLCrV B component sequence (GenBank Accession No. AF224761) from California. Leaves were collected from eight symptomatic squash plants from Citra, FL and used for whitefly transmission assays. Approximately 100 adults of Bemisia tabaci biotype B were released onto each caged leaf and given a 24-h acquisition access period, after which a healthy squash seedling was introduced. Symptoms developed within 10 days on all test plants, and the presence of CuLCrV was confirmed by PCR assays, (primer pairs PAR1c496/PAL1v1978 and PBL1v2040/PCRc154) followed by sequencing. In 2007, similar symptoms were seen in several locations around the state. The same assays confirmed the presence of CuLCrV in watermelon (Citrullus lanatus L.) and squash in the following counties: Collier and Hendry in southwest Florida and Hillsborough, Manatee, and Sarasota in west-central Florida. To our knowledge, this is the first report of CuLCrV, and the first report of any begomovirus in cucurbits in Florida. References: (1) M. R. Rojas et al. Plant Dis. 77:340, 1993. (2) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.

IPM Programs in Vegetable Crops in Australia and USA: Current Status and Emerging Trends

Integrated Pest Management (IPM) in vegetable crops is limited in the breadth and depth of information available. However, as with any IPM program the cornerstone practices involve regular monitoring, and knowledge of key components in the field and greenhouse that will guide sound decisions. We focus on current IPM programs in high value vegetable crops grown in Australia and the USA, and use case studies in Brassica vegetable and tomato systems to show specific tactics and tools used to evaluate the level of success achieved and the evidence for impact. We show that the drivers, which cause change from a single, usually chemical control tactic to a more integrated system relate to a crisis that cause crop loss or restricted market access and includes insecticide resistance, insecticide residues above the maximum allowable limit, or withdrawal of insecticides from lucrative international market. However, market demand and drivers aligned with growers’ experiences and values may be more important in the future. Although the current ‘Best Practice IPM’ in Australia and the USA in vegetable systems includes: (1) routine crop monitoring, (2) using soft chemistries (where impact on beneficials is known) and (3) some monitoring of beneficial insects, IPM could be expanded and have greater integration with cultural control. We conclude by highlighting new advances and emerging trends and making suggestions on how to increase the adoption of IPM.

Reusing Plastic Mulch for a Second Strawberry Crop: Effects on Arthropod Pests, Weeds, Diseases and Strawberry Yields

Abstract Florida is the second largest producer of fresh-market strawberries (Fragaria × ananassa Duchesne; Rosales: Rosaceae) in the United States. The annual hill “plasticulture” production system used to grow strawberries makes this crop one of the most expensive to produce. The cost of production may be reduced if synthetic mulch can be reused and the dead plants (thatch) from the previous season left in the field, without negatively affecting crop yields. Field studies were conducted during the 2010/2011 and 2011/2012 strawberry growing seasons to evaluate the effect of re-using plastic mulch with or without dead strawberry plants from the previous season on arthropod populations, disease incidence, weeds and strawberry growth, and marketable yields of strawberries. The study was conducted in a commercial field in Citrus County, Florida using 2-yr old synthetic mulch on the bed. Two strawberry varieties ‘Albion’ and ‘Florida Festival’ were planted in 2010/2011 and 2011/2012 growing seasons, respectively. During transplanting, one treatment had all strawberry thatch (dead plant debris from previous season) removed from the soil before planting the new strawberry transplants, while in the second treatment the thatch was left to grow with the transplants. Data were collected throughout the growing seasons on plant growth, spider mites and insect pest populations, weeds, disease incidence, and marketable yield of strawberries. Re-using plastic mulch with or without strawberry thatch had no significant effect on plant size or populations of beneficial and pestiferous arthropods. However, re-using mulch with strawberry thatch reduced weed growth but increased the incidence of fungal diseases. As a result of fungal diseases and plant mortality, marketable yield for the variety “Florida Festival”, but not “Albion” was significantly lower in plots with the strawberry thatch than in those without thatch.