Search

Allyl isothiocyanate (AITC) is a glucosinolate produced in cruciferous plant species. AITC is known to act as a pesticide on microorganisms, insects, and weeds. Synthetic AITC is registered as a biopesticide for agricultural soil treatment use in the United States and elsewhere in the world. Although a potent pesticide, reports on the weed and pathogen control efficacy of synthetic AITC applied as soil disinfectant are highly variable. Due to the low vapor pressure of AITC, questions remain as to whether pest and weed control efficacy can be improved by combining it with other chemicals. The objective of this study was to assess the control efficacy of AITC stand-alone applications vs. applications, in which AITC was combined with the standard-fumigants chloropicrin, 1,3-dichloropicrin, and methyl isothiocyanate. Two shank-applied on-farm field trials were conducted in cut flower [delphinium (Delphinium elatum), ranunculus (Ranunculus asiaticus)] fields, and two drip tape applied field trials in strawberry (Fragaria ×ananassa) fields in California. Weed pressure, weed seed viability, nematode survival, and pathogen survival of Pythium ultimum, fusarium wilt (Fusarium oxysporum), and verticillium wilt (Verticillium dahliae) were assessed. Cumulative yearly yield of marketable fruit was assessed in the strawberry field trials. The results of this study show that the use of AITC as a stand-alone treatment provided no consistent weed or pathogen control efficacy. However, our results also indicate that shank and drip applied multitactic fumigation approaches with AITC can efficiently control soil-borne diseases and weeds. These findings have potential implications, especially in those areas where certain fumigants are restricted due to regulations and/or availability.

Theba pisana is a serious snail pest in many parts of the world and affects diverse crops including grain, vegetables, grapevines, and ornamental plants and shrubs. Due to its gregarious nature, ability to reproduce rapidly, and the difficulty of controlling it by conventional methods, it has the potential to become a significant pest where introduced. Mitigating this pest is an important challenge that must be addressed. Phasmarhabditis hermaphrodita, is a gastropod-killing nematode that is commercially available only in Europe (Nemaslug ®) and Sub-Saharan Africa (Slugtech ® SP). The use of effective gastropod-killing nematodes in the genus Phasmarhabditis (P. hermaphrodita, P. californica and P. papillosa) in California may provide one strategy for alleviating the potential damage and further spread of these snails, which are currently limited to San Diego and Los Angeles counties. Laboratory assays demonstrated for the first time that US isolates of P. hermaphrodita, P. californica and P. papillosa at 150 DJs/cm2 caused significant mortality and are equally lethal to T. pisana. Molluscicidal efficacy of these nematodes are comparable with those of iron phosphate, at the recommended high dose of 4.88 kg/m2. Additional trials are needed to determine their effects at lower dose and whether they are dependent on the size or age of the snails.

For phytophagous insects and plant pathogens, the unregulated movement of plant material can inadvertently promote long-distance spread, facilitating biological invasions. Such human-assisted spread has contributed to the invasion of the Asian citrus psyllid (Diaphorina citri), a vector of the pathogens associated with huanglongbing. Following the detection of D. citri in California, regulations were instituted to limit movement of D. citri host plants, by mandating insecticide treatments of citrus nursery stock, and limiting the amount of time host plants can reside at retail sites. We used a set of surveys and a field experiment to evaluate how well these steps mitigate the threat of containerized citrus playing a role in D. citri spread. A qualitative analysis of data collected by state regulators throughout Southern California found that containerized citrus may reside at retail sites for extended durations, in extreme cases upwards of 2 years post treatment. More detailed surveys at nearly 30 retail sites in Southern California showed that the majority of citrus plants were present past the 90 day regulatory limit, 33% had been treated more than 1 year prior, and 90% had imidacloprid residues below those known to be effective against D. citri nymphs. A field experiment confirmed that imidacloprid residues in trees grown in containers were affected by citrus species, watering level, soil mix, and time since treatment. Overall, plants had D. citri-effective residues for approximately 12 weeks, suggesting that imidacloprid treatments should protect the majority of containerized citrus against D. citri for approximately the duration of the 90 day regulatory limit. To further protect trees from infestation, nurseries should be encouraged to adopt practices that maximize the effectiveness of insecticide treatments, including ways to reduce residence times of host plants at retail sites.

The purpose of this study was to involve pest management professionals in the design of application techniques and strategies that would be efficacious and also reduce insecticide runoff. Our study involved measuring both the efficacy of treatments for the Argentine ant, Linepithema humile (Mayr), and the concurrent runoff of fipronil and pyrethroids. Two collaborating companies used low-impact protocols for controlling ants while minimizing runoff. Protocol 1 involved bimonthly treatments, while Protocol 2 was monthly. Both protocols involved an initial treatment with a fipronil spray around the foundation. At the garage door-driveway interface, the fipronil application was done as a pin stream for Protocol 1, and as a crack and crevice application in the expansion joint near the garage for Protocol 2. Protocol 1 replaced most pyrethroid sprays with bifenthrin granules placed around bushes and away from the driveway. For the next treatment on day 63, Protocol 1 also included cyfluthrin spray treatments around the house foundation and crack and crevice applications around the edge of the driveway. For the first treatment in Protocol 2, the fipronil spray was supplemented with spot treatments of cyfluthrin. For subsequent Protocol 2 treatments, botanical insecticides were applied. For weeks 1 and 2 posttreatment combined, Protocol 1 had significantly higher reductions in ant numbers compared with Protocol 2. Thereafter there were no significant differences between the protocols. Runoff of bifenthrin from the granules used with Protocol 1 was much lower than in previous trials involving bifenthrin sprays. Day 1 fipronil runoff for Protocol 2 was significantly lower than that for Protocol 1. This difference may be because of the crack and crevice application applied in Protocol 2. Cyfluthrin runoff was minimal for Protocol 2, which involved spot treatments to supplement the fipronil on day 1, or the botanical insecticides for subsequent treatments. Protocol 1 had a large peak of cyfluthrin runoff at day 63 corresponding to their house and driveway treatments.

According to the United States Census, California is the most urban state in the nation. Although there are many outstanding examples of urban farms in California, in general, urban agriculture (UA) has been slower to gain momentum here than in some other states with large urban populations. Over the past several years, urban agriculture's popularity in California has begun to escalate, with strong emerging interest in San Francisco, San Jose, Oakland, San Diego, Los Angeles and other metropolitan communities. One challenge for urban farmers and municipal decision makers engaged with UA in California has been limited availability of relevant information and technical assistance. A new project team at the University of California Cooperative Extension, part of the Division of Agriculture and Natural Resources (UC ANR) is working to develop web-based educational resources that will be grounded in a needs assessment that is currently underway. The needs assessment includes a literature review, an internal survey of UC ANR personnel, and community clientele interviews. This paper will report on preliminary findings and analyses of the needs assessment, particularly how UC ANR personnel are engaged with UA, and what tools they think would best serve urban farmers. We suggest implications for those involved with UA, such as personnel of land-grant universities, local governments and non-profits seeking to address the needs of urban farmers in an environment of constrained resources.

Population reduction through trapping is among the most common techniques used to mitigate damage caused by pocket gophers in a variety of crops. A new trap called the Gophinator was recently developed that combined many positive attributes of previous pocket gopher traps. Because efficacy data for this trap was lacking, we compared capture rates of this trap to the Macabee trap, the most commonly used pocket gopher trap in the western U.S. We also addressed factors that may influence the efficacy of traps such as cover status of the trap set, season, gender, and weight of the captured pocket gopher. We found the Gophinator trap was more efficacious than the Macabee, likely due to its superior ability to capture larger pocket gophers, which could increase the efficacy of pocket gopher control programs throughout North America. Covered trap sets resulted in greater capture rates during late spring–early summer but not during autumn. However, covered trap sets required more time to implement and did not result in a greater number of captures for an 8-h workday trapping period. If efficacy is paramount, trap sets should be covered during late spring–early summer, but when time is a constraining factor, trap sets left uncovered will be most efficient. Covering trap sets in autumn provided no tangible benefits.

Light brown apple moth is an exotic pest that was confirmed in California in March 2007. It is a tortricid leaf-roller moth native to Australia, which has a broad range of plant hosts with the capacity to cause damage across a wide array of crops, natural areas and ornamental plants. California and federal agencies have issued quarantine orders affecting production and retail nurseries, and potentially fruit and vegetable exports. It is found thus far primarily in nurseries near urban areas. Eradication efforts are under way to prevent its spread into California crop areas and throughout the United States.

Field studies were conducted to compare insect population levels in greenhouse crops covered with plastics that block the transmission of UV light in two wavelength ranges. Crops grown in greenhouses under a plastic that blocked UV light at wavelengths of 380 nm and below had lower numbers of aphids and thrips compared with a plastic that blocked UV light at wavelengths of 360 nm and below. This is consistent with the results found for thrips in previous studies using small, completely enclosed tunnels with no plant material. The effects were not as dramatic in the commercial greenhouses, perhaps due to unfiltered light entering through the open sides of those greenhouses. There was no reduction in greenhouse whitefly, Trialeurodes vaporariorum Westwood, populations under the

Pests and their interactions with crops, ecological landscapes and animals are in continuous flux — they are never static. Pest severity increases or decreases depending on environmental conditions and changes in production or pest control practices. Pest management is made even more challenging by exotic and newly invasive pests. Over its 35-year history, the UC Agriculture and Natural Resources Statewide IPM Program has supported research and extension that has decreased risks of crop losses, improved treatment programs for invasive and endemic pests, and reduced the use of pesticides and their impact on the environment and human health. Its publications are widely used among growers, pest control advisers, research institutions, state agencies, agricultural organizations and gardeners; and integrated pest management has been adopted statewide in agriculture, as well as in managed landscapes and urban areas.

Weed control efficacy of organic mulches as well as a copper hydroxide-coated geotextile (fabric) disk was examined using Rhaphiolepis indica L. or Callistemon citrinus [(Curtis) Stapf] growing in containers. Rout (oxyfluorfen plus oryzalin) and corn gluten meal were included as herbicide treatments. In a second experiment, the effect of subirrigation versus surface irrigation and different depths of pine bark mulch on weed control was studied. In the mulch/herbicide studies, all of the mulch treatments, including the geotextile disk, provided broadleaf weed control, but not annual bluegrass control, similar to that of Rout. Broadleaf weeds were not controlled by corn gluten meal. Although though the number of grass seedlings was reduced 49% from that of the control, Rout reduced the number by 89%. In the mulch depth/irrigation study, mulching reduced weed weight by 92% over that of the control (no mulch and surface irrigated) 8 weeks after transplanting. Subirrigation reduced the number of weeds by at least 95% over that of the control.

We examined the relationship between temperature and emergence of yellow nutsedge tubers to generate predic- tive models for the arid southwestern United States. Field experiments were conducted in California and Arizona to obtain phenological and temperature data needed to gener- ate degree-day models. The effect of air temperature on emergence was tested with available programs using four methods to calculate degree-days (single sine, double sine, single triangle, and double triangle). Separate models were tested for each genotype examined (Arizona source and Cali- fornia source) as no one model was a good predictor of emergence when data were pooled. Results indicate that there is year to year variation in model accuracy but predic- tions of date of emergence can be made to within 2 d of actual emergence. This information can be used to schedule culti- vations to reduce early yellow nutsedge competition in the field. Nomenclature: Yellow nutsedge, C. esculentus L. #3

Experiments were conducted to examine the effects of low soil moisture on yellow nutsedge emergence in relation to thermal and chronological time and test the ability of thermal models generated previously to predict emergence under water stress. Unsprouted tubers from California and Arizona were planted in pots, buried at field sites in California and Arizona, and subjected to wet or dry treatments. Pots were monitored weekly to determine date of emergence and number of emerged shoots. The California genotype emerged 47 to 61 days after planting (DAP) in the dry treatment and 33 to 49 DAP in the wet treatment, depending on planting site. The range for the Arizona genotype was 51 to 76 DAP in the dry treatment and 43 to 61 DAP in the wet treatment. Days and degree-day intervals to first emergence differed between irrigation treatments and planting sites but interactions were not significant. All models were accurate in predicting emergence dates for genotypes in the wet treatment at the California site, while emergence in Arizona was underestimated by 9 d. Tubers subjected to the dry treatment needed a higher number of accumulated degree-day units before emergence occurred and had fewer emerged shoots as compared to the wet treatment. Degree-day models generated for yellow nutsedge under optimal conditions lack sufficient robustness to be predictive under water stress conditions.

Photographic techniques and the point-frame tran- sect method were used to study areal growth of kikuyugrass grown in the field without competition in 1990 and 1991. The effect of cutting height on plant extension was also examined in 1991. There were no differences in sward area between eight selections planted in 1990, except on the first measure- ment date, but selections differed in height and number of primary and secondary stolons. Expansion was irregular in all but one selection, and the patch shape of all irregular selections was defined by the direction and number of the earliest buds to sprout from the stolons. Only two of the eight selections were planted in 1991. Cutting height affected ex- tension from the plot center, linear plant frequency, and plant biomass. The lowest height of cut, 2.5 cm, had the least extension and frequency, the higher cut, 5 cm, was interme- diate, and the unmowed plots had the highest extension and frequency. There were differences between selections in num- ber of nodes per unit area, which resulted in differences in response to mowing. Results from a greenhouse clipping experiment showed that although root weight of stolon sec- tions used as propagules was reduced by defoliation, starch content was not affected. The spreading ability of kikuyu- grass appears to be based on its ability to branch from its stolons presumably due to reallocation of resources. Based on these results, close mowing could slow the process of kikuyugrass invasion into other turf species but is inadequate to control it. Nomenclature: Kikuyugrass, Pennisetum clan- destinum Hochst. ex Chiov. #3 PESCL. Additional index words: Spatial growth, invasion, mowing, turfgrass, PESCL.

Summary Pennisetum clandestinum Hochst ex Chiov. (kikuyugrass) is a C4 grass that has become an invasive weed in temperate climates. We examined ecophysiological mechanisms that have allowed it to become a successful weed in these locations by comparing P. clandestinum and two other common turigrass species, Festuca arundinacea Schreb. (tall fescue cv. Mojave), a C3 cool-season grass, and Stenotaphrum secundatum (Walt.) Kuntze (St. Augustinegrass), a C4 warm-season grass, grown in a warm or cool growth regime. We measured rates of photosynthesis over a range of leaf temperatures and also measured growth rate parameters of these species. At leaf temperatures between 25^C and 40^C P. clandestinum maintained the highest rates of photosynthesis in both temperature regimes. Under warm temperatures, this species rapidly increased biomass and leaf area to a greater extent than either of the other two grasses. Theoretical whole plant photosynthesis (mean leaf area × mean photosynthetic rate) was higher for P. clandestinum than for the other two species in both growth regimes and over most leaf temperatures. Our results suggest that P. clandestinum is a successful weed in Mediterranean climates as a result of its capacity to photosynthesize over the full range of temperatures found in those climates, its rapid growth during warm weather and its apparent tolerance to moderately cool temperatures.

Using starch gel electrophoresis, we examined the genetic variability of kikuyugrass collected from three golf course sites within its geographical range in California. These experiments were conducted to determine the method of spread of kikuyugrass in areas where it is considered invasive. Samples from roughs and fairways of each of these locations were compared. Of the 354 plants examined, 12 different genotypes were identified by isozyme analysis, and only three of the nime putative loci varied among the genotypes. Two genotypes, representing 73% of the plants examined, were found at all three geographic locations. Our results imply that under common golf course practices, kikuyugrass is maintained by clonal reproduction. We conclude that low genetic variation does not preclude a plant species from being an aggressive invader. Nomenclature: Kikuyugrass, Pennisetum clandestinum Hochst. ex Chiov. #3 PESCL. Additional index words. Population maintenance, isozyme analysis, PESCL.

of the State until they have become fully established away from cultivation, or until it is clear they are capable of persisting without human cultivation.” Many of the hor ti cul tur al and agricultural weeds common to human civilization, al though competitive and problematic in disturbed sites, are not invasive according to this defi nition. Others, such as the Brazilian peppertree (Schinus terebinthifolius) in Florida and pampasgrass (Cortaderia sellonana) in coast al California, clearly fi t the defi nition of in va sive plants because they are established in nat u ral hab i tats and are spreading. In the United States, 85% of purpose

A field study was conducted to assess the effect of various commercially available polyethylene plastic greenhouse coverings on the persistence of viable spores of the microbial insecticide Beauveria bassiana. Selected coverings blocked the transmission of UV light with wavelengths of 360 nm and below or 380 nm and below. Two coverings also contained an infrared blocking component. A commercial formulation of B. bassiana was applied for 3 consecutive weeks to plants growing in the plastic covered hoop houses. The percentage of viable spores was calculated up to 13 days after the final application. The persistence of viable B. bassiana spores was significantly longer under the plastic that blocked a greater portion of the UV spectrum (

Author(s): Sartain, Autumn; Ellis, Tracy; Miller, Ryan; Wilen, Cheryl; Salmon, Terrell | Abstract: Cottontail rabbits cause serious damage to ornamental plant production in Southern California. We used a 300-acre Southern California tree nursery as a cottontail CDFA vertebrate pest study site. We evaluated the relationship between nursery practices and the incidence of rabbit damage. GPS technology in combination with GIS software was employed to map and ascribe descriptive characteristics to the growing practices within each nursery bed. To understand the pattern of rabbit damage to irrigation, handheld GPS units were utilized by nursery staff conducting irrigation repair to assess damage caused by vertebrate pests. The waypoints taken by the irrigators superimposed on the map of the nursery had numerous benefits to the study, including demonstrating which growing conditions were most vulnerable to rabbit damage and elucidating if measures to reduce rabbit damage were successful. The same methodology may be helpful to researchers in many IPM fields.

Author(s): Ellis, Tracy; Salmon, Terrell P.; Wilen, Cheryl | Abstract: The anticoagulants chlorophacinone and diphacinone are registered in California to control ground squirrels. Since multiple feedings on these anticoagulants are necessary, bait stations are often used. Several bait station designs have been suggested and used to reduce tampering and also to minimize bait exposure to non-target animals. Potential options to reduced exposure risk strategies are to use a modified-T bait station, underground bait station, or in-burrow baiting. This study evaluated the behavior of ground squirrels with regard to modified-T and underground bait station compared to the standard-T bait station that is commonly used for ground squirrel control.

Author(s): Ellis, Tracy; Sartain, Autumn; Miller, Ryan; Wilen, Cheryl; Salmon, Terrell P. | Abstract: Cottontail rabbits are a serious problem in Southern California. Of particular concern is the damage they do to ornamental plant and tree nurseries. Rabbit browsing reduces plant quality, kills containerized plants, and damages irrigation systems. Although anticoagulant baiting for cottontail rabbits is legal in California, growers should also consider multiple integrated tactics for rabbit damage control. This project employed GPS mapping technology to locate the occurrence of rabbit damage and correlate it with irrigation type, container, planting density, canopy width, and canopy height. GPS was also used to monitor the impact of experimental strategies to reduce rabbit damage. Strategies to reduce rabbit damage included the use of protective covers on irrigation tubing, exclusionary fencing, and trapping. Radiotelemetry was used to confirm the location of suspected rabbit harborages within the nursery. GPS results indicate that 1.27 to 1.9-cm (½ to ¾-in)-diameter irrigation line covers were effective in reducing rabbit damage to the irrigation system. Exclusionary fencing using erosion-control silt fencing acted as an excellent temporary barrier to protect individual growing areas and groups of planting beds, but it was found to be impractical for many nursery situations. Rabbit catch rates increased when traps were used in conjunction with drift fences. General tactics recommended to container nurseries based on these study results include: protecting and modifying irrigation systems, use of exclusionary fencing, trapping in conjunction with drift fencing, and modifying known rabbit harborages where possible.

Recent monitoring shows that the majority of urban streams in the United States are contaminated by pesticide residues, and the contamination is mainly due to runoff from residential landscapes. In this study we evaluated the effect of landscape planting on persistence of the herbicides 2,4-D and dicamba in soil under laboratory conditions. The herbicides exhibited substantially different persistence in the same soil type that had been subjected to different planting practices for about 6 years. In the 0-10 cm surface layer, the half-life of 2,4-D was 30.7 d in soil under trees, which was about 20 times longer than in soil planted with turf grass (1.6 d). The difference in 2,4-D persistence was closely correlated to the number of 2,4-D-degrading bacteria that had evolved in the soils. The half-life of dicamba was much longer in soil under a tree canopy (149 d) than in mulched soil (7.9 d). The rate of dicamba degradation was proportional to soil organic matter content. This study indicates that planting practices can modify soil chemical properties and microbial activity and may further affect pesticide runoff potential by influencing pesticide degradation. Characterizing pesticide behavior as a function of planting covers may improve our understanding of pesticide runoff in urban environments and also help to identify strategies for minimizing pesticide contamination to urban streams.