Three growers are appling1/4th the regular rate of Citrus Fix and MaxCel every 45 days on approximately 1 acre each of Hamlin and Valencia orange trees. Grove locations are Sebring, Babson Park and Ft. Meade. One grower had applied his second application while the other two were making only their first applications. No apparent difference in flush was detected. Tree condition (decline status) is being monitored and will be evaluated at the end of the fall period. Fruit drop will be measured and yields obtained. Flowering will be checked for any difference in timing or intensity.
There was no significant difference between the PGRs, 2, 4-D and Retain, and the Control in any of the 3 trials. Overall preharvest drop rates were 25 to 35, 40 to 45 and 50 to 55 % for the three groves. In two of the groves the treatments had almost 5 % more drop than the control, while at the other location the control had almost 5 % more drop than the treatments.
The preharvest drop values at the Lake Alfred site were low on January 25 (5 % drop) but increased to 18-18 to 30 % by harvest on March 25th. The ProGibb and ProGibb + Citrus Fix had the lowest fruit drop, but the values were not significantly different than the control. The other 2 sites had 33 to 37 % drop and 47 to 58 % drop, not significantly different. Consistent with all of the tests run, healthier trees had lower drop rates than more severely declined trees (20 % versus 30 to 34 % for mild and severely declined trees respectively, at Lake Alfred). In another grove the % drop values ranged from 30-50 % for healthier trees and 50 to 70 % for mild and severely declining trees. In all cases differences were not significant probably partly due to tree condition within the plots.
Low concentrations (1/4 rate) of 2, 4-D and Max-Cel were applied every 45 days to Hamlin and Valencia tree canopies at two locations in central Florida starting in Spring 2014. Concentrations were 12.6 ml Citrus Fix and 480 ml Max-Cel. Every other 45 day period, GA3 (0.04 g ai/tree) was applied in 3 gal of water per each microjet irrigation zone. Treatments were applied from Spring through September. Trees were sampled in late spring for phloem development at three locations in the scaffold system (root flare, trunk, small scoffolds and leaf main veins). Comparable samples will be taken at the end of the growing season to compare phloem development with and without the PGR treatment. We expect to run comprehensive PGR profiles on the treatments with N. Killiny. A root development test was run in the greenhouse using disease free nursery citrus trees ready for planting. GA rates were 0, .00125, .0025, .005, and .0063 g ai/plant. The number of new roots was increased 38 and 31% by the two higher concentrations after 3 weeks. Total and average root length increased by 27 and 28%, respectively, 6 weeks after application and by 21 and 23 % for numbers at the two higher rates after 12 weeks and a second GA3 application at 6 weeks. An attempt to test GA root applications on similar nursery trees that are HLB infected will be done if appropriate plants can be found.
The person to redo the internet model for flowering evaluation was identified and will start on the new format. Recent years will be analyzed for estimates to improve the model for this winter. Leaf flush and flowering data will be collected this spring for orange (2 or 3), grapefruit (2) and mandarin (3 ) cultivars.
Three growers agreed to apply 1/4th the regular rate of Citrus Fix and MaxCel every 45 days on approximately 1 acre each of Hamlin and Valencia orange trees. Grove locations are Sebring, Babson Park and Ft. Meade. One grower applied an application while the other two growers were waiting until the crop was harvested so that they would not be subject to crop destruct rules for this past year’s crop. Comparable control rows are being monitored two rows from the sprayed trees. Approximately one acre was treated in each cultivar and these trees plus controls were categorized as to tree health.
Four growers agreed to treat five one acre Valencia plots with Citrus Fix (2, 4-D) or Retain (AVG). Treatments were applied using 2.8 fl. oz. of 2, 4-D or 100 gm ai/acre of Retain. Two locations were harvested almost immediately after application so that no data was obtained for these locations. The three remaining tests were treated on 2/11 (Lake Placid), 2/13 (east Lake Wales) or 2/19/2014 (Sebring).
Two trials were established that included sprays of Citrus Fix (2..8 floz/ac), Retain (100 g ai/ac), S-ABA (100g,ai/ac), 1-MCP (company determined rate) and the Control. These locations were Auburndale and Lake Wales. A third location did not include 1-MCP. The treatments at the first two mentioned tests were applied from February 10 to 12, 2014, while the third location (Lake Alfred) was treated earlier and twice (September and October).
We worked in collaborative study to characterize the biocontrol potential of Steinernema riobrave and the native Florida species Heterorhabditis floridensis with respect to infectivity over a range of temperatures and insect hosts. A drawback of commercializing S. riobrave is that other EPN species have broader host ranges and market penetration. H. floridensis was equally effective in killing insect larvae as S. riobrave at temperatures ranging from 25-35oC and only H. floridensis was effective at 17oC. At 10oC and 13oC, neither nematode killed the larvae. H. floridensis was equally effective as the widely commercialized H. bacteriophora in killing small hive beetle and Diaprepes root weevil, but not plum curculio. The wide temperature tolerance would make H. floridensis desirable as an EPN that can be used in warm and cold seasons against D. abbreviatus. The nematode also appears to reproduce in vivo at higher levels than is common for EPNs. Those trials are being repeated. Initiated draft of manuscript “Characterization of Biocontrol Traits in Heterorhabditis floridensis: A species with broad temperature tolerance.” Shapiro, Duncan, El-Borai, Koppenhofer and Adams.
Entomopathogenic nematodes: Amending soils to increase biological control of insect pests EPN communities in the Bartow pH trial were characterized by burying caged weevil larvae for seven day and by soil sampling. Soil pH was 5.9 and 7.1 in sulfur-amended and unamended plots. There were no significant differences in numbers of sentinel larvae killed by any or all EPN species in May 2014, despite finding significantly more S. diaprepesi and fewer H. indica in sulfur amended plots 3 months earlier in February. Indeed, numbers of EPNs in sulfur amended plot soil samples in May were 8-fold higher than in untreated controls (P=0.10). There were no differences in numbers of fibrous roots or free living nematodes in either treatment. However, numbers of ectoparasitic nematodes (Belonolaimus longicaudatus and Xiphinema vulgare) in amended plots were just seven percent of those in controls (P=0.02). Citrus nematode (T. semipenetrans) were also reduced by 93% by sulfur treatments, but populations were low in all treatments and the difference was not significant. We evaluated experiments to test whether EPN community structure can be engineered by managing soil pH and water potential (see March 2014 report for experimental details). Mixtures of Sd, Sx, Hi, and Hz were maintained with weevil larvae in soil with factorial treatments of low and high pH and low and high water potential. EPNs that recycle in weevils were periodically added to fresh columns with weevil larvae for several generations (21 days each). After 3 generations few replicates had maintained any EPNs indicating that generation intervals were too short for the conditions. The experiment is being repeated with modified timing and other procedures to correct the deficiency. Subsequent to trials that characterized survival of four endemic EPN species over ranges of soil moisture and pH, two closely related native species, Steinernema diaprepesi and Steinernema sp., were selected to study survival mechanisms. Previously, Steinernema sp. and S. diaprepesi were shown to persist best in saturated and well-drained soils, respectively, both in nature and in the laboratory. Comparative proteomic analysis revealed 24 differences in protein expression by S. diaprepesi maintained for 48 h in well-drained or saturated soil. Twenty-two protein expression differences were detected for Steinernema sp. under those conditions. Detected proteins are being identified by LC-MS-MS to understand mechanisms of habitat adaptation. Understanding the physiological basis of these behaviors could help 1) engineer soil conditions in ways that favor more desirable (effective) EPN species, 2) guide the selection of extant EPN species for use in different ecoregions, or 3) guide the selection of EPN physiological traits in conventional or engineered breeding efforts. Plant parasitic Nematodes: Characterizing a new nematode pest and the prevalence of resistance breaking populations of the citrus nematode. Monitored root mass density and dagger nematode populations in two nematicide trials conducted in east coast grapefruit on swingle. The nematode population density in May exceeded 300/half liter of soil and neither oxamyl or an proprietary comound affected nematode population density. However, the experimental nematicide/fungicide had a significant effect on root mass density. In November 2013, plots treated with two rates of the experimental compound had root mass density higher than that of the untreated plots but differences were not significant. By May 2014, root weights in untreated plots had declined to 33% of previous levels whereas there was no decline of roots treated with either rate of experimental compound. Root Root weights treated with the compound were 3.5 and 7 times greater than that of controls (P=0.02).
This is a cooperative research project between Co-PIs Joseph Morse, Jim Bethke, Frank Byrne, Beth Grafton-Cardwell, and Kris Godfrey. One objective is to collaborate with researchers working on chemical control of ACP in Florida, Texas, Arizona, and elsewhere. Towards that end, Byrne, Grafton-Cardwell, Morse, and Brad White are collaborating with Setamou from Texas and 6 researchers from Florida in a 3-year SCRI proposal that will be submitted in Sept. 2014, titled “Optimizing Area-Wide Management of Asian Citrus Psyllid and Huanglongbing”. For the last several years, Jim Bethke has been rearing ACP in a contained greenhouse at the Chula Vista Insectary (San Diego County; about 6 miles north of the Mexican border) under permit from CDFA. To date, a total of 36 trials have been conducted evaluating the efficacy of organic (21 trials) or traditional pesticides (15) against either nymphs (10) or adults (26). This work will conclude 9-30-14. A spring 2014 Citrograph article summarized all research with organic pesticides at Chula Vista. A second location where we are working with ACP is at UC Riverside, working under permit inside the UCR Insectary Facility. Frank Byrne is continuing his research on the efficacy of various neonicotinoid insecticides against young vs. old ACP nymphs. In addition, he is developing an ELISA system that will measure levels of spirotetramat-enol inside citrus leaf tissue that has received Movento foliar treatments. When Movento (spirotetramat) is applied, it is taken up by the plant and converted to the active and systemic enol derivative. Our aim is to develop an ELISA that is selective only for that enol derivative. Morse’s lab recently concluded baseline susceptibility testing of a CA-dervied lab population of ACP to 12 of the more commonly used ACP pesticides representing 7 classes of chemistry. A total of 73 micro-applicator trials were conducted and these data will be compiled into a Citrograph article for submission in Dec. 2014. Over the current fiscal year (since 10-1-13), four ACP field pesticide trials have been conducted and 1-2 more are planned for this fall. We also ran 7 local field trials (6 organic) in which leaves were treated in the field, allowed to weather naturally, and bioassays were done with adult ACP to determine how long residues continue to kill adults. In 3 of these organic trials we also evaluated impacts on adult Tamarixia radiata. Kris Godfrey is rearing ACP under permit at a 3rd location, i.e. inside UC Davis’ Contained Research Facility. She has run trials evaluating new organic pesticides such as Pest Out and Grandevo. Her screening of new organic products was recently concluded and she will now focus her efforts on the collaborative HLB early detection study. Beth Grafton-Cardwell and Morse recently updated online ACP pest management guidelines. Grafton-Cardwell has been working continuously with the CPDPC treatment liaisons, CDFA, and CCM to incorporate information generated by this project into the ACP management program. In summary, we continue to expand our ability to conduct ACP research in California with a clear focus on management of HLB (rather than ACP).
The project began on May first 2014 with two citrus groves selected for the project. A mature grove owned by English Bothers consists of 20 year-old Hamlin sweet orange trees predominately on Swingle rootstock. Sixteen full row main plots of 40 trees each were selected for irrigation water acidification at one of four target water pH (7.5, 7.0, 6.5, and 6.0). The second experimental site was established in a block of two year old Hamlin sweet orange trees on swingle rootstock at Orange-Co’s Joshua block. Rows of trees with similar treatment plots were selected randomly with one row split into two main plots of 20 trees each. Initial tree measurements, soil nutrient content, root density were taken from both blocks. Acid injection systems will be installed and treatments established in July/August. Twenty-four weighing lysimeters in a greenhouse with half containing Hamlin and the other half Valencia is setup in a factorial design of HLB positive and negative trees of each variety. An injection system was installed in the greenhouse to supply irrigation water with high bicarbonates and pH similar to those encountered in the field. Treatments will be established in the same July/August time period.
The support of the Texas Citrus Producers Board helped us to secure 2400 orange jasmine plants from Southcoast Wholesale Nursery (Owner: Jerry Wade ‘ Harlingen, TX) to be used to supplement the mass production of Tamarixia radiata, biological control agent of the Asian Citrus Psyllid, which is currently being reared at the USDA CPHST Mission Laboratory located in Edinburg, TX. The prior situation with our existing plant stock was not sufficient to maintain the quality and levels of beneficial insects needed in our biological control efforts. The acquisition of the new plants has helped us to overcome these challenges that we were facing in our production. The new supply of plants has relieved the stress that some of our plants were undergoing which was limiting the number and quality of beneficial insects produced and released in south Texas. In FY14, the CPHST Mission Lab mass produced over 468,000 Tamarixia radiata for the biological control of ACP, bringing our cumulative total to over 1.2 Million. Releases are made where plant tissue testing positive for HLB is being detected. In 2010, before we began our releases, we were detecting up 43 immature psyllids per flush in residential citrus. Since our biocontrol releases began, we have seen the populations gradually decline. In 2014 we are only observing 20 immature psyllids per flush. This is a reduction about 50% of the psyllid population. Plus, we are finding the beneficial insects in areas where we had not made releases, indicating the establishment and movement of these beneficial insects. The insects produced also serve as inoculum for use in field insectary cages. In FY14, we have installed over 20 field insectary cages that have produced an additional 240,000 beneficial insects for south Texas bringing our cumulative total to over 555,000 using the field insectary cage approach. This work conducted by working closely with Master Gardeners, Texas A&M AgriLife Extension, and the community to use field insectary cages in the urban environment to mass rear ACP parasitoids in the LRGV of Texas.
This is a project to develop novel approaches to controlling psyllids . Effective techniques to reduce the rate of Huanglongbing (HLB) spread are key to slowing its incidence, especially for new citrus plantings. RNA-interference (RNAi) is a natural regulatory and anti-viral response in eukaryotes and can be manipulated to target mRNAs/gene expression, including to control insects. Our on-going collaboration has found dsRNAs of specific psyllid genes that reduce the survival of these psyllids. In an effort to find an effective and economical method to deploy this strategy, these sequences are being cloned into the Citrus tristeza virus (CTV) vector, to test whether production of RNAi inducer molecules in citrus will prevent the survival and reproduction of psyllids.
This is a project to develop novel approaches to controlling psyllids . Effective techniques to reduce the rate of Huanglongbing (HLB) spread are key to slowing its incidence, especially for new citrus plantings. RNA-interference (RNAi) is a natural regulatory and anti-viral response in eukaryotes and can be manipulated to target mRNAs/gene expression, including to control insects. Our on-going collaboration has found that RNAi inducers, expressed in citrus trees using the Citrus tristeza virus (CTV) vector, reduce the survival of adult Diaphorina citri moving onto the trees, and greatly reduce their reproduction and acquisition of Candidatus Liberibacter asiaticus by progeny. Our goal is to further improve RNAi activity such that it will help to manage D. citri and HLB, allow reduction in pesticide use and lower grower costs for U.S. citrus. Sequences of specific psyllid genes that are thought to be needed for the survival and reproduction of psyllids are cloned into the CTV vector. As the virus replicates in phloem cells, it produces large amounts of dsRNA intermediates that now also produces dsRNAs containing psyllid sequences. The normal plants RNAi defense mechanism processes the dsRNAs into small 21 nt siRNAs that target mRNA degradation. These siRNAs migrate from virus infected cells into the sieve element. As the psyllid feeds, it sucks up these siRNAs that now target the psyllid mRNAs and prevents the psyllid from making this protein. The lack of this protein has detrimental effects on the survival, reproduction, and CLas acquisition of psyllids. So far, we have seen reduction in survival of adult psyllids placed on RNAi expressing plants, but the effects on reproduction of the new generation of psyllids has been much greater. This is likely because the nymphs are rapidly growing an need lots of new protein synthesis and because they uptake large amounts of phloem sap. Although we have found sequences that can prevent normal expression of specific genes in psyllids, we are looking at several genes to identify sequences that work best.
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