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Citrus health management areas (CHMAs) have been implemented throughout Florida to provide regional coordination to manage Asian citrus psyllid (ACP) and spread of HLB.  The Gulf CHMA is going into its 5th season of cooperative action toward these goals.  During the fourth (2011-2012) season we began providing GULF CHMA updates and interactive maps from CHRP data available on the CHMA website www.flchma.com, showing ACP levels and 'hot spots' (i.e. tap samples > 21 ACP for 3 consecutive cycles) on our website, www.imok.ufl.edu.   The ring color of the proportional circle map designates the cycle, and the ring size the number of A adults per 50 taps.  The largest ring represents psyllid numbers of 21 or greater.  The map is readable by anyone with Adobe Reader, and it allows you to click on and off different cycle layers and view data for Cycle #, Cycle Date, County Name, and ACP # thus allowing comparison between two or more sets of data simultaneously and spatially.  This project includes development and testing of a smart phone spray app for use by growers and consultants.  The insecticide spray data will be converted to a map layer that overlays the Gulf CHMA psyllid counts to determine which growers may need help and what chemicals appear to be failing -- a precursor to predicting ACP resistance.  We expect to build better working relationships with the growers by offering individual support of their economic efforts, ACP management, and HLB control.

Diaphorina citri also known as Asian citrus psyllid (ACP) vectors Candidatus Liberibacter asiaticus, causal organism of the Asian “huanglongbing” or citrus greening disease and therefore needs to be managed effectively.  Forty-three insecticides containing 39 active ingredients (a.i) recommended or experimental were tested during the growing season in foliar sprays (171 treatments, 35 a.i) targeted at flushing trees and soil applications (26 treatments, 6 a.i) to control ACP in citrus between 2005-2012.  Psyllid suppression varied with product and lasted 1-7 weeks using foliar sprays on mature trees and 6-33 weeks using soil drenches in young trees.  Experimental insecticides tolfenpyrad (Apta 15 SC), flupyradifurone (Sivanto 200 SL), sulfoxaflor (Closer 240 SC), cyantraniliprole (Verimark), and Chromobacterium substugae (Grandevo/MBI-203 EP) performed equal to or better than recommended products.  Unfortunately, eggs and young nymphs are protected inside unfolded leaves such that insecticidal sprays may kill more predators and parasitoids common during growing season that would otherwise attack immature ACP and other citrus pests.  Addition of new insecticides will broaden the range of products available to control ACP.  Nevertheless, one to two sprays of broad-spectrum insecticides during dormant winter period when most mature trees are not producing new growth and beneficial insects are scarce can provide up to 6 months of ACP suppression into growing season and also conserve beneficial insects.  Therefore, psyllid suppression using one or two dormant winter sprays of broad-spectrum insecticides followed by regular monitoring and rotation of relatively selective chemistries during growing season will help to reduce incidence of huanglongbing, pest resistance to insecticides and secondary pest outbreaks.

Control of the HLB vector, Diaphorina citri Kuwayama, is considered a basic component for management this disease, even in a high HLB incidence scenario. Such control is mostly chemically oriented. However, over use of insecticides would increase costs and be incompatible with biological control. Establishment of economic thresholds for psyllid control under different price scenarios could optimize returns on investment.

Low volume (LV) aerial and ground sprays have become an important method of application in Florida citrus. During Feb 2011, we started a trial in a 10.9 acre plot of 'Valencia' orange in Lee County comparing LV spray of 435 HMO with the Grower Standard (GS) and an Untreated check (UC) in 3x3 Latin square design.  A Proptec rotary atomizer P400D spray machine was used for all treatments. HMO was applied every 2 weeks at 2 gpa.  Significantly fewer ACP were seen on during May 2011 on GS trees than HMO trees, but during June these differences disappeared.  Between Aug – Oct 2011, mean adult ACP populations were lowest for GS, followed by HMO and UC.  Thus, LV oil treatments suppressed ACP, though not as effectively as the GS.  However during winter 2011 HMO treatments were as effective as GS.  Also, highest pound solids were seen from trees receiving HMO followed by UC and GS.  Citrus leafminer (CLM) damage assessments (May/July 2011) using a modified Horsfall-Barratt scale showed less damage with GS compared with Oil which in turn was less than UC.  However, CLM trap catches in Nov were significantly lower with HMO compared to GS and UC even though highest flush density was present on HMO-treated trees.  Canker ratings (2012) for HMO and GS have been significantly less than UC.  Thus, LV application of 435 horticultural mineral oil (HMO) for control of ACP and CLM have shown promising results the last 2 years.

Orchard renewal is a special challenge where HLB is endemic.  Young trees are especially susceptible to the disease and continuously attractive to the psyllid vector due to frequent flushing.  Heavy reliance is placed on systemic insecticides to protect young trees.  However, all presently labeled for citrus are neonicotinoids (IRAC Group 4a) making resistance likely and the long term viability of this strategy questionable.  Rotation partners are needed to forestall selection for resistance. Therefore, we conducted a multiyear study to evaluate rotations of neonicotinoid insecticides rotated with cyantraniliprole a Group 28 insecticide in a block of ‘Hamlin’ orange on ‘US802’ rootstock planted in May 2010. Four treatment programs using two rates of Verimark 20 SC, rotated with Platinum 75 and Admire Pro in two different sequences were compared to an untreated check in an RCBD with 4 replicates.  Adult psyllid populations were monitored monthly and immatures counted when natural flush was present.  Incidence of HLB was assessed by PCR in Aug 2011, and Jan, May and Aug 2012. Psyllid populations on treated trees averaged 1.43 per tap compared to a range of 0 to 0.8 on treated trees.  Incidence of HLB reached 29% in Aug 2011 on untreated trees compared to 0-8.3% on treated trees.  In May 2012 these numbers had increased to 67 % and 11-26% respectively.  Diameter of scions was 33% larger on treated trees in Sep 2012.  Although effective, the 90 day treatment regimen was not enough to protect trees from HLB and additional strategies are necessary.

Huanglongbing (HLB) or citrus greening is a bacterial disease vectored by the Asian citrus psyllid (ACP) and causing mottled leaves, tree decline, and yield loss.  Vector control and foliar nutrition are widely employed in Florida and elsewhere to respectively slow the spread of HLB and mitigate debilitating effects of the disease.  A replicated field study was conducted in a 5.4-ha commercial block of young ‘Valencia’ orange trees through four harvests employing a factorial design to evaluate individual and compound effects of a popular foliar nutrient program and threshold-based vector management.

Polyethylene mulch was evaluated for deterring colonization by Asian citrus psyllid (ACP) Diaphorina citri, reducing incidence of huanglongbing (HLB) or citrus greening disease and accelerating growth of young citrus.  UV reflective low density polyethylene mulch metalized with aluminum, low density whitefaced polyethylene mulch and bare ground all using drip irrigation in a randomized complete block design were tested and compared to the current grower standard using micro-sprinkler irrigation with four replications located at the Southwest Florida Research and Education Center in Immokalee, FL.  Populations of ACP and other arthropods were monitored on new flush while ACP movement was monitored using yellow sticky cards.  Incidence of HLB was evaluated twice during the 20 month study period using qPCR.  Trunk cross sectional area, soil moisture, and surrounding weed biomass were also monitored.  Metalized mulch reduced pest populations and HLB incidence compared to all tested alternatives.  In addition, metalized mulch increased tree growth and soil moisture while reducing weed pressure.  Results of this study present a good case for the use of metalized plastic mulch for young citrus plantings.

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), vectors a pathogen that causes huanglongbing (HLB) in Florida citrus. The need to suppress ACP populations has resulted in greatly increased insecticide use in Florida. Horticultural mineral oils (HMOs), typically applied as 1–2% v/v aqueous emulsions at 937 L water ha −1 , are also used for insect pest management for citrus in Florida. Low-volume applications of other insect control products can reduce costs and application time and are effective for ACP control. The efficacy of low-volume applications of HMOs for ACP has not been tested. We initiated a three-year trial in February 2011 in a commercial Valencia orange grove in Lee County, Florida to compare low-volume (18.7 L ha −1 ) sprays of HMO applied every two weeks to a grower standard (GS) (mixes of insecticide and HMO) and an untreated control. HMO and GS treatments significantly reduced ACP adult and nymph populations. Yields were greater for HMO-treated than untreated trees in the final study year. GS and HMO treatments reduced fruit drop in 2013. Fruit quality was generally unaffected by treatments. ACP suppression, higher yields and eventual production gains indicated that frequent, low-volume application of HMO may be a viable alternative for suppressing ACP populations. [ABSTRACT FROM AUTHOR]

Abstract: Florida vegetable growers have relied on methyl bromide (MeBr) fumigation to manage soil pathogens, nematodes, and weeds. This system combined with raised beds, polyethylene mulch, and seepage and/or drip irrigation has been effective for producing high vegetable yields. Alternatives to MeBr such as solarization and organic amendments have given favorable results in small trials, but there are few large-scale studies. The objectives of this study were to evaluate the effects of long-term organic amendment applications and soil sanitation treatments on weed and nematode populations on pepper (Capsicum annuum L.) and watermelon (Citrullus lanatus [Thunb.] Manst.). During 1998 and 1999 fall vegetable seasons, main plots received a yearly organic amendment (biosolids) application or a non-amendment control, with sub-plots consisting of soil sanitation treatments with solarization, MeBr, Telone® (1,3-dichloropropene), or a non-fumigated control. Each sub-plot was further divided into two sub-sub-plots, one receiving additional weed and without control weed control. During the solarization period (60 d in 1998–1999; 90 d in 1999–2000), percent weed cover was higher in the non-biosolid plots than the biosolid plots for the first part of the solarization period, but there were no differences during the last 30 days in both seasons. Purple nutsedge was able to germinate on the north edge of the beds for a border effect; a point of vulnerability when beds run east–west. With the pepper crop, the number of weeds and percent weed cover were greater in the non-fumigated plots and Telone®-treated plots than in plots treated with MeBr or in solarized plots with and without biosolids. Nematode population densities from plot to plot within the site were highly variable, which likely accounted for the relatively few consistent effects from treatments observed during the experiment. The data do provide some indication of the importance of weeds in the recovery and buildup of nematode populations. During spring 1999, both root-knot and stubby-root nematodes were more abundant in the sub-sub-plots that had not received weed control. The results suggest that solarization and organic amendments can be viable alternatives to MeBr. However, MeBr produced the most consistent results. [Copyright &y& Elsevier]

Abstract: Diaphorina citri Kuwayama (Hemiptera: Psyllidae), is a global pest of citrus and vector of Candidatus Liberibacter, a bacteria that causes huanglongbing or greening, a devastating disease of citrus. Mature citrus trees are dormant in winter and produce most new shoots in spring, followed by sporadic canopy growth in summer and fall. Young shoots are required for oviposition and nymphal development, but adults can survive and overwinter on hardened leaves. Surviving adults reproduce in spring shoots and their progeny are probably responsible for a large portion of disease spread as they disperse to search for food. Therefore, foliar sprays of broad-spectrum insecticides applied to mature trees in winter were evaluated in a commercial citrus orchard as tactic to reduce pest populations and insecticide use in spring and summer when beneficial insects are most active. A single spray of chlorpyrifos (2.8 kg a.i. ha−1) in January 2007 reduced adult psyllids an average of 10-fold over six months compared to untreated trees. The following year, differences with the untreated control averaged 15-fold for over five months following a single spray of chlorpyrifos, fenpropathrin (0.34 kg a.i. ha−1), or oxamyl (1.12 kg a.i. ha−1) applied in January. Spiders, lacewings and ladybeetles were equally abundant during the growing season in both treated and untreated trees both years (P = 0.05). Thus foliar sprays of broad-spectrum insecticides before spring growth suppressed D. citri for five to six months, with no detectible impact on key natural enemies. This tactic has been widely adopted to control the psyllid in Florida, in some cases area-wide. Additional sprays during the growing season should be based on scouting and targeted at adults before anticipated new flush. [Copyright &y& Elsevier]

Abstract: The impact of whitefly-transmitted begomoviruses (Geminiviridae) on tomato yields depends on plant age at time of infection, and is greatest during the first 5 weeks after germination (critical period). A preventative strategy designed to minimize contact between the vector and the tomato plant by masking the crop with living ground covers during the critical period was promoted among small-scale Costa Rican farmers. A large-scale field experiment replicated over time and location was conducted to evaluate this strategy by assessing the effect of different living ground covers in comparison to the conventional control methods (insecticide or reflective mulch). Living covers including perennial peanuts (Arachis pintoi, Fabaceae), “cinquillo” (Drymaria cordata, Caryophyllaceae) and coriander (Coriandrum sativum, Umbelliferae) reduced the number of incoming whitefly adults, delayed the onset of tomato yellow mottle virus (ToYMoV), and decreased disease severity, resulting in higher yields and profits, compared to the bare soil control. Coriander provided additional economic returns when sold and was easier to establish and remove than the other living covers. Whitefly and begomovirus management with ground covers or reflective polyethylene mulch compared favorably with the conventional insecticide treatment using imidacloprid Therefore, living ground covers appeared to offer a viable and economic management alternative for resource-poor farmers. [Copyright &y& Elsevier]

Abstract: Eretmocerus mundus Mercet is indigenous to the Mediterranean basin and the most abundant parasitoid attacking Bemisia tabaci Gennadius on the southern coast of Spain. However, E. mundus was not available commercially until 2002 and the North American Eretmocerus eremicus Rose and Zolnerowich had been used instead to control whiteflies in greenhouse vegetables, including sweet pepper in Campo de Cartagena (Murcia). The ability of these two Eretmocerus species to control B. tabaci on pepper by augmentation was compared with weekly releases of E. mundus and E. eremicus, alone, and in 1:1 combination (three treatments) initiated early in the winter crop cycle in 12 commercial greenhouses. E. mundus rapidly displaced E. eremicus in greenhouses where both were released, and eventually, even where only E. eremicus was released, indicating that a significant portion of the E. mundus population entered the greenhouses from outside. Nevertheless, parasitism rates were greater in greenhouses where E. mundus was released, especially early in the trial. Whitefly populations were lower compared to where E. eremicus was released alone, presumably in response to parasitism. Thus, higher incidence of parasitism and superior control of B. tabaci with E. mundus confirmed the value of early season augmentation with this parasitoid as opposed to E. eremicus under conditions of this test. [Copyright &y& Elsevier]

The whitefly Bemisia tabaci Gennadius is the key pest of protected tomato production in Spain. The predominant form is biotype “Q”, an efficient vector of tomato yellow leafcurl virus (TYLCV), which is the principal cause of damage. Although management has relied primarily on chemical control, factors such as overlapping crop cycles, insecticide resistance and public pressure have spurred development of alternative management tactics. These include TYLCV-tolerant varieties and pest exclusion methods that, along with more selective insecticides, have created a more compatible environment for biological control. Here we describe trials of an integrated pest management (IPM) system conducted during the fall season in 12 commercial greenhouses throughout the production area compared with 7 greenhouses utilizing only chemical control (termed “conventional”). Each IPM greenhouse was divided into 4 equal sections, two receiving weekly releases of the indigenous Eretmocerus mundus Mercet and two receiving the exotic Eretmocerus eremicus Rose & Zolnerowich. Fewer and more selective pesticides were used in IPM greenhouses compared to conventional greenhouses. Early use of broad-spectrum insecticides in IPM greenhouses appeared to be counterproductive in that establishment of parasitioids was delayed with no real gain in control. Incidence of parasitized whiteflies in IPM greenhouses averaged around 50%, with E. mundus predominating, compared to less than 3% in conventional greenhouses originating from immigrating E. mundus. Whiteflies were on average more numerous on plants in IPM greenhouses although there were exceptions. Also, whitefly populations in IPM greenhouses tended to decrease as the crop matured, in contrast to conventional greenhouses. Biological control was most successful where TYLCV-resistant cultivars and exclusion strategies (insect netting) reduced whitefly populations and the risk of virus disease. Continued acceptance of these tactics, and increasing public demand should create a favorable climate for increased implementation of biologically based pest management in protected tomato culture. [Copyright &y& Elsevier]