Studies on host preference and its biological effects on the Red Palm weevil,Rhynchophorus ferrugineus Olivier in Egypt B. vegetable crops

The investigation on some Egyptian vegetables preference by the Red Palm weevil (RPW), Rhynchophorus ferrugineus has been carried out under laboratory conditions to explore a suitability of alternative host plants. The choice test of insect larvae showed that Taro, Squash, Eggplant, common potato, yellow carrot, tomato and sweet pepper were accepted food, while the Table beet (Vegetable) was rejected. Non-choice feeding of R. ferrugineus larvae on vegetables affected larval body weight and increased larval mortality. Highest rate of pupation was recorded from larvae fed on C. pepo (92%) and B. vulgaris (97%). Adult emergence reached 80% and 92% on C. pepo and Sugar beet (field crop) (field crop). The external skin of sugar cane was not acceptable food for insect larvae, while injured sites and internal soft fibres were preferred as food. Therefore, vegetable fruits, stem of sugarcane are believed to be the most vulnerable hosts for red weevil attack. The alternative host plant examined can be used to monitor the dynamics of the population of RPW in order to take effective preventive measures and most powerful tool available for use in pest management.     

Nano essential oils against the red palm weevil,Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae)

The red palm weevil, Rhynchophorus ferrugineus, is the biggest pest of various palm species. The aim of this study was to evaluate the impact of the essential oils of purslane, mustard and castor (bulk and nano) on R. ferrugineus and to evaluate the oviposition deterrent effect to prevent new infestations. Prepared concentrations of essential oils (bulk and nano) were tested for their impact on R. ferrugineus larvae, pupae and adults. The most effective oil was purslane oil (bulk and nano), followed by mustard and the least effective was castor. The percent mortality of larvae was 75.2, 45.3 and 17.9% (bulk phase) and 92.5, 84.4 and 65.5% (nano phase) in purslane, mustard and castor, respectively, when treated with the high concentration. The percent mortality of adults was 67.2, 40.0 and 15.6% (bulk phase) and 83.5, 72.9 and 60.0% (nano phase) in purslane, mustard and castor, respectively, when treated with the high concentration. The number of eggs laid decreased with increasing concentration of the tested oils. Purslane essential oil showed good impact on R. ferrugineus larvae and adults followed by mustard and castor oils as bulk and as nano.     

Assessing Spirulina platensis as a dietary supplement and for toxicity to Rhynchophorus ferrugineus (Coleoptera: Dryopthoridae)

Insects are important for humanity; play role in crop pollination, and biocontrol of harmful pests. The red palm weevil, Rhynchophorus ferrugineus, is a major pest of date palms and has become a serious threat. Scientists needs ample numbers of insects for bioassays to explore control options. The alga Spirulina platensis, is enriched by protein, natural vitamins, minerals, and amino acids, stimulate the development of organisms that feed on it. I assessed the value of Spirulina as a nutritional supplement for red palm weevil larvae by adding its various percentages to the artificial diet. Once a week, the larvae were removed from the containers, washed with distilled water, dried, weighed using an electronic scale, returned to a new container, and supplied with Spirulina mixed fresh diet. Larvae fed with lower concentrations showed vigorous growth and significant weight gain. Particularly, larvae fed 0.5%, 1%, and 2% Spirulina powder supplementation to their diet were healthier and gained more weight than larvae reared with >5% concentration. Overall 40% mortality was recorded in larvae fed with 10% concentration. Higher concentrations were lethal, and all larvae died within two weeks when fed 20% Spirulina. The present research findings indicate that Spirulina used in concentrations from 0.5% to below 5% had a beneficial effect on red palm weevil larval growth but a detrimental effect and even mortality was recorded when used ≥5%.     

The culturable bacterial community of frass produced by larvae of Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) in the Canary island date palm

Aims: Larvae of the red palm weevil (RPW) Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) feed inside palm stem tissues, making galleries and producing a wet fermenting frass. We characterized the culturable bacteria associated with frass produced by tunnelling larvae inside the Canary island date palms and investigated the role of frass and gut bacteria in plant polymers breakdown. Methods and Results: A culture‐dependent method was used to isolate bacteria from frass and noninfested palm tissues. Bacterial isolates were grouped into operational taxonomic units based on polymorphisms in the ITS‐PCR profiles, and representative isolates were identified by partial sequencing of the 16S rRNA gene. Frass bacteria were dominated by 2,3‐butanediol fermenter Enterobacteriaceae. None of the bacterial isolates was able to degrade cellulose; however, cellulolytic and hemicellulolytic bacteria were isolated from the larval gut enrichment cultures. Conclusions: Frass bacteria are specifically associated with the RPW larvae and might play beneficial roles for RPW, other than nutritional, that deserve further investigations. Breakdown of plant polymers probably occurs inside the larvae digestive system. Significance and Impact of the Study: Frass and gut micro‐organisms of R. ferrugineus should be included in studies of the interactions between RPW, its plant hosts, and its enemies.     

Integration of entomopathogenic fungi and eco-friendly insecticides for management of red palm weevil,Rhynchophorus ferrugineus (Olivier)

Red palm weevil (Rhynchophorus ferrugineus) is a voracious pest of date palm worldwide. Pakistan ranks sixth in date palm production globally. Losses to date palm plantations in Pakistan sometimes surpass 10%-20%. Most of the traditional management strategies used by farmers have been found insignificant to combat this voracious pest. The entomopathogenic fungi, Beauveria bassiana [QA-3(L) and QA-3(H)] and insecticides, Nitenpyram (Active 10% SL) [NIT (L) and NIT (H)] were applied to larval (2nd, 4th, and 6th), pupal and adult stages of R. ferrugienus. Integration or alone application of fungi with insecticides at different concentration under laboratory conditions. Combined application was depicted additive and synergistic interactions. Contrarily, highest cumulative mortality (100%) was recorded in 2nd instar larvae as compared to later instar larvae at combined application. The maximum pupal and adult mortality remained 89% and 66% respectively after treatment with [QA-3 (H) + NIT (L)]. The combination of B. bassiana at higher concentration whereas Nitenpyram at lower dose was found more lethal to larvae, pupae and adults of R. ferrugineus. This signifies the need of combining B. bassiana and bio-rational insecticides that can reduce the cost of management with least harm to environment and natural enemies.     

Virulence of entomopathogenic nematodes to larvae of the guava weevil, Conotrachelus psidii (Coleoptera: Curculionidae), in laboratory and greenhouse experiments

The guava weevil, Conotrachelus psidii, is a major pest of guava in Brazil and causes severe reduction in fruit quality. This weevil is difficult to control with insecticides because adults emerge over a long period, and larvae develop to the fourth-instar inside the fruit and move to the soil for pupation. We assessed the virulence of entomopathogenic nematodes to fourth-instar larvae in soil by comparing their susceptibility to nine species or strains: Heterorhabditis bacteriophora HP88, H. baujardi LPP7, and LPP1, H. indica Hom1, Steinernema carpocapsae All and Mexican, S. feltiae SN, S. glaseri NC, and S. riobrave 355. In petri dish assays with sterile sand at a concentration of 100 infective juveniles (IJs) of a given nematode species/strain, larval mortality ranged from 33.5 to 84.5%, with the heterorhabditids being the most virulent. In sand column assays with H. baujardi LPP7, H. indica Hom1, or S. riobrave 355 at concentrations of 100, 200, and 500 IJs, mortality was greater than the control only for H. baujardi (62.7%) and H. indica (68.3%) at the highest concentration. For H. baujardi LPP7 in a petri dish assay, the time required to kill 50 and 90% of the larvae (LT₅₀ and LT₉₀) for 100 IJs was 6.3 and 9.9 days, whereas the lethal concentration required to kill 50 and 90% of the larvae (LC₅₀ and LC₉₀) over 7 days was 52 and 122.2 IJs. In a greenhouse study with guava trees in 20-L pots, 10 weevil larvae per pot, and concentrations of 500, 1000 or 2000 IJs, H. baujardi LPP7 caused 30 and 58% mortality at the two highest concentrations. These results show that H. baujardi is virulent to fourth-instar larvae and has potential as a biological control agent in IPM programs.     

Non-target effects of kaolin and coppers applied on olive trees for the predatory lacewing Chrysoperla carnea

Kaolin clays and copper salts might be considered as alternative chemical control products for controlling olive pests in the contexts of both organic farming and integrated pest management programmes. Chrysoperla carnea (Stephens) (Neur. Chrysopidae) represents one of the most significant generalist predators of olive grove pests. In this study, we evaluated the side effects of these compounds on the predatory lacewing. First, kaolin and two copper salts (copper oxychloride and Bordeaux mixture) were tested on C. carnea eggs to determine their effects on egg viability and larval hatching suppression by topical application. Second, L₃ larvae were exposed to the pesticide residues on treated olive tree leaves. Third, a series of three residual tests in adults were sequentially performed as follows: residues on glass surfaces, on olive tree leaves and on small olive trees. Finally, kaolin- and water-treated eggs of Ephestia kuehniella Zeller (Lep. Pyralidae) were offered to L₃ larvae in both dual- and no-choice tests. C. carnea egg hatching was reduced by the kaolin treatment compared to the control treatment. Residual treatments were harmless to larvae and adults, without any deleterious effects on reproduction. L₃ larvae consistently preferred to feed on water-treated E. kuehniella eggs compared to kaolin-treated eggs. The larvae from the no-choice test that had fed ad libitum until pupation on kaolin-treated E. kuehniella eggs, pupated and emerged as healthy adults in reduced proportions compared with those that fed on water-treated eggs. In conclusion, our data suggest that both kaolin and copper products appeared to be largely harmless or only slightly harmful to the predator.     

Are the palms Washingtonia filifera and Chamaerops humilis suitable hosts for the red palm weevil,Rhynchophorus ferrugineus (Col. Curculionidae)?

The red palm weevil, Rhynchophorus ferrugineus (Olivier) (Coleoptera, Curculionidae), is a widely distributed pest which has recently become the major pest of palms in the Mediterranean Basin. This weevil has been recorded on 19 different palm species, however, the host status of Washingtonia filifera and Chamaerops humilis remains unclear. The present study was carried out to check whether these species had either antixenotic or antibiotic mechanisms of resistance against this pest. Our results show that both W. filifera and C. humilis are resistant to R. ferrugineus. Resistance in W. filifera is based on antibiosis whereas in C. humilis resistance is based on antixenosis.     

Delay expression of limonoid UDP-glucosyltransferase makes delayed bitterness in citrus

Genes encoding limonoid UDP-glucosyltransferase from albedo of six Citrus species with different levels of delayed bitterness are isolated and cloned in vector pTZ57R/T. Our results indicate that gene sequence of sweet lime (with intense juice delayed bitterness) have complete identity with Satsuma mandarin (without distinctive juice delayed bitterness). Also gene sequence of Marsh seedless grapefruit, local orange and Thompson navel orange (with mild juice delayed bitterness) have very similarity with Satsuma mandarin. On the other hand, this gene started to express 60, 120, and 210 days after full blooming in albedo of Satsuma mandarin, sweet oranges and sour orange, and both grapefruit and sweet lime, respectively. Expression pattern of limonoid glucosyltransferase gene in leaves was quite different with albedo. Thus, we supposed the delayed bitterness in this species was related to delay in expression of limonoid glucosyltransferase gene in albedo and lower limonoid glucoside accumulation in fruits.     

Potential of certain natural extracts for the control of the red palm weevil,Rhynchophorus ferrugineus (Oliver)

Abstract

Laboratory bioassays were conducted to evaluate the potential of 13 plant extracts for the control of the red palm weevil, Rhynchophorus ferrugineus. Results indicated that the ethanol extracts of sea ambrosia (Ambrosia maritima), French cotton (Calotropis procera) and curcuma (Curcuma longa) have superior toxicity as compared to the extracts of other tested plants, estimated LC 50 were 0.723, 0.978 and 1.092%, respectively. In field experiments, the percentage of recovered date palm trees reached 90.91% within 15 days when A. maritima extract was applied. The injection of C. procera and C. longa extracts into the tunnels of infested trees resulted in 86.36% and 85.00% of tree recovery, respectively.     

Citrus Tree Decline Caused by Pratylenchus coffeae

The pathogenic effects of Pratylenchus coffeae on growth and yield of tangelo (Citrus paradisi × C. reticulata) scions grafted on rough lemon (C jambhiri), sour orange (C. aurantium) and ''Cleopatra'' mandarin (C. reticulata) rootstocks were evaluated under field conditions for 4 years. Pratylenchus coffeae on inoculated trees increased to significantly damaging population densities on rough lemon rootstock the second year, on sour orange the third and on Cleopatra mandarin the fourth year after planting. Mean growth reduction of P. coffeae-infected trees after 4 years was 80, 77 and 49%, respectively, for the three rootstocks. Noninoculated trees on rough lemon and sour orange rootstocks yielded significantly more fruit than comparable inoculated trees. Natural migration of P. coffeae occurred horizontally on roots for a distance of 4.5 m.     

Volatile host fruit odors as attractants for the oriental fruit fly (Diptera: Tephritidae)

We examined the responses of oriental fruit flies, Bactrocera dorsalis Hendel, to the odors of different stages and types of fruit presented on potted trees in a field cage. Females were most attracted to odors of soft, ripe fruit. Odors of common guava were more attractive to females than papaya and starfruit, and equally as attractive as strawberry guava, orange, and mango. In field tests, McPhail traps baited with mango, common guava, and orange captured equal numbers of females. Traps baited with mango were compared with 2 commercially available fruit fly traps. McPhail traps baited with mango captured more females than visual fruit-mimicking sticky traps (Ladd traps) and equal numbers of females as McPhail traps baited with protein odors. Results from this study indicate that host fruit volatiles could be used as lures for capturing oriental fruit flies in orchards.     

Production of additional allotetraploid somatic hybrids combining mandarings and sweet orange with pre-selected pummelos as potential candidates to replace sour orange rootstock

Summary Sour orange (Citrus aurantium L.) rootstock has historically been a widely utilized eitrus rootstock throughout the world due to its wide soil adaptability and superior horticultural performance. However, quick-decline isolates of citrus tristeza virus (CTV) have demolished entire industries of sour orange rootstock in some countries, including Brazil and Venezuela. CTV is presently destroying millions of trees of sour orange rootstock in Florida and threatens the citrus industries of Texas and Mexico, where sour orange is the predominant rootstock. Efforts to replace sour orange rootstock are combining traditional breeding and biotechnology approaches, including somatic hybridization and transformation. Molecular techniques have confirmed that sour orange is probably a hybrid of mandarin and pummelo. A major focus of our program continues to be the somatic hybridization of superior mandarins with pre-selected pummelo parents. Here, we report the regeneration of allotetraploid somatic hybrid plants from seven new mandarin+pummelo combinations and one new sweet orange+pummelo combination. All new somatic hybrids were confirmed by leaf morphology, ploidy analysis via flow cytometry, and random amplified polymorphic DNA analysis to show nuclear contributions from both parents in corresponding hybrids. These new somatic hybrids are being propagated by tissue culture and/or rooted cuttings for further evaluation of disease resistance and horticultural performance in field trials.     

Etiology of three recent diseases of citrus in São Paulo State: sudden death, variegated chlorosis and huanglongbing

The state of S?o Paulo (SSP) is the first sweet orange growing region in the world. Yet, the SSP citrus industry has been, and still is, under constant attack from various diseases. In the 1940s, tristeza-quick decline (T-QD) was responsible for the death of 9 million trees in SSP. The causal agent was a new virus, citrus tristeza virus (CTV). The virus was efficiently spread by aphid vectors, and killed most of the trees grafted on sour orange rootstock. Control of the disease resided in replacing sour orange by alternative rootstocks giving tolerant combinations with scions such as sweet orange. Because of its drought resistance, Rangpur lime became the favourite alternative rootstock, and, by 1995, 85% of the SSP sweet orange trees were grafted on this rootstock. Therefore, when in 1999, many trees grafted on Rangpur lime started to decline and suddenly died, the spectre of T-QD seemed to hang over SSP again. By 2003, the total number of dead or affected trees was estimated to be over one million. The new disease, citrus sudden death (CSD), resembles T-QD in several aspects. The two diseases have almost the same symptoms, they spread in time and space in a manner strikingly similar, and the pathological anatomy of the bark at the bud union is alike. Transmission of the CSD agent by graft-inoculation has been obtained with budwood inoculum taken not only on CSD-affected trees (grafted on Rangpur lime), but also on symptomless trees (grafted on Cleopatra mandarin) from the same citrus block. This result shows that symptomless trees on Cleopatra mandarin are tolerant to the CSD agent. Trees on rootstocks such as Sunki mandarin or Swingle citrumelo are also tolerant. Thus, in the CSD-affected region, control consists in replacing Rangpur lime with compatible rootstocks, or in approach-grafting compatible rootstock seedlings to the scions of trees on Rangpur lime (inarching). More than 5 million trees have been inarched in this way. A new disease of sweet orange, citrus variegated chlorosis (CVC), was observed in 1987 in the Triangulo Mineiro of Minas Gerais State and the northern and north-eastern parts of SSP. By 2000, the disease affected already 34% of the 200 million sweet orange trees in SSP. By 2005, the percentage had increased to 43%, and CVC was present in all citrus growing regions of Brazil. Electron microscopy showed that xylem-limited bacteria were present in all symptomatic sweet orange leaves and fruit tissues tested, but not in similar materials from healthy, symptomless trees. Bacteria were consistently cultured from twigs of CVC-affected sweet orange trees but not from twigs of healthy trees. Serological analyses showed the CVC bacterium to be a strain of Xylella fastidiosa. The disease could be reproduced and Koch's postulates fulfilled, by mechanically inoculating a pure culture of X. fastidiosa isolate 8.1.b into sweet orange seedlings. The genome of a CVC strain of X. fastidiosa was sequenced in SSP in the frame of a project supported by FAPESP and Fundecitrus. X. fastidiosa is the first plant pathogenic bacterium, the genome of which has been sequenced. Until recently, America was free of huanglongbing (HLB), but in March 2004 and August 2005, symptoms of the disease were recognized, respectively in the State of S?o Paulo (SSP) and in Florida, USA. HLB was known in China since 1870 and in South Africa since 1928. Because of its destructiveness and its rapid spread by efficient psyllid insect-vectors, HLB is probably the most serious citrus disease. HLB is caused by a phloem sieve tube-restricted Gram negative bacterium, not yet available in culture. In the 1990s, the bacterium was characterized by molecular techniques as a member of the alpha proteobacteria designated Candidatus Liberibacter africanus for the disease in Africa, and Candidatus Liberibacter asiaticus for HLB in Asia. In SSP, Ca. L. asiaticus is also present, but most of the trees are infected with a new species, Candidatus Liberibacter americanus.     

Ultra morphology of sensilla on the head and mouth parts of the earwig Anisolabis martima (Bonelli) (Dermaptera: Carcinophoridae)

The earwig Anisolabis maritima is a cosmopolitan insect with a worldwide distribution, omnivorous in feeding, eating the eggs of different insects. Recently recorded in Saudi Arabia as a beneficial predator on eggs and newly hatched larvae of the red palm weevil Rhyncophrous ferrugineus, scanning electron microscopy (SEM) observations revealed the presence of different kinds of receptor sensillae occurring on the head and mouth parts of A. maritime. The sensillae are the same, but differ in numbers on both sexes. The head surface bears three subtypes of trichoid sensillae, one type of ceoloconica. Labrum, labium, labial palps and maxillary palps, possess different kinds of sensillae. Three subtypes of trichoid have been identified on the labrum. The labium contained one type of tricoid and basiconic sensillae. There are great numbers and numerous sensillae cheatica differing in length distributed on the maxillary and the labial palps on all segments between other stutter spines. The last terminal segment of maxillary or labial palps bears the greatest number of the sensillae cheatica. Adult A. maritima may be introduced in the future as a beneficial predator of eggs of R. ferrugineus as a tool for integrated pest management.     

Growth and root hydraulic conductivity of several citrus rootstocks under salt and polyethylene glycol stresses

The water relations responses to salt of several important citrus rootstocks such as Swingle citrumelo, sour orange, and Milam lemon have not been studied in detail before. Studies were set up to compare growth and root hydraulic properties of these rootstocks to other citrus rootstocks by exposing them to NaCl and polyethylene glycol (PEG) stresses. Seedlings of 7 citrus rootstocks were irrigated for 5 months with nutrient solutions containing NaCl or PEG that had been adjusted to osmotic potentials of -0.10, -0.20 or -0.35 MPa. The 7 rootstocks studied were sour orange (Citrus aurantium), Cleopatra mandarin (Citrus reticulata Blanco), Swingle citrumelo (C. paradisi x P. trifoliata), Carrizo citrange (C. sinensis x P. trifoliata), rough lemon (Citrus jambhiri Lush), Milam lemon (C. jambhiri hybrid), and trifoliate orange (Poncirus trifoliata [L.] Raf.). In both shoot and root growth, Cleopatra mandarin and sour orange were the least sensitive to salt, Milam and trifoliate orange were the most sensitive, and rough lemon, Swingle, and Carrizo were intermediate in sensitivity. Even though the roots were exposed to solutions of equal osmotic potentials, plant growth and root conductivity were reduced more by the PEG treatments than the corresponding NaCl treatments. At -0.10 and -0.20 MPa, shoot and root dry weights were reduced 16 to 55% by NaCl and 24 to 68% by PEG. Shoot root ratio was lowered at the higher concentrations, particularly by PEG. There was a major decrease in root conductivity caused by NaCl at -0.10 MPa (19 to 30% in sour orange and Cleopatra mandarin and 78 to 85% in trifoliate orange and Milam). Conductivity decreased more at -0.20 and -0.35 MPa, but not proportionally as much as at -0.10 MPa. Root weight per unit length increased at the higher salt levels, particularly in trifoliate orange. Water flow rate through root systems followed the same trend as root conductivity; salt affected sour orange and Cleopatra mandarin the least and trifoliate orange and Milam the most. However, reductions in fibrous root length by salt treatment differed. Root lengths of Swingle and Carrizo were least affected by salt while sour orange. Milam, and rough lemon were the most affected. Hence, even though sour orange and Cleopatra mandarin were more tolerant than the other rootstocks in terms of water flow rate or root conductivity, these 2 rootstocks showed a proportionally greater decrease in root length than Carrizo, Swingle, or trifoliate orange.     

Effect of proteinase inhibitors on Indian alfalfa weevil (<Emphasis Type="Italic">Hypera postica</Emphasis> Gyll.) growth and development

Three families of proteinase inhibitors, namely, serine, cysteine (thiol) and aspartic (carboxyl) were examined for their inhibitory effects on growth and development of Indian alfalfa weevil (Coleoptera: Curculionidae). Proteinase inhibitors are considered as a part of alternate strategy to control the herbivorous insect as they inhibit the digestive enzymes of the insects. Larval leaf feeding, survival, pupation and adult emergence were significantly decreased by pHMB, (p-hydroxy-mercuribenzoic acid), cystatin and E-64 (trans-epoxysuccinyl-l-leucylamido-(4guanidino)-butane) belonging to cysteine class of proteinases, at a concentration of 0.1 and 0.5%. Serine and aspartic classes of inhibitors have low detrimental effects on larvae. The results demonstrate the inhibitory response of specific proteinase inhibitors on alfalfa weevil larval leaf feeding, survival, pupation and adult emergence. Weevil resistant species, namely, Medicago scutellata showed high level of leaf consumption under forced feeding in vivo bioassay indicated the presence of resistance factors other than proteinase inhibitors.     

Azadirachtin-induced effects on larval-pupal transformation of Spodoptera mauritia

Abstract. Penultimate (fifth) and last (sixth) stadium larvae of Spodoptera mauritia Boisd. (Lepidoptera: Noctuidae) of various ages were injected with 0.5 μg, 1 μg or 2 μg azadirachtin and the effects on moulting and larval-pupal transformation were analysed. Higher doses (1 μg and 2 μg) of azadirachtin induced a prolongation of the fifth stadium in larvae treated on day 0 and day 1. The resulting sixth stadium larvae failed to pupate. Sixth stadium larvae injected with 0.5 μg, 1 μg or 2 μg azadirachtin showed prolongation of sixth larval period. Azadirachtin treatments completely prevented normal pupation in 'day 0' and 'day 1' larvae even though the percentage of pupation increased in treated larvae of other age groups. Injection of 2 fig azadirachtin prevented normal pupation in larvae of all age groups. Injection of 4 μg ecdysterone to sixth stadium larvae pre-treated with 1 fig azadirachtin (on day 0) promoted normal pupation in the majority of animals.     

Efficient propagation and rooting of three citrus rootstocks using different plant growth regulators

The influence of various basal medium and plant growth regulators on the efficient micropropagation of nodal explants from mature trees of alemow, sour orange, and ??Cleopatra?? mandarin citrus rootstocks was studied. All three citrus rootstock shoot cultures showed a preference for high-salt media, like Murashige and Skoog or Driver and Kuniyuki Walnut medium. Several combinations of N ⁶-benzyladenine (BA) and adenine (AD), kinetin (KIN) or gibberellic acid (GA) were tested to optimize the shoot proliferation phase. BA/GA combinations improved the proliferation of all the rootstocks studied, especially alemow. The addition of BA and AD to the culture medium improved shoot proliferation in sour orange and ??Cleopatra?? mandarin in the same way as BA and GA. The addition of different combinations of BA/KIN did not result in further improvement of any of the studied variables. The transfer of in vitro shoots to rooting media, containing different concentrations of indolebutyric acid (IBA) and indoleacetic acid (IAA), resulted in regeneration of complete plantlets. Alemow and ??Cleopatra?? mandarin shoots rooted well using these plant growth regulators; however, all combinations of IBA and IAA tested resulted in very low rooting percentages in sour orange. To improve rooting in sour orange and ??Cleopatra?? mandarin, different combinations of naphthaleneacetic acid (NAA) and IBA were tested. All NAA/IBA combinations produced higher rooting percentages than did the IBA/IAA combinations, and in sour orange nearly 100 % of explants developed roots. An efficient and simple protocol for the micropropagation of three citrus rootstocks, alemow, ??Cleopatra?? mandarin, and sour orange, by culturing nodes from mature plants, has been established.     

Effect of root feeding by Diaprepes abbreviatus (Coleoptera: Curculionidae) larvae on leaf gas exchange and growth of three ornamental tree species

Diaprepes abbreviatus L. (Coleoptera: Curculionidae), feeds on a variety of ornamental plants grown in southern Florida. Studies were conducted to evaluate the effects of root feeding by D. abbreviatus larvae on leaf gas exchange and growth of three ornamental tree species commonly grown in southern Florida that are known hosts of this weevil: green buttonwood, Conocarpus erectus L.; live oak, Quercus virginiana Mill.; and pygmy date palm, Phoenix roebelenii O'Brien. These hosts were grown in containers and infested with weevil larvae. Net CO2 assimilation, transpiration, and stomatal conductance of CO, were measured monthly. Leaf, stem, and root fresh and dry weights of each species also were determined. In one of two tests, larval root feeding significantly reduced net CO2 assimilation, transpiration, and stomatal conductance of CO2 of infested green buttonwood trees. Leaf gas exchange of live oak was not affected by larval infestation. In addition to testing cumulative effects of multiple infestations of larvae, the effects of incremental infestations on leaf gas exchange and fresh and dry weights also were tested for each plant species. Net CO2 assimilation, transpiration, stomatal conductance of CO2, and dry weights of green buttonwood were reduced as a result of larval root feeding, whereas there was no effect of incremental larval infestations on leaf gas exchange of live oak or pygmy date palm within the experimental time frame. There was no effect of incremental larval infestations on dry weights of live oak, but leaf, stem, and dry root weight of pygmy date palm were lower for infested plants than for noninfested plants. Overall, green buttonwood was more susceptible to larval root feeding damage than either live oak or pygmy date palm.