Distribution and diversity of leaf-cutting ants in Northeastern Argentina: species most associated with forest plantations

Abstract

Leaf-cutting ants (LCA) are considered one of the main herbivores and one of the most destructive pest insects of the Neotropics. Northeastern Argentina harbors the greatest species richness of these ants and in turn comprises the highest surface with forest plantations. Our aim was to establish which species of leaf-cutting ants are most commonly associated with forest plantations by analyzing their geographic distribution using published and unpublished species occurrence data. Also, estimate their potential areas of distribution along a latitudinal gradient that entirely encompasses northeastern Argentina using Ecological Niche Modeling. Only seven of the 20 species recorded were strongly associated with productive systems along the gradient, but only 2–3 species in each region could be considered high-risk species for forest plantations. High-risk species composition shows a turnover between regions. Our models show the potential distribution areas where LCA could become more abundant and dominant, and possibly causing a detrimental effect on the forest plantations in the studied region. We find that ecological niche models are useful tools to assess the environmental suitability of important LCA.     

Resistance to polyoxin AL and other fungicides in Botrytis cinerea collected from sweet basil crops in Israel

A total of 568 B. cinerea isolates were collected from diseased sweet basil plants and the air in 10 sweet basil greenhouses. Mycelial growth tests were used to evaluate the sensitivity of these isolates to benomyl, fenhexamid, iprodione, polyoxin AL and pyrimethanil. EC₅₀ values for polyoxin, the main botryticide on sweet basil in Israel, ranged from 0.4 to 6.5 μg ml^?1 and had a bimodal distribution; the EC₅₀ values for sensitive isolates ranged from 0.4 to 1.5 μg ml^?1 and the EC₅₀ values for low-level resistant isolates ranged from 4 to 6.5 μg ml^?1. Among populations that had not been exposed to polyoxin treatments, 20 to 35 % of the collected isolates were low-level resistant for polyoxin. Polyoxin treatments in an experimental greenhouse shifted the equilibrium in favour of low-level resistant isolates, and the change occurred rapidly: from a frequency of 20 % low-level resistant isolates in the population that had never been treated with polyoxin to a frequency of 72 % after a few treatments over two seasons. Prolonged use of polyoxin in Israeli basil crops (in some sites for more than 10 years) does not appear to have led to the development of high-level resistance, but low-level resistant isolates were found in commercial greenhouses with the frequency of up to 73 %. High-level resistance to benzimidazoles was common (60 to 80 % of isolates) in greenhouses with a history of benzimidazole treatments; whereas 15–25 % of the isolates from greenhouses in which fungicides were not used were resistant. Low-level resistance to dicarboximides was fairly widespread (frequency of 30 to 80 % depending on the greenhouse) and a few cases of moderate resistance to dicarboximides were also noted (frequency of 0 to 9 %). Neither high- nor low-level resistance to anilinopyrimidines was common in sweet basil commercial greenhouses (0 to 7 %). However, 34 % of the isolates were strongly resistant in the experimental greenhouse, following a few treatments with anilinopyrimidine fungicides during the previous season. Before those treatments, the proportion of anilinopyrimidines resistant isolates had been 1 %. About 3 % of the isolates exhibited low-level resistance to fenhexamid and no isolates were found to be strongly resistant to fenhexamid. Low-level resistance to one fungicide was often associated with low-level resistances to other fungicides. Thirty-two phenotypes exhibiting resistance to one or more of the tested fungicides were noted among B. cinerea isolates. Resistant isolates showed similar or reduced fitness parameters in comparison to wild-type isolates.     

Fruit and seed diversity of domesticated carob (Ceratonia siliqua L.) in Morocco

The carob tree (Ceratonia siliqua L.) is an important economic resource for Morocco's rural populations. This species is used in reforestation actions and its cultivation in modern orchards is being undertaken to valorize marginal lands and substitute for drought sensitive species. However, little data is available on its intra-specific variability and its adaptability. Morphological characters of pods and seeds from 13 ecoregions of private-domesticated carob were used to assess phenotypic variation of this species. These stands extend from south-west to north-east and cover a wide range of Morocco's ecoregions. Pods length, width, thickness, seeds number, pulp weight, seeds yield and seeds length, width, thickness and weight were measured for 390 trees (30 trees per ecoregion). Statistically significant differences were found between ecoregions for all characters which were examined, what indicates a high phenotypic diversity. Principal component analysis (PCA) and hierarchical cluster of all ecoregions lead to identify two major and opposite groups (the northern ecoregions; and the central and south-western ecoregions). Ecoregions of the north of Morocco exhibited the largest and the thickest pods with the highest pulp weight while other ecoregions have relatively short pods but largest proportion of seed yield. Similarly, the northern ecoregions are characterized by the heaviest seeds. A correlation matrix between morphological characters, geographic parameters and precipitation exhibits a positive and a negative correlation of pods thickness and pulp weight with the latitude and the altitude, respectively. Seed yield and weight are negatively and positively correlated to pod width, pod thickness and pulp weight, respectively. In addition, seed weight is positively correlated with the latitude. The geographic pattern of the carob tree and its variability are discussed in this paper.     

Polyhydric alcohol liquefaction of some lignocellulosic agricultural residues

Liquefaction of bagasse and cotton stalks was conducted by using polyhydric alcohols (polyethylene glycol PEG#400 and glycerin) in the presence of sulfuric acid (SA) as a catalyst. The effects of different liquefaction conditions, such as ratio raw material/liquefying solvent, effect of PEG#400/glycerin, acid concentration, liquefaction temperature and time on the liquefaction yield have been investigated. The hydroxyl and acid numbers for some liquefied samples were also determined. The results showed that the minimum residue content was obtained at 1/5 raw material to liquefying solvent. PEG#400 alone is not favoured as liquefying solvent as it gives ∼19% residual content for bagasse and ∼22% for cotton stalks at the optimum studied reaction conditions. Replacing 10% of PEG#400 with glycerin as well as increasing the SA concentration, liquefaction temperature or time, decreased the amount of residue for both bagasse and cotton stalks to less than 10%. The hydroxyl number of the produced polyols slowly decreased from 253 to 223 mg KOH/g on extending the reaction time till 120 min and the residual polyols prevented re-condensation of the liquefied components. It seems that this system can be applied on various types of lignocellulosic agricultural residues.     

Bioactivity of some formulations of neem seed extracts against the whiteflyBemisia tabaci (Genn.)

The bioactivity of different formulations of neem seed extracts against the whiteflyBemisia tabaci (Genn.) was assayed in semifield trials during 1992. Tomato plants variety UC-97 were cultivated in pots and left to natural infestation with whitefly in an open field and sprayed with various concentrations of each extract. The high concentrations of all the extracts tested exhibited obvious activity. Also, the different treatments reduced the population density of the adult whiteflies compared with the control. The percentage reduction in the population reached its maximum level one hour after treatment with any tested extract.With one table     

Laboratory evaluation of some pesticides on the cabbage aphid,Brevicoryne brassicae L. and their side effects on some important natural enemies

The susceptibility of adults of the cabbage aphid,Brevicoryne brassicae and two of the most important predators,Coccinella undecimpunctata andChrysopa carnea to pesticides was assessed. Most of the organophosphorus and carbamate compounds tested were toxic to the aphids. Profenophos was highly toxic to the adult virginoparous aphid at Lc50 level. Malathion demonstrated the highest toxicity to, the aphids. The application of profenophos for the cabbage aphid at Lc50 level exhibited no toxicity forCoccinella but was highly toxic forChrysopa. Pirimicarb proved to be the most selective of the compounds tested for the control of aphids when it was used at a concentration that caused 50% mortality as it was found to be unharmful to bothChrysopa andCoccinella. Dimethoate, on the other hand, was found to be very harmful and highly toxic to bothCoccinella andChrysopa adults and would probably be destructive to those natural enemies in the field. Laboratory evaluation indicates that both pirimicarb and malathion have potentials for use, in IPM program for vegetable pest control.     

Anhydrous goat's milk fat: thermal and structural behaviors studied by coupled differential scanning calorimetry and X-ray diffraction. 2. Influence of cooling rate

Crystallization and melting properties of triacylglycerols (TGs) in anhydrous goat's milk fat (AGMF) are investigated by X-ray diffraction as a function of temperature (XRDT) coupled with high-sensitivity differential scanning calorimetry (DSC), using synchrotron radiation and Microcalix. The polymorphic behavior of AGMF was monitored by varying the cooling rates between 5 and 1 degrees C/min from 45 to -20 degrees C with their subsequent melting at 1 degrees C/min. Quenching of AGMF at -20 degrees C was also examined to determine the metastable polymorphic form of AGMF. At intermediate cooling rates, TGs in AGMF crystallize, from about 18 degrees C in two different lamellar structures with triple chain length 3Lalpha stacking of 72 A and a double chain length 2Lalpha stacking of 48 A, which are correlated to two overlapped exothermic peaks recorded by DSC. A reversible transition sub alpha <--> alpha was observed. Subsequent heating at 1 degrees C/min shows numerous structural rearrangements before final melting. At fast cooling of AGMF (5 degrees C/min), similar unstable crystalline varieties are formed while three endotherms are recorded. Several new unstable lamellar structures are observed after quenching. All of these data are compared to those previously reported at slow cooling (0.1 degrees C/min) showing a relative stability of the structures formed. In spite of general similitude, the thermal and structural behavior of the goat's milk is more complex than that of the cow's milk.     

Vegetative compatibility of cotton-defoliating <Emphasis Type="Italic">Verticillium dahliae</Emphasis> in Israel and its pathogenicity to various crop plants

Verticillium dahliae isolates recovered from a new focus of severe Verticillium wilt of cotton in the northeast of Israel were tested for vegetative compatibility using nitrate non-utilizing (nit) mutants and identified as VCG1, which is a new record in Israel. Other cotton isolates of V. dahliae from the northern and southern parts of the country were assigned to VCG2B and VCG4B, respectively. VCG1 isolates induced severe leaf symptoms, stunting and defoliation of cotton cv. Acala SJ-2, and thus were characterized as the cotton-defoliating (D) pathotype, whereas isolates of VCG2B and VCG4B were confirmed as the earlier described defoliating-like (DL) and non-defoliating (ND) pathotypes, respectively. This is the first record of the D-pathotype in Israel. The host range of representative isolates of each VCG-associated pathotype was investigated using a number of cultivated plants. Overall, the D isolates were more virulent than DL isolates on all tested host plants, but the order of hosts (from highly susceptible to resistant) was the same: okra (Hibiscus esculentus local cultivar), cotton (Gossypium hirsutum cv. Acala SJ2), watermelon (Citrullus lanatus cv. Crimson Sweet), safflower (Carthamus tinctorius cv. PI 251264), sunflower (Helianthus annuum cv. 2053), eggplant (Solanum melongena cv. Black Beauty), and tomato (Lycopersicon esculentum cv. Rehovot 13). The pattern of virulence of ND isolates differed from that of D and DL isolates, so that the former were highly virulent on eggplant but mildly virulent on cotton. Tomato was resistant to all cotton V. dahliae isolates tested. RAPD and specific PCR assays confirmed that the D isolates from Israel were similar to those originating from other countries.     

Role of erythropoeitin in prevention of chemotherapy-induced peripheral neuropathy

Neurotoxicity complicates the use of several commonly administered chemotherapeutic agents (platinum based alkylating agents, taxanes and vinca alkaloids), with chemotherapy-induced peripheral neuropathy being the most common manifestation. Structural damage to the peripheral nervous system results in positive symptoms, e.g., allodynia, hyperalgesia and pain with unpleasant features as burning and shooting. Patients are unable to complete full or optimal treatment schedules. The pathophysiologic basis of nerve injury in chemotherapy-induced peripheral neuropathy is incompletely understood and appears to be unique for each class of the chemotherapeutic agents. Erythropoeitin (EPO), a well-established hematopoietic factor, is a very effective and widely used treatment for anemia in cancer patients undergoing chemotherapy. It also possesses generalized neuroprotective and neurotrophic properties. Co-treatment of chemotherapy and erythropoietin has been proposed for preventing or reversing the disabling peripheral neuropathy induced by the different chemotherapeutic agents. This study first describes the pathophysiological background of the clinically relevant chemotherapeutic agents-inducing peripheral neuropathy. Secondly, the possible mechanisms that might underlie the neuroprotective effect of erythropoietin in chemotherapy-induced neuropathy. Further clinical trials of EPO in cancer patients receiving chemotherapy and suffering from neurological symptoms seem to be warranted in the future. This might improve the quality of life in cancer patients.