Effect of apple cultivar and of temperature on the biology and life table parameters of the twospotted spider mite<Emphasis Type="Italic">Tetranychus urticae</Emphasis>

Development duration and reproduction rate of the twospotted spider miteTetranychus urticae Koch (Acarina: Tetranychidae) were studied on five different apple cultivars (‘Amasya’ (local cultivar), ‘Golden Delicious’, ‘Granny Smith’, ‘Starking Delicious’ and ‘Starkrimson Delicious’) at 25°C, 65±10% r.h. and 16:8 L:D. In addition, the same parameters were determined on Golden Delicious leaves at three constant temperatures (20°, 30° and 35°C, 65±10% r.h. and 16:8 L:D) in the laboratory.T. urticae performed better on Granny Smith than on the other cultivars, due mainly to high daily egg production (4.6 eggs/♀/day) and the intrinsic rate of natural increase (r _m , which was 0.243 ♀/♀/day). The lowestr _m was observed on Amasya variety (0.231 ♀/♀/day). Development periods of immature stages ofT. urticae varied from 6.5 to 15.5 days at 35° and 20°C, respectively, for females, and from 5.9 to 14.5 days at 35° and 20°C, respectively, for males. The development thresholds of the eggs and pre-adult stages, respectively, were 10.78° and 8.43°C, and total effective temperatures were 57.80 and 172.41 degree-days. Mean generation time (T _o ) of the population ranged from 9.94 days at 35°C to 25.99 days at 20°C. The net reproduction rate increased from 66.99 ♀/♀ at 20°C to 92.19 ♀/♀ at 25°C, and decreased to 84.34 ♀/♀ at 30°C and to 12.04 ♀/♀ at 35°C. The highest r _m occurred at 30°C (0.302 ♀/♀/day) and the lowest at 20°C (0.161 ♀/♀/day). http://www.phytoparasitica.org posting Dec. 19, 2003.     

<Emphasis Type="Italic">In vitro</Emphasis> Selection of Maize Rhizobacteria to Study Potential Biological Control of <Emphasis Type="Italic">Aspergillus</Emphasis> Section <Emphasis Type="Italic">Flavi</Emphasis> and Aflatoxin Production

The aims of this study were to select bacterial isolates from the non-rhizophere of maize soil and to examine their antagonistic activity against Aspergillus section Flavi strains. The first selection was made through ecophysiological responses of bacterial isolates to water activity (a_w) and temperature stress. Subsequently, an Index of Dominance test (I_D), ecological similarity and inhibition of the lag phase prior to growth, growth rate and aflatoxin B₁ accumulation were used as criteria. From the first assay nine bacterial strains were selected. They grew well at 25 and 30 °C, with growth optima between 0.982 and 0.955 a_W using 48 h of incubation. There was ecological similarity between the bacterial strains Bacillus subtilis (RCB 3, RCB 6), Pseudomonas solanacearum RCB 5, Amphibacillus xylanus RCB 27 and aflatoxigenic Aspergillus section Flavi strains at 0.982 at 25 °C. The predominant interaction between all selected bacteria and fungi in dual culture was mutual intermingling at 0.982. Mutual inhibition on contact and mutual inhibition at a distance was observed at 0.955 a_w, between only four bacteria and some Aspergillus strains. Bacillus subtilis RCB 55 showed antifungal activity against Aspergillus section Flavi strains. Amphibacillus xylanus RCB 27, B.␣subtilis RCB 90 and Sporolactobacillus inulinus RCB 196 increased the lag phase prior to growth and decreased the growth rate of Aspergillus section Flavi strains. Bacillus subtilis strains (RCB 6, RCB 55, RCB 90) and P. solanacearum RCB 110 inhibited aflatoxin accumulation. Bacillus subtilis RCB 90 completely inhibited aflatoxin B₁ accumulation at 0.982 a_W. These results show that the bacterial strains selected have potential for controlling Aspergillus section Flavi over a wide range of relevant environmental conditions in the stored maize ecosystem.     

Note: Survey of seedborne fungi of sudanese cultivars of onion,with new records

Through incubation of onion (Allium cepa L.) seed samples on potato dextrose agar and moist filter papers at 28±2°C, 32 species and four varieties belonging to 19 genera of fungi were determined as seedborne in this crop. Among them, 23 species are new reports to the mycoflora of onion seeds.Aspergillus (11 species and three varieties, ∼42.1% of the total colony count of fungi) was the most prevalent genus:A. niger (∼19.7%) was found at the highest rate in the seeds, followed byA. parasiticus (∼17.3%,A. oryzae (∼17.3%) andA. flavus (∼14.5%). The genusAspergillus was followed byPenicillium (∼12.4%),Sclerotium (∼7.1%),Fennellia, Rhizopus, Chaetomium, Drechslera andAlternaria (∼12.4%),Fusarium, Emericella andByssochlamys (∼7.1%), whereas the remaining eight genera displayed a low level of infection (∼10%). Twenty-seven species, three varieties and 12 genera represent Hyphomycetes; four genera, three species and one variety — Ascomycotina; one genus and one species — Zygomycotina; two genera and two species — other Deuteromycotina; and one genus — Oomycetes. Some species, which are known to cause devastating pre- and postharvest diseases to onion crops, were recovered from the seeds of this crop, suggesting the high possibility of their transmission by seed. http://www.phytoparasitica.org posting July 14, 2004.     

Influence of temperature on toxicity of propylene oxide at low pressure against<Emphasis Type="Italic">Tribolium castaneum</Emphasis>

Toxicity of propylene oxide (PPO) at low pressure against the most common stored-product insect,Tribolium castaneum (Herbst), over a short exposure time, was tested at three different temperatures (16°, 22° and 30°C). Toxicities of PPO at 100 mm Hg were strongly influenced by ambient temperature. LD₅₀ and LD₉₉ toxicities ranged from 4.7 to 28.9 mgl ⁻¹ and from 10.5 to 72.6 mgl ⁻¹ respectively, showing that susceptibility was positively correlated to the temperature. The LD₉₉ values for all life stages (except the larval stage) were significantly lower at 30° than those at 16° and 22°C. However, the LD₉₉ values for all life stages (except the pupal stage) at 16° were not significantly different from those at 22°C. A concentration × time (Ct) product of 291, 171 and 98 mg h/l was required to obtain complete mortality (99%) ofT. castaneum at 16°, 22° and 30°C, respectively. Thus, the efficacy of PPO at 100 mm Hg to all life stages ofT. castaneum also decreased as the temperature decreased from 30° to 16°C. http://www.phytoparasitica.org posting Sept. 28, 2004.     

Biological control of gray mold on apple fruits byBacillus licheniformis (EN74-1)

Bacillus licheniformis (EN74-1) was evaluated for the control of gray mold of apple caused byBotrytis mali. Dual culture, cell-free metabolite and volatile tests showed thatB. licheniformis (EN74-1) inhibited growth of the pathogen. Inhibition varied from 46.2% to 65.4% in the dual culture tests; 58.6% to 58.8% in the cell-free metabolite tests; and 28.4% to 33.8% in the volatile tests.B. licheniformis (EN74-1) appeared to be a good antagonist of gray mold on apples at 20° and 4°C. It reducedB. mali lesion diameter to 9–11 mm compared with to 32–41 mm in the control at 4°C. At 20°C the lesion diameter was reduced to 3.6–8.4 mm for the antagonistic treatment and to 25.8–38.2 mm for the control treatment after 14 days. http://www.phytoparasitica.org posting Dec. 11, 2007.     

Application of <Emphasis Type="Italic">Pantoea agglomerans</Emphasis> CPA-2 in combination with heated sodium bicarbonate solutions to control the major postharvest diseases affecting citrus fruit at several mediterranean locations

We determined the potential of using a formulated product based on Pantoea agglomerans CPA-2, either alone or in combination with heated sodium bicarbonate (SBC) solutions, to control the major postharvest diseases affecting citrus crops in the Mediterranean region. Treatments applied either individually or in combination were tested in semi-commercial and commercial trials carried out with oranges and mandarins from the Algarve, Andalusia and Catalonia. Firstly, several formulations of the biocontrol agents were tested in laboratory trials; one of them, a freeze-dried formulation of P. agglomerans strain CPA-2 called FD10-3, was chosen for combined with SBC. This formulation, applied at 2 × 10⁸cfu ml⁻¹ and the SBC treatment, applied at 3% 50°C for 20–40 s, demonstrated that it was possible to reduce decay development in laboratory trials. Semi-commercial applications of FD10-3 and 3% SBC solution at 50°C for 40 s showed excellent control of decay in unwounded mandarins and oranges artificially inoculated with both Penicillium digitatum and P. italicum. No rind injuries or residues attributable to hot water or SBC were observed on treated fruits. Combined treatment provided better control than the two treatments applied separately. Commercial trials demonstrated an important reduction in natural decay with the treatment of SBC 3% at 50°C for 40 s. Furthermore, bacterial-product formulation treatment significantly reduced the percentage of infected fruit and in some cases this reduction was equal to chemical treatments. Even so, no improvement in efficacy was observed with the combination of FD10-3 and SBC in the commercial test. We also assessed the ability of FD10-3 to grow at the wound site in oranges, whether alone or in the presence of SBC, and also its compatibility with standard citrus packinghouse practices.     

<Emphasis Type="Italic">Pythium</Emphasis> and <Emphasis Type="Italic">Phytophthora</Emphasis> species associated with root and stem rots of kalanchoe

Pythium and Phytophthora species were isolated from kalanchoe plants with root and stem rots. Phytophthora isolates were identified as Phytophthora nicotianae on the basis of morphological characteristics and restriction fragment length polymorphism (RFLP) analysis of the rDNA-internal transcribed spacer regions. Similarly, the Pythium isolates were identified as Pythium myriotylum and Pythium helicoides. In pathogenicity tests, isolates of the three species caused root and stem rots. Disease severity caused by the Pythium spp. and Ph. nicotianae was the greatest at 35°–40°C and 30°–40°C, respectively. Ph. nicotianae induced stem rot at two different relative humidities (60% and >95%) at 30°C. P. myriotylum and P. helicoides caused root and stem rots at high humidity (>95%), but only root rot at low humidity (60%).     

Development ofClonostachys rosea and interactions withBotrytis cinerea in rose leaves and residues

The effect of microclimate variables on development ofClonostachys rosea and biocontrol ofBotrytis cinerea was investigated on rose leaves and crop residues. C.rosea established and sporulated abundantly on inoculated leaflets incubated for 7–35 days at 10°, 20° and 30°C and then placed on paraquat—chloramphenical agar (PCA) for 15 days at 20°C. On leaflets kept at 10°C, the sporulation after incubation on PCA increased from 60% to 93% on samples taken 7 to 21 days after inoculation, but decreased to 45% on material sampled after 35 days. A similar pattern was observed on leaves incubated at either 20° or 30°C. The sporulation ofC. rosea on leaf disks on PCA was not affected when the onset of high humidity occurred 0, 4, 8, 12 or 16 h after inoculation. However, sporulation was reduced to 54–58% on leaflets kept for 20–24 h under dry conditions after inoculation and before being placed on PCA. The fungus sporulated on 68–74% of the surface of leaf disks kept for up to 24 h at high humidity after inoculation, but decreased to 40–51% if the high humidity period before transferral to PCA was prolonged to 36–48 h. The growth ofC. rosea on leaflets was reduced at low inoculum concentrations (10³ and 10⁴ conidia/ml) because of competition with indigenous microorganisms, but at higher concentrations (10⁵ and 10⁶ conidia/ml) the indigenous fungi were inhibited. Regardless of the time of application ofC. rosea in relation toB. cinerea, the pathogen’s sporulation was reduced by more than 99%. The antagonist was able to parasitize hyphae and conidiophores ofB. cinerea in the leaf residues. AsC. rosea exhibited flexibility in association with rose leaves under a wide range of microclimatic conditions, and in reducingB. cinerea sporulation on rose leaves and residues, it can be expected to suppress the pathogen effectively in rose production systems.     

Effect of temperature,relative humidity,leaf wetness and leaf age on <Emphasis Type="Italic">Spilocaea oleagina</Emphasis> conidium germination on olive leaves

The effects of temperature, relative humidity (RH), leaf wetness and leaf age on conidium germination were investigated for Spilocaea oleagina, the causal organism of olive leaf spot. Detached leaves of five ages (2, 4, 6, 8 and 10 weeks after emergence), six different temperatures (5, 10, 15, 20, 25 and 30°C), eight wetness periods (0, 6, 9, 12, 18, 24, 36 and 48 h), and three RH levels (60, 80 and 100%) were tested. Results showed that percentage germination decreased linearly in proportion to leaf age (P < 0.001), being 58% at 2 weeks and 35% at 10 weeks. A polynomial equation with linear term of leaf age was developed to describe the effect of leaf age on conidium germination. Temperature significantly (P < 0.001) affected frequencies of conidium germination on wet leaves held at 100% RH, with the effective range being 5 to 25°C. The percent germination was 16.1, 23.9, 38.8, 47.8 and 35.5% germination at 5, 10, 15, 20 and 25°C, respectively, after 24 h. Polynomial models adequately described the frequencies of conidium germination at these conditions over the wetness periods. The rate of germ tube elongation followed a similar trend, except that the optimum was 15°C, with final mean lengths of 175, 228, 248, 215 and 135 μm at 5, 10, 15, 20 and 25°C, respectively after 168 h. Polynomial models satisfactorily described the relationships between temperature and germ tube elongation. Formation of appressoria, when found, occurred 6 h after the first signs of germination. The percentage of germlings with appressoria increased with increasing temperature to a maximum of 43% at 15°C, with no appressoria formed at 25°C after 48 h of incubation. Increasing wetness duration caused increasing numbers of conidia to germinate at all temperatures tested (5–25°C). The minimum leaf wetness periods required for germination at 5, 10, 15, 20 and 25°C were 24, 12, 9, 9 and 12 h, respectively. At 20°C, a shorter wetness period (6 h) was sufficient if germinating conidia were then placed in 100% RH, but not at 80 or 60%. However, no conidia germinated without free water even after 48 h of incubation at 20°C and 100% RH. The models developed in this study should be validated under field conditions. They could be developed into a forecasting component of an integrated system for the control of olive leaf spot.     

Effects of different cucurbit species and temperature on selected life history traits of the ‘B’ biotype ofBemisia tabaci

The development time and survival rate were determined at three constant temperatures for the ‘B’ biotype ofBemisia tabaci on cucumber (Beit Alpha F₁), cantaloupe (Anzer F₁), squash (Sakız F₁), and watermelon (Galactica F₁). The development time for immature stages at 20, 25 and 30±1°C was, respectively, 33.5, 19.3 and 16.8 days on cucumber; 36.5, 20.8 and 19.60 days on cantaloupe; 37.2, 20.1 and 19.8 days on squash; and 38.9, 23.8 and 21.9 days on watermelon. At 20, 25 and 30°C, the respective percentage survival of immature instars was 73.2, 83.2 and 72.9% on cucumber; 72.9, 84.9 and 75.6% on cantaloupe; 52.1, 76.1 and 57.5% on squash; and 37.6, 64.8 and 40.1% on watermelon. http://www.phytoparasitica.org posting May 14, 2006.     

Biological control ofBotrytis cinerea in residues and flowers of Rose (Rosa hybrida)

Microbial isolates from living petals, petal residues and leaf residues of rose, and from laboratory collections, were evaluated for control ofBotrytis cinerea in rose. In leaf residues artificially infested withB. cinerea, isolates of the filamentous fungiGliocladium roseum, FR136 (unidentified) andTrichoderma inhamatum reduced sporulation of the pathogen by >90%, other filamentous fungi were 25–90% effective, and those of yeasts and bacteria were <50% effective. In artificially inoculated petal residues, no microbe reduced sporulation ofB. cinerea by >75%, but isolates ofCladosporium oxysporum and four yeasts were 51–75% effective, and three filamentous fungi, eight yeasts andBacillus subtilis isolates were 26–50% effective. Isolates ofT. inhamatum, C. oxysporum andG. roseum performed best againstB. cinerea among isolates evaluated in leaf residues naturally infested with the pathogen and indigenous microorganisms. Totals of ten isolates of filamentous fungi (includingC. oxysporum andC. cladosporioides), two of yeasts and five ofBacillus subtilis completely prevented lesion production byB. cinerea in detached petals, and a further six isolates of filamentous fungi (includingG. roseum) and six yeasts were 90–99% effective. Isolates ofC. oxysporum, C. cladosporioides andB. subtilis, the most effective microorganisms againstB. cinerea in flower buds, reduced number of lesions in the range of 42–65% compared with 59–89% for à standard fungicide (vinclozolin). It is suggested that application of leading antagonists Jo living rose leaves and flowers should optimize control of inoculum production byB. cinerea when the tissues die. Optimal biocontrol of lesion production in flower buds requires a better understanding of the microenvironment of petals.     

Isolation of pathogenicity- and gregatin-deficient mutants of <Emphasis Type="Italic">Phialophora gregata</Emphasis> f. sp. <Emphasis Type="Italic">adzukicola</Emphasis> through <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated transformation

Phialophora gregata f. sp. adzukicola, a causal agent of brown stem rot in adzuki beans, produces phytotoxic compounds: gregatins A, B, C, D, and E. Gregatins A, C, and D cause wilting and vascular browning in adzuki beans, which resemble the disease symptoms. Thus, gregatins are considered to be involved in pathogenicity. However, molecular analyses have not been conducted, and little is known about other pathogenic factors. We sought to isolate nonpathogenic and gregatin-deficient mutants through Agrobacterium tumefaciens-mediated transformation (ATMT) for cloning of pathogenicity-related genes. The co-cultivation of P. gregata and A. tumefaciens for 48 h at 20°C with 200 μM acetosyringone resulted in approximately 80 transformants per 10⁶ conidia. The presence of acetosyringone in the A. tumefaciens pre-cultivation period led to an increase in T-DNA copy number per genome. Of 420 and 110 transformants tested for their pathogenicity and productivity of gregatins, one nonpathogenic and three gregatin-deficient mutants were obtained, respectively. The nonpathogenic mutant produced gregatins, whereas the gregatin-deficient mutants had pathogenicity comparable to the wild-type strain. This is the first report of ATMT of P. gregata. Further analysis of these mutants will help reveal the nature of the pathogenicity of this fungus including the role of gregatin in pathogenesis.     

Inhibition of sterol biosynthesis in cell-free extracts of Botrytis cinerea by prochloraz and prochloraz analogues

The sensitivity of cytochrome-P450-dependent sterol 14α-demethylase (P450_14DM) to prochloraz and several prochloraz analogues was studied in a cell-free assay of Botrytis cinerea Pers. ex Fr. The EC₅₀ values (concentrations which inhibited radial growth of B. cinerea by 50%) of the compounds tested ranged from 3.3 × 10 ?8 to 1.7 × 10 ?5 M. The IV₅₀ values (concentrations which inhibited cell-free C₄-demethyl sterol synthesis by 50%) in cell-free assays of B. cinerea ranged from 2.6 × 10 ?9 to 4.4 × 10 ?7 M. Ranking compounds in terms of their relative inhibitory potencies showed quite similar trends to the order of fungitoxicity, but the IC₅₀ values did not quantitatively reflect the differences in toxicity. Therefore, the differential inhibition of cell-free P450_14DM activity by these compounds cannot fully account for their differences in activity towards B. cinerea. Additional mechanisms must be involved. The compounds tested were generally more potent in the B. cinerea assay than in similar assays developed for Penicillium italicum Wehmer and, in particular, Saccharomyces cerevisiae Meyen. This correlated with the relatively higher activity of most test compounds to B. cinerea. Results suggest that the cell-free assay of B. cinerea is more useful to evaluate candidate fungicides as inhibitors of sterol 14α-demethyiase activity than similar assays from model organisms. The present study confirms that the affinity of prochloraz analogues for P450_14DM depends on the nature of the N-1 substituent of the imidazole and the azole ring. It was also found that addition of an amino group at C-2 of the imidazole moiety of prochloraz gave a compound (6) which inhibited 4, 4-demethyl sterol biosynthesis in B. cinerea at a different site from the P450_14DM. This was confirmed by the observation that laboratory-generated triadimenol-resistant isolates of B. cinerea showed reduced sensitivity to triadimenol and prochloraz, but not to compound 6.     

Temperature-dependent development rates of <Emphasis Type="Italic">Bracon vulgaris,</Emphasis> a parasitoid of boll weevil

The duration of development of Bracon vulgaris Ashmead, parasitoid of the boll weevil Anthonomus grandis Boheman, was determined at nine constant temperatures between 18°C and 38°C. Nonlinear regression analysis was used to test the fit of temperature-dependent development rates to the Sharpe and DeMichele and Lactin et al. models. At the highest tested temperature (38°C) all the parasitoid eggs died before hatching and no evidence of development was observed. The high values of R ² for the models of Sharpe and DeMichele (0.8432 to 0.9834), and Lactin et al. (0.9071 to 0.9795) indicated that these models are suitable to estimate the development rate of B. vulgaris as a function of temperature. B. vulgaris showed tolerance to high temperature which is represented by the high value of H _H (change in enthalpy associated with high-temperature inactivation of the enzyme) for the prepupa stage of this insect obtained with the Sharpe and DeMichele model. According to that model, B. vulgaris exhibits thermal stress at 35.7°C, which indicates that maximum thermal stress estimated by this model was close to the real one.     

Combination of hot water, <Emphasis Type="Italic">Bacillus subtilis</Emphasis> CPA-8 and sodium bicarbonate treatments to control postharvest brown rot on peaches and nectarines

The aim of this study was to evaluate the effect of hot water (HW), antagonists and sodium bicarbonate (SBC) treatments applied separately or in combination to control Monilinia spp. during the postharvest storage of stone fruit. Firstly, we investigated the effect of HW temperatures (55–70°C) and exposure times (20–60 s), seven antagonists at two concentrations (10⁷ or 10⁸ cfu ml⁻¹) and four SBC concentrations (1–4%). The selected treatments for brown rot control without affecting fruit quality were HW at 60°C for 40 s, SBC at 2% for 40 s and the antagonist CPA-8 (Bacillus subtilis species complex) at 10⁷ cfu ml⁻¹. The combinations of these treatments were evaluated in three varieties of peaches and nectarines artificially inoculated with M. laxa. When fruit were incubated for 5 d at 20°C, a significant additional effect to control M. laxa was detected with the combination of HW followed by antagonist CPA-8. Only 8% of the fruit treated with this combination were infected, compared to 84%, 52% or 24% among the control, CPA-8, and HW treatments, respectively. However, the other combinations tested did not show a significant improvement in effectiveness to control brown rot in comparison with applying the treatments separately. When fruit were incubated for 21 d at 0°C plus 5 d at 20°C, the significant differences between separated or combined treatments were reduced and generally the incidence of brown rot was higher than when fruit were incubated for 5 d at 20°C. Similar results were observed testing fruit with natural inoculum.     

Thermal requirements and development of<Emphasis Type="Italic">Bracon vulgaris</Emphasis>, a parasitoid of the cotton boll weevil

The development ofBracon vulgaris Ashmead (Hymenoptera: Braconidae), parasitoid of the cotton boll weevilAnthonomus grandis Boheman (Coleoptera: Curculionidae), was studied at constant temperatures of 18, 20, 23, 25, 28, 30, 33, 35 and 38°C, 70±10% r.h. and 14:10 L:D period. The period from egg to adult ofB. vulgaris varied from 8.6 (35°C) to 32.9 days (18°C). The eggs of this parasitoid became desiccated and did not hatch at 38°C. The lower development threshold (LDT) and thermal constants for development varied withB. vulgaris instar, but they were similar for males and females. The duration of the 1st, 2nd, 3rd and 4thB. vulgaris instars required, respectively, 9.36 degree-days above one LDT=12.27°C, 13.48 degree-days above one LDT=6.83°C, 11.65 degree-days above one LDT=9.41°C, and 12.82 degree-days above one LDT=10.78°C.B. vulgaris has physiological adaptations to different threshold temperatures and it shows high potential to be used againstA. grandis in cotton crops.     

Movement of <Emphasis Type="Italic">Cucumber Mosaic Virus</Emphasis> Is Restricted at the Interface between Mesophyll and Phloem Pathway in <Emphasis Type="Italic">Cucumis figarei</Emphasis>

Viral movement in the leaf tissues of a resistant host, Cucumis figarei, inoculated with the pepo strain of Cucumber mosaic virus (CMV) and incubated at 24°C or 36°C was investigated by fluorescence in situ hybridization (FISH), leaf-press blotting, tissue printing and immunogold-silver staining techniques. Observation by FISH revealed that at 24°C most infection sites with CMV at 0.01 mg/ml or 0.1 mg/ml were limited to a single cell during the incubation period, that the number of infection sites increased from 24hpi (hours post inoculation) to 80 hpi in the leaves inoculated with CMV at 0.5 mg/ml, and that the size as well as the number of infection sites rapidly increased with time in the leaves inoculated with CMV at 2.0 mg/ml. These results suggested that one factor for the resistance of C. figarei at 24°C might be an inhibition of viral movement in and out of the infection sites. Leaf-press blotting and tissue blotting indicated that CMV remained in the infection sites at 24°C, whereas it spread from the inoculated leaves to other parts of the plants through vascular systems at 36°C. Immunogold-silver staining demonstrated that at 24°C CMV infected bundle sheath (BS) cells in minor veins, whereas at 36°C it invaded not only BS cells, but also phloem parenchyma (PP)/ companion cell (CC) or PP/intermediary cell (IC) complexes in minor veins in the regions with chlorotic symptoms. These results indicated that at 24°C CMV had difficulty in passing through the interface between BS and PP/CC or PP/ IC complexes and that viral entry from mesophyll to the phloem pathway was inhibited in the inoculated leaves. Received 26 August 1999/ Accepted in revised form 14 December 1999     

Effects of photoperiod on the development and growth of <Emphasis Type="Italic">Podisus nigrispinus</Emphasis>, a predator of cotton leafworm

The effects of photoperiod on nymphal development, growth and adult size in Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) were studied. Predators were collected in cotton fields in Patos (7°S, 37°W), Paraíba State, Brazil. A randomized block experimental design was used, with treatments consisting of photoperiods of 10L:14D, 11L:13D, 12L:12D, 13L:11D, 14L:10D, 15L:9D and 16L:8D (LD, in h), at a constant temperature of 28 ± 1°C and relative air humidity of 70 ± 10%. Treatments were distributed in four replications, with each experimental unit composed of 40 nymphs. The development period for each instar of P. nigrispinus varied according to the photoperiod exposure. Regardless of the photophase (PhP), the 5th instar nymphs exhibited the longest development period, except for the 15-h PhP, in which the development period of 2nd instar nymphs (4.13 days) was as long as that of the 5th instar nymphs (4.23 days). In the 1st, 3rd and 5th instars of P. nigrispinus, the development period was inversely proportional to the increase in light period in which the nymphs developed, for the PhP intervals of 10–14 h, 12–14 h, and 12–15 h, respectively. Predators exposed to a 14-h PhP developed a wider pronotum than those exposed to extreme PhP’s (of 10 h, 11 h and 16 h). Conditions from 14 h to 15 h of light resulted in higher daily growth rates in P. nigrispinus than those obtained with the other PhP’s tested. P. nigrispinus females exhibited faster daily growth rates than did males.     

The effect of a mixture of seed-borne Microdochium nivale var. majus and Microdochium nivale var. nivale infection on Fusarium seedling blight severity and subsequent stem colonisation and growth of winter wheat in pot experiments

Greenhouse experiments were conducted in order to determine the impact of seed-borne Microdochium nivale var. nivale and var. majus inoculum, and seed treatment with a carboxin+thiram mixture, on the development of seedling blight, and on subsequent stem colonisation and growth of winter wheat (cv. Cadenza). Experiments were conducted at temperatures favourable (3°C) and unfavourable (22°C) to M. nivale. Seed-borne inoculum resulted in seedling blight symptom development when plants were grown at 3°C, but not when plants were grown at 22°C. For seedlings grown at 3°C, plants arising from heavily blighted seedlings developed more severe symptoms of stem colonisation, when compared with those arising from seedlings from carboxin+thiram treated seeds. In addition, the vigour of such plants (assessed by determining the number of tillers and ears per plant, stem length, green leaf area, dry weight and yield) was also significantly lower than for plants arising from carboxin+thiram treated seeds. Microdochium nivale var. majus and var. nivale appeared to have little effect on plant vigour from seedlings grown at 22°C. This is the first recorded incidence of seedling blight affecting subsequent plant growth. Microdochium nivale var. majus and var. nivale stem colonisation increased from growth stage (GS) 40–49 to harvest in plants raised from seedlings grown at both temperatures. Microdochium nivale var. majus and var. nivale were isolated from the second node at GS 40–49 and the third node at harvest of plants from seedlings grown at 3°C. For plants from seedlings raised at 22°C, M. nivale var. majus and var. nivale were isolated from the first node at GS 40–49 and the second node at harvest. Carboxin+thiram seed treatment decreased the extent and severity of stem colonisation on plants from seedlings grown at 22°C.     

Environmental persistence of<Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> products tested under natural conditions against<Emphasis Type="Italic">Thaumetopoea wilkinsoni</Emphasis>

Information on persistence ofBacillus thuringiensis (Bt) is needed to improve the microbial pest management programs against the pine processionary mothThaumetopoea wilkinsoni in pine forests in Israel. The persistence of the microbe under natural conditions of rain and sunlight was evaluated and is documented here for the first time. Pine saplings were sprayed with three commercialBt products, Foray 48B, Delfin WG and Dipel DF, all used at 32,000 IU mg⁻¹ in a formulation with 1% (w/v) of condensed milk. In experiments conducted in November and December of 2004, the saplings were either exposed to rain and sunlight or were sheltered to avoid these environmental factors. The lowest rainfall recorded in the 8-day experiments was 16.5 mm (test 2) and the heaviest was 71.1 mm (test 1). Solar irradiation ranged from 9.4 to 10.9 MJ m⁻². The minimum temperature was close to 10°C and the maximum was less than 23°C. Needles of the treated saplings and their controls were sampled after 0, 1, 5 and 8 days, and were fed to 1 ^st or 2 ^nd instar larvae. Dipel DF persisted better than Delfin WG and still retained its initial activity of 80–100% mortality on day 8 at low rainfall (test 2). Dripping ofBt from upper to lower branches was quantified with the larval bioassays. The milk formulation proved to be an effective rain-fasting adjuvant. http://www.phytoparasitica.org posting May 4, 2007.