For the first time, the predatory arthropods of aubergine fields in South Sumatra, Indonesia, were studied by pitfall trapping and by square flooding in two four-week periods; first, early after transplanting, and second, during harvest. Plant cover and insecticide use were very low in the first (I) and high in the second period (II). In 20 pitfall traps were caught (I) 3,794, and (II) 2,875 specimens of predatory arthropods. The high number in period I was mainly due to Pheidole sp. The frequency of two predator groups decreased significantly from period I to period II, and further six groups showed the same tendency of decrease. But the frequency of 12 other predator groups increased from period I to II. Concerning the ants Pheidole sp. and Tapinoma sp., square samples revealed that apparently the temperature on bare soil stimulated a high activity and also a high abundance. Both species were not negatively affected by the insecticide sprays. In all, the effects of the seven weekly insecticide sprays on the epigeal predators proved to be low, presumably mainly due to the plant cover. The average predator numbers per m2 were 18.1 (with 5.8 mg/m2) (period I), and 70 (with 13.7 mg/m2) (period II). Over both periods, spiders were represented in traps/squares with 23.2/25.9 % of all predators, ants with 59.3/46.1 % and gryllids with 10.5/15.3 %. All other predator groups shared less than 10 %. Ants (Formicidae) were represented with 17 genera, spiders (Araneae) with ten families. The results are discussed concerning the low effect of the insecticides on the epigeal predators, and the effects of plant cover of soil.
Greenhouse experiments were conducted at Khartoum (Sudan) with the aphid predator Hippodamia variegata , two botanical and one synthetic insecticides: neem seed water extract (25 g fresh seed powder per l of water), NeemAzal T/S® (1 % azadirachtin A) and fenvalerate (Sumicidin® 20 % EC). An equivalent of 400 l/ha was applied with a plastic hand sprayer, containing 0.2 l Sumicidin (40 g/ha fenvalerate), 1.6 l NeemAzal (16 g/ha azadirachtin A) or 10 kg of neem seed powder (ca. 30 g/ha azadirachtin A was applied as neem seed water extract). The beetles were fed on Aphis gossypii reared on cucumber leaves. Four different stages of the predator were sprayed topically with the test preparations. In addition, beetles were fed on A. gossypii either topically sprayed or collected from cucumber plants, which soil was treated four days earlier. The preparations varied in their effects on the different stages of the predator. Neem weed water extract was less harmful to the predator than NeemAzal T/S. In topical treatments with NeemAzal T/S the corrected mortality (%) was: eggs 37.7, larvae 40.0, pupae 38.2, and adults 16.7; with neem seed water extract: eggs 15.1, larvae 26.7, pupae 29.4, and adults 10.0; with fenvalerate: eggs 86.8, larvae 100, pupae 73.5, and adults 100. Feeding L2 larvae and adults on contaminated aphids resulted in the following corrected mortalities (%): Sumicidin 100, NeemAzal ca. 40 and neem seed water extract 20/17 (larvae/adults). Feeding on aphids treated via the soil with neem seed water extract resulted at maximum in 26.4/16.7 % corrected mortality (larvae/adults), while no effects on the longevity of adults could be observed. So, in contrast to Sumicidin, neem preparations (being effective against pests) proved to be harmless for the beneficial beetle. The results are discussed concerning their importance for plant protection.
In two experiments young cabbage plants in the 4/6-leaf stage were supplied for eight weeks with nutrient solutions without nitrogen (oN), phosphorus (oP), calcium (oCa) or potassium (oK) in order to investigate the impact of withholding essential major elements on the development of black spot disease (Alternaria brassicicola) in intact leaves (variant Int) and detached leaf segments (variant Seg). A complete solution (Co) that contained all mineral elements essential for the growth of the host plant served as control. Lesion size in millimetres was measured as parameter of the pathogen activity. In the first trial, solutions oN, oP, oCa, and Co were tested simultaneously in four replications. Lesion size was estimated 5 days after inoculation (dai). In the second trial, only the solutions oK and Co were supplied in one replication and lesions were determined at 5 and 22 dai.
The effects of infections of Barley yellow dwarf virus (BYDV), Fusarium culmorum and F. graminearum alone as well as double infections of BYDV and Fusarium spp. on assimilation of 14 CO 2 by flag leaves and translocation of photosynthates in winter wheat cultivars ‘Agent’ (susceptible to Fusarium head blight (FHB)) and ‘Petrus’ (moderately resistant to FHB) were studied in outdoor pot experiments in 2001 and 2002. Wheat plants were inoculated with BYDV-PAV strain by Rhopalosiphum padi at growth stage (GS) 51 in 2001 and at GS 39 in 2002. Control plants were inoculated with virus free aphids. In the middle part of spikes single florets of wheat plants of both cvs were inoculated at GS 65 with conidia suspensions of F. culmorum in 2001 and F. graminearum in 2002. Exposure of flag leaves with 14 CO 2 revealed that photosynthetic fixation was most pronounced at GS 71 and declined from GS 75 to GS 85. F. culmorum infections diminished absorption of 14 CO 2 by flag leaves in cv. ‘Agent’ and very low percentages of photosynthates were transported into the middle and upper head parts, while absorption of 14 CO 2 in cv. ‘Petrus’ was only slightly reduced and high proportions of 14 C assimilates were translocated also into the middle and upper spike sections. BYDV infections markedly reduced 14 CO 2 assimilation by flag leaves and export of photosynthates into wheat spikes of both cvs, especially in cv. ‘Petrus’. In double infected plants (BYDV and Fusarium spp.), photosynthetic fixation by flag leaves of both cvs at the first and second exposure times corresponded with that of BYDV-infected plants. However, export of assimilates in spikes was more effectively reduced in cv. ‘Agent’ than in cv. ‘Petrus’. Preinfestation with R. padi slightly reduced assimilation of 14 CO 2 in both cvs. In cv. ‘Agent’, translocation of 14 C assimilates into the upper spike section was more impaired than in cv. ‘Petrus’. Assimilation of 14 CO 2 and distribution pattern of 14 C assimilates in R. padi -preinfested plus Fusarium -infected plants of both cvs resembled that of fungus-infected plants at the first two exposure times. Absorption of 14 CO 2 by flag leaves and translocation of assimilates into spikes was markedly affected by severity of virus infection. The earlier BYDV inoculation in 2002 at GS 39 resulted in more severe virus infection and, therefore, drastically diminished 14 CO 2 absorption by flag leaves and translocation of photosynthates into spikes compared to 2001 when wheat plants were inoculated at GS 51. The differential translocation of photosynthates into Fusarium -infected spikes of the two cvs ‘Agent’ and ‘Petrus’ reflects the varying susceptibility of both cvs to FHB. The studies also revealed severe effects of BYD-disease on FHB development. This interaction may result in practical consequences.
S. Trdan1*, N. Vali·1, I. ¤eælina2, K. Bergant3, D. ¤nidar·i·4 1 University of Ljubljana, Biotechnical Faculty, Department of Agronomy, Chair of Entomology and Phytopathology, Jamnikarjeva 101, SI-1111 Ljubljana, Slovenia 2 Agricultural and Forestry Institute Nova Gorica, Pri hrastu 18, SI-5000 Nova Gorica, Slovenia 3 Nova Gorica Polytechnic, Laboratory of Astroparticiple Physics, Vipavska 13, SI-5000 Nova Gorica, Slovenia 4 University of Ljubljana, Biotechnical Faculty, Department of Agronomy, Chair of Vegetable Growing, Jamnikarjeva 101, SI-1111 Ljubljana, Slovenia * Corresponding author, stanislav.trdan@bf.uni-lj.si
Studies on the effect of temperature on the development of the yam moth, Dasyses rugosella Stainton were carried out in the laboratory at four different temperatures, 20°C, 24°C, 29°C and 33°C. The mean fecundity per female at 20°C, 24°C, 29°C and 33°C was 37.6±1.9, 84.2±2.7, 112.3±3.9 and 109.3±3.9 eggs, respectively. Oviposition period ranged from 4.7 days at 20°C to 2.9 days at 33°C. Hatchability of eggs was highest at 29°C with 70.0% and lowest at 20°C with 15.0%. The developmental time decreased with increase in temperature. The mean developmental time at 20°C, 24°C, 29°C and 33°C was 13.8±0.3, 7.8±0.2, 5.1±0.2 and 3.9±0.2 days for the egg, 90.0±0.7, 50.1±0.7, 36.1±0.8 and 23.6±0.8 days for the larval stages, 22.3±2.6, 12.2±0.2, 10.1±0.1, and 7.8±0.2 days for the pupa and 126.1±0.8, 70.1±0.8, 51.3±0.9, and 35.1±0.8 days for the period from egg hatching to adult emergence, respectively. Since fecundity, oviposition and development of the moth were impaired at 20°C, storage of yam tubers at low temperatures (well below 20°C but not lower than 12°C to avoid chilling injury) will significantly retard the development of D. rugosella and help in its control. Unmated individuals lived longer than their mated counterparts. Adult females were always larger than the males. The wing span of the female ranges from 16.9–18.5 and in males from 13.0–15.0mm. The body length for males ranged from 5.0–6.5 and was 6.5–9.0mm for females.
Different methods of artificial inoculation were tested for evaluation of cotton genotypes for resistance to bacterial blight caused by Xanthomonas axonopodis pv. malvacearum (Xam). Among them sandpaper inoculation method recorded the maximum disease incidence of 85 per cent followed by pressurized spraying (75 per cent) and hypodermic syringe (70 per cent) methods. Symptoms were expressed 1521 days after inoculation in the form of typical water-soaked spots and vein blight on leaves; black arm on stem and boll rot on bolls. Seven varieties and three hybrids of cotton were screened against the incidence of bacterial blight using eight pathogenic isolates of Xam collected from different cotton-growing regions of Tamil Nadu, India. Among them cultivar K-11 showed 100 per cent resistance reaction against all isolates of Xam under greenhouse conditions.
Weeds, epigeal predatory arthropods and their interactions were studied in two maize fields at Laloki/ Port Moresby, Papua New Guinea (PNG) with two methods: 1), 10 pitfall traps per field, which were emptied weekly, and 2), 10 squares of 0. 1 m(2) per field which were sampled for predatory arthropods at three dates. The biodiversity of epigeal predatory arthropods was determined in arable fields in PNG for the first time. The weed flora of the fields, three weeks after sowing, covered nearly 100 % of the soil surface and consisted mainly of seven weed species, Rottboellia exaltata (Poaceac) prevailing. 8,447 predatory arthropods were caught in 20 pitfall traps. Predatory beetles proved to be very rare in the traps (in contrast to Europe and other tropical fields, no carabids were found at all), while ants were significantly dominating with 89.9 %. Spiders were 6.8 %, while gryllids, earwigs and predatory bugs were rather rare. The weed cover, increasing during the study, influenced negatively the activity of the most common ant species (Oligomyrmex sp.). Per m(2), ants formed 65.2 % of all predators, and spiders 32.3 %. In total, 34 specimens of predatory arthropods occurred per m(2), with a dry bio-mass of 36 mg/ m(2). The results are discussed, concerning the necessity of weed control, and also the density and composition of predatory arthropods.
The susceptibility of the citrus rootstocks Sour Orange, Carrizo citrange, and Swingle citrumelo on Phytophthora cactorum, P. citrophthora, P. parasitica and P. citricola was evaluated. Apart from P. cactorum isolates, all others used were pathogenic on citrus rootstocks with similar virulence. In laboratory experiments, the susceptibility of citrus rootstocks did not differ. In field experiments, significant differences were found in the virulence of the isolates. The isolates 1263 (P. parasitica) and PI7 (P. parasitica) were the most virulent. No significant difference was observed among the isolates PI7 (P. parasitica), 1267 (P. citrophthora) and 1262 (P. citrophthora). The length of necrosis caused from the isolate PI4 (P. citricola) was least. The susceptibility of rootstocks differed from isolate to isolate. Generally, the rootstock Swingle citrumelo was the most resistant. No significant differences were found between the rootstocks Sour Orange and Carrizo citrange.
HPLC analysis of various parts of chickpea (Cicer arietinum) 24, 48, 72 and 96 h after infection with Sclerotium rolfsii indicates that the plants contain high amount of secondary metabolites. Analysis of 24 h-colonized rot collar region, plant leaves and roots of chickpea showed that gallic, o-coumaric and salicylic acids were maximum in these parts as compared to control (uninoculated) plant parts. In the collar region after 48 h, gallic acid was maximum followed by tannic, chlorogenic, salicylic and o-coumaric acids but vanillic and cinnamic acids were in traces. The un-inoculated collar region contained only five phenolic acids. After 72 h of colonization, the level of phenolic acids was drastically changed in collar, leaves and roots. Gallic acid was maximum followed by vanillic and other phenolic acids as compared to un-inoculated leaves. However, in collar the number and amount of phenolic acids was drastically reduced with increased amount of gallic and tannic acids. The chlorogenic and salicylic acids were in traces as compared to the control. Roots Of inoculated and un-inoculated plants had four phenolic acids. In 96 h-colonized chickpea plants, leaves had only four phenolic acids in which gallic acid was maximum followed by vanillic, coumaric and salicylic acids. In the un-inoculated plant leaves, six phenolic acids were present in which gallic acid was maximum followed by vanillic, tannic, chlorogenic, salicylic and coumaric acids. In colonized and un-inoculated collar regions, gallic and tannic acids were maximum but others in traces. The un-inoculated roots were rich in phenolic acids as compared to inoculated.
Cowpea aphid-borne mosaic virus (CABMV; genus Potyvirus, family Potyviridae) was isolated and characterized as a second component from previously described mixed-infected Crotalaria juncea (sunhemp) plants exhibiting mosaic, distortion and puckering symptoms in Nigeria. The virus induced both local and systemic symptoms in Chenopodium quinoa, Dolichos biflorus, Nicotiana occidentalis, Phaseolus aborigineus, P. lathyroides and several Cultivars of P. vulgaris. It induced systemic symptoms in Cajanus cajan, Canavalia ensiformis, Cassia occidentalis, some Crotalaria spp., N. benthamiana, P. lunatus and some cultivars of Vigna unguiculata ssp. unguiculata. Aphis craccivora failed to transmit the virus. ELISA with blackeye cowpea mosaic virus and cowpea aphid-borne mosaic virus antibodies indicated that the virus was a strain of CABMV that is here designated CABMV-Cr.
Greenhouse heaters using natural gas produce large quantities of combustion waste gas containing about 10 % CO2. The upper most part of waste gas is formed at cooler night temperatures. Our investigations test for the first time the possibility of using CO, as inexpensive and residual-free insecticide for greenhouse plants, applied overnight. In an experimental gadget tomato plants were fumigated for one week (12 h/d) with different CO2 concentrations overnight and the effect on the mortality and reproduction rate of aphids was determined. Further, morphological and physiological parameters of the tomato plants were analyzed, in order to judge possible negative effects of the CO, fumigation on the plant. With a CO, concentration of more than 8.5 % in the atmosphere the aphid populations were reduced by about 50 %, without any visible or physiological harm to the plants. The differences between controls and treated plants concerning total protein, total phenol and peroxidase activity indicated that the plants had negligible physiological stress up to 10 % CO2.
Four native African and three European trichogrammatid egg parasitoid species/strains were compared on the basis of biological attributes namely; capacity of parasitism, progeny production and adult longevity. Investigations were undertaken using the factitious host Sitotroga cerealella Olivier which was also used to rear the species. One European species, Trichogramma dendrolimi parasitized the greatest number of eggs while another, T cacoeciae, the only thelytokous species tested had the highest longevity. There were no significant differences in parasitism, progeny production and longevity between most of the parasitoid species/strains tested. Trichogramma sp. nr. mwanzai (L), T sp. nr. mwanzai (M) and Trichogrammatoidea sp. m. lutea (H) among the native African species/strains were identified as promising candidates with high potential for utilization for practical biological control in Kenya.
beta-aminobutyric acid (BABA) is a simple, nonprotein amino acid that exhibits postinfectional activity against nematodes, fungi, bacteria and tobacco mosaic virus (TMV), but its activity against phytoplasmas has never been examined before. The aim of this research was to examine possible postinfectional activity of BABA against phytoplasma reference strains AY-A and KVI in Catharanthus roseus shoots grown in vitro. Shoots were grown on Murashige and Skoog (MS) medium supplemented with different concentrations of BABA (10 mu M, 100 mu M, 1 mM, 10 mM, 100 mM), through five subcultures. The length of the shoots infected with phytoplasma strain AY-A was measured at the beginning and at the end of the first three subcultures. Only in the first subculture BABA supported shoot elongation. The presence of phyroplasmas was confirmed by nested PCR in both AY-A and KVI-infected shoots after the first and the Fifth subculture, showing that in these experimental conditions BABA had no curative effect against phytoplasmas.
Six experimental trials were carried out in order to develop an effective seed treatment against Fusarium wilt of lettuce, caused by Fusarium oxysporum f. sp. lactucae. Thirty percent of seeds belonging to two varieties of lettuce were inoculated with the pathogen and treated with a number of chemical and biological products. In the presence of a high disease incidence, the best results in terms of disease control were shown, among fungicides, by carbendazim and prochloraz, followed by mancozeb and dichlofluanid. Among the biocontrol agents tested, Fusarium oxysporum MSA 35 provided a good and consistent disease control, comparable to that provided by fungicides. No phytotoxicity was observed Linder the experimental conditions adopted with all the tested compounds.
Studies on the establishment and dispersal of Serangium parcesetosum Sicard, a predatory beetle of the citrus whitefly, Dialeurodes citri (Ashm.) were carried out in the East Mediterranean region of Turkey. Serangium parcesetosum was surveyed in released orchards by walking around the periphery of each tree for 10 min. A strike technique was also employed for this purpose. The releases of S. parcesetosum in citrus orchards resulted in the establishment of this predator on citrus and its dispersal throughout the region. The minimum and maximum temperatures were -5.3 and 40.9 degrees C during the study (19901997). This showed S. parcesetosum could tolerate large temperature intervals in the region. The success in colonisation of the predatory beetle within a certain period shows its high potential of searching capacity in addition to prey suitability. The predator is now an important factor in the suppression of the citrus whitefly on citrus.
The ladybird, Serangium parcesetosum Sicard (Coleoptera: Coccinellidae) is a specialist predator of whiteflies. To use it for the biological control of Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae), it was important to investigate its biology and prey consumption with this whitefly species. Therefore, the present work aimed to study the development, mortality, longevity and fecundity of S. parcesetosum as well as its prey consumption during the entire larval instars' development and through three different periods of adults' longevity with T vaporariorum as prey at a temperature of 30 degrees C on cucumber in the laboratory. The results showed that T vaporariorum was found to be a suitable prey for S. parcesetosum to develop on. Mean total developmental duration from egg to adult emergence was a mean of 17.4 (Y Y) and 16.9 (X X) days. The mortality occurred during all developmental stages of S. parceserosum, where the total mortality during development from egg to adult emergence was 26.4 %. Mean longevity of females with 70.8 days was significantly longer than males with 59.9 days. The females began oviposition after five days of adult emergence with a mean total fecundity of 27.8 eggs/y. The mean daily and total prey consumption by the larval instars of the predator with nymphs or puparia of T vaporariorum increased gradually with the progress of development. Females and males of S. parcesetosum consumed a mean total of 1012,1 and 868,7 nymphs, or 184,0 and 175,8 puparia, respectively. The mean daily prey consumption by females and males of S. parcesetosum fluctuated irregularly over the three studied periods of longevity. The mean total prey consumption over the three periods valued 3842.2 (Y Y) and 3507.2 (X X) nymphs or 1482.2 (Y Y) and 1367.7 (X X) puparia. Both sexes significantly consumed more nymphs rather than puparia. Also, the females consumed significantly more nymphs or puparia than the males.
The influence of time of sowing of beans, Phaseolus vulgaris, on level of infestation and parasitism of the bean stem maggot (BSM), Ophiomyia spp. (Diptera: Agromyzidae), was studied during the cropping season of beans at Madira Farm, Arusha Region, northern Tanzania. Three sowing dates were investigated: early, conventional and late in a split-plot design. The abundance of BSM pupae in bean stems and plots planted with beans was used to establish infestation levels at different sowing dates. Ophiomyia spencerella was the dominant bean fly maggot infesting the crop. Sowing dates had significant (P < 0.001) influence on BSM population. Early sown beans had low infestation relative to the conventional and late sown crop. The levels of infestation by BSM were significantly affected by parasitism. Braconids were the dominant parasitoids and the relationship to the host population was density dependent. Parasitism and other unidentified factors reduced emergence of BSM by 81.9 %, with parasitism accounting for 38.9 % of total pupal mortality. BSM parasitism was density dependent and a functional response showed increased parasitism with increasing host population. This relationship indicates that braconid parasitoids are a very important factor in controlling BSM infestations in beans in northern Tanzania. To increase natural control of the BSM in bean cropping systems, it is necessary to use other non-disruptive methods, including appropriate cultural techniques, resistant/tolerant varieties and manipulation of sowing calendar.
Clavibacter michiganensis subsp. sepedonicus [further Cms], causing ring rot of potato, is a quarantine bacterium. Diagnosis of Cms is carried out by means of IFAS and bioassay on eggplant (EU directive No. 93/85/EEC), but PCR, ELISA and individual nutrient tests are also recommended. The latter could be substituted using BIOLOG (Biolog Inc., USA) or fatty acid analysis (FAA). According to colony morphology, Cms occurs mostly as fluidal (smooth, mucoid), but sometime as intermediate (less fluidal) and nonfluidal (rough, nonmucoid) variants, too. In this study, commercial monoclonal antibodies (Agdia, USA), Pastrik primers PSA-1/PSA-R and dot blot hybridization with digoxigenin-labelled probe were used for determination of Cms strains representing all forms. All Cms strains were reliably identified by IFAS, although apart from typical also atypical cells were sometime recorded in populations of several rough strains. The fluidal Cms strains were more reliably identified using DAS-ELISA and the Biolog GP MicroPlate System (TM) than rough and intermediate strains. The rough Cms strains showed decreased metabolic activity as compared to fluidal strains and that is why they were identified by the BIOLOG system only to the species level or were not identified at all. Differences among fluidal, intermediate and rough Cms strains were also recorded in a bioassay on eggplants. The rough and some intermediate Cms strains caused atypical or no symptoms as compared to fluidal strains. To the contrary, all Cms strains were identified by FAA and IF test regardless of different morphology. All Cms strains used in PCR, BOX-PCR and dot blot hybridization gave a positive reaction. Differences in signals between fluidal and rough strains were not found. The most reliable techniques appeared to be PCR, IFAS, FAA and bioassay with some difficulty for some rough Crus strains.
Growth of Phytophthora cambivora, P. cinnamomi, P. citricola and P. quercina was evaluated on basal media supplemented with polyethylene glycol 3350 and 6000. Optimum growth were at approx. -0.35 MPa, and declined with decreasing osmotic potential between -1.18 and -1.75 MPa. Mycelium growth was severely reduced at -3.00 MPa, and it was completely inhibited at -3.98 MPa. P. cinnamomi and P. cambivora showed the best performance under osmotic stress. No differences in growth rate were evaluated between the two polyethylene glycol preparations differing in molecular weight. The composition of basal medium had an additive and positive effect on growth of Phytophthora between -1.75 and -3.98 MPa, although variable responses were reported among the four species. This study suggests that minimum amounts of water are essential for mycelial growth of Phytophthora spp. The ability of these oomycetes to overcome osmotic and water stress for a long time period is supposed.
