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Edmund Carl February Nicky Allsopp Tirello Shabane Dawood Hattas 《Plant and Soil》2011,349(1-2):253-260
Here we aim to demonstrate that in arid environments the competitive balance between species can be determined by niche separation with either nitrogen or water as the relevant niche axis. To do this we sampled roots <2 mm in diameter for 5 soil pits equidistant between two coexisting species, a shrub and a grass. Using stable carbon and nitrogen isotope ratios of fine roots we determine both photosynthetic pathway and rooting depth. We also examine the distribution of soil moisture and nitrogen relative to root biomass. Our results for root biomass and stable isotope ratios of fine roots demonstrate both niche separation and competition for resources. Root biomass is highest at the top of the profile where soil nitrogen is highest and soil moisture is lowest. We conclude that while there is competition for resources in the middle of the profile, competition is mitigated by photosynthetic pathway. The facultative CAM shrub grows whenever the soil at the surface is wet enough. The C4 photosynthetic pathway of the grass is more nitrogen and water use efficient making it better adapted to the low nitrogen in the middle of the profile and low summer rainfall. 相似文献
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Alberto Pozzebon Shakeel Ahmad Paola Tirello Mauro Lorenzon Carlo Duso 《BioControl》2014,59(5):585-596
The effect of the provision of pollen on the impact of pesticides on the predatory mite Kampimodromus aberrans was assessed at individual and population levels. In the laboratory we evaluated the influence of pollen amount and pollen application frequency on lethal and sub-lethal effects of chlorpyrifos and spinosad. In a potted plant experiment, the effects of pesticides and pollen were assessed on predatory mite population abundance. In the laboratory, survival and fecundity of predatory mites were reduced by insecticides, and spinosad was more toxic than chlorpyrifos. In the same experiment, high pollen application frequency alleviated the sub-lethal effect induced by chlorpyrifos. On potted plants, pollen applications reduced the impact of chlorpyrifos on K. aberrans, whereas without pollen applications the impact of spinosad and chlorpyrifos on the predatory mite population was similar. Results obtained here highlight that the provision of fresh pollen is of particular importance for predatory mites when pesticides are applied. 相似文献
3.
The predatory mite Kampimodromus aberrans (Oudemans) is a key biocontrol agent in vineyards in Italy and Southern Europe. Its susceptibility to common pesticides (e.g.,
organophosphates) has been considered an important factor in preventing successful biocontrol of phytophagous mites. Nevertheless,
populations of K. aberrans apparently resistant to organophosphates (OPs) have been reported to occur in Northern Italian vineyards. The resistance
of K. aberrans to fungicides (e.g., mancozeb) has been demonstrated in the laboratory in France, but little is known about the toxicity
of insecticides towards K. aberrans. Of these pesticides, the OP chlorpyriphos is extensively used in viticulture to control lepidopterans and homopterans. The
present study investigated the dose–response effect of chlorpyriphos in four K. aberrans strains characterized by different levels of exposure to OP insecticides in the past: from never to frequently exposed. Resistance
to chlorpyriphos is demonstrated for populations collected from vineyards and apple orchards. Resistance factors exceeded
145,000× for the three strains collected in vineyards and orchard. LC50 values for resistant strains were 1.85–6.83 times higher than the recommended field dose of chlorpyriphos for vineyards and
orchards (525 mg a.i./l). 相似文献
4.
Tirello P Pozzebon A Cassanelli S Van Leeuwen T Duso C 《Experimental & applied acarology》2012,57(1):53-64
Problems with Tetranychus urticae are frequently reported in protected crops in Italy, particularly in roses where many introduced acaricides show a progressive
loss of effectiveness. We have conducted bioassays to assess the response of some Italian strains of T. urticae to a number of acaricides. These include compounds that were widespread and frequently used in the past, but also some recently
registered compounds. We investigated two T. urticae strains collected from rose growers where control failures were reported (SAN and PSE), together with a strain collected
from unsprayed vegetables (BOSA). Adult females of the rose strains (SAN and PSE) were resistant to tebufenpyrad (Resistant
Ratio—RR, RR50 = 48.4 and 163.6) and fenpyroximate (RR50 = 74.1 and 25.9) when compared to the susceptible BOSA strain. Lethal concentrations for these products were higher than
the registered field rate. The PSE strain proved to be highly resistant to abamectin (RR50 = 1,294.1). Variation in bifenazate susceptibility was detected amongst strains, but LC90 values of SAN and PSE were still in the range of the registered field rate. In egg bioassays, the SAN and PSE strains exhibited
high resistance levels to clofentezine (RR50 = 66,473 and 170,714), hexythiazox (RR50 = 70,244 and 159,493) and flufenoxuron (RR50 = 61.9 and 117.9). But the recently introduced ovi/larvicides etoxazole and spirodiclofen exhibited high activity on all
strains. The activity of detoxifying enzymes such as esterases, glutathione-S-transferases (GSTs) and cytochrome P450 monooxygenases
(MFOs) was determined in these strains as a preliminary attempt to identify potential resistance mechanisms. Enzymatic assays
showed that the rose strains exhibited 2.66 and 1.95-fold increased MFOs activity compared to the susceptible strain. Assays
for GSTs revealed that only the SAN strain exhibited a significantly higher activity. In contrast, only the PSE strain showed
a significant higher hydrolysis of 1-naphthyl acetate. 相似文献
5.
Carlo Duso Valeria Malagnini Alberto Pozzebon Filippo Maria Buzzetti Paola Tirello 《Biocontrol Science and Technology》2008,18(10):1027-1040
Phytoseiulus persimilis Athias-Henriot (Acari Phytoseiidae) is a major predator of Tetranychus urticae (Acari Tetranychidae). The performance of P. persimilis in controlling T. urticae may be altered by pesticides used to manage other pests. Therefore, knowledge of the side-effects of pesticides is essential for IPM. A number of laboratory methods were suggested to evaluate pesticide side-effects on predatory mites. Most methods assess residual effects only, and a number of them are characterised by high predator escape rates from experimental units. A method aimed at evaluating the topical and residual effects of pesticides on P. persimilis is herein described. Mites were treated by microimmersion and then reared in holding cells, on bean leaves previously dipped in a pesticide solution. Three insecticides (pyrethrins, spinosad and thiamethoxam), an insecticide-acaricide (abamectin), and two fungicides (azoxystrobin and tolylfluanide) were evaluated. The strain of P. persimilis used for evaluation was collected from unsprayed vegetable plants. All the pesticides affected the survival and fecundity of P. persimilis. Pesticides did not affect the egg-hatching of P. persimilis females exposed to pesticides. Pyrethrins and abamectin proved to be more toxic than other pesticides, and thiamethoxam was more toxic than spinosad, azoxystrobin and tolylfluanide. The escape rate from experimental units was lower than 5% in all trials. Additional experiments were performed on P. persimilis eggs by dipping leaves with eggs in the pesticide solution. None of the pesticides affected egg survival. Semi-field trials conducted on potted bean plants obtained results similar to those reported in laboratory trials. 相似文献
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Carlo Duso Shakeel Ahmad Paola Tirello Alberto Pozzebon Virna Klaric Mario Baldessari Valeria Malagnini Gino Angeli 《Experimental & applied acarology》2014,62(3):391-414
Kampimodromus aberrans is an effective predatory mite in fruit orchards. The side-effects of insecticides on this species have been little studied. Field and laboratory experiments were conducted to evaluate the effects of insecticides on K. aberrans. Field experiments showed the detrimental effects of etofenprox, tau-fluvalinate and spinosad on predatory mites. Spider mite (Panonychus ulmi) populations reached higher densities on plots treated with etofenprox and tau-fluvalinate than in the other treatments. Single or multiple applications of neonicotinoids caused no detrimental effects on predatory mites. In the laboratory, spinosad and tau-fluvalinate caused 100 % mortality. Etofenprox caused a significant mortality and reduced fecundity. The remaining insecticides did not affect female survival except for imidacloprid. Thiamethoxam, clothianidin, thiacloprid, chlorpyrifos, lufenuron and methoxyfenozide were associated with a significant reduction in fecundity. No effect on fecundity was found for indoxacarb or acetamiprid. Escape rate of K. aberrans in laboratory was relatively high for etofenprox and spinosad, and to a lesser extent thiacloprid. The use of etofenprox, tau-fluvalinate and spinosad was detrimental for K. aberrans and the first two insecticides induced spider mite population increases. The remaining insecticides caused no negative effects on predatory mites in field trials. Some of them (reduced fecundity and repellence) should be considered with caution in integrated pest management programs. 相似文献
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