Selective and Non-Selective Control of Invasive Plants: The Short-Term Effects of Growing-Season Prescribed Fire, Herbicide, and Mowing in Two Texas Prairies

Conservation of North American grasslands is hampered by the impact of invasive herbaceous species. Selective control of these plants, although desirable, is complicated by the shared physiology and phenology of the invader and the native components of the invaded plant community. Fortunately, there is evidence that some management practices, such as prescribed fire, herbicide, and mowing, can cause differential responses in native and invasive grassland species. However, timing of treatment is critical, and fire has been shown to increase rates of invasion when implemented during the dormant season. Bothriochloa ischaemum, an introduced C4 Eurasian grass is an increasing problem in grasslands, particularly in southern and central regions of North America. To date, there has been little success in effective selective control. Two invaded grassland sites representative of Blackland Prairie and Edwards Plateau ecoregions were subjected to two growing‐season prescribed fire treatments, single and double herbicide applications, and single and double mowing treatments. Mowing had no effect on either B. ischaemum or other dominant species at either site one‐year posttreatment. However, growing‐season fire and herbicide were both effective at reducing the abundance of B. ischaemum, with other codominant species responding either negatively to herbicide or neutrally or positively to fire. The vulnerability of B. ischaemum to growing‐season fire may be associated with the ecology of its native range. The negative growth response to growing‐season fire, combined with its lower implementation costs, indicates that this method warrants further investigation as a selective management tool for other problematic species in invaded grasslands.     

Antagonistic effects of the endophytic fungus Meira geulakonigii on the citrus rust mite Phyllocoptruta oleivora

AIMS: The fungus Meira geulakonigii has been shown to reduce populations of citrus rust mite (CRM; Phyllocoptruta oleivora) on citrus leaves and fruits, in both the field and laboratory. However, attempts to isolate the fungus from leaves and fruits have been unsuccessful. The aims of this study were therefore to determine whether M. geulakonigii is a citrus endophyte, and to assess possible mechanisms involved in its mite-antagonist activity. METHODS AND RESULTS: A quantitative real-time PCR and regular PCR approaches were developed to detect M. geulakonigii in both the field and laboratory. The fungus was detected throughout. Different methods revealed that M. geulakonigii is an endophyte, which colonizes both the peel of grapefruits. Applications of conidia protected the grapefruits against CRM, and fungal secretions extracted from growth media caused 100% CRM mortality. CONCLUSIONS: Meira geulakonigii is a beneficial endophyte of grapefruits that colonizes the fruit's peel, and protects it from CRM. SIGNIFICANCE AND IMPACT OF THE STUDY: Findings from this study demonstrate the endophytic nature of M. geulakonigii in its interaction with grapefruits. In addition, a molecular approach was developed to specifically detect the fungus inside the grapefruit peel. This approach can be used to assess the natural occurrence of M. geulakonigii in grapefruit.     

Attenuation of genotoxicity under adhesion-restrictive conditions through modulation of p53,γ H2AX and nuclear DNA organization

Interactions between tumor cells and their substratum influence cancer progression by modulating cell proliferation and survival. We now investigated whether signaling responses to UV irradiation differ on adhesion-permissive or restrictive substrates. The latter conditions diminished spreading and proliferation of neo 6.3/C8161 melanoma in which metastasis is suppressed by introduction of neo-tagged chromosome 6, but permitted proliferation of human metastatic C8161 melanoma. Apoptosis-associated PARP cleavage and DNA fragmentation induced by UV irrradiation were diminished on the restrictive substrate in C8161 melanoma. Genotoxic responses to UV irradiation like persistent increases in the phosphorylation of histone H2AX, induction of the tumor suppressor p53 protein and greater binding of this protein to its DNA consensus sequence, were all decreased on the restrictive substrate. The latter also promoted a 2 fold increase of DNA condensation in chromatin and enhanced activation of the survival - and invasion-associated MMP-9 gelatinase B, preferentially in metastatic C81261 melanoma. Our data suggest that adaptation to restrictive substrates in metastatic C8161 melanoma decreases UV-induced apoptosis, partly through attenuation of DNA damage signaling responses and changes in genomic organization. Mary Strasberg Rieber and Manuel Rieber: This research was supported by the Terry Fox Run for Cancer Research (CIC-CCA) to MR.     

Temporal generalization accounts for response resurgence in the peak procedure

The peak interval (PI) procedure is commonly used to evaluate animals' ability to produce timed intervals. It consists of presenting fixed interval (FI) schedules in which some of the trials are replaced by extended non-reinforced trials. Responding will often resume (resurge) at the end of the non-reinforced trials unless precautions are taken to prevent it. Response resurgence was replicated in rats and pigeons. Variation of the durations of the FI and the non-reinforced probe trials showed it to be dependent on the time when reinforcement is expected. Timing of both the normal time to reinforcement, and the subsequent time to reinforcement during the probe trials followed Weber's law. A quantitative model of resurgence is described, suggesting how animals respond to the signaling properties of reinforcement omission. Model results were simulated using a stochastic binary counter.     

茶黑刺粉虱的生物学特性及防治

茶黑刺粉虱Aleurocanthus spiniferus Quaintance是茶树的主要害虫之一。该虫在山东省薛城1年发生4代,以幼虫在叶片中越冬。对成虫、初孵幼虫和越冬幼虫的田间化学防治试验,结果显示,分别选用1.8%阿维菌素2500倍液或2.5%吡虫啉2000倍液防治成虫或幼虫效果较好。     

两种蚜小蜂对烟粉虱寄主的产卵选择性（英文）

双斑恩蚜小蜂和桨角蚜小蜂是华南地区烟粉虱的两种优势种寄生蜂。本文研究了两种寄生蜂对不同龄期烟粉虱寄主的产卵选择特性。结果表明: 两种寄生蜂均可寄生烟粉虱的1～4龄若虫。当只有1个龄期的烟粉虱若虫存在时,双斑恩蚜小蜂更多地寄生3龄和4龄若虫,较少寄生1龄和2龄若虫;而桨角蚜小蜂则更多地寄生3龄和2龄若虫,较少寄生1龄和4龄若虫。在4个龄期若虫同时存在时,双斑恩蚜小蜂会明显增加对3龄和4龄若虫的产卵寄生,降低对1龄和2龄若虫的寄生;而桨角蚜小蜂则增加对2龄和3龄若虫的寄生,减少对1龄和4龄若虫的寄生。寄主植物的差异不影响这二种蚜小蜂对各龄期烟粉虱若虫的产卵选择倾向。结果提示,烟粉虱若虫3龄和4龄是双斑恩蚜小蜂最适宜的寄主,而桨角蚜小蜂最适宜的寄主是烟粉虱2龄和3龄若虫。     

Effects of gamma-irradiation on midgut proteolytic activity of the mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae)

The Mediterranean fruit fly (medfly), Ceratitis capitata (Wiedemann), is a key pest of citrus in Spain because of significant yield losses and to quarantine restrictions. Biologically based control methods, such as the Sterile Insect Technique (SIT), which relies on the sterilization by irradiation of large numbers of insects, is gaining an increasing role in the control of medfly in Mediterranean areas. However, gamma-irradiation might damage the midgut epithelium cells, causing a lowering of nutritive assimilation that can negatively affect adult performance. Irradiation effects on digestive physiology are well established for a number of insect pests, but there is no information on medfly. Our aim was to determine the effects of gamma-irradiation on C. capitata digestive protease activity. Both larvae and adults were found to use a similar proteolytic system based on aspartyl-, trypsin-, chymotrypsin-, amino peptidase-, and carboxypeptidase A- and B-like activities. Pupae of the Vienna-7 (tsl) strain were irradiated at 70 or 140 Gy, two days before emergence, and the adults fed during 5 days on sugar-protein (4:1) diets. Protease activity was measured in midgut extracts and compared with males non-irradiated reared in the same conditions. The results showed that the irradiation doses tested had no effect on the digestive proteolytic activities of medfly adults. Moreover, the longevity of irradiated medflies at the highest dose (140 Gy) was similar to that of controls.     

The Endocannabinoid System and Extinction Learning

The endocannabinoid system has emerged as a versatile neuromodulatory system, implicated in a plethora of physiological and pathophysiological processes. Cannabinoid receptor type 1 (CB1 receptor) and endocannabinoids are widely distributed in the brain. Their roles in learning and memory have been well documented, using rodents in various memory tests. Depending on the test, the endocannabinoid system is required in the acquisition and/or extinction of memory. In particular, the activation of CB1 receptor-mediated signaling is centrally involved in the facilitation of behavioral adaptation after the acquisition of aversive memories. As several human psychiatric disorders, such as phobia, generalized anxiety disorders, and posttraumatic stress disorder (PTSD) appear to involve aberrant memory processing and impaired adaptation to changed environmental conditions, the hope has been fuelled that the endocannabinoid system might be a valuable therapeutic target for the treatment of these disorders. This review summarizes the current data on the role of the endocannabinoid system in the modulation of extinction learning.     

Effects of the novel allelochemical ethyl 2-methylacetoacetate from the reed (<Emphasis Type="Italic">Phragmitis australis</Emphasis> Trin) on the growth of several common species of green algae

Bioassays were performed to investigate the effects of the novel allelochemical, ethyl 2-methylacetoacetate (EMA), isolated from the reed (Phragmitis australis) on the growth of three common species of algae; Scenedesmus obliquus, Selenastrum capricornutum and Chlamydomonas reinhardtii. The results demonstrated that EMA has three quite different types of effect on these three species of algae. The growth of S. capricornutum was significantly inhibited by EMA during the whole cultivation period. The EC₅₀ values of EMA on S. capricornutum was 0.6 mg L⁻¹(7 days). However, the inhibitory effect of EMA on S. obliquus was apparent during the first 4 days of batch cultivation and then the inhibitory effect disappeared, and a stimulating effect was observed instead. The EC₅₀ value of EMA on S. obliquus was 0.43 mg L⁻¹(4 days). In addition, following the addition of EMA, the cells of S. obliquus and S. capricornutum became significantly larger than the normal untreated one and the algal cells changed morphologically. The microstructure of the algal cells was disrupted by the addition of EMA. There was no significant inhibition of the growth of C. reinhardtii by EMA, but cell motility was affected.