Bioherbicidal Potential of Eucalyptus and Clove Oil and their Combinations on Four Weedy Species

Essential oils of eucalyptus leaves and clove buds were isolated and tested for their bioherbicidal potential on different annual weed species. Gas Chromatography-Mass Spectrophotometry analysis (GC-MS) identified thirteen compounds representing around 87.11% of the total isolated eucalyptus oil. The main constituent was 1,8-cineole, which accounted for 68.15% of the total identified compounds. As for clove oil, eleven compounds were identified, representing 90.03% of the total compounds. Eugenol was the dominant compound and accounted for 73.89%. The bioherbicidal efficacy of the two oils and their combinations by three concentrations (2.5, 5, and 10%) were tested on four weedy species, namely Chenopodium album, Raphanus raphanistrum, Melilotus indicus, and Sisymbrium irio. The isolated oils significantly affected the dry weight and inhibited the seedling growth of the four weedy species. Using the two essential oils, individually or within their combinations, showed the highest bioherbicidal efficacy against the targeted weeds in comparison with the synthetic herbicide. In addition, utilization of the two essential oils as natural bioherbicides caused an electrolyte leakage as a result of membrane disruption and loss of integrity of weed seedling tissues. The results showed the possibility of using eucalyptus and clove essential oils individually or in combination as a desirable alternative to synthetic herbicides for sustainable weed management.

Fallopia convolvulus (black bindweed).

F. convolvulus is a weedy species of gardens, cultivated fields, open habitats, orchards, non-crop areas, waste areas, and disturbed sites. It is well-adapted to a wide range of climatic conditions and soils. This species is a prolific seed producer and has the potential to produce up to 30,000 seeds/plant. Seeds can be dispersed by farm machinery, and water. It is also a common contaminant of wheat and other cereal crops. F. convolvulus is often a serious weed in cereals, vegetables and horticultural crops (FAO, 2015). Currently, it is listed as invasive in the Dominican Republic, Cuba, Australia, New Caledonia, and New Zealand (Webb et al., 1988; MacKee, 1994; Wilson, 2008; Acevedo-Rodriguez and Strong, 2012), but it is also ranked as a serious weed in 20 crops in more than 41 countries around the world (Holm et al., 1991). Distribution.

Physiological, Ecological and Genetic Interactions of Rice with Harmful Microbes

Rice is one of the most important food crops for mankind and suffers significant crop loss annually due to rice diseases. Availability of genome sequences of rice has served as a springboard to utilize its innate immunity to prevent rice diseases. Knowledge on interactions of rice and rice pathogens has rapidly accumulated. Effective resistance genes have been identified from cultivated, weedy species of rice, and wild rice relatives and their roles in plant innate immunity have been uncovered. Presently, rice diseases are being managed using host resistance genes and pesticides in diverse culture systems around the globe. This chapter presents a simple review of interactions of rice with harmful microbes causing the two major damaging diseases, rice blast and sheath blight. The review is written to target new readers in life sciences. Knowledge and critical literatures on physiological, genetic, and ecological aspects of host-pathogen interactions are presented to gain insights leading to sustainable disease management systems.

Restoration management of cattle resting place in mountain grassland

This study investigated the effect of restoration management of a weed-infested area, previously used as cattle resting place, on herbage production and nutrient concentrations in the soil and herbage. The experiment was undertaken from 2004 to 2011 at the National Park of Nízké Tatry, Slovakia. Three treatments were applied: (i) cutting twice per year, (ii) herbicide application, followed after three weeks by reseeding with a mixture of vascular plant species and then cut twice per year, and (iii) unmanaged. Treatments had significant effect on biomass production and concentration of nutrients in the soil and in herbage. Nutrient concentrations in herbage and in soil declined progressively under the cutting treatments and reached optimum ranges for dairy cattle at the end of the experiment when herbage N was less than 15 g kg-1 and herbage P was 3.4 g kg-1. There was also a strong positive relationship under the cutting treatments between soil nutrient concentrations and herbage nutrient concentrations for N, P, K, Mg and Ca. Although the cutting management as well as the combination of herbicide application with cutting management reduced nutrient concentrations in the soil and in herbage, the nutrient concentrations remained relatively high. We can conclude that restoration of grassland covered with weedy species like Urtica dioica and Rumex obtusifolius, with excessive levels of soil nutrients, cannot be achieved just by cutting and herbicide application.

Ailanthus altissima (tree-of-heaven).

A. altissima, native to China, is a short to medium-size deciduous tree valued chiefly for timber, shade and urban amenity plantings. It is tolerant of drought, poor soils and pollution and so can be grown in difficult urban locations, although it is considered as a potentially weedy species in the USA (Shah, 1997). It is an aggressive pioneer species, characterized by rapid juvenile growth and prolific seed production and has a very high ability to coppice once established. It requires well-aerated and moist soils to produce good, single-stemmed trees.

Do Weeds Hinder the Establishment of Native Plants on a Reclaimed North American Boreal Mine Site?

The majority of plant diversity in the boreal forest of northern Alberta, Canada is comprised of native understory plant species that are continuously facing competition from other species, including both undesirable native and weedy species. In oil sands mine reclamation, cover soils rich in organic matter are used to cap overburden materials. The aim of this study is to understand the role of weeds on different reclamation cover soils (forest floor-mineral mix and peat-mineral mix) and determine if they hinder the establishment of the native plant community. This study was conducted four growing seasons after site establishment in June 2019. At that time, both soil types had approximately 45% total cover, had 21 species per plot, and were composed of mainly native vegetation. Competition from non-native forbs (11% average cover, mainly Sonchus arvensis and Melilotus alba) did not seem to impact the development of the native vegetation community on either soil type given the high cover and richness of native forbs. However, native graminoids (predominantly Calamagrostis canadensis) were associated with reduced native forb cover and richness at graminoid cover greater than 17%. Overall, non-native forbs appeared to have little impact on the native forb community on either soil type while native graminoids had a negative influence. We suggest that the classification of what is considered an undesirable weedy species should be evaluated in the context of ecosystem management goals rather than simply the presence of non-native species.

A new species of Neohydatothrips (Thysanoptera: Thripidae) from India

With 120 described species (ThripsWiki 2020) Neohydatothrips is the most species-rich genus in the Thripidae subfamily Sericothripinae. Although widely distributed almost 70% of the species are from the New World (Lima & Mound 2016), with only seven species recorded from India (Rachana & Varatharajan 2017). The biology of most species in the genus remains unknown, but they apparently feed and breed on the leaves and/or flowers of various unrelated plants. A few species are economically important as plant pests as well as virus vectors, such as N. variabilis (Beach) (Zhou & Tzanetakis 2013; Lima & Mound 2016; Han et al. 2019). N. samayunkur (Kudo) is a pest on flowers and leaves of Tagetes spp. in many countries including India (Nakahara 1999; Bhatti et al. 2003). Even though N. gracilipes (Hood) was described originally as damaging cotton in Mexico, it is associated with weedy species of Sida in several countries including central India (Lima & Mound 2016). In southern China, N. flavicingulus Mirab-balou, Tong & Yang is reported as damaging leaves of Manglietia fordiana. In California, avocado crops are sometimes damaged by N. burungae (Hood) and this species is also recorded as distorting the young leaves of Passiflora in Colombia (Mound et al. 2019). N. gracilicornis (Williams) is reported as damaging Pinaceae and Betulaceae in Spain and South Italy (Marullo 2009). The purpose of this article is to describe a new species from India that was collected in the flowers of Jasminum sambac (Oleaceae) in Assam, northeastern India. A detailed structural diagnosis of this genus is provided by Masumoto and Okajima (2020).

Annual weedy species of Erigeron in the northern Iberian Peninsula: a review

A revision of the alien Erigeron L. species formerly included in Conyza Less. found in the central-northern Iberian Peninsula is presented. A close examination of numerous specimens collected by the authors as well as voucher specimens preserved at several herbaria has helped clarify several aspects regarding this group. Four species have been recognised in the study area: Erigeron canadensis (=Conyza canadensis), E. bonariensis (=C. bonariensis), E. sumatrensis (=C. sumatrensis) and E. floribundus (=C. floribunda, including C. bilbaoana). They occupy anthropogenic habitats, such as road edges, abandoned fields, crops and waste ground, as well as natural and semi-natural communities, such as nitrophilous river bar communities and ruderal communities on coastal dunes subjected to substantial levels of anthropogenic disturbance. Erigeron sumatrensis and E. floribundus emerge as the two most frequent taxa. Erigeron canadensis, regarded in the past as the most widespread species of the group, is almost absent from the study area, especially from the Atlantic watershed. Furthermore, an important number of specimens previously identified as E. bonariensis do actually correspond to E. sumatrensis. No hybrids have been found. A detailed identification key highlighting the main features that help to separate the four Erigeron species is presented. Finally, as E. floribundus is the most controversial species in the group and the last to arrive, a study of its expansion across western Europe in the last century is included, where it has become a frequent alien especially along the Atlantic regions.

Sida repens (Javanese fanpetals).

Sida repens is a perennial herb native to Central America and parts of South America that grows as a weed in disturbed sites, wastelands, pastures and on roadsides. It has been classified as a weed in Cuba and as invasive in Puerto Rico and the Virgin Islands. This weedy species produces prickly fruits that attach to animal fur or human clothing, facilitating seed dispersal.