Biology and Management of Ragweed Parthenium (Parthenium hysterophorous L.) in Tomato, Pepper, Cucurbit, and Strawberry Production

Ragweed parthenium is an herbaceous annual or short-lived perennial weed. It is difficult to manage in many fields due to known resistance to commonly used herbicides. There are a limited number of modes of action that can be used in some vegetable and berry crops. This new 4-page publication of the UF/IFAS Environmental Horticulture Department provides management recommendations. Written by Nathan S. Boyd, Shaun M. Sharpe, Chris Marble, and Shawn Steed.https://edis.ifas.ufl.edu/ep613

BIOCHEMICAL ANALYSIS OF FLOWERS OF Vinca major, A MEDICINAL WEED PLANT OF HILLY AREAS OF PAKISTAN

Vinca major L. is an evergreen perennial weed of family Apocynaceae, growing naturally in hilly areas of Hazara region of Khyber Pakhtunkhwa, Pakistan. Flowers of this weed were collected from Khanspur, Ayubia during June 2021, shade dried and extracted in pure methanol for two weeks. After filtration, the extract was analyzed by GC-MS for identification of possible bioactive compounds. α-Amyrin was the major compounds (32.49%) followed by lup-20(29)-en-3-ol, acetate, (3β)- (25.72%). Moderately abundant compounds included γ-sitosterol (8.78%), β-amyrone (7.25%), cyclohexane, 1,3,5-triphenyl- (7.01%), olean-12-en-3-ol, acetate, (3β)- (5.68%), and n-hexadecanoic acid (3.18%). Some of the identified compounds have various important biological properties including anti-inflammatory, antimicrobial, anticancer, antimalarial, antioxidant, antidiabetic, antitumor etc.

Glyphosate residues alter the microbiota of a perennial weed with a minimal indirect impact on plant performance

Purpose In cold climates, glyphosate residues may linger in soils, with effects on plant–microbe interactions and, consequently, plant performance. Here, we explore the influence of glyphosate residues on the endophytic microbiota (bacteria and fungi) and performance of the perennial nitrogen-fixing weed Lupinus polyphyllus. Methods In a common garden, we grew plants from six populations of L. polyphyllus in glyphosate-treated or untreated control soils, with or without additional phosphorus. We sampled plant microbiota (leaves, roots, nodules) and assessed plant performance based on six traits: height, retrogression probability (i.e. shrinkage), biomass, root:shoot ratio, nodule number, and nodule viability. Results The richness of plant endophytic microbial communities was determined by soil phosphorus level rather than by glyphosate treatment. However, for bacteria, the composition of these communities differed between glyphosate-treated and control soils across plant tissue types; no difference was observed for fungi. The plant bacterial communities in both soil types were dominated by potential nitrogen-fixing bacteria belonging to family Bradyrhizobiaceae, and particularly so in glyphosate-treated soils. Overall, though, these changes in plant bacterial communities had a minor effect on plant performance: the only difference we detected was that the probability of retrogression was occasionally higher in glyphosate-treated soils than in control soils. Conclusion Our findings indicate that glyphosate-based herbicides, when applied at the recommended frequency and concentration, may not have critical effects on the growth of short-lived weeds after the safety period has passed; however, the endophytic microbiota of such weeds may experience longer-lasting shifts in community structure.

​Management Options of Mikania micrantha: A Review

The world’s problematic perennial weed Mikania micrantha hampers in crop production and causes enormous losses due to its interference. Management of M. micrantha by mechanical and chemical methods has not met with any reasonable success. So, it has become a target for classical biological control. Numerous natural indigenous plant species, fungi and insects were tried as bio-control agents for effective control of M. micrantha. However, along with bio-control, appropriate mechanical, chemical and cultural methods are required to be integrated for controlling it. Thus, integrated management approaches for control of M. micrantha should be evolved against this invasive weed in long run.

Weed communities with alien plant species on the south-east area of the Orenburg Region

The presence of agrocoenotic factors constantly acting on segmental (weed-field) communities leads to a high level of community invasion - a potential opportunity to accept new species. In many cases, it is through synanthropic communities that invasions of alien species occur in the Urals, which cause significant damage to both agriculture and the entire economy of the region as a whole. The aim of investigation is to survey and identify the coenotic diversity of communities involving alien species in the steppe zone of the southeastern part of the Orenburg Region. The paper provides data on weed communities with the participation of Acroptilon repens , the Sisymbrium volgense and Artemisia sieversiana . Communities were identified in spring wheat crops in the southeast of the Orenburg Region (Dombarovsky and Svetlinsky administrative districts). Communities develop on dark chestnut soils in arid conditions of the steppe zone. As a result of a synaxonomic analysis, communities were classified into three new variants of the association Lactucetum tataricae Rudakov in Mirkin et al. 1985 previously described in the Republic of Bashkortostan. Perennial weed species prevail in the agrobiological spectrum of the coenoflora nucleus of the studied segetal communities, the share of which is 70%. The most active of them are root-sprung perennials, which are found with high constancy and often dominate: Acroptilon repens , Fallopia convolvulus , Cirsium arvense , Convolvulus arvensis , Lactuca tatarica , Euphorbia virgata . Using the indirect ordination method (DCA), the features of ecological differentiation of communities are demonstrated. The studied phytocoenoses are associated with the driest habitats with poor soils.

Differential germination response of Navua sedge (Cyperus aromaticus) populations to environmental factors

Navua sedge (Cyperus aromaticus) is a hard to control C4 perennial weed species in tropical regions of Australia. Knowledge of its seed biology could help to develop integrated weed management programs for this species. This study was conducted in laboratory and screenhouse conditions to evaluate the effect of alternating day/night temperatures, light, pretreatment high temperatures, burial depth, and flooding depth on the germination and emergence of two populations (Ingham and Tablelands) of C. aromaticus. Both populations germinated at temperatures ranging from 20/10 to 35/25 C; however, the Ingham population germination (76%) was greater than the Tablelands population (42%) at the highest temperature regime (35/25 C). None of the populations germinated at 15/5 C. Darkness completely inhibited germination in both populations, suggesting that the seeds are positively photoblastic. Seeds (dry and wet) of both populations germinated after exposure to pretreatment temperatures of up to 100 C for 5 min. After pretreatment at 150 C, only the Ingham population germinated, and the germination of dry seeds (62%) was greater than wet seeds (1%). None of the populations germinated after the exposure to 200 C. For both populations, maximum germination was observed for seeds at 0 cm, and a burial depth of 0.5 cm completely inhibited emergence of the Tablelands population and 2.0 cm inhibited germination of the Ingham population. A flooding depth of 10 cm greatly reduced emergence in both populations compared with 0 cm (62 and 78%) but 12 to 14% of seedlings still emerged, suggesting the need to integrate flooding with other management tools. The results also suggest that the Ingham population may have a greater potential to spread into new areas or become more invasive than the Tablelands population. Knowledge gained from this study can be used to manage C. aromaticus by fire/burning, tillage, and flooding.

Potential-Growth Indicators Revisited: Higher Generality and Wider Merit of Indication

The notion of a potential-growth indicator came to being in the field of matrix population models long ago, almost simultaneously with the pioneering Leslie model for age-structured population dynamics, although the term has been given and the theory developed only in recent years. The indicator represents an explicit function, R(L), of matrix L elements and indicates the position of the spectral radius of L relative to 1 on the real axis, thus signifying the population growth, or decline, or stabilization. Some indicators turned out to be useful in theoretical layouts and practical applications prior to calculating the spectral radius itself. The most senior (1994) and popular indicator, R0(L), is known as the net reproductive rate, and we consider two others, R1(L) and RRT(A), developed later on. All the three are different in terms of their simplicity and the level of generality, and we illustrate them with a case study of Calamagrostis epigeios, a long-rhizome perennial weed actively colonizing open spaces in the temperate zone. While the R0(L) and R1(L) fail, respectively, because of complexity and insufficient generality, the RRT(L) does succeed, justifying the merit of indication.

Potential-Growth Indicators Revisited: More Merits of Indication

The notion of potential-growth indicator came to being in the field of matrix population models long ago, almost simultaneously with the pioneering Leslie model for age-structured population dynamics, albeit the term has been given and the theory developed only recent years. The indicator represents an explicit function, R(L), of matrix L elements and indicates the position of the spectral radius of L relative to 1 on the real axis, thus signifying the population growth, or decline, or stabilization. Some indicators turned out useful in theoretical layouts and practical applications prior to calculating the spectral radius itself. The most senior (1994) and popular indicator, R0(L), is known as the net reproductive rate, and we consider two more ones, R1(L) and RRT(A), developed later on. All the three are different in what concerns their simplicity and the level of generality, and we illustrate them with a case study of Calamagrostis epigeios, a long-rhizome perennial weed actively colonizing open spaces in the temperate zone. While the R0(L) and R1(L) fail respectively because of complexity and insufficient generality, the RRT(L) does succeed, justifying the merit of indication.

IPSIM-Cirsium, a Qualitative Expert-Based Model to Predict Infestations of Cirsium arvense

Throughout Europe, Cirsium arvense is the most problematic perennial weed in arable crops, whether managed under organic or conventional agriculture. Non-chemical control methods are limited with partial efficacy. Knowledge is missing on their effect across a wide gradient of cropping systems and pedoclimates. To achieve effective Cirsium arvense management ensuring crop productivity while limiting the reliance of cropping systems on herbicide, expert-based models are needed to gather knowledge on the effect of individual levers and their interactions in order to (i) design and assess finely tuned combinations of farming practices in different pedoclimates and (ii) support decisions for Cirsium arvense control. Based on expert-knowledge and literature, we developed IPSIM-Cirsium, a hierarchical qualitative model which evaluates the infestation of Cirsium arvense as a function of farming practices, climate conditions, soil descriptors and their interactions. IPSIM-Cirsium is a multi-attribute model considering all possibilities of interactions between factors, it estimates the infestation rate of the field graded according to a four-level scale. The model outputs were confronted to independent field observations collected across 6 fields, over a 16-year period in 3 sites. IPSIM-Cirsium showed a satisfactory predictive quality (accuracy of 78.2%). IPSIM-Cirsium can be used as a tool for crop advisors and researchers to assist the design of systems less reliant on herbicides, for farmers and advisers to assess ex-ante prototypes of cropping systems, and for teachers as an educational tool to share agroecological weed management knowledge.

Cynodon dactylon (Bermuda grass).

Genetics: The chromosome number reported for C. dactylon varies from 2n = 18 to 2n = 36 with diploid and polyploid populations (Cook et al., 2005). Ramakrishan and Singh (1966) and Sarandon (1991) have found differences in total biomass and biomass partition according to the origin of the population. Sarandon (1991) points out that characters are highly heritable, which means that high genetic variability for biomass production and variable architecture allows an ample base for selection, which in most cases is induced by herbicides, mechanical control or forage production. Reproductive Biology: C. dactylon is wind-pollinated and generally self-incompatible, suffering from inbreeding depression when genotypes are self-pollinated. Quantitative traits such as seed yield and forage yield can be dramatically negatively affected by inbreeding depression (Cook et al., 2005). In diploid populations, caryopses are formed after zygote formation. In polyploids, which are sterile, caryopses may be apomictic. Physiology: This C4 plant (Kissmann, 1991) has high rates of accumulation under adequate irradiance, water and nutrient supply and may consume 75 kg of N, 20 kg of P and more than 1,500,000 litres of water for 5000 kg/ha of biomass dry matter (Fernandez, 1991). In the south of Santa Fe province, Argentina, a maximum biomass of 8000 kg/ha may be generated under a summer crop of maize or sunflower with >75% located in the first 10 cm of the soil profile (Lombardo, 1973), whereas in Balcarce (Argentina) about 5000 kg/ha is commonly found in maize or sunflower stubble. Phenology: A photoperiod of 13 hours induces flowering. Low night temperatures coupled with high diurnal temperatures induces blooming (Nir and Koller, 1976). A reduction in irradiance drastically decreases inflorescence production (Moreira, 1975). In North America, annual plants reproduce during spring and perennial plants reproduce all year long (USDA-NRCS, 2014). Longevity: C. dactylon grows as both an annual and perennial grass. The annual growth-form becomes dormant and turns brown when nighttime temperatures fall below freezing or average daytime temperatures are below 10°C (Cook et al., 2005). Activity Patterns: Seeds may be the route of invasion in weed-free fields through the faeces of cows (Rodriguez, personal communication). Rhizome biomass exhibits an annual cyclic pattern and, as with any perennial weed, low temperatures reduce biomass and viability is lost as a consequence of the consumption of materials due to respiration and maintenance. The digestibility of stocked material is severely decreased, implying a loss in forage quality (Vaz Martins, 1989). This is a character that has largely improved in cultivated varieties. Each node has a physiological self-governing structure in relation to the apex, but is highly dependent on substances from other plant parts. The mother plant determines the runner growth pattern on the soil surface according to the sugar-gibberellin balance (Montaldi 1970). Node disconnection may be caused by natural decay and cultivation and produces damage in the breakdown zone and changes in hormone and nutrient relationships. It is widely demonstrated that rhizome or runner fragmentation induces the activation of buds. The proportion of activated buds increases as the number of buds per segment decreases (Moreira, 1980; Kigel and Koller, 1985; Fernandez and Bedmar, 1992). The cultivation method is mainly responsible for vegetative propagation fragmentation. The higher the cultivation intensity, the smaller the segments produced (Kigel and Koller, 1985). Population Size and Structure This weed produces an enormous number of small seeds (0.25-0.30 mg), the viability and dormancy of which are highly variable according to genotype and the conditions when formed. The seed is important because it confers high genetic variability on the population. Perez et al. (1995) recorded a very low germination rate. Uygur et al. (1985) obtained up to 15% germination at constant temperatures of 35-40°C, and 50% at temperatures alternating between 20 and 30°C. Moreira (1975) obtained up to 80% germination with the help of nitrate, chilling and alternating temperatures, and Elias (1986) recorded up to 96% germination from heavier samples of seed. Seeds remain viable in the soil for at least 2 years (Caixinhas et al., 1988). As a rule, cultivars have relatively high viability. Osmo-conditioning of Bermuda grass seeds with PEG followed by immediate sowing improved seed germination and seedling growth under saline conditions (Al-Humaid 2002). The probability of emergence and successful establishment of C. dactylon decreases with the depth of the fragment, but increases with the weight of the node and internode (Perez et al., 1998). Growth from plants originated from a runner may exhibit a different biomass partition than that from plants originated from a rhizome (Fernandez, 1986). From sprouting onwards, weed growth is controlled mainly by temperature (optimum 25-30°C) and radiation, but also by humidity and soil fertility. The efficiency of carbohydrate reserve usage during sprout growth is highly dependent on temperature and the type of vegetative structure; it is maximum at 20°C and is higher for rhizomes than for stolons (Satorre et al., 1996). Runners and rhizome growth begins 30 days after growth but only if soil temperature is >15°C. Rates of 15 g/g/day have been recorded in Argentina (Lescano de Ríos, 1982).