Weed Science - Science topic

I agree with the suggestions provided by @Andrew Paul McKenzie Pegman and @Medhat Elsahookie. Moreover, in field conditions, you may think of re-seeding/planting to maintain the same upto a certain period.

The best post-emergence herbicide in Cotton is Hit Weed Maxx (Pyrithiobac sodium 6% + Quizalofop ethyl 4%) @ 500ml/acre. It should be sprayed between 15-25 days after sowing the crop and weeds should be at 2-3 leaf stage @ Manan Khan

احمد المشهداني

Mohammed Akram Alobaidy

Mr Himanshu,

As for analysis in ANOVA is concerned, we expect variation between the treatment, whether it is weed-free or weed check or any other treatment. The very purpose of the transformation is to reduce the within treatment variation, rather between the treatment.

Hello Susan; I'm very curious to know what finally came of your question. Did you learn what you needed to know? Were you able to act on it? Best regards, Jim Des Lauriers

yes

Cheatgrass (Bromus tectorum) is an invasive plant. Please see the below given RG links.

Please take a look at the following RG link.

Dear Mohamed Abdelaal

Please have a look at these useful RG links.

Good luck!

Dear Viji N

This Published paper could help you.

For soil applied herbicides,

Calculate as 1 mg ai. per kg of soil.

For field application, take weight of 15 cm furrow slice in 1 ha area as Bulk Density x 1000000 kg (on an average).

So for 1 ppm conc. = Value of BD kg/ha active ingredient.

For example, a soil having 2.1 g/cc BD will need 2.1 kg of herbicide ai per ha to reach a concentration of 1 ppm.

Dear Ankur,

Please have a look at these useful links.

Good luck!

thank u @Andrew Paul McKenzie Pegman 。I were doing work on field last  5 months,so i had no chance to reply u。I am puzzling about its seed，could you show me some seeds ？thank u very much

Dear Taab

Please find the attached papers related to your request.

All the Best,

Ramin

When I think of plant extraction for chemicals I always think of Quechers as a good place to start.  Do a google search for quechers, many companies now provide kits for this type of extraction (Waters, Sigma, Agilent, Restek, Phenomonex...etc)  You would use this protocol to extract the norflurazon from the plant material, then analyze as stated in the soil or water analytical/instrumental method.  See attached link for norflurazon in tobacco using quechers

Hi: you can collect from plant that infects with dodder

It is interesting to know that the sustainability of cropping systems can be increased by introducing a cover crop, provided that the cover crop does not reduce the cash crop yield through competition. The cover crop may be sown at the same time as a cash crop in the crop rotation.

Please check the PDF attachments.

I would guess that the approach to weed management is dependent on who is teaching the course and where the course is being taught. In part it may also be an issue in how to deal with the problem. A grower might want to quarantine all new shipments that come into his area to prevent some weed from invading his field. Yet one grower has neither the political power to make this happen nor the infrastructure to inforce the quarantine. That is the role of governments and police forces. At the point that a grower must do something it is already too late for regulatory weed management strategies to prevent the spread of the weed. Even if borders are secure enough to enable a quarantine approach, there will be smugglers to contend with.

    I would also suggest that by the time a problem has gotten large enough to mobilize the political will to enact a quarantine, that the effort is already too late. The quarantine may slow the spread but that is the best that can be hoped for. The problem is with detection. So I need to prevent a new weed from invading my island. Every car or truck entering my island is carefully washed. All produce is screened, all hay is sterilized.  Yet one seed lands 73 feet past the left side of my house. I have already lost, though I will not know this until several months later when the plant from that seed has produced 800 more and my scout happens upon one of these plants. I just cannot afford to have my entire island searched millimeter by millimeter twice per week to find that one initial plant. The other problem is with collective action. If even one farmer allows the weed to grow on his land, all the neighbors will suffer. Also who pays for taking care of the problem? Some farmers can't pay, others are perfectly happy forcing you to pay.

   The best the grower (as an individual) can do is deal with the problem after the weed has become established. Some places are luck to have a grower that is liked/respected/feared that has political connections and can energize collective action. However, internal conflicts and outside interests make quarantine a difficult proposition at best.

   Partly, the issue is frequency. most of the weeds that growers must deal with are already abundant in their fields. The threat of one new weed from some foreign land is mostly too far away given the 65 weed species that are already at your doorstep.

  Partly, it is economic. So I spent 10 billion to prevent this weed from entering my country. I did this every year for 20 years. This includes border patrol agents to prevent spread by land/air/sea, and shipments of goods that were lost because they could not pass quarantine in time. So what economic benefit have I gained that offsets this cost? Here is what we spent on quarantine _________ and if we had not implemented the quarantine here is the economic damage that would have resulted _______. Was it worth it? Mostly the problem is complex and some people will argue yes and others no. Both will be right depending on where the numbers come from.

This problem is further complicated by perception. So I can go into my field and spray with an herbicide. I have dead weeds and a clear knowledge that I improved my yield this day. In contrast I paid some government another 3% of my earnings to pay some official money to do something. A friend of my neighbor said it was to help stop a new weed that I have never seen from invading. If I don not have strong confidence in my government, this might as well be money to prevent Martians from landing on Earth. So far all the tax dollars spent to prevent a Mars invasion of Earth have worked.

One might also consider what defines a weed. A rancher imports a cactus to act as a fence for cattle. The cactus grows elsewhere and becomes a weed. If only it had stayed just where it was planted.

I want to sincerely thank you all so much for your suggestions. They were indeed very helpful. Thanks.

I agree with José Luis Fernández-Alonso y Sonnia Hill

Ahmed Abd El-Gawad and the Line Intercept Method that he mentions, is almost exactly like the Evens & Love Toe point, except it takes more time to set up, whereas with the Toe Point, you just walk and record what plants the toe of your shoe touches.  

A few dozen people and I tested the Toe point vs the Line Intercept a few years ago in a field, and the Toe Point was about five times faster than the Line Intercept, and produced very closely, the same measured results.

The quadrat method takes even more time, and that is a good method if you are studying the details of a natural plant community and you want to measure very detailed percentages of  plant cover.  I use that method when I want to get every single species, even those that have less than 1% cover within an ecosystem, and the quadrat method misses nothing.  But it takes maybe 20 times the amount of time to do that amount of detail, compared to the Toe-Point.

But for weeds in a cotton field, I hope that you have tried the Toe Point and found it the fastest and easiest method of vegetation cover measurements?  Only 100 paces gives you a very detailed look at what is out there, and that the Toe Point can be done so quickly, means that there is a better chance of getting the data you need on the weeds, instead of having to set up the rquipment to do any of the dozen or so other vegetation cover measurement method. 

Pyroxasulfone, saflufenacil, mesotrione and 2,4-D are some good options available for conventional weed control on corn.

You may want to consult a Weed Control Guidelines of your state.

If you're interested on testing products based on natural compounds, I've attached a publication with some examples you may want to look at.

Good luck on your research!

As the plant is evergreen or may only lose some leaves in unfavorable conditions, it is clearly a phanerophyte. However, you might want to keep in mind that Raunkiaer's life forms are mainly created for (highly) seasonal (esp. temperate) floras. Tropical taxa often don't fit or differ extremely in form (cacti, trees, evergreen vines, epiphytes are all phanerophytes!) although being in the same Raunkiaer class. That's why most species are not put in one of those categories. There are other life form classifications though.

Dear Dr Lock

Thanks for the comment...I got point

Try with stratification. Put seeds on 4^OC for some period (month-two). It usually improve germination. Also, I mentioned seed have better germination in the period of year when seeds of that species germinate in the field.

Hi,

In the Caribbean this plant species is considered sometimes as an alien species, sometimes as a native species (!), but it seems that nobody consider it a problem !.  A great number of habitats are now invaded with this plant. Often, people introduce this plant on small ponds, gardens and other standing water habitats.  People consider it as a beautiful plant that increase attractivity of ponds. We do not know any factors really helpful to limit its growth except manual withdrawal. I don't know of any tests carried out in this region against this species.

Since this species is not a problem for boats or for other commercial activity in the West Indies there is no policy considering E. crassipes

Ponds colonized by this species are also the only habitat, in the West Indies, for the dragonfly Miathyria marcella.

Best

Mr Shergill and Mr Jalaludin, I will collect some seeds of Elleusine indica from some locations. Would you like give me advice? stage seed or age of eleusine that can be collected ? thank you

looks to me like birds nest fern.

i did my Ph.D work on Parthenium extracts against onion thrips you can also download my paper published in weed science journal

Goats are primarily browsers, and are used to clear invasive shrubs in WI.  I've attached a guide to using goats for brush control from a USDA RC&D group and an article on using goats to clear invasive plants on oak savannas.  You can even rent a goat herd for brush control from a company that specializes in this service in SW WI.  For larger shrubs that may need knocking down for a thorough overbrowsing, we use shaggy highland cattle which prefer browsing to grazing if available.

For grazing out grasses, you may want to look at the succession of grazers we see (or saw) in natural grasslands.  Typically, migratory mixed herds are lead into new, ungrazed areas by equines: horses, asses, and zebras.  Equines can handle very course grasses and will provide the initial grazing and clearing access to more tender, higher quality grass and shoots.  Equids are followed by large grazers like cattle, bison or the large antelope which are in turn followed by smaller "nibblers" like sheep and small antelope.  Knowing this, perhaps you should start your grazing with horses or donkeys and after they've mowed it back bring in cattle or sheep depending on the coarseness of the remaining grasses.  Use sheep for the final overgrazing.   

Dear Fungai Mukange

The lesson for future is integrated weed management to reduce the selection pressure.

No single method ever is going to be stable therefore diversity is the key.

After reflexion, it's a Podophyllaceae, like Bongardia chrysogonum ; see http://www.avonbulbs.co.uk/s/bongardia-chrysogonum/52/Product.aspx

It looks like corn spurry to  me. (Spergula arvensis L.). It is a fairly common weed in the United States and has been recently identified in Alaska.

The most important thing would be to test the crop of interest to see if it is susceptible to injury.

Hi Eajaz,

We collect seed for susceptible checks from non-agricultural areas with no history of herbicide use (e.g. public park, home garden, roadsides, other natural areas, etc.). This seems to work well. I think there are a variety of approaches you can use here, as long as you can justify that the check should be susceptible, I think you should be good.

Scott

You seem to have a very good understand many of the limitations with visual phytotoxicity assessments. Additional problems include the issue of many researchers not doing this assessments blind (they take a plot plan with them and know what plots they are rating) so the potential for bias is VERY high. My question would be why use them at all? Because of these problems most journals will not allow publication of papers without additional truly quantitative data such as biomass and yield. Because of this we will use them sometimes as a semi-quantitative way of describing herbicide phytotoxicity but I am not sure of there utility for anything beyond that. However for those that are screening massive amounts of herbicide plots they may be a necessary tool. Looking at other disciplines that have done a better job may be informative - plant pathology in particular has been much more rigorous in there development of scales for plant pathogen symptoms.  This approach probably could be transferred to contact herbicides fairly well. The issue always will be that there are large differences between herbicide MOA and plant species. In addition for many MOA most obvious symptomatology is the cessation of plant growth that requires the comparison of the untreated plots with treated and therefore removes part of the blind rating. So is this impossible - no, but I think one has to consider if the data will really be that much better. 

Weed management costs money and so some kind of economic threshold estimation is wise, but most managers opt for reducing risk, and the thresholds they use often lead to over-investment.  This is unsurprising because penalties for failure can be severe, and weed impacts vary from site to site in ways that are not easily predicted.  Typically a regional analytical approach is taken, but with weeds targeted in a more site specific way.  A competent manager will know that certain weeds are likely on specific site types, and that the consequences of lack of control from those weeds generally justify control.  However, just to be sure they are likely to over-invest.

The question is complicated by the longevity of forest crops.  Have a look at types of responses to site management treatments as outlined in the following papers:

Snowdon, P. and H. D. Waring (1984). Long-term nature of growth responses obtained to fertiliser and weed control applied at planting and their consequences for forest management. IUFRO symposium on site and site productivity of fast growing plantations, Pretoria and Petermaritzberg, South Africa

Mason, E. G. (1991). A forest establishment or regeneration decision framework. Proceedings of the IUFRO symposium on Efficiency of stand establishment operations, Rotorua, Zealand Forest Research Institute Bulletin

Mason, E. G. (1996). "Planning forest establishment operations with a computerised decision-support system: a case study analysis of decision-making over a full rotation." New Zealand Journal of Forestry Science 26.(1/2): 222-234

Mason, E. G. (2005). "Effects of soil cultivation, fertilisation, initial seedling diameter and plant handling on the development of maturing Pinus radiata D.Don on Kaingaroa gravelly sand in the Central North Island of New Zealand." Bosque 25(2): 43-55

Mason, E. G. and P. G. Milne (1999). "Effects of weed control, fertilization, and soil cultivation on the growth of Pinus radiata at midrotation in Canterbury, New Zealand." Canadian Journal of Forest Research 29: 985-992.

Mason, E. G., A. G. D. Whyte, et al. (1997). "A model of the growth of juvenile radiata pine in the Central North Island of New Zealand: links with older models and rotation-length analyses of the effects of site preparation." Forest Ecology and Management 97(2): 187-195.

The term "weed" can be applied to almost any plant, depending on the situation and the perspective of the person referring to a particular plant as being a "weed".  For example, glyphosate-resistant Zea mays could be a weed if it is found growing and competing with glyphosate-resistant Glycine max. 

Crop-weed associations could be due a number of factors: similarities in growth habit, life cycle, management practices, etc. 

Most weeds tend to be herbaceous because this type of plant tends to have the traits of a fast-growing colonizer that can utilize available resources after a disturbance.  Woody species can be "weedy", but this type tends to appear in later stages of succession. 

Sampling weed species largely depends on several factors; including cropping pattern, size of plot or area covered, etc. The most common technique is using ''quadrant'. This can be temporary or permanent (fixed) or movable quadrant. Dimension may vary depending on some of the factors mentioned above. I usually use 0.25m^2' or 1m² for sampling weeds in experimental plots. All weed species within the quadrant are collected, counted and identified according to species type.  I also usually make two or three throws of quadrant per plot. Total count per specie type and for all three throws are added together to give relative abundance of each specie per treatment. In addition, I also usually determine % weed  cover, ease of control and level of aggression per weed specie type. I hope this information can be helpful.

SMKanteh,

Njala University

As i know, the name swallowort is a common name of Chelidonium majus and doesn't use for C. acutum. One of the common names of C. acutum is "Kudzu".

Shahid, therefore biological replicates will normalize such variations and give you probably a better average or conclusions.

climate of one year may be not enough, as climate is changeable, it is better to take in consideration the climate of several years. Of course, there is a relation between distribution, growth performance, etc of your studied weeds.  

If you are always studying the same species, you can do a calibration curve by measuring actual area, length and width of a leaf, and then you'll only have to measure length and with and enter them in the regression equation

Invasive shrubs such as Mimosa diplotricha C. Wright ex Sauvalle (=Mimosa invisa Mart. ex Colla) (Mimo-saceae) that impact negatively on existing plant communities  pose a threat to biodiversity, agriculture and human livelihoods. Mimosa diplotricha is a fast growing, annual (short-lived) or perennial shrubby legu-minous vine native to the Americas.

A number of herbicides such as isoxaflutole (balanced), atrazine, diuron, paraquat, etc. (applied singly or as a mixture) have been recommended for the control of M. diplotricha. In the Pacific Islands, paraquat + diuron applied postemergence has provided good control of M. diplotricha and 2,4-D + atrazine has been applied as an overall spray especially in pasture situations to control young to semi-matured stands. In Nigeria, Alabi et al. [28] reported that atrazine + me-tolachor, bentazon + propanil and acetochlor + atrazine controlled M. diplotricha satisfactorily but reduced the yield of cassava compared to hand weeded control. While it is generally advisable to apply herbicides before the onset of flowering and fruiting, repeated applications may be required depending on type of crops and the ef-ficacy of the herbicides. Melifonwu et al. [30] showed that the application of primextra (a formulated mixture of atrazine and metolachlor) followed by hand weeding were able to achieve considerable control of the weed in cassava fields in southeastern Nigeria.

Pendymethalin is used mixed with propanil 8-12 days after sowing as pre-emergent for weeds (post emergent for directed seeded rice). Could be a small affectation of rice (in not covered seeds), especially in roots (wider tips) but easily recuperated. Pendimethalin have poor solubility in water, in a normal application it remain in the soil surface and not reach the root area (position´s selectivity). Also can be used as pre-emergent in rice. In Central America is registered for rice.

Thanks

As such Cassia tora has limited industrial uses.However,it can used as greenmanure, may be by drying and making briqutes as concentrated greenmanure

This plant most likely is Lysimachia debilis Wall. In Flora of Pakistan it is synonymized with Lysimachia japonica - see http://www.efloras.org/florataxon.aspx?flora_id=5&taxon_id=250081204 . However, in Flora of China both species are kept separate - see http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200017002 and http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200017036 . I cannot find good photos of Lysimachia debilis, but as it should look similar to Lysimachia japonica, you may compare also with the latter - see http://www.asianflora.com/Myrsinaceae/Lysimachia-japonica.htm. Compare also a scan of the type specimen of Lysimachia debilis: http://plants.jstor.org/specimen/bm000021265 .

this could be a good start

Sorry the title is in english: "purple jewelweed impatiens glandulifera royle in the ojcow national park"

Try the journal called Weed Science.

Like some other weeds, "Cynodon dactylon" can be found growing under very diverse climatic conditions, and you asked for mechanisms of "adaptability".

You got several answers pointing diverse traits that can help a plant to survive in harsh dry and hot climates : C4 and CAM photosyntic physiology, accumulation of organic osmotica, particular fungal symbionts, thick or dense leaves, high concentrations of oils...

Ways of adaptation to stressing conditions are multiple. Each species, each individual displays a specific combination of more or less well adapted traits. Natural selection (and chance) act to retain only some combinations.

Phenotypic plasticity (the ability to change the phenotype in response to changes in the environment) is one of the traits that can be selected, and that can help a species to be "highly adaptable". But it may not be the only way. For instance, seed dormancy offers the ability to survive long periods that are incompatible with vegetative growth (not matter if it is because ot heat or of cold).

What is the mechanism of adaptation?

-- some mechanisms are knwon, some are still unknwon, and facing a new plant, you can not know a priori which mechanisms this particular species has got.

Do these plants contain adaptation genes?

-- of course adaptation is largely due to genes, and to the gene / environment interaction. BUT these genes are not the same in the various species.

Can these genes be transferred "transcript" to other plants?

-- for some of them it may be possible, but their identification will take some time, and you are never sure that the transfer of one gene to an organism with a different genetic background will have the effect that you expect.