The tropical soda apple plant is a herb that grows quite fast and can take over a field in a year or two. Its aggression calls for swift action before the plant can establish itself. When left unmanaged, this plant can infest pasturelands, leaving little foliage available to animals.
This species can produce as many as fifty thousand seeds per plant. Once the seeds are mature, dispersal takes place by way of animals and birds. The most notable means of dispersal are birds, cattle, and raccoons, which frequent the infested areas.
Humans, too, are to blame for the dispersal of the seeds. Not only do they use infested manure on crop fields, but they also use machinery in infested areas. There have been cases where people cultivated grass contaminated with the seeds, thereby aiding in the spread.
Once this herb establishes in an area, it forms a form of monoculture by weeding out the native species. It can do this at a fast rate, and that is why most patches of its establishment are in the ranges of hectares.
According to the US department of agriculture, the tropical soda apple is a noxious weed. Some of the affected regions include Florida, Puerto, Vermont, Mississippi, and Tennessee. In other areas, it falls under the classification of a weed.
This weed is likely to infest areas with overgrazing, as well as drought-affected regions. It also affects natural habitats such as forests and riverbanks. Plantation crops are also not safe from its effects. Given how large the infestations are, it would be great if animals could feed on the foliage. But this is not the case as they find it unpalatable. Instead, they feed on fruits and pass on the seeds over a large area.
Let us take a closer look at this plant and what you can do to prevent or control its growth.
Tropical soda apple identification
When mature, this species will have a height ranging from three to six feet, depending on the conditions available. Its width also varies, and it can be as wide as it is tall.
The stems, leaves and flower stalks all have broad bases. The leaves measure four to seven inches in length, and two to six inches in width. They have broad and pointed leaves with clear divides. Thorns can be white or yellow, and they measure up to zero point four inches in length.
The tropical soda apple is a flowering plant with white or yellow stamens occurring along the stems, under the leaves. From these arise fruits that measure about one inch in diameter. When mature, the fruits turn bright yellow. Inside the fruits are red-brown seeds, which measure about a tenth of an inch. They are slightly flattened, and they occur in a gummy layer. A single fruit can contain up to four hundred seeds.
Roots have a budding system which leads to the generation of new shoots. The root system can be extensive where the conditions are ideal, featuring feeder roots a few inches below the ground.
Identifying this plant is easy thanks to the ovate leaves and yellow fruits. All you need to remember is that it is a herbaceous and broad-leaved perennial plant with yellow fruits. If you come across such a plant in your outdoors, you need to take action immediately before dispersion begins.
Look-Alikes
There are many Solanum species in the globe, and this can lead to confusion during identification. A good example would be the Solanum capsicoides, which is quite similar to S. viarum. However, you can tell the two apart by looking at the fruits. For the capsicoides, the fruits are bright orange. But for the tropical soda apple, the fruits feature a yellow color.
You can always distinguish the Viarum by looking for straight thorns, petioled leaves, and yellow berries.
Affected Regions
This weed has spread to different places since its introduction, but some regions seem to have suffered its effects more than others. It is native to the south of Brazil, Paraguay, Argentina, and Uruguay. It got introduced to states to the southeast of the United States as well as some parts of Asia, Mexico, Honduras, and South Africa. Asian countries affected include India and Nepal.
Where it has affected a region, most of the concern lies in the fate of agriculture, as well as foliage production for animals. India is especially affected by tropical soda apple as it occurs in most regions in the country.
This invasive plant can spread to other areas with ease, thanks to its aggression. It is, therefore, necessary that people take steps to control it before it makes its way to other subtropical and tropical regions.
Tropical soda apple introduction
All invasive plants have a history of introduction to places where they were not native. What followed was naturalization before people realized that the plants were a threat to their ecosystems. The same goes for the tropical soda apple, which is native to South America. It got introduced to other regions such as Asia, Africa, and North America.
In India, its cultivation took place over a long time owing to its medicinal benefits. By the time it was evident that the plant was indeed a weed, it had spread over a large distance.
In the United States, the spread occurred as the seeds adhered to people, animals, and machinery traversing the infested areas. Also, contaminated grass seeds are to blame for most of the spread. Take Florida as an example. The first recording of tropical soda apple, coupled with its collection, took place in 1988.
Studies show that the introduction probably took place via cows carrying undigested seeds of the weed. The cows were from Brazil, where the plant is a native. From here, it was easy for the plant to spread to other states, such that the weed is now present in California. It has taken over four hundred thousand hectares of pasturelands in Florida, earning it a place in the noxious weeds list.
In Australia, a sighting of tropical soda apple took place in New South Wales in 2010. However, studies show that the plant was probably present in the land for a long time before this sighting. Subsequent studies show that it has spread to more areas in the East, raising concerns over the safety of the pasturelands.
Other affected regions include South Africa, where the sighting took place at the beginning of the 21st century, and Puerto Rico, where detection took place in 2006.
Spreading to these regions in a short period shows how aggressive this weed can be. It has not only affected pasturelands but also weeded out native plant communities in the areas affected. What’s more, it also threatens crop fields, therefore, posing a threat to agricultural land productivity. And if left uncontrolled, there is no telling how many more regions it could affect.
Tropical soda apple spread
Several studies have focused on the tropical soda apple, and they all seem to come to the same conclusion- this plant is highly invasive. For one, it can produce thousands of seeds per plant. Two, animal and human activities greatly aid in the dispersal of the seeds. Three, it can survive through regeneration from the thriving root system. Therefore, its spread is imminent in any area it establishes.
It gets worse because some communities rely on it as a source of medicine. Pharmaceutical companies also reap compounds from this plant, most notably solasodine. As such, efforts to eradicate this plant may get thwarted by attempts to establish new growths in other regions.
However, there are measures in place to ensure that tropical soda apple does not spread to other regions. In the USA, this plant lists as a noxious weed. It is, therefore, illegal to possess, sell, or release it into the environment.
Where and how does tropical soda apple grow?
Its growing conditions will depend on where it establishes. Where it grows in a native area such as Brazil, it will thrive in disturbed places. That is to say, you can find it along river banks, roadsides, forest trails, and other such areas. It also shows a preference for thickets and grasslands where the conditions prove favorable.
Where it gets introduced in an area, such as Florida, the growth pattern changes. As such, it will establish like a common weed would. It takes over natural areas, agricultural land, and pasturelands. In this way, it threatens native species, crops, and animal foliage. It also takes a liking to disturbed areas with a lot of human activity.
Reproduction
When a plant establishes, it flowers when the conditions prove to be ideal. The flowers lack nectar but have pollen, which insects can collect. The flowers depend on insect pollination, with bees forming the larger part of the insect visitors. Fruits then develop releasing mature seeds into the environment. It helps to note that seed production from a single plant is quite high in the ranges of thousands. Plus, the seeds can survive in the soil for up to one year before they sprout.
Other than surviving on seed production, the plant can also grow from root regeneration. Where frost kills shoots, the plant can reproduce through the formation of new shots from the extensive root system.
When seedlings emerge from the ground, they take an average of two to three months before they can start flowering. You should note though that this will depend on the photoperiods at the time. Plants require an average of eight hours of sunlight for flowering to start.
The temperatures should range from twenty degrees Celsius going up. If they are lower than this, flowering will not take place. When frost is present, leaves can get damaged, and this would negatively affect the flowering process.
It is also important to note that though this is a perennial weed, it can start fruiting processes within its first growing season. It thus has some characteristics that are similar to what you would find in an annual plant.
Germination
The flowering and fruiting processes will depend on the area in which the plant establishes. In its native region, the tropical soda apple will produce flowers and fruits throughout the year. In this way, seed production is at a very high level. But in non-native regions, these processes take place during a set period.
Take Florida as an example. The reproduction period lasts from September to May, taking a break for about three to four months, before it continues. However, you will find that fruits are present on the plant throughout the year, though some may not be mature. In this way, seed production is high, and a plant can release as many as fifty thousand seeds in a year.
Seedlings start emerging as of August, and this continues till March. However, the presence or lack thereof of the seedlings will depend on the prevailing conditions. Some seedlings emerge from the dispersed seeds, while others are a result of root regeneration.
Germination of the seeds relies on the presence of light, as dark conditions limit the success rate of the same. It also depends on the temperature range prevailing at the time. When the temperature range is between ten and thirty degrees Celsius, the germination rate is high. But when it goes below five or over forty degrees Celsius, no germination takes place. Thirty degrees Celsius is the optimum temperature for germination, with the highest rates recorded for this weed.
The depth of the seeds will also affect their germination. The closer they are to the ground surface, the higher their chances of emerging. Where the seeds are deeper than five inches in the soil, they will not germinate. However, disturbance could bring them closer to the surface. And if this happens within a year of dispersal, they could grow.
Seeds have a higher chance of germination if they are at least one inch inside the soil, up to two and a half inches. The best results show when the seeds are two inches in the ground.
Scarification of the seeds also affects germination. However, it does not affect the chance, but rather, the rate of the same. Pre-treated seeds will emerge at a faster rate than those without this exposure.
As such, it is clear that the germination of seeds, or lack thereof, will depend on the prevailing economic conditions and the state of the seeds. That is why the germination rates and chances vary from one region to the other.
Growth
The tropical soda apple does best under sunny conditions where the temperatures range from twenty to thirty-five degrees Celsius. Rainfall should range from seven hundred to two thousand millimeters per year for the plants to do best. Where the plants are in waterlogged soils or icy conditions for a long time, they will not thrive.
Who/ what does tropical soda apple affect?
The tropical soda apple mainly affects cattle farming and crop cultivation. It thrives in pasturelands where it weeds out native grass species. In this way, animals have less feed, and this affects the cattle carrying capacity of the said land. What’s more, it also acts as a host for crop viruses that affect potatoes, tomatoes, cucumbers, and tobacco. Thus, when the weed establishes in a crop field with these plants, the chances of disease spread increase. Insects also use this plant as a habitat, aiding in the spread of disease-causing organisms.
Can you use tropical soda apple?
All through this article, there have been mentions of the usefulness of the tropical soda apple in medicine. India is an excellent example of this. Farmers actively plant tropical soda apple in the hope of reaping compounds that they can use for both traditional and modern medicine. Why is that?
Well, this weed contains solasodine, which has uses in the contraception industry. There have thus been numerous studies on what can get done to increase the solasodine levels in the fruits. Some studies have delved into the productivity of the fruit when grown in fallow land, as well as intercropping the weed.
Traditionally, Indians have used the fruit as a cure for colds, coughs, and other respiratory problems. It also works for toothaches and wounds. The seeds work great in dealing with menstrual issues, and they are highly effective as contraceptives. They additionally use the fruits to treat dogs suffering from Dirofilaria immitis. See? There is a silver lining on this cloud, after all.
Tropical soda apple threats
Let us take a look at how this plant could spread over a large area and its impact on the affected regions.
Dispersal
The tropical soda apple has two means of dispersal: seeds and shoot generation. Thanks to its extensive root system, it can form new shoots as it spreads below the ground. Additionally, it relies on seed production, with a single plant giving rise to as many as fifty thousand seeds. Once the seeds are mature, dispersal takes place through animals that feed on the fruits. Animals do not have a liking for the foliage as it is unpalatable. However, they enjoy the fruits, and they spread the seeds through fecal matter.
Humans then come into the picture. When purchases of cows take place over long distances, a farmer would likely buy cattle with undigested seeds. Once the animals pass fecal matter, the seeds would spread over a large area. The seeds also make their way into hay and manure, which also get distributed over vast distances. When this happens, it gets termed as an accidental introduction. It is where you introduce a new species into a non-native environment, without an intention to do so.
Where the plant grows near water sources, dispersal is possible through the water channels. This form of dispersal falls under natural means.
And then, there is an intentional introduction. A good example would be in India, where people look to this crop as a source of medicine. Through actively cultivating it, farmers encourage its spread over large areas.
The main modes of dispersal at present are movement of cattle, manure, and hay across regions and animal activities.
Impact
The introduction of the tropical soda apple weed to a non-native region will have both environmental and economic implications as shown:
Economic
This weed thrives in pasturelands and crop fields, as well as disturbed areas such as roadsides. It can spread at a fast rate, more so when it establishes in grasslands. Environmental conditions could also favor its growth. For example, if a region is undergoing drought, animals would feed on the remaining foliage while avoiding this weed. As a result, the weed would have little or no competition as it spread through an area.
Animals cannot feed on the foliage and stems of tropical soda apple, and the cattle carrying capacity of the land in question would reduce. And a farmer would lose out on returns they would have gotten were it not for the invasion.
Furthermore, this weed forms a monoculture and will thus occupy a large patch of the land. This dense growth keeps the animals from accessing both foliage and shade in the heat. As a result, farmers have to come up with measures to deal with the weed. Studies show that farmers in Florida have to invest an average of six to sixteen million dollars in control methods each year.
Heat stress resulting from lack of access to shade leads to losses amounting to two million dollars per year. And that is not all. There have been cases where ingesting of the stems and foliage of the tropical soda apple has poisoned goats. All these scenarios have resulted in avoidable losses in revenue.
Crop farmers are not safe from the effects of this weed as they, too, have had their share of encounters. This plant acts as a host to a ton of viruses that affect potatoes, tomatoes, and cucumbers, among other crops. In so doing, it predisposes plants in invaded crop fields.
Furthermore, insect pests such as potato beetles and green peach aphids use the weed as a habitat. Farmers, therefore, have to be wary of its presence and deal with it immediately. Not only do they lose millions of dollars owing to affected crops. But they also incur considerable amounts of money in controlling the invasion.
Where farmers resort to using herbicides on the invaded lands, they can expect to spend as much as sixty dollars per hectare. Mowing will set them back an average of fifty dollars per hectare. Florida, alone, has recorded as much as fifteen million dollars in losses, owing to control measures in the state. That is a lot of money.
Environmental
If a tropical soda apple plant establishes in an area, the ecosystem balance will be at risk. It competes with native plants for nutrients and water by creating a monoculture and shading the plants. In this way, the native vegetation lacks what it needs to thrive and starts reducing in numbers. It does not help that tropical soda apple spreads fast, which gives it the upper hand over other plants.
Wild animals bear the brunt of its spread as it keeps them from accessing grazing areas. They are also unable to move through natural areas with ease, owing to the monocultures around them.
Summary
With animals and plants under threat, biodiversity is at risk. To make matters worse, it can adapt to a range of environments and will tolerate browsing pressure, mutilation, and fires. It grows fast and reproduces even faster as it releases seeds into the environment, which can last up to a year.
As a result, it damages the ecosystem by forming monocultures and threatening native species. It adversely impacts the livelihoods of people dependent on crop cultivation and cattle farming while altering the conditions of the habitats. Controlling it is costly, and it dents farmers’ economic returns.
Tropical soda apple management
At this point, it is evident that lack of control measures would only lead to the spread of tropical soda apple, owing to its aggressive nature. Here are ways to keep it from spreading, as well as how to deal with invasions.
Prevention
If you do not have the tropical soda apple weed on your farm, you are in luck. All you need to do is to ensure that it does not get introduced.
Abide by the law
The first thing you should note is that it is a noxious weed. You should thus ensure that you do not play any part in possessing, moving, or releasing tropical soda apple to the environment. If you come across anyone selling this plant, be sure to educate them on the same. It also helps to talk to your neighbors about the effects of this weed to keep them alert on its dangers.
Talking to relevant authorities will also help you stay in the know when any introductions happen. You will also have adequate material on how to deal with invasions according to laws in your area.
Control Movement
If you buy cattle, always keep them in a restricted area for at least a week. In this way, you can monitor the cows and ensure that they pass all fecal matter before releasing them. If they come from an infested area and have ingested any seeds, they can pass them, and you can get rid of the same. This restriction also helps you look out for any ailments that they could pass to the rest of the herd.
It is also crucial that you buy weed-free pasture as this will ensure that the cattle do not pass infested fecal matter. If your farm has an infestation and you wish to sell the animals, start by restricting them to a confined area. Here, you can feed them weed-free pastures to ensure they do not spread seeds to the buyer’s land.
If you use equipment in an infested area, you should ensure that you clean it thoroughly before using it on a clean patch. Failure to do so can lead to the spread of seeds or root fragments. Vehicles entering your farm should get cleaned to ensure that they do not bring in any contaminants. If your land has an infestation, you should clean cars as they leave to prevent any spread.
Prevention of weed spread starts with you.
Tropical soda apple control
Suppose you already have an invasion, all is not lost as there are many measures you could take. It is important to note, though, that eradicating tropical soda apple is difficult. As such, you will need to employ various tactics when dealing with the infestation. Here are some considerations before using any control measure:
Points to note
When choosing a control method, you need to think about the size of the population, the amount of capital and labor you can afford, and the success rate of the same.
Also, the use of herbicides should take place based on the rules in your region. As such, you should always consult with the relevant authority before purchasing any chemical. You should also consider its effect on the native vegetation in your area, lest you end up distorting the ecological balance. Manufacturers always state the guidelines for each chemical, and abiding by the same would prove safe for you and native species. That said, let’s delve into the specific methods.
Physical
Using manual means calls for the use of labor, and the costs of the same can thus run high. Whether you use mowing or pulling will depend on the extent of the invasion.
For small infestations, pulling and burning of the plants and fruits has been shown to work. When pulling out weeds, you should wear gloves as the plants have prickles that can injure the hands. As long as you remove all the roots and their fragments, regeneration will not take place. However, repeat procedures may be necessary to deal with the infestation adequately. Disturbances in formerly infested areas are not advisable as they could encourage re-sprouting.
Where you are dealing with a large invasion, you will need to integrate the control methods for enhanced success. The best thing would be to start dealing with the invasion before the fruiting season, as this will prevent the spread of seeds. A good integration, in this case, would be mowing, followed by herbicide application.
The mowing process should be continuous and aimed at reducing the plant sizes to less than four inches. You should do this every two months or so before fruiting starts. In this way, the plants can die off to some extent. Most importantly, fruiting will not take place, and seeds cannot get dispersed.
Physical methods, on their own, are not sufficient for large infestations, and it is, therefore, necessary to use integration.
Biological
Biological agents to control the tropical soda apple have been in place since the beginning of the 21st century. The first introduction was the Gratiana boliviana, a beetle from Argentina and Paraguay. Given the high infestation in Florida, the first introduction took place in the state. To date, more than a hundred thousand beetles have established within Florida and nearby states. The beetles spread at a distance of one to ten miles per annum, working on the foliage of the tropical soda apple.
Their introduction has been a success as they have not adversely affected native vegetation in the affected areas. However, their success rate depends on the extent of the infestation. For small monocultures, the beetles would be an ideal control measure. The same does not hold for large outbreaks as using beetles for eradication would take a considerable amount of time.
Other biological agents are under research at the time, with hopes that they, too, will have positive results. A bio-herbicide is now in circulation, aiding in the eradication of tropical soda apple.
Chemical
Using herbicides on tropical soda apple has proven to be an effective means of control. For best results, farmers should collect fruits and burn them to ensure that they do not disperse any seeds. Leaving them around would lead to the establishment of weeds over time. When choosing a chemical, be sure to choose one suited for tropical soda apple and one that will not affect native plants.
The application of the herbicide will be as per the given manufacturer guidelines. Timing plays a vital role in the effectiveness of the said chemical. Some require application after cold months, others bi-annually, and others will work at any time. The visibility of the results will depend on how fast a chemical works.
Mowing, followed by herbicide application, has been shown to work best. Compared to biological and physical methods, using chemicals on large infestations works best.
Integration
Integrating various methods is the best way to deal with any infestation. You start by ensuring that you contain infestations and that they cannot spread to other areas. Doing this is possible through controlling animal movement, buying uncontaminated feeds, and using control measures. Combining bio-herbicides, herbicides, and manual controls is an excellent way to deal with large infestations. For small infestations, you can combine biological and manual methods, coupled with periodic monitoring.
Conclusion
Dealing with the tropical soda apple will set you back a couple of hundred dollars, depending on how large your farm is. But letting the weed spread over a large area could be the end of your farm’s productivity, both in crop and animal farming. It is thus best to deal with the problem immediately it occurs.
