Instead of toxic chemicals, use helping plants to get rid of crop pests

by Piter Kehoma Boll

Finding efficient ways to deal with agricultural pests in crops is a challenging work. Currently, as we all known, the main strategy to control such pests is the use of chemical pesticides. However, this approach only serves the interests of those seeking profit over well-being, as we all know that such pesticides increase the risk of several health issues in those consuming the crops. More than that, chemical pesticides not only kill the targeted pest but many other life forms, causing a devastating effect on ecosystems.

The cross-striped cabbageworm (Evergesis rimosalis) is a common pest in plants of the genus Brassica (kale, cabbage, mustard) in the eastern United States. Photo by iNaturalist user margaridamaria.*

Fortunately, there has been an increasing interest in finding alternative, healthier ways to deal with the problem. One way is the production of genetically modified organisms (GMOs) that are naturally resistant to pests. There are, however, two main problems with this approach. The first one is that the population in general has an irrational fear of GMOs, apparently believing that they can be more harmful than the poisonous chemical pesticides, which is completely absurd. The second problem with GMOs is that the technology to create them is dominated by the same companies that produce most pesticides and, as all big companies, only seek profit and do not give a damn about the people and the environment.

A third strategy is the use of natural enemies of the pests to control them in organic farms. Although many natural enemies are great doing their job, they may also cause negative impacts by interfering with the surrounding ecosystems. Many crop pests are not native from the area where they are pests, i.e., they are invasive species and, in order to control them efficiently, a predator from its native area must be introduced as well, and this predator may end up becoming a threat to other species that it elects as food.

Coleomegilla maculata is a common predatory lady beetle in the eastern United States. They are great to control agricultural pests locally but should not be deliberately introduced elsewhere. Photo by Riley Walsh.*

Fortunately, some nice strategies have been recently developed. One of them includes the use of additional plants in the fields that change the way that pests behave without posing a threat to surrounding areas. These additional plants consists of two types: trap crops and insectary plants.

The common buckwheat Fagopyrum esculentum has been used as an insectary plant. Photo by iNaturalist user jimkarlstrom.*

A trap crop, as the name suggests, is an additional crop that is not intended to be commercially exploited, but serves as a trap for the pests. Instead of attacking the main crop (called the ‘cash crop’), the pests are attracted to the trap crop, reducing their density in the cash crop. This system is more efficient if the trap crop is similar to the cash crop, such as another plant of the same genus, or another variety of the same species, because it must be as attractive to the pest as the cash crop, or perhaps even more attractive.

Insectary plants, on the other hand, are intended to attract other insects to the plantation, especially predatory insects that prey on the agricultural pest. Insectary plants should produce flowers in abundance, thus attracting many insect species, which will increase the interest of predators in the area. However, when used alone, insectary plants will only provide predators to control the pest in crop plants that are near the insectary plants and, as they are usually planted in an area surrounding the plantation, they would not protect the plants that are near the center of the plantation.

In a recent study, Shrestha et al. (see references) decided to combine trap crops and insectary plants together with the cash crops in a strategy that they called a ‘botanical triad’. The cash crap was organic cabbage (Brassica oleracea var. capitata) planted in the eastern United States; the trap crops were three other crops of the genus Brassica: mighty mustard (Brassica juncea), kale (Brassica oleracea var. acephala) and collard (Brassica oleracea var. italica); and the insectary plants were buckwheat (Fagopyrum esculentum) and sweet alyssum (Lobularia maritima).

Kale (Brassica oleracea var. acephala). Photo by David Adreas Tønnessen.*

As a result, the number of herbivores (i.e., crop pests) was larger in the trap crops than in the cash crop. The trap crops were, therefore, more attractive than the cash crops for the pests. The presence of insectary plants increased the number of predatory and parasitoid insects, such as lady beetles and parasitoid wasps, in the trap crops when compared to treatments without insectary plants. The number of parasitized pests also increased in the presence of insectary plants.

Field layout of the study by Shrestha et al. (2019).**

In general, the “team work” of trap crops and insectary plants greatly reduced the influence of agricultural pests on the cash crops. The trap crops attracted the pests to an area close to the insectary plants, allowing the predators to reach them.

Efficient ways to raise crops organically are possible. We just have to focus on a healthy ecosystem and not on money. If we work together, we can defeat the “Big 6” corporations that dominate the food production in the world. They are the real pests.

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Reference:

Shrestha B, Finke DL, Piñero JC (2019) The ‘Botanical Triad’: The Presence of Insectary Plants Enhances Natural Enemy Abundance on Trap Crop Plants in an Organic Cabbage Agro-Ecosystem. Insects 10(6): 181. doi: 10.3390/insects10060181

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* This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

** This work is licensed under a Creative Commons Attribution 4.0 International License.

Green turtles mistake plastic debris for dead squids, eat them, and die

by Piter Kehoma Boll

Plastic pollution is a popular topic recently and it is not rare to find pictures of animals that died due to plastic ingestion or other complications, such as asphyxia, caused by plastic pieces. However, the cause of plastic ingestion by most species is yet unknown.

Albatross with its stomach filled with plastic pieces.

The leatherback turtle, Dermochelys coriacea, is often mentioned as a species that suffers from plastic ingestion due to its diet composed primarily by jellyfish, which floating plastic bags can be mistaken for. However, another widespread sea turtle, the green turtle, Chelonia mydas, is also a common victim of plastic ingestion and amounts as small as 1 g are enough to kill juvenile specimens by blocking their guts. The diet of juvenile and adult green turtles is composed mainly by seagrass and algae, so the ingestion of plastic must be the result of another cause and not its similarity to jellyfish.

A decaying plastic bag in the ocean looks like a jellyfish. Photo by Wikimedia user Seegraswiese.*

Despite being almost strictly herbivorous, green turtles ingest animal matter when they are very young and can eventually consume animals as adults too, probably as a strategy to survive when their main food source is scarce. The ingestion of animal matter is usually done by scavenging, and a common scavenged item in their diet are dead squids.

A green turtle surrounded by seagrass, its main food source. Photo by Wikimedia user Danjgi.**

A recent study has investigated the relationship between scavenging behavior and plastic consumption in the green turtle and found out that the amount of plastic ingested by individuals feeding on dead squids is much higher than that ingested by individuals that do not present a scavenging behavior. In Brazil, plastic ingestion accounts for about 10% of the deaths of green turtles but this number may be as high as 67% among green turtles that feed on squid carcasses.

The ingestion of dead animals used to be an efficient way for green turtles to gain high amounts of protein. However, the fact that, currently, most floating material in the ocean is plastic and not dead animals turned a successful strategy into a deadly trap. If humans do not start controlling plastic waste production there will be only two possible outcomes for the green turtles in face of this new selective pressure: adaptation or extinction.

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References:

Andrades R, Santos RA, Martins AS, Teles D, Santos RG (2019) Scavenging as a pathway for plastic ingestion by marine animals. Environmental Pollution 248: 159–165. doi: 10.1016/j.envpol.2019.02.010

Mrosovsky N, Ryan GD, James MC (2009) Leatherback turtles: the menace of plastic. Marine Pollution Bulletin 58(2): 287–289. doi: 10.1016/j.marpolbul.2008.10.018

Santos RG, Andrades R, Boldrini MA, Martins AS (2015) Debris ingestion by juvenile marine turtles: an underestimated problem. Marine Pollution Bulletin 93(1–2): 37–43. doi: 10.1016/j.marpolbul.2015.02.022

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* This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

** This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Antidepressants in wastewater are unbalancing food webs

by Piter Kehoma Boll

Leia em português

Wastewater is one major cause of water pollution on a global scale and this includes domestic wastewater. With the increase in the use of pharmaceuticals of many types to treat a variety of health conditions, these substances end up in domestic wastewater and, even in places with wastewater treatment, such drugs are not always completely removed.

The most commonly detected drugs in aquatic environments include antidepressants. Although in very low concentrations, their effects on organisms are poorly known.

A recent study investigated how the presence of two antidepressants, citalopram (a selective serotonin reuptake inhibitor) and tramadol (a serotonin-norepinephrine reuptake inhibitor) affect the predatory activity of dragonfly nymphs of the species Aeshna cyanea. The insects were exposed to concentrations of about 1 microgram per liter of the substances, a concentration similar to that found naturally in environments affected by wastewaters. Additionally, they used effluents from wastewater treatment plants that included a mix of several drugs in real concentrations.

A nymph of Aeshna cyanea. Photo by André Karwath.*

The results indicate that dragonfly nymphs increase the amount of time they spend searching for food in the presence of the two antidepressants and spend more time handling prey but their feeding rate decreased, i.e., they eat less than nymphs of the control group, i.e., in water without antidepressants. On the other hand, nymphs exposed to effluent from wastewater treatment plants ate more than nymphs of the control group. The exact reason for the opposite effect caused by normal wastewater is unknown, but may be related to the combined effect of several drugs.

Although the effects do not seem to be that problematic at first, an increase or decrease in feeding rate by predators may unbalance the population of the prey species by making it increase or decrease and eventually reach a point that leads to a collapse in the ecosystem.

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Reference:

Bláha M, Grabicova K, Shaliutina O, Kubec J, Randák T, Zlabek V, Buřič M, Veselý L (2019) Foraging behaviour of top predators mediated by pollution of psychoactive pharmaceuticals and effects on ecosystem stability. Science of The Total Environment 662: 655–661.

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* This work is licensed under a Creative Commons Attribution-Share Alike 2.5 Generic License.

Friday Fellow: Beggar’s tick

by Piter Kehoma Boll

What if the cure for cancer has been living in your garden all this time and you have been trying to get rid of it because it is an annoying weed?

I cannot assure you that the answer lies in today’s Friday Fellow, but it certainly has a good potential. Its name is Bidens pilosa, commonly known as beggar’s tick, beggar ticks, black jack, cobbler’s pegs or Spanish needle.

Not extravagant, but discrete. This is Bidens pilosa. Photo by Wibowo Djatmiko.*

Native from the Americas, where it grows in open fields and forest glades, the beggar’s tick is now found worldwide, from Eurasia and Africa to Australia and the Pacific Islands. At first it does not call much attention while growing among other weeds. It grows up to 1.8 m tall and has small discrete flowers in a daisy-like head, with a handful of white ray florets and a small disc of yellow florets.

The problem with this fellow happens when you have to pass among them after the flowers have turned into fruits.

The terrible evil infructescence of the beggar’s tick. Photo by Wibowo Djatmiko.*

The fruits of the beggar’s tick are small, stiff, dry rods with about 2–4 small heavily barbed awns at the end. They are arranged in spherical infructescences are are eager to stick on any passing animal. The small barbed awns catch onto fur and clothes and the fruits are easily dispersed to other areas. It is a classical example of zoochory, i.e., seed dispersal by animals. If you live in an area where this plant is common, you most likely have had the experience of finding your clothes full of those prickling seeds, especially after playing, working or simply walking through a field.

But the beggar’s tick is much more than a dull and annoying weed. In Subsaharan Africa, it is one of the most widely eaten plants. Its leaves are edible when cooked, but have a strong and unpleasant taste.

Furthermore, the beggar’s tick is used in traditional medicine in South America and several studies have found out that it is indeed a powerful medicine. Extracts from the plant have shown several medicinal properties, including:

• Antibacterial and antifungal activity
• Antimalarial activity
• Anti-herpes simplex activity
• Ability to reduce tumoral and leukemic cells
• Immunosuppressive and anti-inflammatory effects

If this were not enough, the beggar’s tick has the ability to bioacumulate cadmium in its tissues, so that it can be used to depollute cadmium-contaminated soils.

The next time you find your clothes full of beggar’s ticks, remember that it is more, much more, than simply an annoying weed.

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References:

Brandão, M., Krettli, A., Soares, L., Nery, C., & Marinuzzi, H. (1997). Antimalarial activity of extracts and fractions from Bidens pilosa and other Bidens species (Asteraceae) correlated with the presence of acetylene and flavonoid compounds Journal of Ethnopharmacology, 57 (2), 131-138 DOI: 10.1016/S0378-8741(97)00060-3

Chang, J., Chiang, L., Chen, C., Liu, L., Wang, K., & Lin, C. (2001). Antileukemic Activity of Bidens pilosa L. var. minor (Blume) Sherff and Houttuynia cordata Thunb. The American Journal of Chinese Medicine, 29 (02), 303-312 DOI: 10.1142/S0192415X01000320

Chiang, L., Chang, J., Chen, C., Ng, L., & Lin, C. (2003). Anti-Herpes Simplex Virus Activity of Bidens pilosa and Houttuynia cordata The American Journal of Chinese Medicine, 31 (03), 355-362 DOI: 10.1142/S0192415X03001090

Deba, F., Xuan, T., Yasuda, M., & Tawata, S. (2008). Chemical composition and antioxidant, antibacterial and antifungal activities of the essential oils from Bidens pilosa Linn. var. Radiata Food Control, 19 (4), 346-352 DOI: 10.1016/j.foodcont.2007.04.011

Kviecinski, M., Felipe, K., Schoenfelder, T., de Lemos Wiese, L., Rossi, M., Gonçalez, E., Felicio, J., Filho, D., & Pedrosa, R. (2008). Study of the antitumor potential of Bidens pilosa (Asteraceae) used in Brazilian folk medicine Journal of Ethnopharmacology, 117 (1), 69-75 DOI: 10.1016/j.jep.2008.01.017

Oliveira, F., Andrade-Neto, V., Krettli, A., & Brandão, M. (2004). New evidences of antimalarial activity of Bidens pilosa roots extract correlated with polyacetylene and flavonoids Journal of Ethnopharmacology, 93 (1), 39-42 DOI: 10.1016/j.jep.2004.03.026

Pereira, R., Ibrahim, T., Lucchetti, L., da Silva, A., & de Moraes, V. (1999). Immunosuppressive and anti-inflammatory effects of methanolic extract and the polyacetylene isolated from Bidens pilosa L. Immunopharmacology, 43 (1), 31-37 DOI: 10.1016/S0162-3109(99)00039-9

Sun, Y., Zhou, Q., Wang, L., & Liu, W. (2009). Cadmium tolerance and accumulation characteristics of Bidens pilosa L. as a potential Cd-hyperaccumulator Journal of Hazardous Materials, 161 (2-3), 808-814 DOI: 10.1016/j.jhazmat.2008.04.030

Wikipedia. Bidens pilosa. Available at < https://en.wikipedia.org/wiki/Bidens_pilosa >. Access on July 31, 2016.

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This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.

Friday Fellow: Red Euglene

by Piter Kehoma Boll

Don’t be as fool as the Egyptian Pharaoh in the myth of the Plagues of Egypt. If you happen to find a lake with red water, as in the picture below, it is certainly not blood. It’s simply… a toxic alga!

Sometimes one may find the waters of a lake turned red. Photo extracted from naturamediterraneo.com/forum/, posted by user Carlmor.

The creature responsible for this coloration is today’s Friday Fellow: Euglena sanguinea, or the red euglene, a microscopic freshwater protist with a worldwide distribution. This unicellular organisms has a red color due to the presence of astaxanthin, a pigment also found in some fish, like salmon, and in crustaceans, like shrimp and crayfish. Some birds may also have this pigment in their feathers. In red euglenes, astaxanthin acts as a protection against ultraviolet radiation, so that the higher the amount of UV radiation, the redder the algae become.

A fraction of a population of red euglenes under the microscope. Photo extracted from naturamediterranea.com/forum/, posted by user Carlmor.

When the conditions are adequate, usually due to high temperatures and high amounts of nutrients, the red euglene may overpopulate and cover the entire surface of water bodies, making it appear red. Water pollution, especially from domestic wastewater, is one of the main causes of nutrient increase in water bodies and thus a direct cause of many algal blooms.

The red euglene is known to produce euglenophycin, a very potent ichthyotoxin, i.e., a compound that is toxic to fish. As a result, red euglene blooms can lead to high fish mortality, making it an organism of major concern to fish breeders.

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References:

Gerber, S.; Häder, D-P. 2006. Effects of enhanced UV-B radiation on the red coloured freshwater flagellate Euglena sanguinea. FEMS Microbiology Ecology, 13(3): 177-184. DOI: 10.1111/j.1574-6941.1994.tb00064.x

Wikipedia. Euglena sanguinea. Available at <https://en.wikipedia.org/wiki/Euglena_sanguinea&gt;. Access on  January 07, 2016.

Zimba, P. V.; Rowan, M.; Triemer, R. 2004. Identification of euglenoid algae that produce ichthyotoxin(s). Journal of Fish Diseases, 27: 115-117.

The World Beyond Your Trash Bag

by Piter Kehoma Boll

It’s been a while since I had the idea of writing a post about the garbage problem, but it’s difficult to find the best way to start it, so let’s try to simply talk and see how it flows.

Some months ago, as part of a field activity, I visited with some colleagues and a professor some places intended to manage waste. At first we thought it would be a boring day seeing garbage everywhere, but it wasn’t boring at all. In fact it was very enlightening.

After that day, I can say for sure that we have no idea about the horror caused by our garbage. We are used to simply throw our waste in the trash bag and let the truck take it away, just as it would miraculously disappear and everything would be fine. Well… that’s not what happens.

We visited a landfill in the city of Campo Bom, which has a population of only 64 thousand people and receives about 50 tons of waste every day.

Garbage accumulated in the last hours. Beautiful, huh? Photo by Piter Kehoma Boll.

The place was full of vultures and herons scavenging the waste. Photo by Tiago Finger Andreis.

A recycling plant operates with the landfill where about 40 workers sort the garbage on a conveyor belt, but only about 4 to 6 % is recycled.

Conveyor belt where the garbage is sorted. Photo by Tiago Finger Andreis.

The rest is sent to the landfill where it will be buried, leading to many potential impacts to the environment, including soil and water pollution due to the leakage of contaminants, as well as by the solid residues themselves. It can also pollute the air by releasing methane from the decay of organic material and cause injuries to wildlife.

The landfill already full. This waste will never be recycled. Photo by Piter Kehoma Boll.

All those impacts could be greatly reduced if most of the waste material could be reused. So we may ask why so little of it is recycled. Well, in part it is our own fault because we don’t care so much about the way we discard our waste.

Most people simply throw everything together. Organic and inorganic waste are not set apart and, even when people separate fruit peels from plastic, they still mix a dirty plastic container with remains of yogurt with paper and other stuff, causing the organic remains to flow over other clean materials and many times causing them to become unfeasible to recycle.

Recycling, however, faces many other challenges. Many materials are not designed to be recycled, so the most common forms of “recycling” don’t include the reuse of the material for the same purpose, but rather to another. For example, most white paper is recycled to become paperboard and not new white paper. It does, of course, reduce the amount of raw material necessary, but not always targeting the most critical points.

That’s why recycling is connected to the other 2 Rs in the 3R concept: reduce, reuse, recycle. We should try to use less resources and buy less things (reduce), but once we acquired something, we must try to use it as many times as possible (reuse) and, after not being able to go on using it, we got to find a purpose other than throwing it away (recycling).

I’m telling all this stuff and you are probably thinking that you hear that all the time. Yeah, maybe, but I wish everybody visited a landfill someday to see with their own eyes the tragedy that we are causing to our planet due to our unbridled consumption of resources.

To finish, I would like to share an interesting graph that was presented to me by Meika Jensen from MastersDegree.net. It deals with the problem of ocean pollution, something directly related to waste management. Take a look: