Mexican Researchers Observe Self-Governing Control of Scale Insects

Biologist Juan Manuel Vanegas-Rico

This will be a reprint of an article Entomology Today April 6 2016, which I bookmarked for later use. The fascinating subject is about that common white scale insect (Dactylopius opuntiae) which feeds on Prickly Pear Cactus. This insect turns blood red when you mess with it. I've really only ever found it on the common Cactus Plantation cultivators brought up from Mexico, (Opuntia megacantha) when I live in California, but often encountered it in the urban commercial landscapes I once maintained in and around San Diego, California. My way of control was using a high pressure washer with a water wand setting at a low volume, but high powered action. Even then those little buggers were tough to detach from the cacti pads.

Photo by J.A. Cruz-Rodríguez

 A prickly pear plantation in Axapusco,
Estado de México, México.

Entomology Today:

"Scale insects known as cochineals are major pests of prickly pear in Mexico, and pesticides are often used to control them. However, one prickly pear farmer has been controlling them without the use of insecticides since the year 2000."

"The farmer tipped off a team of scientists from the Universidad Autónoma Chapingo, and he told them that other insects were feeding on the scale insects. The researchers decided to investigate, and they found that the farmer was right. During the entirety of the research, the abundance of scale insects never reached pest status. Furthermore, when populations of scale insects increased, populations of predators increased at the same time, therefore regulating the growth of the scale insect populations. Their observations are described in an article in Environmental Entomology 

Did you take special note of a few key points in the article ? First the farmer of this plantation has been controlling the white scale insects without pesticides since the year 2000. He contacted researchers about predators doing the job for him. Now pay close attention to this single sentence from that second paragraph below here:

"During the entirety of the research, the abundance of scale insects never reached pest status."

The Scale insects never reached "pest" status ??? That would lead one to believe that the white scale is not all that evil when it is in balance. This is true of most all insects, even things we consider weeds in the plant world. Humans tend to judge things in Nature on human terms. Even Darwin did this when he wrote that letter to a minister named Asa Gray in 1860, where he referenced the example of a parasitic wasp which lays eggs on a caterpillar for the expressed purpose of it's young feeding on their host while going through a life stage development. To Darwin, this was absolute  proof that there could not be an omnipotent benevolent God. But exactly how did Darwin arrive at that conclusion ? He was a scientist right ? So what experiment or testing did he use to arrive at such a conclusion of what an intelligent entity which he said never existed, would or wouldn't do and can this experiment be repeatable for any one of us to arrive at the same conclusion ? Today Darwin's staunchest and most diehard defenders use these same fallacy arguments by using untestable metaphysical statesments for their scientific worldview. That's not to say that any of these questions are not legitimate ones, they definitely are. But they are religious questions, not scientific ones. Even the conventionally religious people cannot draw on any conclusions about why their God would do things in such and such a way through any experimentation. This doesn't mean they can't believe or have a faith in a certain way, but using science to test the whys and/or hows of creation by means of scientific research and writing a paper about it are near impossible. Take the origin of liffe experiements, both sides lose here. No one can prove by science how life emerged on Earth by experiment to create life. To be totally fair, this conclusion wasn't Darwin's fault either. Darwin like all of us was a human being on Earth who judged Nature on the basis of human concepts of good, bad, righteous, evil, etc. But still today, we all do this. Even myself at times. Hence when farming, landscaping, gardening or anything else, we all tend to judge any pests as an evil that needs to be obliterated from off the face of our own little world. Then we turn to industrial science for the poisons they manufacture to provide us relief. But it's not just the average person who reasons this was, highly education individuals with alphabet soup initials after their names on a business card follow this same flawed human reasoning as well, see the example here (Scientists Justify Mosquito Extermination from Earth)  Okay, let's continue:

"The farmer originally thought that ants were controlling the cochineals, but it turned out to be other insects. Six known predators of cochineals were found on the plantation, including different species of beetles, moths, lacewings, and flies — but no ants."

"This finding is important because the two most common ways to control scale insects in prickly pear in Mexico are 1) to use organophosphates, a class of insecticide that Mexican regulatory agencies do not recommend for this use, or 2) to knock the insects off of the plants using mechanical brooms. This study suggests there might be an alternative: natural control as a result of biodiversity, also known as autonomous self-governing control."

Photo by J.A. Cruz-Rodríguez

Colonies of scale insects (Dactylopius opuntiae)
 on fruits of a prickly pear (Opuntia megacantha)

"However, Dr. J. A. Cruz-Rodríguez, an author on the paper, warns that this method of control isn’t necessarily one that can be applied at will to other plantations or crops."

"Autonomous biological pest control cannot be considered a technology that is applied or not depending on the level of the pest,” he said. “It is a process that is established and maintained if the agroecosystem retains structural complexity and diversity of species."

"In other words, a lot of conditions must be met in order for autonomous self-governing control to be viable."

This is where people need to sit back and ponder, meditate and slow down and reason on any action to be taken with regards any possible biological controls and not automatically dismiss the idea that it cannot be done under every situation. While the researchers say the success the Mexican cacti plantation farmer had cannot be replicated for other crops, their next statement gives clues as to the error in their judgement on this:

"Autonomous control requires an ecological infrastructure that supports a network of interactions that limit the explosive growth of herbivores,” Cruz-Rodríguez said. “Intercropping, agroforestry systems, non-use of biocidal products (or its more rational application) — they all contribute to the formation of the biotic network that prevents the development of pests.This study shows that if the conditions are right, farmers can potentially use natural predators for autonomous control."

(Source)

This last paragraph really says it all and actually allows for the door for biocontrol for other crops to remain open. Not only scientists, but anyone should proceed and experiment on their own as a sort of what is being called a "citizen scientist" and share successful results with others. Believe it or not, professional researchers learn very much from people considered layman who have a natural passion for a specific phenomena found in Nature. Remember, even in healthy forested environments where all vegetation looks perfectly healthy, the insects and plants otherwise considered pests or weeds are still present, but their numbers are kept in check through a complex infrastructure of biological controls. Learning what those are can be fun and rewarding. Now let's look below at some information about this white scale insect you probably never knew. Did you know that in many places around the globe like Mexico and Iran, they are farmed for their red dye ingredients potential for the fabrics industry ? Below is a photo of an Iranian Cacti  plantation which has these little baskets attached to prickly pear pads. Click on the link below the photo of an Iranian website in English which goes into great deal on how this so-called pest is an income earner for some Iranian Farmers.

Farming Cochineals scale insects (Dactylopius opuntiae), for their raw material for the manufacture of Red dye

http://iranpazirik.com/htmls/cochincal.htm

"Cochineals are farmed in the traditional method by planting infected cactus pads or infecting existing cacti with cochineals and harvesting the insects by hand. The controlled method uses small baskets called Zapotec nests placed on host cacti. The baskets contain clean, fertile females which leave the nests and settle on the cactus to await insemination by the males. In both cases the cochineals have to be protected from predators, cold and rain. The complete cycle lasts 3 months during which the cacti are kept at a constant temperature of 27 °C. Once the cochineals have finished the cycle, the new cochineals are ready to begin the cycle again or to be dried for dye production."

"To produce dye from cochineals, the insects are collected when they are approximately ninety days old. Harvesting the insects is labor-intensive as they must be individually knocked, brushed or picked from the cacti and placed into bags. The insects are gathered by small groups of collectors who sell them to local processors or exporters."

Wasn't that a fantastic explanation on a subject most of us had no clue existed or could even imagine possible ? You'll find similar circumstances with many other plants and insects throughout the world. Believe it or not, most people in the industrial countries are often totally ignorant of the reality of the natural world around them and the potential for ecologically viable business possibilities. Finally one last look at that website and a quote about other nation economies who make a living with this, *cough-cough*,  Pest.

http://iranpazirik.com/htmls/cochincal.htm

"As of 2005, Peru produced 200 tonnes of cochineal dye per year and the Canary Islands produced 20 tonnes per year. Chile and Mexico have also recently begun to export cochineal. France is believed to be the world's largest importer of cochineal; Japan and Italy also import the insect. Much of these imports are processed and reexported to other developed economies."