Citrus leafminer: the nature learned to control it

For the small bird Chiffchaff its larvae are a food of Gods

The citrus leafminer is an insect of scientific name Phyllocnistis citrella that in its larvaria phase lives as parasitic under cuticle of the leaves and tender shoots of  the citrus trees of any species, feeding on the vegetal cells to which empty perforating its cytoplasmic membrane and sucking its liquid content. Exceptionally, in the absence of leaves, also it can parasitize the green fruits.

 Citrus leafminer in underside of a leaf of mandarin tree very affected in the middle of July of year 2006. The plague was at the algid moment of its expansion. It is appraised as the caterpillar goes with well-taken care of of not breaking cuticle that serves to it as protection. It advances taking off it of the cells and after perforating the cellular membrane it absorbs all their content

This parasite is original of Southeast Asia, where it has coexisted with its guest, the citruses, during million years. Due to the height of the commerce and interchange of plants and animals at world-wide level at the end of century XX it began to expand towards Australia, Near East and Africa, arriving at the south of the Iberian Peninsula in August of 1993, being detected for the first time in Malaga. In the following months it went extending towards all the coastal subtropical and Mediterranean climate regions from the Mediterranean river basin where citruses are cultivated and in 1994 it arrived at the Island of Majorca. The Soller Valley, famous by its great plantations of excellent citruses, few months one became a very harmful plague, preventing the trees to renew its leaves when destroying the new buds.

Detail of the caterpillar of the citrus leafminer who is leaving behind himself a thread of defecations. In the other half of the leaf there is another leafminer.

 When the caterpillar reaches the adequate size after happening through four phases of growth, it realises the last dumb and it is transformed into pupa, whose mouth in the form of tube secretes threads of soothes to generally form the pupal camera closely together of the edge of the leaf. Finished their work of weaver, the threads of soothe are dried and dissuaded, which causes that the leaf bends on the pupal camera, thus being protected and outside the view of its predators. Days later the winged adult leaves and after the fertilization the female looks for tender buds and puts its transparent eggs on the future leaves that still are forming.

 Already empty pupal camera in September after the exit of the adult. The edge of the leaf is seen well that bent inside towards protecting the nymph while it was being metamorphosed.

The leaves very affected are become deformed, the eaten part is dried and the tree finishes coming off itself them. When the attack is very intense the citrus is not able to bring forth new leaves and must survive with old, that is to say, those that already it had before the beginning of the plague, which they hold without falling more time of the normal one so that the tree does not die drowned for want of leaves that are its lungs and their food factory through the energy of the sun. Four years after the beginning of the plague many trees practically were defoliated, realising the photosynthesis through the green crust of their more tender stems. They were condemned to a safe death in two or three years.

The fruit and vegetable agriculturists of Soller were scared before the virulence of the plague and looked for remedies in the Cooperative. Nobody knew nothing of this new disease of the citruses. At the outset they tried with classic insecticides, but they did not work, soon arrived from the USA the supposed specific pesticide for this parasite at a prohibitive price for the battered economy of subsistence of the majority of agriculturists. Thousands of former pesetas were spent without no result. The frustration and the sensation of impotence were very great, until the point that many market gardeners occurred by won and accepted to lose for always their magnificent orange trees, lemon trees, mandarin trees and grapefruits. They let then fumigate its citruses with useless pesticides with the conviction that in fact everything had been a assembly to remove the money to them, including the appearance and inexplicable sudden expansion of the plague, as if some multinational was behind everything. 

Tender leaves of the citrus Severina buxifolia attacked by the citrus leafminer. In my garden I could verify as the leafminer did not have any special preference by a determined species of citrus, it the same attacked but them all whenever they tried to bring forth new leaves. Aside from the orange trees, lemon trees, mandarin trees, clementin trees, grapefruits and the Severina of the photo, also affect to Fortunella margarita or Kumquat, the pamplemusa, the chironja of Puerto Rico, the citron " Buddha´s hand" , the Atalantia citroides, the citrangequat, the limequat and the calamondin.

 Leaves of the Australian citrus Microcitrus australasica half dry after partially being eaten by the leafminer of the citruses.

And then came the moment of master acting of nature. From the year 2000, about 6 years after its arrival to the island, the plague began to diminish inexplicably, every spring were less affected buds, many leaves managed to grow whole and the citruses little by little were covered again with splendid treetops of intensely green healthy leaves. What was happening? 

The scientists of the University of the Balearic Islands along with the technicians of the Council of Agriculture studied the strange phenomenon and discovered that a few native insects predators of other insects, as wasps Dacnusa sibirica and Diglyphus isaea, had proliferated exaggeratedly and they had specialized in feeding on the citrus leafminer. Without needing most expensive pesticides of the multinationals, the wisdom of the nature had managed to reduce to tolerable limits the plague of the leafminer. I was glad to much when reading this news and also by to have resisted the temptation to buy insecticides to multinationals. In my garden nonuse pesticides nor chemical fertilizers. I save much money and much work, the earth is very healthy flood of earthworms and I can directly be eaten the fruit of my trees to bites without needing peeling it nor washing it to clear no poison. The majority of " plagues" of my trees perfectly they are controlled by the own nature. 

A day about 7 years ago taking a walk by my garden a tiny small bird, Phylloscopus collybita, drew attention to me, that jumped of small branch in small branch on an old lemon tree and watched underneath each leaf. Of as much as soon as it found a small worm, it squashed a little with its smallest tip of insectivore and swallowed it as if outside delicious food. The bird overflowed joy and realised a species of dance with small jumps and movements of the tail whenever a worm swallowed. I was observing it during a good short while and it did not seem to bother my presence, so engrossed was with its big spread. When it was sated of worms went flying until the drinking trough of geeses, drank several times and it disappeared. Suspecting that it had been fed on leafminer larvae, I look under the leaves where the bird had been and indeed all cuticle had broken and the larva had disappeared.

After 17 years of the beginning of the plague today I have wanted to verify the state of the new buds of this year of the orange trees, lemon trees and mandarin trees and I have only been able to find two affected leaves. The intelligent action of the nature has been spectacular, a full success.

Nun bearings: a pleasure for faquires

Bearing of nun, seat of nun, seat of mother-in-law, seat of shepherd, very startling names for a plant, truth?. Then thus we call to a set of shrubs, generally of high mountain and coastal zones, that in spite of belonging to different botanical families have evolved of a convergent way and all of them display a cleared and flattened form with small overlapped branches and frightful thorns that protect them of snout of the herbivores: goats, ewes, rabbits, etc. Similar plants are in many places of the world, but in the Balearic Islands they are especially abundant perhaps by the extreme dryness of the Mediterranean climate, the constant wind whip strong and the existence during million years of a unique herbivore, Myotragus balearicus, that with its browse gave form to these peculiar plants that adapted to the aggression to be able to survive. In Balearic islands we called "Coixinets de monja".

Gorgeous image of high Majorcan mountain to about 1,100 msnm. The nun bearings dominate the set out open spaces more to the solar radiations. They take advantage of the poorest and stony grounds. In the image they are numerous Astragalus balearicus with some unit of Teucrium balearicum of more grayish color. Sometimes they grow so together that they are superposed. I recommend to you to extend this one and the following photographies to appreciate better its strange beauty. 

Another image of the same zone of the Serra de Tramuntana of Majorca. Some Asphodelus aestivus are seen growing between the bearings. To the bottom it dominates to a forest of high Mediterranean mountain with Pinus halepensis, Pistacia lentiscus, Juniperus oxycedrus ssp. oxycedrus, Olea europaea var. sylvestris, Quercus ilex ssp. ilex, Ephedra fragilis, Ampelodesmos mauritanica, Asparagus albus, etc...

 Complete skeleton of Myotragus balearicus in excellent state of conservation. It is possible to be seen in the Balearic Museum of Natural Sciences.

Same skeleton seen on the other side.

Impressive skull that seems to watch to us accusingly from the past remembering to us that we were who we ended its species. Incisive inferiors of rat draw attention both that grew continuously as they were spent with the browse. The jaw inferior is very robust resemblance to the one of the rabbits to be able to crush the coriáceas Mediterranean plants. Their great eyes had a frontal position what makes suppose that they had an excellent stereoscopic vision. Their two horns grew backwards like those of the present antelopes.

You will ask yourselves: what is coixinet?. In Majorca we called coixinet to the small cushion of the basket of the seamstresses used to nail the needles to sew and to embroider. For that reason we give this name to these gorgeous plants because its thorny surface remembers these bearings of seamstress. 

In this image we see several Astragalus balearicus of different sizes. The ground is very poor with few centimeters of thickness and is based on a calcareous rocky base.

Thorny surface of a Astragalus balearicus with the typical leaves of a legume. 

 Detail of the frightful thorns that they protect to this endemismo of Majorca, Menorca and Cabrera.

The flowers are white with a slight pink dye. The thorns are not any obstacle for the polinizadoras bees that go golosas to libar the tiny drop of nectar of the bottom of each flower. 

Another abundant bearing of nun is the Teucrium balearicum, a tirrénico endemismo that lives in Majorca, Menorca, Cabrera and Sardinia. Its scientific name has undergone several changes in the last decades because the botanists did not manage to put themselves in agreement. At first it was called Teucrium marum ssp. occidentale and also Teucrium subspinosum bar. balearium. It belongs to the family of the Labiatae.

 Teucrium balearicum with its typical grayish color in the high Majorcan mountain. In its right side balearicus is a small Astragalus that has been integrated perfectly in the cleared structure of the Teucrium, as if a symbiosis it was. Both endemismos share the same habitat. 

Graft thorns of Teucrium balearicum that excel over the small leaves to which they protect.

Teucrium balearicum is frequent victim of a parasitic plant, Cuscuta epihymum, that does not have own roots and lives directly absorbing the water and the nutrients on the roots of the Teucrium. 

Smallest pink flowers of the Teucrium balearicum with the typical form of the Labiatae.

Another bearing of nun of the family of the labiadas ones is the Teucrium subspinosum, a tyrrhenian endemism that lives in Menorca, Cabrera and Sardinia. Like the Teucrium balearicum, its scientific name also has been reason for discord between the botanists. During years it has been called Teucrium marum ssp. subspinosum, Teucrium marum ssp. spinescens, Teucrium subspinosum ssp. spinescens, etc… At the moment finally they have been agreed and they consider a separate species with own name. 

Teucrium subspinosum cultivated in the Soller Botanical Garden to preserve it of the extinction. Its number in wild state is very little and its habitat continuously is threatened by the human greed. 

The Teucrium subspinosum well-known defers from the Teucrium balearicum by its small, fine and much more little sharp thorns, of there its name of subspinosum. The leaves and flowers of both endemismos are identical. Their small branches are less overlapping and has a less compact aspect. In the photo the mature fruits are seen after the dispersion of the seeds at the beginning of September.

A spectacular bearing of nun who in the heat of flowering seems a gold ball is the Anthyllis hystrix, endemic of Menorca, the family of the Leguminosae. Unlike the previous bearings that have preference by mountains this one lives in the coastal zones of Menorca, whipped permanently by winds of the north.

Anthyllis histrix in the middle of September in the heat of estivación, cultivated successfully in the Soller Botanical Garden to preserve it of the extinction. In spring its aspect is completely different, a beautiful combination of the intense yellow of the flowers and the green brilliant of the leaves. 

Leaves and thorns of the previous Anthyllis histrix. As it happens in the majority of bearings, the thorns excel over the leaves. 

In this image we see the frightful graft thorns in the form of red deer horn excelling over the leaves that are perfectly prote'ge'es of the depredation of the goats and ewes. 

The change in spring is spectacular. Numerous small yellow flowers confers to Anthyllis histrix a beautiful aspect of gold ball. 

Considering that all the bearings of the Balearic Islands have evolved throughout million years to protect themselves of their two main enemies: the wind and the depredation of the herbivores, all make suppose that they were fauces of the mythical already extinct antelope dwarfed, the Myotragus balearicus, endemic of Majorca, Menorca, Cabrera and Dragonera, those that modeled their cleared form, eating all the leaves and buds that excelled over the thorns. This tiny antelope of not more than 50 centimeters of height in the cross, very short legs and to ramble slow was extinguished about 4,000 years ago, agreeing with the arrival of the first humans who ended all the Myotragus in a few decades. Its ecological niche was empty by few years, because the goats concerned by the first settlers from the distant Eastern Mediterranean replaced to it in the depredation of the bearings. Centuries later arrived the ewes that especially in the Serra de Tramuntana of Majorca are operated in conditional release regime and must look for the sustenance by their account.

Another spectacular bearing of nun is Femeniasia balearica, an endemism that like the Anthyllis histrix also is exclusive of the Island of Menorca. It belongs to the great family of the Compositae. Their favorite habitat a little moved away the sea are the coastal zones where the splashes do not arrive from the waves. This one is perhaps the one of the most important endemisms of Menorca, since as much Femeniasia sort as the balearic species is exclusive of this beautiful Mediterranean island that makes 6 million years, during Miocene, was the top of a mountain surrounded by dry valleys and very salty lakes.

Old Femeniasia balearica of about 25 years of age cultivated with great success in the Soller Botanical Garden to preserve it and to maintain a viable population outside its natural habitat. As all the bearings are protected by the catalogued law and in serious danger of extinction. The photo was taken at the beginning of September with the plant in the heat of estivation. Its parched aspect is deceptive, because she is full of life. With the first rains of the autumn it will turn green again spectacularly.

Lateral vision of previous Femeniasia balearica with its stems finished in frightful thorns. 

Near vision of the previous stems with a deceptive parched aspect, since in the end of some of them green thorns in growth are seen. 

Tender stem of  Femeniasia balearica at the beginning of June. Each one of the small buds finish in three divergent thorns.

It is very peculiar that in Ibiza and Formentera, where the Myotragus balearicus did not live, does not exist any plant with aspect of nun bearing, with the exception of endemic sarsaparilla that grows in all the archipelago and could have arrived at the Pitiusas Islands after the extinction of the Myotragus through seeds transported by the birds.

Femeniasia balearica blooms in May and June. Their flowers open in the end of the stems and have a beautiful yellow-lemon color. 

Detail of a flower of Femeniasia balearica seen of side. On the contrary that the leaves, the flowers excel over the thorns to facilitate the pollination by the bees and bumblebees. 

Melífera bee sucking the nectar of a flower of  Femeniasia balearica at the beginning of June.

After the fertilization the seeds mature and at the beginning of the autumn they are dispersed by the wind. 

Leaves and seeds of Femeniasia balearica. The leaves are linear-lanceoladas and have a white line in their face superior. The seeds are equipped with radial hairs in the form of helicopter vanes that facilitate the flight and its dispersion to them by the wind to the conquest of new territories.

Another bearing of nun of the family of the composed ones is the Launaea cervicornis, endemic of Majorca, Menorca and Dragonera. Its specific name makes reference to its frightful thorns in the form of horn of red deer (cervicornis). Their favourite habitat is the cliffs and coastal rocks.

Gorgeous Launaea cervicornis covered with yellow flowers as a full star firmament in the middle of June. This unit belongs to the collection of endemic bearings of nun of the Balearic Islands cultivated in the terraces of the Soller Botanical Garden to preserve them of the extinction.

Flower and thorns in the form of red deer horn. As it happens with the Femeniasia, this bearing also has the flowers over the thorns.

Flowers of Launaea cervicornis in the heat of month of June. 

Leaves and thorns of Launaea cervicornis. 

Sometimes the distinction between leaves and thorns is not far from easy, since frequently there are many intermediate forms. In the image enough leaves with thorns are seen. It is possible that this phenomenon is an adaptive mechanism to avoid the depredation of their succulent leaves by the herbivores.

On protected coastal rocks of the splashes of the waves another bearing lives on nun, the Dorycnium fulgurans, endemic of Majorca, Menorca and Cabrera. It belongs to the family of the Leguminosae. 

Dorycnium fulgurans cultivated in the Soller Botanical Garden. Their thorns are the ends of the very graft and overlapped stems that they finish in end. Their small and little leaves are similar to those of the Dorycnium pentaphyllum. 

Thorny ends of the stems of Dorycnium fulgurans. 

Lateral vision of the thorny surface of this coastal bearing.

Tiny target-pink flowers of Dorycnium fulgurans. This endemismo usually blooms from May to August. The flowers appear directly of the stem, unlike the Dorycnium pentaphyllum whose flowers are abren in the end of pedúnculo.

 Detalle de las diminutas flores del Dorycnium fulgurans. Se ven varias hojas ligeramente carnosDetail of the tiny flowers of the Dorycnium fulgurans. Several leaves slightly fleshy are seen.

 Mature fruits of Dorycnium fulgurans at the end of the summer.

In all the Balearic Islands sarsaparilla lives one endemic very thorny that when it grows in the ground takes the form of a nun bearing, Smilax aspera ssp. balearica. Usually it has few leaves or to even lack completely them, realising the photosynthesis directly in the greenish stems. It can live from the level of the sea to the top of mountains.

Smilax aspera ssp. balearica in the form of nun bearings growing in the high mountain closely together of a dam.

Endemic other sarsaparilla of the Balearic Islands with its typical aspect of thorny bearing growing between rocks of a cliff. This plant is a clear example of convergent evolution: a same strategy of survival shared by different species.

Very small and narrow leaves of Smilax aspera ssp. balearica.

And to finish another plant that has adapted to the depredation of the herbivores, the endrino or arañón, Prunus spinosa, that when it lives in the high mountain and it undergoes the constant ramoneo of the goats and ewes, grows like a nun bearing. It belongs to the family of the Rosaceae.

Prunus spinosa in the form of nun bearing growing in the high Majorcan mountain to 1,000 msnm. Their small branches thousand times grazed by the goats and ewes are very graft and overlapping. 

Detail of the surface of the previous bearing. Peculiarly one is not an endemic subspecies different from the normal endrino, since if is seeded their seeds are born endrinos with the own aspect of the species and if one of these bearings is taken and it migrates to a place without herbivores grows like a normal with the long and abiertas branches and barely thorny endrino.

 I want to finish this long article with these beautiful small flowers of Prunus spinosa.