Pests That Thrive With Climate Change (and Kill Plants)

In less than two years, starting from a simple couple of insects, the family can expand up to seven billion between uncles, cousins ​​and nephews. There turtle mealybug, native to a vast area from Canada to Mexico, has no problems with falling birth rates. And it’s a problem because on pine trees this little animal behaves like a vampire by feeding on the sap of plants. The cochineal has few natural antagonists and with milder temperatures it can reveal extraordinary reproductive capacities. In the Caribbean it has almost made a clean slate of the indigenous species Pinus caribaea. In Italy it was reported for the first time in 2015 in Campania and since then it has spread unstoppably in Lazio and other regions, also devastating the pine forest of the presidential residence of Castelporziano.

But the turtle cochineal is only one of the most dangerous plant parasites which in recent years have been favored by global warming with all the accompanying prolonged droughts and extreme climatic events. These invasions follow a script that seems to repeat itself in different forms.

“At the origin of the devastation there are often involuntary introductions of infected plants and fruits but the unwanted guest can also hide in a container or in packaging – he explains Pio Federico Roversidirector of the National Reference Institute for Plant Protection (CREA Difesa e Certificazione) – the increase in temperatures and prolonged drought then act as accelerators both by weakening the plants and by reducing the adaptation times of these exotic parasites to our environments “.

According to the international scientific community the introduction of alien species it is one of the first causes of biodiversity loss worldwide also due to climate change. in Italy there are no immune plants. From agricultural cultivars to ornamental varieties to forest species, they all have an insect, a bacterium or a fungus that has been bothering them ever since the thermometer lost its bearings. Many of these diseases are quarantined and require the elimination of specimens to prevent the infection from spreading. Here is a review of the new and most dangerous parasites.

The Vampire of the Pines

Pines are among the species most affected by these new insects favored by milder temperatures. There turtle mealybug, in its original environment, does no damage but when it goes outside the borders it becomes a natural disaster. In the absence of harsh winters, which practice a sort of natural selection on these insects, the cochineal can reproduce more easily. In each brood the female can lay up to 500 eggs. In Italy it is in a rather rapid phase of diffusion and risks eliminating the stone pine, that is the tree from which not only pine nuts are obtained but which is part of the natural landscape of many Italian cities such as Rome.

For the moment, the only cure to stop the turtle cochineal is the injection into the trunk of an insecticide mixture derived from a bacterium that lives in the soil. But it is a temporary buffer, a kind of treatment that cannot go on indefinitely. In a few weeks, the CREA researchers will leave for a mission to the Caribbean islands of Turks and Caicos where it seems that the introduction of the cochineal has triggered an environmental reaction capable of containing its spread. Another enemy of these plants on the doorstep is the Bursaphelenchus xylophilus or pinewood nematode. It is a tiny worm that in Portugal has brought the maritime pine to the brink of disappearance. In Italy this nematode has so far been found only in a consignment of pine bark from Portugal and intended for mulching for gardens. Against this nematode there are no cures other than the destruction of the affected trees. Experts estimate if it manages to spread in Europe, there is a risk of losses in the timber sector of over 20 billion euros.

Turkish bath for the vine

In Italy the golden flavescence and its vector insect Scaphoides titanus they are one of the main threats to viticulture despite the fact that today it is still confined to the agricultural areas of the northern regions up to the latitude of Tuscany (but it has also been traced to Ischia in 2011).

Flavescence is an epidemic disease in grapevine discovered in the late 1950s in France, now present in most of Europe. The scientific community believes that the worsening of this disease is also due to the climatic changes underway due to the influence exerted on the pathogen and the vegetative stress caused to the plants. For flavescence, there is no cure but it can be prevented by sterilizing the nursery material by immersing it in water at 55 degrees for 45 minutes. For the control of the vector insect, a leafhopper, the University of Padua in collaboration with CREA has launched a study program to verify the feasibility of biological control interventions with natural antagonists from the area of ​​origin of the leafhopper.

Botany

Broom and orchids, so plants adapt to toxic environments

by Fabio Marzano

06 April 2023

Pests from extreme events

Global warming can also have indirect effects on plant health. As for the spruce bark, a small beetle that normally attacks weak or nipped plants. This insect, present in Italy from the Alps to the Apennines, can also colonize entire woods following extreme events. Storm Vaia in 2018 paved the way for this beetle to attack healthy plants once a sufficient population has developed. Also because many of the spruce trees in our forests are maladapted, if we may say so: most of them come from seeds of central European origin where the trees have less water stress than those currently recorded in our latitudes.

The Asian woodworm arrived with bonsai

Lombardy has spent more than ten million euros to counter the invasion of Asian woodworm, Anoplophora chinensis. The city of Rome, with CREA, has stopped its spread by eliminating one by one the plants affected close to the Aurelian Walls.

In Tuscany, hectares of nurseries had to be razed to the ground. Also known as long antennae citrus cerambycid, Anoplophora chinensis, of Asian origin, attacks more than one hundred species of trees. It particularly favors broad-leaved trees which make up the main street trees of many cities such as plane trees, beeches, maples and horse chestnuts. But it does not disdain fruit plants such as pear and apple trees as well as some ornamental shrubs in gardens such as roses. The Asian woodworm has often been identified in the stem of infected bonsai trees. With climate change, the distribution of this parasite is widening globally. To date, the felling of the affected plants is also mandatory in Italy for the Asian woodworm.

Just a fly

Like the Asian woodworm also the oriental fruit fly it’s a good mouth. This insect, which also arrived accidentally from Asia, can develop in the fruits of more than five hundred agricultural cultivars: from the apple tree to the peach to the persimmon.

The species is included in the lists of quarantine organisms for the European Union due to its danger. With the current climatic trends, the fly is also spreading to other territories. The presence of the parasite has led to the establishment by the Campania Region of a special crisis unit for this emergency which represents a serious threat to fruit exports, so much so that a special monitoring program has been launched at the Italian level which affects the whole National territory.