Aphids, Moths and Pested pines

The Woolly Pine Aphid and the Predatory Fly

Since 2006, KKL‑JNF foresters have been combating a fatal aphid that has been wreaking havoc on Israel's pine trees. The woolly pine aphid kills from 10 to 25 percent of the trees it attacks, and the tree most sensitive and vulnerable to this aphid is the Umbrella pine, also known as Pinus pinea. This aphid was identified first in Northern Israel, in Baram Forest in the Upper Galilee, and in several other forests, but it spread and reached forests in the Jerusalem region.

The pest control solution for the woolly pine aphid was found in a fly which preys on this aphid, a fly that was used as a biological pesticide in Hawaii about thirty years ago to solve a similar problem. Research done by KKL‑JNF foresters found that the US Forest Service had imported the fly from Pakistan and acclimatized it in Hawaii. The usefulness of the fly as a pesticide to control the aphid proved to be very effective, and, consequently, it is hard to find this aphid in Hawaii at present (or the predatory fly).

Pursuant to information about the successful pest control of the woolly pine aphid in Hawaii, David Brand, KKL-JNF Chief Forester, and Prof. Zvi Mandel of the Volcani Institute, went to the islands of Hawaii. Assisted by the US Forestry Service and the US Department of Agriculture (USDA), they succeeded in locating the predatory fly and gathered a number of flies in containers. The flies were brought to Israel, and, after thorough testing done by the Plant Protection Service of the Israel Ministry of Agriculture, they will be set free for their first “job” in Baram Forest in the Upper Galilee.

What is the Woolly Pine Aphid?

The woolly pine aphid (Pineus Pini) is an aphid from the Adelgidae family, a family of harmful insects that live in conifers of the Pinea family. When the insect reaches the tree, it settles under the bark and is therefore hard to discover. It then spreads to the branches, and the females lay their eggs in whitish woolly wax covered sacs. By then, one can observe from afar that “something is wrong” with the tree. A mass of white webs on the trunk, on the branches and on the growing edges, will attest to the woolly pine aphid. When they are hatched, the larvae will proceed to the young foliage and suck the content of the cells. On a diseased tree one sees phenomena such as yellowing leaves, desiccated branches, and distortions in the new growth. The aphids also cause the development of black soot, as they excrete a sticky sweet liquid called “honeydew” on which a parasite mold develops and creates a black coating of spores. Ten to twenty-five percent of the trees afflicted by the woolly pine aphid wither and die.

The origin of the woolly pine aphid is in Europe and Western Asia. In our region it was already observed in 1964 in the Jericho area. In early 2006, it appeared in a pine grove in Jerusalem. In order to prevent diffusion of the aphid, the Plant Protection Department of the Israel Ministry of Agriculture made sure to fell and burn the infected trees. Nevertheless, the aphids reappeared in November 2006, this time in the Baram Forest in the Upper Galilee, and in 2007, massive withering of pine trees was observed in the Upper Galilee.

“As of today,” said Prof. Zvi Mandel of the Agricultural Research Authority (ARA), “one can see the woolly pine aphid all over Northern and Central Israel. The aphid is flourishing especially in the cool and damp areas—in the hills, in the Galilee, in the Golan and in Samaria. The aphid is dispersed mainly by the wind, which blows the larvae from one tree to another. Apparently, the aphid reached Israel from Lebanon.” The aphid’s diffusion and proliferation pose a grave threat to the pine forests of Israel.

A Biological Pesticide

Aphids, like other harmful insects, have been attacking natural vegetation and agricultural crops from time immemorial. Already in the early 19th century, farmers were systematically using chemical poisons as pesticides. Over the years, new pesticides were developed such as the famous DDT and organic phosphates, which were highly effective in controlling pests but were also very dangerous for human health and for the environment. Only in the middle of the 20th century did the world begin to understand the high ecological and health price of chemical pesticides, many of which are toxic for people, animals and plants. Their decomposed elements remain in the earth, reach the groundwater, create environmental pollution and are an ecological hazard. Moreover, by using chemicals for pest control, new species of pests develop, which are impervious to the sprays.

An alternative to the chemical pesticides of last century is the use of biological pesticides—having the pests decimated by their natural enemies. All the creatures in nature are part of a food system in which each creature serves as a source of energy for another creature. The principle underlying biological pesticide is to allow the natural enemy to decrease the population of the pest and to stabilize it.

But what was the natural enemy of the woolly pine aphid? As we said, the woolly pine aphid is not an indigenous aphid, and it arrived in Israel without its natural enemy—a predatory fly originating in Pakistan, so in Israel it became a pest without any biological controls.

A Delegation Tracks the Fly

Years ago, as it turns out, the pine forests in Hawaii also suffered from the woolly pine aphid. In the 1980s, the US Forest Service located the natural enemy of the woolly pine aphid, a predatory fly originating in Pakistan (Neolucopis tapiae), and acclimatized it in Hawaii. The fly, which subsists solely on woolly pine aphids, devoured the aphids on the islands so effectively that it is hard to find any of the aphids there any longer or any of the predatory flies.

In order to eliminate the woolly pine aphid in Israel in a similar way, a joint project was undertaken by KKL‑JNF and the ARA, for which David Brand, Director of the KKL‑JNF Afforestation Department, and Prof. Zvi Mandel of the ARA, traveled to the forests of Hawaii in order to locate, gather and import this predatory fly to Israel.

With the assistance of Dr. Tom Coolney from the US Forest Service, the delegation visited three islands—Maui, Oahu and Hilo. Local entomologists and ecologists joined the expedition, and the delegation succeeded in finding colonies of the woolly pine aphid on pine trees populated by larvae of the predatory fly.

The plant material was gathered, sorted and packed in the labs of the Hawaii Department of Agriculture in Honolulu and sent to Israel. When the plant material and the insects on it arrived in Israel, they were quarantined in the Plant Protection and Control Service station. Isolation is a very important stage of the process. “During the quarantine,” explained Prof. Mandel, “the scientists examine how the flies develop on local pine saplings, and the specificity of the fly to the aphid is also checked. Freeing the fly is approved only after it is proven without a doubt that it will not harm other local insects or interfere with the ecological balance in Israel’s forests, and only then is it permitted to disperse it in the areas afflicted by the aphid.”

In mid 2011, the isolated testing of the predatory fly was completed successfully, and its dispersion in afflicted areas began. There was some concern about the fly's ability to survive the winter, but today, a half a year later, it can be definitively stated that the predatory fly has successfully acclimated in Israel. Final conclusions will be reached only after seeing if the fall and spring growth of the pines is not damaged by the aphids. Based on the example of other countries in the world, it is hoped that the predatory fly will be able to decimate the woolly pine aphid, limit its diffusion and save the pine forests of Israel.

* Scientific information: David Brand, KKL-JNF Afforestation Division and Prof. Zvi Mandel, Agricultural Research Authority (Volcani Institute)

The Pine Processionary Moth (Thaumetopoea wilkinsoni)

Thaumetopoea wilkinsoni, also known as the pine processionary moth, is a moth from the Thaumetopoidae sub-family. It is found in pine forests and populates pines in the Mediterranean Basin and in Southern Europe, where its populations have been moving north due to global warming. The pine processionary moth in Central and Western Europe is known as Thaumetopoea pityocampa but it is the same species. The moth populates all kinds of pine trees, but the sensitivity of the trees varies in different regions. The sensitive pines in Israel are the Jerusalem pine, also known as the Aleppo pine (Pinus halepensis), the Calabrian pine (Pinus brutia) and the Canary Island pine (Pinus canariensis). The pines it does not usually populate are the Stone pine, also known as the Umbrella pine (Pinus pinea), and the Maritime pine (Pinus pinaster). The processionary moth is a harmful pest in pine forests and constitutes a health hazard. The name of the moth derives from the processionary motion of the larvae from the hatching stage to the pupation stage. Among the other caterpillars found in Israel, the most common is Thaumetopoea solitaria.
Nest of pine processionary moth caterpillars. By Chiswick Chap - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17764484

Seasonal Activity of the Pine Processionary Moth

End of summer to autumn (August – October) is when the mature moths emerge from the ground, fly around in the evening and live for a day or two. The flying range of the females is limited, around 1km, while the males may fly tens of kilometers. The eggs are laid on a pair of pine needles in what is called an "egg mass".

In early winter (October – December), the larvae emerge and start munching the pine needles. First and second stage larvae are active mainly in the daytime and eat the outer layer of the needle, as a result of which the group of affected pine needles dry out and turn brown. This desiccation is the first conspicuous sign of larvae activity, and it is the optimal time for controlling the larvae.

Mid-winter to spring (December – March) is when third stage larvae eat whole pine needles. They are active in the dark. In the daytime they spin the permanent nest, which grows over time. The nest reaches its peak size usually at the end of February or March.

In the spring (March – April) the larvae descend in single file to pupate on the ground, usually a few meters from the tree at a depth of 5 to 30cm. The larvae spend the summer asleep. Only some of them will emerge in the autumn. The others will emerge in the autumn 2 to 6 years from pupation.

The Ecological Significance of Feeding on Pine Needles

In a mature forest, the processionary moth strikes once every few years, usually after a rainy winter. In older sections of the forest, the moth population is smaller. The pine processionary moth prefers young trees with strong growth energy. Eating considerable amounts of foliage slows down the growth of the trees, but also exposes the forest floor to sunlight, and the excretions of the larvae fertilize the soil. An affected tree is not usually attacked in the following winters, which, as a result, facilitates its recovery. In cities and other areas where pine trees enjoy a lot of water, they may be attacked by the moth year after year.

Natural Enemies

The action of its natural enemies is not sufficient for reducing the damage to the forest, most of which action is taken by young parasite wasps that attack the eggs. There is also a trend to increase the role of birds that eat the larvae.

Hazards and their Prevention

The health hazard is caused by the hairs on the caterpillars that sting. These urticating hairs appear on the larvae starting from the third stage. The number of stinging hairs continues growing in the fourth and fifth stages of the caterpillar (up to about 600,000 urticating hairs per caterpillar). These stinging hairs are hollow and contain a protein called thaumetopoein, which causes the release of histamines in an allergic reaction with stinging and irritation of the skin and the mucous membranes of the eyes and the nose. The hairs are present on the live caterpillars, on the shells inside the abandoned nests and even on the ground, where the caterpillars have pupated, and near the pupa. The hairs tend to scatter easily in the wind, especially in dry, hot weather. Irritation may occur immediately or after a number of hours and depends on the level of sensitivity and the extent of exposure.

Protective Measures

In most forests there is no danger of being harmed by the processionary moth. Precautions should be taken when nests are sighted. One should not touch the nests, the live or dead caterpillars, the pupa or the ground near them, with bare hands. One should stay away from the nests and their remains. All contact with the pine processionary caterpillar should be done with protection—gloves, goggles and clothing that cover all parts of the body. Affected groves should not be visited, and parking under affected trees should be avoided. Special attention is necessary in the spring, when the larvae are at the peak of their development and descend to pupate on the ground.

Pesticide Interface for the Pine Processionary Moth

The best time for controlling the moth is when the larvae hatch, from November to December. Spraying at this stage is done with chemical preparations in the Bt group or with insect growth regulators. At a later stage, the pest can be controlled by removing the nests, by lopping the branch that bears the nest (unless it is a main branch, in which case it should not be cut). This should be done carefully, fully clothed, with gloves and goggles. Nests should not be removed on days that are hot and dry, or when there are strong winds. On tall trees, in recreation areas and in residential areas, the moth is controlled by means of systemic chemical preparations that are injected into the tree trunk. The right time for this is from the end of November to the beginning of January (depending on the chemical preparation). The chemical preparations must be permitted by law. In municipalities and local councils, the local sanitation department is in charge of controlling the pine processionary moth.

First Aid in Case of Injury

In case of injury, one should flush the affected area with water and remove the clothes that were exposed to the urticating hairs. Laundering will remove the hairs from clothing. In the event of severe injury one must see a doctor. Medicines based on antihistamines, corticosteroids and painkillers may alleviate the irritation.

KKL-JNF Afforestation Division R&D

The Forestry and Development Department of the Afforestation Division, together with scientists from the Agricultural Research Authority and personnel from the Ministry of Environmental Protection are working to minimize the damage caused by the pine processionary moth. The Forest Protection Unit and the foresters investigate the damage to the forests and manage the pest control. Additionally, the Afforestation Division initiates research and development programs with a view to reducing the population of the moth by means of promoting its natural enemies and developing innovative pest control methods using means that are environmentally friendly.