G. Allard, J. Ghent, I. Mironic and L. Spitoc
Gillian Allard is Forest Protection Officer in the FAO Forestry Department, Rome.
John Ghent is Forest Entomologist with the United States Department of Agriculture – Forest Service, Asheville, North Carolina, United States.
Ion Mironic is Head of the Forest Guard and Protection Section of the State Forestry Agency “Moldsilva”, Chisinau, Republic of Moldova.
Liliana Spitoc works in the Forest Research and Management Institute, Chisinau, Republic of Moldova.
Transfer of technologies and equipment helps developing countries and countries with economies in transition cope with catastrophic outbreaks of forest insect pests.
Among the challenges to forest health faced by many countries, sporadic outbreaks of insect pests can lead to death of trees, resulting in economic and environmental resource losses. When an insect outbreak reaches epidemic proportions covering large and sometimes inaccessible areas, aerial application of biopesticides is sometimes the only resort to treat the infestation effectively and to protect high-value forests. But the high cost of aerial application programmes generally prevents large-scale treatment except in developed countries.
Technologies have been developed to ensure that aerial application is accurate, cost effective and environmentally sound. However, for the most part, developing countries and countries with economies in transition rely on outdated or obsolete spray equipment and aircraft with minimal navigational or communication capabilities. Also lacking are the necessary skills and training to carry out these operations safely, effectively and economically.
Severe large-scale insect defoliation of forests is not a common occurrence in any one location or region. Catastrophic outbreaks of native forest defoliators tend to be cyclic and may occur only once or twice in a forester’s career. For this reason, land managers usually have limited or no expertise and experience in the aerial application of biopesticides. In such cases international assistance can help avert disaster.
In 1999, the Republic of Moldova faced an extensive outbreak of several species of defoliating moth infesting the country’s sparse forest resources. The threat of unacceptable levels of mortality was compounded by winter storm damage and repeated summer droughts. Because of antiquated equipment and lack of resources, the country’s attempts to manage the pest problems were rather limited and not cost effective. After making every possible effort, the government requested assistance from FAO.
FAO, under the umbrella of the Technical Cooperation Programme (TCP), collaborated with the United States Department of Agriculture (USDA) Forest Service to respond to this request. In the United States the gypsy moth (Lymantria dispar), accidentally introduced and established in 1869, has required the aerial treatment of forests somewhere in the country almost every year since the late 1940s. As a result the USDA Forest Service has developed extensive expertise in aerial application technology and has fostered continuous research efforts aimed at reducing treatment costs, improving the effectiveness of treatment and minimizing the impacts on the forest environment. The Forest Service also has an extensive programme for training and assisting various land management agencies in newly infested areas in the use of proper aerial application techniques.
In cooperation with FAO, since 1998 entomologists from the USDA Forest Service have provided in-country technical assistance in the design and implementation of aerial application projects in Bulgaria, Mongolia, Romania and The Former Yugoslav Republic of Macedonia, in addition to the Republic of Moldova.
This is a two-way exchange, as the United States also benefits from collaboration with national forest protection professionals, through the exchange of ideas on forest health management and through expanded knowledge of potential exotic pests, new survey techniques and innovative approaches to managing forest pest problems.
Effects of an outbreak of defoliating insects on an ash (Fraxinus spp.) forest in the Republic of Moldova |
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I. MIRONIC |
Forest and other wooded land (all owned by the State) accounts for only about one-tenth of the Republic of Moldova’s 3.3 million hectares of land. Two-thirds of the forest is available for wood supply, while most of the rest is retained for nature conservation and protection, particularly protection against soil erosion, as land degradation is a major problem throughout the country. Virtually all of the forest area is classed as semi-natural; small areas have been planted, mainly to prevent erosion. Broad-leaved species account for all but a small part of the growing stock, with oak (Quercus) species alone making up about half. Other important species are beech (Fagus spp.), hornbeam (Carpinus spp.), maple (Acer spp.), ash (Fraxinus spp.), lime (Tilia spp.), birch (Betula spp.), poplar (Populus spp.) and false acacia (Robinia pseudoacacia), the last being an introduced species.
Energy is the main use of wood in Moldova. More than half of all wood consumed in the country is used as fuelwood or charcoal. Forests are also important to the population as a source of non-wood forest products such as nuts, fruits, berries, medicinal herbs, honey, mushrooms, fodder and forage. The forest industry is mainly State-owned and its output is not sufficient to meet the needs of the domestic markets, owing to shortage of raw materials and low production capacity.
The Republic of Moldova State Forestry Agency “Moldsilva” is responsible for management of the State forested lands. Moldsilva manages approximately 87 percent of Moldova’s forest. Municipalities or agricultural farms manage the rest but depend on Moldsilva for management direction.
Moldsilva has an exceptionally strong forest protection programme with highly skilled staff. Personnel at the Forest Protection Station annually monitor forest health conditions throughout the country. Decision-making and planning for possible treatments are based on the severity of current damage, hazard rating of forest stands and available resources. The organizational structure for forest health monitoring and the survey intensity exceed those in the United States. However, financial constraints and outdated application equipment have limited an effective response to large-scale outbreaks.
Outbreaks of defoliating insects have occurred throughout the Balkan Peninsula and southeastern Europe over the past decade. A combination of extended drought and the advanced age of forest stands has increased the susceptibility of the forests to outbreaks of native forest defoliators. These conditions mirror many of the conditions that have led to extensive outbreaks of forest defoliators in some regions of the United States.
When the Republic of Moldova requested international assistance at the beginning of 1999, an estimated 95 700 ha of the country’s forest were affected by leaf-eating pests: Tortrix viridana (green oak tortrix); Erannis defoliaria (mottled umber moth); Operophtera brumata (winter bud moth); and Lymantria dispar (European gypsy moth). Moldovan researchers estimated that the damage caused by leaf-eating pests could result in up to 60 to 90 percent losses of annual growth in standing trees, i.e. about 200 000 m3. Since 1993 the average annual area infested with leaf-eating pests has been 50 000 to 70 000 ha (16 to 22 percent of wooded land), of which 30 000 to 40 000 ha are forests that warrant aerial treatment owing to their high economic or genetic value and high level of infestation.
The first phase of assistance involved working with the country to develop an integrated pest management approach. To protect the environment, FAO encourages the use of biological (non-chemical) pesticides, such as Bacillus thuringiensis var. kurstaki (Btk) or insect growth regulators for control of Lepidoptera (moths and butterflies). Such products have low impacts on non-target insects, many of which are beneficial to a healthy forest ecosystem. New high-potency formulations of Btk are specially formulated to be applied undiluted and at low volume (2 to 3 litres per hectare). Application of products at low volume can contribute to considerable savings in terms of both the biopesticide and application costs.
To provide good foliage protection with such low volumes, Btk must be applied as very small droplets measuring only about 100 μm – barely bigger than the diameter of a human hair. Insect growth regulators using water as a carrier (which evaporate quickly and must therefore be applied when relative humidity is above 60 percent) are applied at a higher volume rate of 5 to 9 litres per hectare with larger droplets of 150 μm. Insect growth regulators can also be applied using an oil formulation allowing lower application volumes of 3 litres per hectare and smaller droplets of 80 to 100 μm.
FAO provided modern aircraft spray systems capable of applying the low-volume sprays. The local agricultural spray aircraft used for the forest spraying (KA-26 helicopters) had older hydraulic nozzle spray systems adapted to the high volumes and large droplets needed to protect agricultural crops. To obtain the small droplets needed for spraying low-volume Btk and insect growth regulators, modern rotary atomizer spray systems were retrofitted on to the existing aircraft. These atomizers can be adjusted to produce a variety of droplet sizes, including the desired small droplets for Btk.
The project also provided training in current application techniques used in forest spraying. The use of low-volume application techniques entails new operational considerations.
In particular, small changes in environmental conditions can influence the effectiveness of the treatment. Project managers were instructed about the optimum conditions and timing for spraying. Sprays consisting of small droplets are similar to a light mist or fog. When the spray is released 15 m above the forest canopy, a light wind of 2 to 3 m per second can move the spray cloud 100 m. Low humidity and high temperatures can cause the droplets to evaporate, and the spray can be transported upwards on rising warm air as the earth warms during the day. The optimum spray conditions usually occur between sunrise and 10.00 hours – a shorter spray period than is typical in agricultural spraying.
It is important to be aware that conditions at the airport can be very different from those in the treatment area. For this reason, portable weather instruments and good communications between weather monitors and project directors are essential.
Spray deposit assessment is important in determining the quality of the application. The project provided classroom and field training to introduce techniques for monitoring deposition and the quality of the treatment programme. One of the simplest techniques is the use of water-sensitive paper cards treated with a yellow dye that turns blue when exposed to water-based sprays. These cards provided an easy way to measure droplet size and density of the deposit. To assist in droplet measurements, hand-held micrometers and free public-domain software were provided. Bioassay field tests can be carried out to determine the level of Btk deposit on foliage, showing project managers whether spray was deposited evenly within the block or whether sufficient material remains after rain.
Training in the use of the spray model AgDisp, developed by the USDA Forest Service, was provided to demonstrate effects of weather, atomizer set-up and droplet sizes on spray deposit. The model can also be used to evaluate factors that affect drift off target or to ensure the protection of sensitive areas near sprayed areas.
Local agricultural spray aircraft (KA-26 helicopter) with an older hydraulic nozzle spray system, inappropriate for spraying forests with biopesticides at low volumes |
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J. GHENT |
Modern rotary atomizer spray systems were retrofitted on to the existing aircraft to obtain the small droplets needed for spraying low volume Btk and insect growth regulators |
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G. ALLARD |
Biopesticide spray operation in action |
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I. MIRONIC |
In 2000, aerial application was carried out on 7 600 ha of high-value forest in the Republic of Moldova. The efficacy of the treatments was estimated at 96 to 98 percent control using the equipment and technologies provided through the project. These operations thus prevented significant defoliation of forest plantations and decreased the possibility of transboundary transfer. Cost savings were estimated to be as high as 45 percent compared with the use of less efficient products and outdated equipment.
There is a need to manage forests to minimize the risks of future large-scale outbreaks of pests and diseases, and a need to monitor the pest situation on a continuing basis to allow interventions at an early stage if problems arise. The project helped to develop monitoring techniques and to establish a database for long-term management of the forests to update and complement the existing systems.
Similar approaches have shown success in Bulgaria, Romania, The Former Yugoslav Republic of Macedonia, Mongolia and the Democratic People’s Republic of Korea, suggesting that this type of project which transfers information from one country to another is extremely beneficial for protection of forests.
