Monitoring is an action used to understand insect activity in order to make pest management decisions. Traditionally, surveillance to determine fluctuations in fruit fly populations involves the use of traps usually baited with attractants (lures), manual counting, as well as a tool for assessing fruit fly populations inside orchards and infestation levels.

Currently, there are several methods that can be used with success as alternatives to spraying the entire tree canopy. These include bait-sprayings and mass trapping, by using reduced-risk methods and insecticides. Nevertheless, these methods are based on early detection, which makes trapping and sampling essential for their successful deployment. In the case of invasive fruit fly species, early detection and warning of low population density is even more important, as it is directly related with the of initiation of immediate actions aimed at eradicating the insects from the first entry or low prevalence areas.

FruitFlyNet overall objective is to contribute to the development and implementation of environmentally effective e-monitoring and ground spraying control solutions based on prototypes, technological innovations and knowledge transfer for specific key-pests in the Mediterranean area. This process includes several activities, such as digitization of the test areas, deployment of the Wireless Sensor Network (WSN), development of the  Real-time Trapping Incest Counting (ReTIC) traps, establishment of surveillance traps, analysis of the population monitoring system (trapping system, e-monitoring, spatial deployment of sampling points), decision making based on environmental data, biological traits and spatial tools, development of decision making algorithms, development of users interface guidelines.

FruitFlyNet project focuses on prototyping solutions by targeting species of the Tephritid population, the olive fruit fly, the medfly, the cherry fly and invasive species (i.e peach fruit fly, Ethiopian fruit fly). Bellow background information as well as all processes involved in monitoring these species.

Olive fruit fly, Bactrocera oleae

The Olive fruit fly, Bactrocera oleae, is practically a monophagous species that can complete development in wild and cultivated olives (Olea europaea). In Europe, it attacks cultivated olives but in Africa it is associated with wild olives. In the major olive producing areas of the Mediterranean region, the olive fruit fly is by far the most important pest species.

Eggs are laid below the skin of the host fruit; a female may lay more than 400 eggs but unlike most other Bactrocera spp. these are laid singly. Eggs hatch within 2-4 days and the larvae feed for another 10-14 days. Pupation takes place either in the soil under the host plant or, when unripe fruit are attacked inside the fruit. Pupae development takes about 10 days but may be delayed for several weeks under cool conditions. Adult’s activity occurs throughout the year in southern-warmer Mediterranean areas but only during the warmer periods of the year (spring autumn) in cooler areas. It seems that overwintering is accomplished either at the adult or the pupae stage. Adults mature after about a week, and may live 2 – 3 months under field conditions.

Critical points in population monitoring and control:

• Does not respond to standard fruit fly male lures, no strong (parapheromone) male lures are known and therefore, accurate adult detection is often problematic.
• Mass trapping systems for both sexes have been developed, with variable results.
• Field monitoring is conducted by sampling susceptible fruits for larvae, or by trapping adults.
• Population monitoring also includes fruit sampling.
• Many countries, such as the mainland USA, do not allow import of this species, or of fruits that are already infested. In this context, there are strict directions for quarantine and pre-shipment treatments for this species.
• Cultural control methods include keeping orchard areas cleared of fallen fruit.
• Attempts for biological control have not been very successful in many of the areas that were tested.
• Usual treatment involves cover and bait sprayings.

Mediterranean fruit fly, Ceratitis capitata

The Mediterranean fruit fly, Ceratitis capitata is a highly polyphagous species. The species of coffea seems to be the ancestral host of medfly. The current list of medfly host includes more than 300 fruit species including many wild growing. For example, box-thorn, Lycium europaeum, is an important overwintering host in North Africa, while several wild hosts are recorded in Zimbabwe and Kenya. The list of medfly hosts, include several citrus, pome and stone fruits, as well as several tropical and subtropical fruit species of high economic value.

The eggs of C. capitata are laid below the skin of the host fruit. They hatch within 2-4 days (up to 16-18 days in cool weather) and the larvae feed for another 6-11 days (spring and summer). Pupation takes place in the soil under the host plant, the adults emerge after 6-11 days (24-26°C; longer in cool conditions) and they live for up to 2 months (field-caged). Medfly overwinters as larvae within infested hosts in the most temperate areas of its existence. High populations of medfly occur in areas where citrus fruits are cultivated. There are several studies employing bioclimatic models to define areas suitable for medfly establishment and prediction future distribution under a global warming scenario.

Critical points for population monitoring and control:

• Ceratitis capitata can be monitored by traps baited with male lures.
• Trapping efficiency may also be enhanced by the use of fluorescent colors, particularly light green.
• Many countries, such as the mainland USA, consider medfly as a quarantine species, and require specific treatment protocols at the post-harvest stages during import, such as fumigation, heat treatment, cold treatments etc.
• Control methods include:
  • Sterile insect technique (SIT) requires the release of millions of sterile flies into the wild population so that there is a strong likelihood of wild females mating with sterile males.
  • Male annihilation for mild suppression on feral population.
• Biological control has been attempted in many areas, but introduced parasitoids were not very successful in most of the cases tested.
• Usual treatment involves cover and bait spray.

European cherry fruit fly, Rhagoletis cerasi

The European cherry fruit fly, Rhagoletis cerasi is a major pest for sweet and sour cherries in many European countries including Greece and is characterized as the only serious tephritid pest in central and northern Europe. Recorded hosts are black cherry (Prunus serotina), mahaleb cherry (P. mahaleb), sour cherry (P. cerasus) and sweet cherry (P. avium). Some wild cherries (Prunus spp.) are reservoir hosts for R. cerasi, which may also attack wild honeysuckle (Lonicera spp.). The phenology of R. cerasi differs between cherry and honeysuckle associated populations with the honeysuckle population being a rather differentiated host race. The cherry fruit fly has also been recorded to attack berberis (Berberis vulgaris), but that was probably based on a misidentification of R. berberidis, which is a very similar looking species.

Rhagoletis cerasi is a univoltine species (1 generation per year) and undergoes obligatory pupal diapause. Adults emerge at the end of spring or the beginning of summer (depending on the climate of the area), just before or during the ripening period of cherries, which consists a critical period of cherry damage (fruit color change from yellow to reddish). Therefore, the period of damage depends on yearly climatic conditions and the maturing period of cherry varieties. Adults become reproductively mature and females usually oviposit one egg in each ripe or semi-ripe fruit by drilling a hole on the fruit with their ovipositor. Females mark the oviposited cherries by depositing a host marking pheromone. It is estimated that the average fecundity range from 100-300 eggs per female. Young larvae, soon after hatch, feed in fruit mesocarp. Fruits are destroyed by larval activity coupled with secondary fungi or bacterial infections. Mature larvae leave fruits, fall on the ground, and pupate in the soil. Rhagoletis cerasi is an oligophagous species (sweet and sour cherries) with high economic importance for the cherry cultivation, especially the late maturing varieties (infestation levels up to 80%).

 Critical points for population monitoring and control:

• Adult population monitoring is performed using three-dimensional yellow, sticky traps, while so far there is no effective attractant for this species.
• Upon detection, infected fruit must be removed and destroyed. If possible, wild and abandoned host trees should also be destroyed.
• Biological control has not been successful, in most of the cases tested
• The host marking pheromone is a potential management tool and the sterile insect technique has been tested in Switzerland with limited success.
• Control strategies mostly rely on systemic organophosphates, such as organophosporous compounds (dimethoate), pyrethroids (deltamethrin), and neonicotinoids (thiamethoxam).
• More environmentally acceptable techniques have been tried; namely bait sprays which can be applied as a spot treatment; soil application of insecticide to destroy pupae; and juvenile hormone analogues which can be applied to the soil. 

 

Peach fruit fly, Bactrocera zonata

The Peach fruit fly, Bactrocera zonata, is native to South and South-East Asia and can now be found in more than 20 countries. It is a tropical species and unable to survive in extreme cold. B. zonata a very distactive, polyphagous species, with high reproductive potential (as many as 600 eggs in a lifetime), high biotic potential and long range dispersal ability.. Its current geographic range includes at least three African countries (Egypt, Sudan, and Libya) several islands of the Indian Ocean (Mauritius and Réunion) and several countries of the Arabian Peninsula (Oman, Saudi Arabia; United Arab Emirates and Yemen). The recent report of B. zonata at the Gezira region of Sudan indicates a southward spread and potential risk for the Sub-Saharan regions of Africa. Following introduction, B. zonata can easily adapt and spread, especially in South Eastern Europe.

The peach fruit fly is of quarantine significance for the EPPO (the European and Mediterranean Plant Protection Organization) countries. The pest is included in the A1 List of Pests recommended for regulation as quarantine pests.

Adults of B. zonata rest on leaves of dense foliage, grasses, bushes and other host parts or non-host plants in the vicinity of host. Bactrocera zonata overwinters mainly in the pupal stage and the adults emerge when the ambient temperature increases. Mated female, after selecting a suitable host for oviposition, inserts their ovipositor in the host tissues and deposits three to nine eggs at one time. The hatched larvae feed and grow inside the host. The duration of immature stages varies at different temperatures. No stages develop at 15°C or less, the optimum temperature is 25-30°C. Full-grown larvae enter the soil for pupation. Pupal duration is quite long during winter. Adults emerge from pupae, mainly in the early hours of the morning.

 Critical points for population monitoring and control:

• The peach fruit fly has similar wing pattern and adult morphology in general, with few other tephritids, such as Bactrocera correcta and Dacus ciliatus. Particular care should be taken not to confuse it with Bactrocera affinis, a very similar species that attacks wild fruits in some areas of southern India.
• Population monitoring of B. zonata can be achieved using adult traps baited with the male-specific lure methyl eugenol and/ or carrying a killing agent.
• The use of chemical control based on bait sprays and relatively less hazardous insecticide such as malathion seem to be the most convenient and efficient control methods available.
• The FAO/IAEA peach fruit fly action plan gives very detailed indications on trapping, monitoring and control of B. zonata (FAO/IAEA, 2000).
• These methods should be used in conjunction with fruit sanitation programs and phytosanitary regulation activities.
• Preventive sprays may be applied in areas that are at risk.
• The male annihilation technique is the most suitable method available to date for the eradication and control of B. zonata.
• The use of lure-and-kill stations is often preferred.

 

Ethiopian fruit fly, Dacus ciliatus

The Ethiopian fruit fly, Dacus ciliatus, is an oligophagous species, attacking mainly cucurbit fruit (melon, watermelon, zucchini, cucumber, etc.). In South Israel the fly is active year-round with two main peaks in spring and fall. Extreme temperatures (both high and low) reduce the fly’s activity and the fruit damage. The fly seems to have invaded the South of Israel from Sinai, Egypt, several years ago. It is now established in the Arava desert. In laboratory conditions, one generation of the fly (from egg to sexually mature adult) may take approximately 30 days at 25˚C. In the Arava, economic damage is reported in melon (Cucumis melo), but other crops, such as zucchini and cucumbers are also affected. Damage in melon is more severe during the early stages of fruit formation, when the skin is soft and before color break. However, in soft skin fruits, damage by D. ciliatus can be recorded during all developmental stages. Due to its recent establishment, no clear control protocols have been developed for this invasive fly.

 Critical points in population monitoring and control:

• There is little information regarding the efficacy of traps to detect D. ciliatus.
• Adult males do not respond to synthetic male lures used to detect most other pest species of Dacus or Bactrocera.
• Both sexes may be monitored using protein bait traps.
• Recent experiments led to the conclusion that the fly seems to be attracted to low concentrations of some “food lures” and to volatiles emanating from mature melons. Yellow Sticky Traps have been shown, at least in desert areas, to be very effective as a monitoring tool.
• Insecticide protection is possible by using a cover spray.  
• Dacus ciliatus adults are sensitive to low concentrations of spinosad baited with 1% yeast hydrolysate and 10% sucrose as phagostimulant
• A garlic barrier (GB Ag; garlic juice 99.98% pure) reduces the infestation of D. ciliatus when used on gherkin cultivation.
• Entomopathogenic nematodes, Steinernema feltiae (NC) and Heterorhabditis bacteriophora (BA1) efficiently controlled D. ciliatus larvae and pupae, whereas treatment with profenofos and pirimiphos-methyl caused even higher mortality. However, these insecticides are not registered for these types of applications in many countries, including EU.
• Physical protection, cultivation in tunnels, provides a more environmentally acceptable approach.