The Peach Fruit Fly, B. zonata, is a serious pest of fruits and vegetables in South-East Asia. It causes damage to horticultural crop losses 25- 100% in mango, peach, guava, apricot, and figs. Chemical insecticides against peach fruit fly are effective and in practice for several decades, however, have several drawbacks.
Methods For Management of Peach Fruit Flies
The peach fruit fly (Bactrocera zonata) affects more than 42 different fruit crop species including apple, apricot, avocado, citrus, custard apple, eggplant, guava, kumquats, mango, nectarine, okra, papaya, peach, pear, quince, rockmelon, sapodilla, tomato and watermelon. It represents a serious threat to fruit and vegetable production and marketing in the areas where it occurs, particularly because of its broad host range.
There are several methods for management peach fruit flies that have potential and are the best alternatives to chemical control such as sanitation, plant resistance, harvesting time, fruit bagging, bait application technique, male annihilation technique, sterile insect technique, parasitoids, predators, entomopathogens, and botanicals.
Chemical Control
Chemical control is the most common method used and several pesticide formulations have shown effectiveness for various fruit fly species. Despite the disadvantages of pesticide applications for the environment, this method is still used alone or in combination with other control agents against numerous fruit flies species.
In Pakistan, endrin, dialordin, dipterex, dimecron, diazinon, and malathion were used as a cover spray-on mango orchards against peach fruit fly. Different chemicals target various developmental stages of the fruit flies. Malathion targets the adults while diazinon, target the popping larvae and emerging adults.
It is reported that at 24 hours after treatment, diazinon was the most toxic compound to the peach fruit fly, followed by Malathion, Lufenuron, and Methoxy fenozide, males had LC50 values of 0.20, 0.48, 8.97, and 9.73 ppm, while females had LC50 values of 0.26, 0.91, 11.26, and 14.12 ppm. Diazinon has been used extensively in soil drench applications to control immature fruit fly stages, mature larvae, pre-pupae, and pupae.
Direct application of chemicals has led to a number of detrimental effects like accumulation of pesticide residues in the environment, mortality of non-target species that can be beneficial to the ecosystem, development of resistance, also exposing the consumers and producers to health risks.
The results suggest that B. zonata has developed resistance to trichlorfon, malathion, bifenthrin, λ-cyhalothrin, and spinosad. These insecticides have successfully contributed to the suppression of peach fruit fly populations when combined with traps and attractants.
Physical Control
Pre-harvest fruit bagging and post-harvest quarantine treatments are two physical methods of fruit fly control. Fruit bagging is an effective method for keeping the environment and the fruit physically apart. It is mainly based on the wrapping or bagging of individual fruits to prevent female oviposition.
In addition to disease and insect pests, fruit bagging reduces mechanical damage, fruit cracking, sunburn, bird damage, and agrochemical residues. This is done before the fruits reach the stage of maturity at which they are susceptible to infestation. There have also been reports of fruit bagging for contribution in reducing peach fruit fly infestation by fruit flies.
It is suggested that the use of double-layer brown-colored bags would be an eco-friendly management measure against the infestation of fruit flies. However, mango farmers must bag their mango after 40-55 days of fruit set.
Cultural Control
These techniques include the selection of a tolerant variety, early harvesting prior to fruit maturity, ensuring field sanitation by collecting and destroying infested, dropped, damaged, and overripe fruit, and raking and plowing to expose the pupae to sunlight and predators. Multiple research and reports have shown that cultural approaches minimize the rate of adult emergence of various species of fruit flies. In mangoes, there is a strong variability of fruit fly resistance consistent with efficiency and consistency.
The fruit peel is responsible for oviposition resistance. Infestation of fruit flies may also be prevented by harvesting crops before the stage of maturity where the fruit or vegetable is not vulnerable to fruit fly attack and can minimize fruit damage or decrease fruit damage. Proper field sanitation is important to minimize B. zonata populations, infested fruits should be harvested from a field, buried at least 50 cm below the soil surface, or put in plastic bags and left out in the sun for about 10 days for most of them to die for infestation-free fruit.
Behavioral Control
Behavioral Control of fruit fly management included two main tactics that are Sterile Insect Technique (SIT) and Attract and Kill technique. Which is further divided into the Male annihilation technique (MAT) and the Bait application technique (BAT).
Bait Application Technique (BAT)
Management of peach fruit fly mainly depends upon the use of food baits mixed with an agent used for killing. Bait spray is currently successfully used in some fruit fly control programs. Many studies have demonstrated that baiting is an effective to control either used alone or in combination with other control agents against many fruit flies species. Both male and female fruit flies are attracted to these lures.
Researchers have find out that a formulation containing beef extract, borax, molasses, and malathion can be used to track and manage the peach fruit fly, B. zonata. Mostly, commercially these attractants provide sugar and protein sources to adults. Several natural compounds (corn, milk, and soy), synthetic lures (ammonium and trimethylamine), bacteria (Enterobacteriaceae) have been evaluated as food-bait attractants and have become commercially available to detect and control peach fruit fly adults.
In attraction adults of peach fruit fly, Ammonium Acetate was the strongest possible attractant in synthetic food-odor lures. The bait Application Technique has minimum effect on natural enemies and pollinators. This method is less time-consuming and less laborious.
Male Annihilation Technique
In this method, pheromones are used in controlling fruit flies. This strategy use to attract and kill technique and consists of pheromones which attract the male adults onto a killing agent (insecticide). MAT aims to reduce the population of the males of the peach fruit fly hence reducing the chances of mating and the most effective in controlling peach fruit fly. Fruit fly pheromones are extremely species-specific and effective at attracting fruit flies from long distances Many types of attractants have been reported to attract fruit flies.
Methyl eugenol and Cuelure are widely used as attractants for males of peach fruit fly. Findings show that methyl eugenol attracts male peach fruit flies, and that using a methyl pheromone trap, we can easily reduce the population of adult peach fruit flies. This tactic is useful if it is used with an “area-wide” suppression strategy.
This approach is used as spot treatments, with several dispensers acting as carriers of methyl eugenol and toxicant (such as neutral cord, cotton cord, felt block, and plant fiber blocks). Insecticides used in MAT are mostly organophosphorus compounds including Malathion, Dichlorvos, and Naled. From a distance of 1km, 2g of poison Linate and 2cc of lure will attract the peach fruit fly, B. zonata, and kill it easily for up to 15 days.
Sterile Insect Technique (SIT)
The sterile insect technique (SIT) has been used to control other tephritid pests, and it could be used to control peach fruit fly as well. This method involves artificially sterilizing male fruit fly populations and then releasing massive groups of sterile males into infested areas, where they mate with wild females. This is done to interrupt the normal reproductive cycle of insects and leads to the leads the females to produce infertile eggs or not lay eggs, it is species-specific.
Fruit flies are exposed to Xrays, gamma rays, and electron beams. The effects of Gamma rays on B. zona ta include adult emergence, sex ratio, male and female sterility and deformed pupae, pupal size, flight ability, female fecundity, and mating competitiveness of peach fruit fly sterile males. It is stated that there is possibility peach fruit fly management/or eradication at Gamma rays radiation dose 3.5 Kr in SIT. Sterile males can also use as a vector to transmit the diseases to adults.
In a sterile insect release program, the sterile peach fruit fly. males may be used as B. bassiana vectors to supplement pest suppression. When compared to wild males, the fruit fly mass-rearing process and radiation sterilization of the males in SIT can sometimes result in a reduction in the consistency of the released sterile males. So far, there are limited scientific data available for the suppression of peach fruit fly population using sterile insect technique.
Botanicals Control
Botanical insecticides are typically pest-specific and relatively safe for non-target species, such as humans. They are also biodegradable and environment friendly. Moreover, unlike traditional insecticides, which are limited to a single active ingredient, plant-derived insecticides are made up of a variety of chemical compounds that work together to affect both physiological and behavioral processes. As a result, the likelihood of pests developing resistance to such substances is reduced.
The acetone extract of turmeric outperformed the petroleum ether, acetone, and ethanol extracts as a growth inhibitor and repellent against peach fruit fly. It is demonstrated that Curcuma longa, Acorus calamus, and A. indica, all have repellent and growth-inhibiting properties against peach fruit fly. Three plant species, Peganum harmala, Saussurea lappa, and Valeriana jatamansi were evaluated after being isolated in petroleum ether (a mixture of C5-7 alkanes). The most successful oviposition deterrent for B. zonata was P. harmala.
The most promising repellents against peach fruit fly were petroleum ether extract of C. longa, ethanol, and acetone extract of P. harmala. P. harmala acetone extract, V. jatamansi ethanol extract, and S. lappa petroleum ether extract was also found to be effective oviposition deterrents. The overall egg-laying was suppressed by C. colocynthis. The egg repellency effect of neem on eggs deposited in orange fruits after being sprayed with previous concentrations was high, reaching 5.0% eggs/puncture/fruit, compared to 65.8% for the control. Furthermore, at 600 ppm, the percent of eggs hatching decreased to 76.2 %, compared to 89.0 % in the control group.
Biological Control
Biological control is an economical method and poses less threat than pesticides to humans and the environment. There are various strategies, including inoculation, inundation, classical and conservation biological control for introducing biocontrol agents within insect control programs. Natural enemies, parasitoids, predators, and pathogens are commonly used in biological control, which act by feeding on the pest, parasitizing the pest, and causing diseases.
Conclusion
The peach fruit fly represents a serious threat to fruit and vegetable production and marketing in the areas where it occurs, particularly because of its broad host range. Farmers currently use spraying pesticides for the control of pests and diseases. Not only did these behaviors exacerbate over time the pest rating over, but they also influenced the risks associated with insect killers. Therefore, there is a need for the period to shift from insect-killing plant protection to integrated pest management to decrease the use of pesticides, mainly in horticultural crops.
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