Entomology, Ornithology & Herpetology: Current Research
Open Access

The Major Sweet Potato Weevils; Management and Control: A Review

Kyereko WT, Hongbo Z^*, Amoanimaa-Dede H, Meiwei G and Yeboah A ^*Correspondence: Hongbo Z, Zhu Hongbo, Key Laboratory of Molecular Breeding, Department of Biotechnology, College of Agricultural Sciences, Guangdong Ocean University, Huguang Yan East, Zhanjiang 524088, Guangdong Province, China, Tel: +86 13553488884, Email:

Author info »

Introduction

Sweet potato belongs to Convolvulaceae family with more than a hundred developing countries, known to cultivate sweet potato and are ranked the 5^th most essential foodstuff in over 50 of those countries [1] and globally, 7^th amongst the entire food production [2], but has lesser experimental work than other staples such as potato (Solanum tuberosum) and wheat (Triticum aestivum). Sweet potato as an economic value crop, the vital staple food, grown in over one hundred different countries, its main root and tuber grown in the tropical and subtropical regions of the world in the developing world [3]. Although sweet potato is known to originate from South and Central America, Asia is known to be the world producer, particularly China carrying the highest yield of the sweet potato nationwide [4].

Due to sweet potato superior qualities, it has given great potential for reducing hunger, specifically, in low-income households in developing countries [5]. Different sweet potato varieties have nutritionally beneficial compounds [6]. Sweet potato provides a source of calories, vitamins, dietary fiber, and potassium, especially in rural areas [7,8]. Currently, researchers have found that sweet potato contains anti-oxidative properties [9], making sweet potato increasing the importance in developed countries, but in less developed areas, hower, attention is towards raising the nutritional value of the product [10,11]. Carotenoids in sweet potato have helped in avoiding nutritional deficiency in children [7,12,13].

Despite the economic demand for sweet potato, roots are highly perishable, if not well treated and adequately stored, and are mainly threatened by insect pests that can lead to severe economic loss. By far, the absolute limit of sweet potato yield worldwide is damage of the plant caused by weevils [14,15]. Sweet potato weevils are widely spread throughout the tropical regions of the world, but the methods of control are the significant problem faced by growers in most countries producing sweet potato. Cylas formicarius (Fabricius), Euscepes postfasciatus (Fairmaire), Cylas brunneus (Fabricius) and Cylas puncticollis (Boheman), are the 4 key species of sweet potato weevils that cause the most enormous damage to sweet potato cultivation area [16,17]. This review aimed to summarize the infestation of sweet potato weevils, mode of infestation of weevils on sweet potato and various control strategies towards decreasing infestation of weevils in sweet potato plantation, hence increasing yield.

Major sweet potato weevils; mode of Infestation

Generally, weevils cause severe feeding destruction to sweet potato roots, vines, stems and leaves through their life cycle, beginning from the egg stage to adult stage. After mating, females lay eggs, create tunnels in holes inside the roots below the surface, the laid eggs are covered with dark colour excrement [18], making it unattractive for a market.

Hatching generally occurs a week after oviposition. Several tunnels are constructed within the root and feeding within the circle by the hatched larvae [19]. The larvae then fill tubes inside sweet potatoes with excrement. Continuous feeding by the larvae, result in unpleasant smells on the sweet potato as well as terpene odor, making it unacceptable for consumption by humans or animals. The occurrence of terpenoid decreases the market value and quality roots [20]. Physically the appearance of root tubers turns out to be soft, dark in color and filled with cavities caused by mining of larvae in the sweet potato, leading to the main damage cause to sweet potato.

Due to destructive action by weevils, United States quarantine actions are tough on growers, since it has a significant economic effect on the whole crop, and this has made farmers abandoned production of sweet potato [21].

Clearly, after a heavy infestation of weevils, the vine becomes yellowish, and this mark as symptoms of weevil infestation [22–24] (Figure 1). Considering the significance of soil cover, weevils of sweet potato is a critical obstacle in arid seasons [25,26]. At hand, there are four life cycle stages that weevils undergo [3] and their life span for each stage is much dependent on the climate and the temperature of the location.

Figure 1: Weevil feeding damage on root, stem, vine and leaves of sweet potato.

Several research works have determined that the increase in temperature, the higher the rate of population of insect growth, and the threat and severances of the insect occurrence [27,28]. At lower elevations of less than 2000 m above sea level, damage to the crop tends to be more [26,29]. In the drier period, the higher the temperature, the higher the frequency, may be the possible influence on sweet potato weevils [26].

The infestation of sweet potato weevils depends mostly on cracks in dry soil to get to the firm root since weevils cannot dig into the ground under buried soil. Cracks in the soil can also be developed when there is stress from soil moisture and development of roots close to the soil surface and then subjecting roots to sweet potato weevils.

The 4 sweet potato weevils infest sweet potato equally in the field and at storage, causing extensive losses of up to 60% to 100% [30]. Rough weevil, striped weevils, and peloropus weevils are other weevil pests of sweet potato [16,31,32]. The different Cylas spp are located in distinct geographic regions, but their mode of action and damage symptoms to sweet potato plant are similar (Table 1) [33-45].

Table1: The life cycle and mode of infestation of weevils.

Causes of Infestation of Sweet Potato Weevils

Stage of stem cutting

In older parts of vines, female weevils lay eggs, especially when the storage roots are absent. Cuttings that are younger are not often infested with sweet potato weevils. Asian Vegetable Research and Development Center recorded that high intensification of weevils in vines is caused by the rise in vine age. Vines can be free from weevil infestation by dipping into a solution of insecticides [46].

Altitude and season

Location of altitude and season of the planting of sweet potato has a connection in weevil infestation. Numerous research studies stated that an increase in temperature may give a higher growth rate of the population of insects and severity of occurrences [27,47]. At planting period from August-November, the number of weevil infestation increase at a rate of 87% as compared to the period of planting from June-July, where the infestation of weevil rate at 10.9% in India [48]. In India, research conducted indicated that damage on tubers increased at a higher rate of 71% during the season of summer from February to May as compared to the wet season at a rate of 45% from June to September [49].

At an altitude, a research conducted in Kerala shows that damages on tubers by weevil infestation was observed to be lower of up to 22% at lowland level whiles at upland level, weevil infestation damage on tuber increase at a rate of 4%-50% [49]. Also in Uganda, studies reported that there is an increase in a number of weevil infestation at a rate of 77% at lowland above sea level at 1814 m compared to the amount of weevil infestation at altitude, higher at a rate of 23% up to 1992-2438 m above sea level [26].

The weevil infestation may also be affected by planting method, cultivar planted as well as the level of sanitation. The infestation of weevils can decrease by the use of cultivars with good resistance against weevils, proper harvesting time and location for planting since observation has shown that the destruction of incidence caused by weevils of sweet potato was detected to be lower during the rainy season, because there is no crack to access the roots as compared to the dry season [50].

Physical characteristics of sweet potato

Physical qualities including shape, thickness, and length of neck and colour of the skin of sweet potato influence weevil infestation. Round and oval shape tubers of sweet potato were also infested by weevil more severely as compared to longer ones. Besides, brown and white colored cultivars are more susceptible to weevil infestation as compared to red and pink cultivars of sweet potato [51].

Early maturing of 90-120 days and deep-rooted cultivars are less prone to infestation as compared to the late maturing of more than 180 days and shallow-rooted, since 95% or more of female weevil’s oviposition takes place in vines at the first 35 cm [52].

Control and management strategies of sweet potato weevils

Intercropping

Intercropping sweet potato with yam, cowpea, maize, ginger, and rice decreases the occurrence of weevils. There was a drastic decrease in Cylas formicarius species in India where the sweet potato was intercropped with cowpea, taro or rice [37]. In India, a study revealed several agronomic importance such as weevil suppression and soil moisture conservation, intercropping with different kinds of crop species [53]. In Taiwan, different crops of about 103 were tested, the best result was recorded from intercropping with coriander (Coriandrum sativum L.) [54].

Effective cultural practices

Cultural practices are aimed at preventing infestation of weevil. Weevils can feed on sweet potato and weeds in the same plant family, thereby making cultural controls as a potentially useful control method in sweet potato production [55,56]. Some cultural practices in sweet potato include the elimination of dead crops, separation of un-infested planting material, elimination of unwanted plant and alternative wild host as well as rotation of crops in order to set up a free pest material and avoiding frequent buildup in new crops [37,57]. Some cultural practices in controlling of sweet potato weevils are shown in Table 2 [58-65].

Table 2: Sweet potato cultural practices.

Soil management

Management of soil helps to avoid cracks in the soil, which aimed to minimize crop destruction as much as populations are existence. Weevils of sweet potato cannot tunnel into the soil, but instead, they like cracked or dry soil which gives them the right entry to the roots.

Mounding soil or mulching are frequently used in preventing soil cracking [66]. Plastic materials, as well as straw ensure a barrier for the development of weevils into the soil [57,67]. Mulching with elephant grass at a level between 1 and 5 tonnes per hectare decrease the infestation of weevil as well as help to improve the yield of storage root [68].

Sterile Insect Technique (Sit)

The use of SIT is an important approach to decrease the population of weevil in sweet potato production. SIT means irradiation of weevil with gamma rays, and are used for tubers that are put in storage for a prolonged period of time or export purposes. SIT has mostly used for the sterilization of weevils [69,70] and eradication programs where there is a release of irradiated weevils into the environment [71]. In Japan, Okinawa Prefecture programs for eradication for sweet potato weevil species Euscepes postfasciatus [39,45,71].

The central importance of the releasing sterile male helps populations decrease, together with other methods, helps to make the location a pest free. Sterile males during mating with females will not result in progeny, which then produce in total decreased in population in the next generation [72]. For example, radiations cause adverse effects on somatic cells and lower insect viability, which affects fertility when there is an increase in absorption. [73]. Again, radiation destroys the midgut epithelium, which disturbs the process for insect’s nutrition [74]. Due to the long generation, time for eradication program is most expected to take place at a more prolonged period, and difficulties occurred throughout the mass rearing [45].

Sterile Insect Release (Sir)

SIR is one of the essential methods in controlling sweet potato weevil infestation. In 2001, some researchers performed long-term research to look into the effectiveness of the SIR technique to clear and destroy weevil species, Cylas formicarius in the field [75].

In 1994 and 1995, weevils were irradiated with 80 Gy by some researchers; they stained with fluorescent dyes, free them in a relief zone. In 1994 to 1995, root and pheromone traps were used to monitor the weevils, and in 1996, the sterile weevil-free effect was rechecked. But in 1995, the number of the unmarked results reviewed that weevils captured in the free zone was lessened to virtually nothing whilst in 1996, in both pheromone and root traps no living weevils were obtained at the time of rechecked in the release zone. All results obtained in various years indicated that the SIR technique is a beneficial method in preventing infestation of weevil [76].

In 2008, another research scientist performed a trial to find out the effect of irradiation 200 Gy dosage on the mating capacity in sweet potato weevils, Cylas formicarius elegantulus, main aimed to compare various characteristics such as performance on mating,longevity and mating effectiveness with the control male. At the end of the trial, the existence of male weevils was reduced once it was being irradiated with gamma rays [71].

Pheromone control

Field and laboratory observations show that there are perhaps sex pheromones for Cylas puncticollis and Cylas formicarius. In rearing rooms, the behavior of gregarious clumping was known, and the definite attraction of males to the females [77] whilst in the field, males, are mostly set up under foliage seeking for females. Tests at the laboratory have pointed out that, males are attracted to females. The probability of using unmated females and virgin as baits for males in traps was examined in Kenya [78].

In a timely manner, a pheromone has been explicitly improved for examining weevil species, Cylas formicarius so that control methods can be carried out [38,79].

The pheromone (Z)-3-dodecen-1-ol (E)-2-butenoate has shown to be more effective mating for the prevention of Cylas formicarius [80,81], mainly for trapping both sexes of weevils. With a dose of 100 mg of sex pheromone, 60.88% weevils were attracted. During different parts of the day, the weevil trap varies significantly.

Traps that are fixed close to the ground trapped more males compared to those set above the ground [81], several kinds of traps for preventing weevils are sticky, a plastic funnel, water, and light pheromone.

Japan has developed an insecticides or pheromone supply system in the way of low volume formulation insecticide and pheromone permeated into a blue ball of diameter 2 mm where male weevils would attempt to mate by coming into contact with the pheromone or insecticides [82]. The combination of B. bassiana and B. pheromone attracts male weevils [56,83,84]

Host plant resistance

The selection of different cultivars over the years by the farmer was based on a higher resistance to weevils, for instance, the use of deeprooted cultivars can make the roots less accessible for oviposition female weevils [37,85,86].

Orange-fleshed varieties are exposed to superior resistance [87]. Dry matter content influences the resistance of weevils [88], with an increase in dry matter content, cultivars tend to reduce susceptibility [89]. Landrace varieties are generally acceptable to local consumers since they have traits and have good adaptability to the environment [90-92].

Varieties with resistance to weevils are as a result of hydroxycinnamic acid esters on the exterior and the root latex, decreases weevil’s nourishment and oviposition. Hydroxycinnamic acid esters now will be implemented as a character in breeding approaches, which were conducted in recent research work in Africa [93]. This research work gives other chances for sweet potato location where the collection of germplasm that exists can be examined for similar compounds that provide resistance to the importance of weevil species.

Researchers in different countries have expressed views in using Bacillus thuringiensis in production of sweet potato. For instance, in sub-Saharan agriculture, the application of transgenic Bacillus thuringiensis sweet potato is considered as an attractive alternative to lowering the mobility of conventional breeding for the resistance of host-plant and other pest management selection in which few thought about it to be more costly for growers to practice [94,95].

Currently, Transgenic sweet potato cultivars expressing Cry proteins of Bacillus thuringiensis are in progress [96]. Bacillus thuringiensis protein expression in sweet potato has been introduced in Cuba [97], China [98] and India [99].

Integrated Pest Management (Ipm)

IPM managements are used in several approaches to control a large number of damage pest including; cultural practices such as field sanitation, crop rotation, site selection, correct planting season, plant spacing, companion cropping and soil water management, biological control such as natural enemies which feeds and protect crops, mechanical control such as hand picking and screening and chemical control, but most farmers practice is limited [100], because of their lack of knowledge on the biology of the pest.

IPM approach programs such as pheromones trap, Entomopathogenic fungi, cultural method and resistant cultivars has improved the yield in Cuba from 6 tonnes per hectare to 15 tonnes per hectare [101]. Also, the IPM program implemented in Taiwan has helped the local farmers; these applied methods include crop rotation, alternate host removal, continuous pheromones trap and mulching [102]. The IPM implementation depends on proper dissemination of information, likewise training of farmer [103]. Strategies used in IPM has gain approval from growers, which helped growers to raise funds as soon as they are related to cultivars or techniques that can increase profit [104].

Chemical control

The use of insecticides in control of pest in sweet potato are usually too expensive or inaccessible to growers [90], even though insecticides are generally used in controlling sweet potato weevil in developed countries [16,37] but less among poor farmers.

Parathion and chlorpyrifos insecticides have shown greater toxicity and higher effectiveness in overcoming weevil infestation on sweet potato [80]. In Ethiopia, screening trials for both Deltamethrin and pirimiphos methy1 insecticidal showed reasonable control of sweet potato pests, especially when an application is made 3 months after planting [78]. A mixture of vine dipping of 0.05% monocrotophos and three sprays of foliar with endosulfan of 0.05% showed entirely useful as compared to the application of phorate granules at basal [105].

Time of applying insecticide can be range from one factor to systematic factor applications [37,106]. But for certain chemicals also, persistent toxicity is a problem through a residual observable for 10 months, whereas others, residual at harvest had no detection.

Planting vines that are dipped into insecticides are relatively at a low cost; the most commonly used insecticides by farmers. But most farmers usually lack basic knowledge on personal use of protective clothing and dangers of insecticides to the health of human leading to the potential danger to smallholder farmers [90]. Recently, some researchers reported spinosad and azadirachtin as low-risk insecticides to be active against Cylas formicarius in a trial work at the laboratory, but then their activeness was not examined in the field [107].

Drenching of Soil at 50 and 80; 60 and 90; and 50, 65 and 80 days after planting were similarly effective in destroying the incidence and intensity of weevil damage [108]. Amongst the single soil drenching, the 65th day application was assessed to be the most effective against the weevil. Endosulfan, fenthion, and fenitrothion each at 0.05% as applied by means of drench soil at 50 and 80 days after planting were efficient, and their damages in tubers during harvesting were lesser compared to the noticeable level [109].

Biological method

Different classes of insect have been identified as predators of Cylas spp [16,22,33], in different geographical regions, but the cost and technical know-how associated with their biological controls remains a challenge in the small scale farming system (Table 3) [110- 121].

Table 3: Biological methods for control of sweet potato weevils.

Conclusion and Recommendation

Sweet potato is one of the fastest and main growing crops in many countries, but due to the infestation of weevils, there is drastic loss in yield, especially in less developed countries on poor farming families. It is a clear indication from the review that sweet potato weevils are major constraints in production all over the world. But occurrence differs in different locations depending on the type of cultivar used and management methods adopted.

Weevils are not the same in different locations. Therefore control strategies are difficult by growers leading to low productivity. In order to decrease the impact of weevil’s infestation we have to develop an integrated pest management approach, such as cultural methods, based on the manipulation of weevil’s behavior, effectiveness pheromone trap makes it a significant approach within integrated pest management with the expectation of controlling sweet potato weevil, host plant resistance, biological control, time and appropriate rate of chemical application, natural enemies, reduction of insecticides impact on the environment and weevil-resistance varieties. Henceforth, the evolvement of integrated pest management strategies is important compared to a single management strategy.

Research teams now researching on transgenic weevil resistance can release long-awaited transgenic sweet potato with foreign genes that are resistant to the weevil’s infestation.

Extension officers should educate growers on sweet potato on the importance of using healthy planting materials and demonstrations approach should be performed on farms for growers to be skilled in controlling weevils at the early stage and variety screening by means of identifying traits that are best for combating the previous pests.

Conflict of Interest

The authors declare no conflict of interest.

Funding

The name of the Funder is National Natural Science Foundation and award number is U1701234.

References

1. Faostat F. Global production and consumption of root and tuber. In FAO corporate document repository. Report on the inter-center review of root and tuber crops research in the CGIAR. 2012.
2. Clark CA, Ferrin DM, Smith TP, Holmes GJ. Compendium of sweetpotato diseases, pests, and disorders. St. Paul, MN: APS press. 2013.
3. Lebot V. Tropical root and tuber crops: cassava, sweet potato, yams and aroids. Cabi. 2009;7.
4. Zhang L, Wang Q, Liu Q. Sweetpotato in china. Springer, Dordrecht. 2009:325-358.
5. Amoah RS. The effects of ethylene on sweetpotato storage. Cranfield University, England. 2014.
6. Islam S. Sweetpotato (Ipomoea batatas L.) leaf: its potential effect on human health and nutrition. J Food Sci. 2010;71:R13-R121.
7. Low JW. Biofortified crops with a visible trait: The example of orange-fleshed sweet potato in Sub-Saharan Africa. Handbook of Food Fortification and Health. 2013:371-384.
8. Mohanraj R, Sivasankar S. Sweet potato ( Ipomoea batatas [L.] Lam) - A valuable medicinal food: a review. J Med Food. 2014;17:733-741.
9. Nestel P, Bouis HE, Meenakshi JV, Pfeiffer W. Biofortification of staple food crops. J Nutr. 2006;136:1064-1067.
10. Ruel MT, Alderman H. Maternal and child nutrition study group. Nutrition-sensitive interventions and programmes: how can they help to accelerate progress in improving maternal and child nutrition. Lancet. 2013;382:536-551.
11. Woolfe JA. Sweet potato: an untapped food resource. Cambridge University Press, USA. 1992.
12. Kismul H, Van den Broeck J, Lunde TM. Diet and kwashiorkor: a prospective study from rural DR Congo. Peer J. 2014;2:e350.
13. Fuglie KO. Priorities for potato research in developing countries: Results of a survey. Am J Potato Res. 2007;84: 353.
14. Rees D, Van Oirschot QE, Amour R, Rwiza E, Kapinga R, Carey T. Cultivar variation in keeping quality of sweetpotatoes. Postharvest Biol Technol. 2003;28:313-325.
15. Chalfant RB, Jansson RK, Seal DR, Schalk JM. Ecology and management of sweet potato insects. Ann Rev Entomol. 1990;35:157-180.
16. Korada RR, Naskar SK, Palaniswami MS, Ray RC. Management of sweet potato weevil [Cylas formicarius (Fab.)]: An overview. J Root Crop. 2010;36:14-26.
17. Onwueme IC, Charles WB. Tropical root and tuber crops: production, perspectives and future prospects. Food Agr Org. 1994;126.
18. Uritani I, Saito T, Honda H, Kim WK. Induction of furano-terpenoids in sweet potato roots by the larval components of the sweet potato weevils. Agr Biol Chem. 1975;39:1857-1862.
19. Jackai LE, Ewete FK, Lajide L. Bioactive fractions of n-hexane extracts from Vigna pods against the legume pod borer, Maruca vitrata Fabricius. African J Biotechnol. 2006;5:1846–1850.
20. Sherman M, Tamashiro M. The sweetpotato weevils in Hawaii: their biology and control. Hawaii Agric Exp Sta Res Bull. 1954;23:1-36.
21. Jansson RK, Raman KV. In Sweet potato pest management a global perspective. International Potato Center. 1991.
22. Kuriwada T, Kumano N, Shiromoto K, Haraguchi D. Effects of intra- and inter-specific competition on fitness of sweetpotato weevil and West Indian sweetpotato weevil. J Appl Entomol. 2013;137:310-316.
23. Okonya JS, Kroschel J. Incidence, abundance and damage by the sweet potato butterfly (Acraea acerata Hew.) and the African sweet potato weevils (Cylas spp.) across an altitude gradient in Kabale district, Uganda. Int J Agri Sci. 2013;3:814-824.
24. Gomi T, Nagasaka M, Fukuda T, Hagihara H. Shifting of the life cycle and life-history traits of the fall webworm in relation to climate change. Entomol Exp Appl. 2007;125:179-184.
25. Ladányi M. The effect of climate chan ge on the population of sycamore lace bug (Corythuca Ciliata, Say, Tingidae Heteroptera) based on a simulation model with phenological response. Appl Ecol Environ Res. 2014;4:85-112.
26. Lutulele RP. Sweet potato variety developments in the PNG highlands: implications for future research and extension focus. Proc Papua New Guinea Food Nutr. 2001;683-688.
27. Sorensen KA. Sweetpotato insects: identification, biology and management. Springer, USA. 2009;161-188.
28. Skoglund LG, Smit NE. Major diseases and pests of sweetpotato in eastern Africa. International Potato Center (CIP), Peru.1994:67.
29. Ames T. Sweetpotato: major pests, diseases, and nutritional disorders. International Potato Center. 1997.
30. Waterhouse DF, Norris KR. Biological control: Pacific prospects. Inkata Press. Suppl 1: 1987.
31. Austin DF, Jansson RK, Wolfe GW. Convolvulaceae and cylas: a proposed hypothesis on the origins of this plant/insect relationship. Trop Agric. 1991;68:162-170.
32. Horton DE, Ewell PT. Sweet potato pest management: a social science perspective, Westview Press, USA. 1991;407-427.
33. Kandori I, Kimura T, Tsumuki H, Sugimoto T. Cold tolerance of the sweet potato weevil, Cylas formicarius (Fabricius) (Coleoptera: Brentidae) from the southwestern islands of Japan. Appl Entomol Zool. 2006;41:217-226.
34. Korada RR, Naskar SK, Palaniswami MS, Ray RC. Management of sweet potato weevil [Cylas formicarius (Fab.)]: An overview. J Root Crop. 2010;36:14-26.
35. Jansson RK, Raman KV. Sweet potato pest management. A Global Perspective. International Potato Center. 1991.
36. Moriya S, Miyatake TS. Eradication programs of two sweetpotato pests, Cylas formicarius and Euscepes postfasciatus, in Japan with special reference to their dispersal ability. Japan Agr Res Q. 2001;35:227-234.
37. Ondiaka S, Maniania NK, Nyamasyo GH, Nderitu JH. Virulence of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae to sweet potato weevil Cylas puncticollis and effects on fecundity and egg viability. Ann Appl Biol. 2008;153:41-48.
38. Mohamed AEZB. Biology, ecology and management of the sweetpotato weevil, Cylas puncticollis Boheman (Coleoptera: Brentidae). University of Khartoum, Sudan. 2005.
39. Smit NE, Van Huis A. Biology of the african sweetpotato weevil species Cylas puncticollis (Boheman) and C. brunneus (Fabricius)(Coleoptera: Apionidae). Int J Trop Insect Sci. 1998;18(2):93-100.
40. Katsuki M, Omae Y, Okada K, Kamura T, Matsuyama T, Haraguchi D, et al. Ultraviolet light-emitting diode (UV LED) trap the West Indian sweet potato weevil, Euscepes postfasciatus (Coleoptera: Curculionidae). Appl Entomol Zoo. 2012;47:285-290.
41. Kumano N, Haraguchi D, Kohama T. Effect of irradiation on mating ability in the male sweetpotato weevil (Coleoptera: Curculionidae). J Econ Entomol. 2008;101:1198-1203.
42. Sato Y, Miyai S, Haraguchi D, Ohno S, Kohama T, Kawamura K, et al. Population dynamics of the West Indian sweetpotato weevil Euscepes postfasciatus (Fairmaire): a simulation analysis. J Appl Entomol. 2010;134:303-312.
43. Smith N, Odongo B. Integrated pest management for sweet potato in Eastern Africa. International Potato Center (CIP). Peru. 2002.
44. Ladányi M, Hufnagel L. The effect of climate change on the population of Sycamore lace bug (Corythuca ciliata, say, tingidae heteroptera) based on a simulation model with phenological response. Appl Ecol Environ Res. 2006;4:85-112.
45. Kurup GT. Tropical Tuber crops: problems, prospects and future strategies. Sci Publ. 1996.
46. Rajamma P. Biology and bionomics of sweet potato weevil Cylas formicarius Fabr. Biol Bionomics Sweet Potato Weevil Cylas Formicarius Fabr. 1983;87-92.
47. Sutherland JA. Damage by Cylas formicarius Fab. to sweet potato vines and tubers, and the effect of infestations on total yield in Papua New Guinea. Int J Pest Manag. 1986;32:316-323.
48. Teli VS, Salunkhe GN. A search for sources of resistance to sweet potato weevil. I Morphological Traits J Maharashtra Agr Univ. 1995;20:400-402.
49. Lima M, Morales A. Estudios comparativos de clones precoces de boniato. Agr Eng Thesis Univ. 1992.
50. Nedunchezhiyan M, Rajasekhara RK, Laxminarayana K, Satapathy BS. Effect of strip intercropping involving sweet potato (Ipomea batatas L.) on soil moisture conversation, weevil infestation and crop productivity. J Root Crop. 2010;36:53-58.
51. Stathers T, Namanda S, Mwanga RO, Khisa G, Kapinga R. Manual for sweetpotato integrated production and pest management farmer field schools in sub-Saharan Africa. 2005.
52. Talekar NS. Characteristics of infestation of sweet potato by sweet potato weevil Cylas formicarius (Coleoptera: Apionidae). Int J Pest Manag. 1995;41:238-242.
53. Nottingham SF, Kays SJ. Sweetpotato weevil control. In I International Conference on Sweetpotato. Food Health Future. 2001;583:155-161.
54. Jackson DM, Bohac JR, Dalip KM, Lawrence J, Clarke-Harris D, McComie L, et al. Integrated pest management of sweetpotato in the caribbean. Acta Horti. 2002:143-154.
55. Komi K. Eradication of sweetpotato weevil, Cylas formicarius Fabricius, from Muroto City, Kochi, Japan. Food Fertilizer Tech Center. 2000.
56. Geisthardt M, Van Harten A. Noxious beetles of the Cape Verde Islands with additional reference to West Africa: an illustrated guide to the identification of actual and potential coleopterous pests of crops, stored food and wood. 1992.
57. Asian Vegetable Research and Development Center (AVRDC). Sweet potato breeding and sweet potato entomology. AVRDC Progress Report. 1987;163-198.
58. Ebregt E, Struik PC, Odongo B, Abidin PE. Pest damage in sweet potato, groundnut and maize in north-eastern Uganda with special reference to damage by millipedes (Diplopoda). J Life Sci. 2005;53:49-69.
59. Powell KS, Hartemink AE, Eganae JF, Walo C, Poloma S. Sweet potato weevil (Cylas formicarius) incidence in the humid lowlands of PNG. Aus Centre Int Agr Res. 2001:736-746.
60. Streffer C, Shore R, Konermann G, Meadows A, Uma PD, Preston JW, et al. Biological effects after prenatal irradiation (embryo and fetus). A report of the International Commission on Radiological Protection. Ann ICRP. 2003;33:5-206.
61. Otto N, Russel M, Eric C. Sweet potato weevil. A review of recent management advances and appraisal of previous research in Papua. 2006.
62. Nair GM. Cultural and manurial requirements of sweet potato. Prod Technol Tuber Crop Cent Tuber Crop Res. 2000:44-64.
63. Smit NE. The effect of the indigenous cultural practices of in-ground storage and piecemeal harvesting of sweetpotato on yield and quality losses caused by sweetpotato weevil in Uganda. Agric Ecosyst Environ. 1997;64:191-200.
64. Talekar NS. Effects of a sweet potato weevil (Coleoptera: Curculionidae) infestation on sweet potato root yields. J Econ Entomol. 1982;75:1042-1044.
65. Mansaray A, Sundufu AJ, Moseray MT, Fomba SN. Sweet potato Weevil (Cylas puncticollis) boheman infestation: cultivar differences and the effects of mulching. Open Entomol J. 2015:9.
66. [69] Follett PA. Irradiation as a phytosanitary treatment for aspidiotus destructor (Homoptera: Diaspididae). J Econ Entomol. 2006;99:1138-1142.
67. Hallman GJ, Phillips TW. Ionizing irradiation of adults of angoumois grain moth (lepidoptera: gelechiidae) and indianmeal moth (lepidoptera: pyralidae) to prevent reproduction, and implications for a generic irradiation treatment for insects. J Econ Entomol. 2015;101:1051-1056.
68. N. Kumano, Haraguchi D, Kohama T. Effect of irradiation on mating ability in the male sweetpotato weevil (Coleoptera: Curculionidae). J Econ Entomol. 2008;101:1051-1056.
69. Kumano N, Kuriwada T, Shiromoto K, Haraguchi D, Kohama T. Prolongation of the effective copulation period by fractionated‐dose irradiation in the sweet potato weevil, Cylas formicarius. Entomol Exp Appl. 2011;141:129-137.
70. Calkins CO, Parker AG. Sterile insect quality. Springer, Netherlands. 2005: 269-296.
71. Bakri A, Mehta K, Lance DR. Sterilizing insects with ionizing radiation. Springer, Netherlands. 2005:233-268.
72. Setokuchi O, Sugimoto T, Yamaguchi T, Izumi S, Tokunaga T, Kawasoe K, et al. Efficiency of the sterile insect release method as an eradication measure for the sweet potato weevil, Cylas formicarius(Fabricius)(Coleoptera: Brentidae) in the field. Appl Entomol Zool. 2003;36(1):161-167.
73. Smit NE, Downham MC, Laboke PO, Hall DR, Odongo B. Mass-trapping male Cylas spp. with sex pheromones: a potential IPM component in sweetpotato production in Uganda. Crop Prot. 2001;20:643-651.
74. Allard GB. Integrated control of arthropod pests of root crops: Nov 1988-Dec1989. Mid term report. 1990.
75. Heath RR, Coffelt JA, Sonnet PE, Proshold FI, Dueben B, Tumlinson JH. Proshold identification of sex pheromone produced by female sweetpotato weevil, Cylas formicarius elegantulus. J Chem Ecol. 2005;12:1489-1503.
76. Mason LJ, Jansson RK. Disruption of sex pheromone communication in Cylas formicarius (Coleoptera: Apionidae) as a potential means of control. Florida Entomol. 2006;74:469.
77. Yasuda K . Mass trapping of the sweet potato weevil Cylas formicarius (Fabricius)(Coleoptera: Brentidae) with a synthetic sex pheromone. Appl Entomol Zoo. 1995;30:31-36.
78. Yasuda K, Hongo T, Etoo N. A new type of pheromone formulation with visual stimulation for control of sweet potato weevil, Cylas formicarius (Fabricius), Japanese. J Appl Entomol Zoo. 2004.
79. Yasuda K. Auto-infection system for the sweet potato weevil, Cylas formicarius (Fabricius)(Coleoptera: Curculionidae) with entomopathogenic fungi, Beauveria bassiana using a modified sex pheromone trap in the field. Appl Entomol Zoo. 1999;34:501-505.
80. Reddy GV, Wu S, Mendi RC, Miller RH. Efficacy of pheromone trapping of the sweet potato weevil (Coleoptera: Brentidae): Based on dose, septum age, attractive radius, and mass trapping. Environ Entomol. 2014;43:767-773.
81. Talekar NS. Integrated control of Cylas formicarius, sweet potato pest manag. A Glob Perspect. 1991;139-156.
82. Ames T. Sweet potato: major pests, diseases, and nutritional disorders. International Potato Center, Peru. 1997.
83. Jackson DM, Harrison Jr HF. Insect resistance in traditional and heirloom sweetpotato varieties. J Econ Entomol 2013;106:1456-1462.
84. Gerpacio-Santa Cruz MT, Chujoy E. Heritability estimates of some root character in sweetpotatoes. Philipp J Crop Sci. 1994;19:19 27-32.
85. O’Hair SK. Growth of sweet potato in relation to attack by sweet potato weevils. Westview Press, USA. 1991;59-78.
86. Abate T, van Huis A, Ampofo JK. Pest management strategies in traditional agriculture: An African Perspective. Ann Rev Entomol. 2002;45(1):631-659.
87. Bassey EE. Field evaluation of yield and resistances of local and improved sweet potato (Ipomoea batatas (l) lam) accessions to cylas puncticollis and meloidogyne incognita in Southeastern Nigeria. Asian J Agr Sci. 2019;4(6):390-394.
88. Nwankwo IIM, Bassey EE, Afuape SO, Njoku J, Korieocha DS, Nwaigwe G, et al. Morpho-agronomic characterization and evaluation of in-country sweet potato accessions in southeastern Nigeria. J Agr Sci. 2012;4:281.
89. Anyanga MO, Muyinza H, Talwana H, Hall DR, Farman DI, Ssemakula GN, et al. Resistance to the weevils Cylas puncticollis and Cylas brunneus conferred by sweet potato root surface compounds. J Agr Food Chem. 2013;61(34):8141-8147.
90. Rukarwa RJ, Prentice K, Ormachea M, Kreuze JF, Tovar J, Mukasa SB, et al. Evaluation of bioassays for testing Bt sweetpotato events against sweetpotato weevils. African Crop Sci J. 2013;21(3):235-244.
91. Rukarwa RJ, Mukasa SB, Odongo B, Ssemakula G, Ghislain M. Identification of relevant non-target organisms exposed to weevil-resistant Bt sweet potato in Uganda. 3 Biotech. 2014;4(3):217-226.
92. Prentice K, Ormachea M, Rivera C, Manrique S, Kreuze J, Rukarwa R, et al. Weevil resistant sweetpotato through biotechnology. In II genetically modified organisms in horticulture symposium. 2011;974: 91-98.
93. Morán R, Garcıa R, López A, Zaldúa Z, Mena J, Garcıa M, et al. Transgenic sweet potato plants carrying the delta-endotoxin gene from Bacillus thuringiensis var. tenebrionis. Plant Sci. 1998;139(2):175-184.
94. Yang J, Bi HP, Fan WJ, Zhang M, Wang HX, Zhang P. Efficient embryogenic suspension culturing and rapid transformation of a range of elite genotypes of sweet potato (Ipomoea batatas [L.] Lam.). Plant Sci. 2011;181(6):701-711.
95. Shekhar S, Agrawal L, Buragohain AK, Datta A, Chakraborty S, Chakraborty N. Genotype independent regeneration and agrobacterium mediated genetic transformation of sweet potato (Ipomoea batatas L.). Plant Tissue Culture Biotech. 2013;23(1):87-100.
96. Okonya JS, Mwanga RO, Syndikus K, Kroschel J. Insect pests of sweetpotato in Uganda: farmers’ perceptions of their importance and control practices. Springer. 2014;3(1):303.
97. Lagnaoui A, Cisneros F, Alcazar J, Morales F. A sustainable pest management strategy for sweetpotato weevil in Cuba: A success story. Food Fertilizer Technology Center. 2000.
98. Talekar NS, Pollard GV. Vine borers of sweet potato. Sweet potato pest management: A Global Perspective. 1991;327-339.
99. Bohac JR, Dalip KM, Lawrence J, Clarke-Harris D, McComie L, Gore J, et al. Integrated pest management of sweetpotato in the Caribbean. Acta Horticulturae. 2001;143-154.
100. rr A, Ritchie JM. Learning from failure: smallholder farming systems and IPM in Malawi. Agr Sys. 2004;79(1):31-54.
101. Misra AK, Singh RS, Pandey SK. Relative efficacy of chemicals and botanical insecticide against sweet potato weevil, Cylas formicarious fab. Annals Plant Prot Sci (India). 2001.
102. Hwang JS, Hung CC. Evaluation of the effect of integrated control of sweetpotato weevil, Cylas formicarius Fabricius, with sex pheromone and insecticide. Chinese J Entomol. 1991;1:140-146.
103. Leng PH, Reddy GV. Bioactivity of selected eco-friendly pesticides against Cylas formicarius (Coleoptera: Brentidae). Florida Entomol. 2012;1040-1047.
104. Palaniswami MS, Mohandas N. Effect of soil drenching with insecticides at different stages of sweet potato on the control of Cylas formicarius and persistent toxicity of insecticides to adult weevil. Trop Tuber Crop. 1996;340-346.
105. Palanaswami MS, Visalakshi A, Mohandas N, Das L. Evaluation of soil application method of insecticides against Cylas formicarius (F.) and its impact on soil microflora in sweet potato ecosystem. J Root Crops. 2002;28:55-60.
106. Maeto K, Uesato T. A new species of Bracon (Hymenoptera: Braconidae) parasitic on alien sweetpotato weevils in the south‐west islands of Japan. Entomol Sci. 2007;10(1):55-63.
107. Palaniswami MS, Rajamma P. Biological control of sweetpotato weevil and cassava spider mites. Annual Progress Report for the period January-December. 1986;90-92.
108. Jansson RK, Lecrone SH, Gaugler R. Comparison of single and multiple releases of Heterorhabditis bacteriophora Poinar (Nematoda: Heterorhabditidae) for control of Cylas formicarius (Fabricius)(Coleoptera: Apionidae). Biol Control. 1991;1(4):320-328.
109. Sar SA, King A, Van de Fliert E, Opasa R, Atoai M, Appa A, et al. Engaging stakeholders through participatory research: farmer innovations in the use of predatory ants for pest management in Papua New Guinea. In Innovation Asia Pacific Symposium, Nepal. 2009.
110. Jansson RK, Lecrone SH. Application methods for entomopathogenic nematodes (Rhabditida: Heterorhabditidae): aqueous suspensions versus infected cadavers. Florida Entomol. 1994;77(2):281.
111. Georgis R, Koppenhöfer AM, Lacey LA, Bélair G, Duncan LW, Grewal PS, et al. Successes and failures in the use of parasitic nematodes for pest control. Biol Control. 2006;38(1):103-123.
112. Mannion CM, Jansson RK. Comparison of ten entomopathogenic nematodes for control of sweetpotato weevil (Coleoptera: Apionidae). J Econ Entomol. 1992;85(85):1642-1650.
113. Nderitu J, Sila M, Nyamasyo G, Kasina M. Effectiveness of entomopathogenic nematodes against sweet potato weevil (Cylas puncticollis Boheman (Coleoptera: Apionidae)] under semi-field conditions in Kenya. J Entomol. 2009;6(3):145-154.
114. Yamaguchi T, Kawasoe K, Izumi S. Pathogenicity of steinernematid nematodes on the sweet potato weevil, Cylas formicarius (Fabricius)(Coleoptera: Brentidae) and their feasibility for suppression of the weevil population. Japan J Appl Entomol Zoo. 2006.
115. Su CY. Screening of soils pernicious to sweet potato weevil, Cylas formicarius, and use of Beauveria bassiana. Chin J Entomol. 1991;11:198-203.
116. Li Z, Alves SB, Roberts DW, Fan M, Delalibera JI, Tang J, et al. Biological control of insects in Brazil and China: history, current programs and reasons for their successes using entomopathogenic fungi. Biocontrol Sci Tech. 2010;20(2):117-136.
117. Reddy GV, Zhao Z, Humber RA. Laboratory and field efficacy of entomopathogenic fungi for the management of the sweetpotato weevil, Cylas formicarius (Coleoptera: Brentidae). J Invertebrate Pathol. 2014;122:10-15.
118. Villacarlos LT, Granados-Polo MFU. Potential of Metarhizium anisopliae for the control of the sweet potato weevil, Cylas formicarius (F.)(Curculionidae: Coleoptera). Philippine. J Crop Sci. 1989;14(3), 109-114.