Effects of gamma irradiation used to inhibit potato sprouting on potato tuber moth eggs Phthorimaea operculella Zeller (Lep., Gelechiidae)

Abstract: Different age groups of potato tuber moth, Phthorimaea operculella Zeller, eggs were exposed to gamma irradiation at incremental doses up to 150 Gy (the upper dose limit allowed for potato sprout inhibition). Young eggs were more likely to be sensitive to gamma irradiation than older eggs and the sensitivity level declined with age of the eggs. The exposure of 3–3.5-day-old eggs to 150 Gy resulted in a 26% increase in the egg incubation period compared with unirradiated eggs. The minimum dose required to prevent 4–4.5-day-old eggs from hatching was 1 kGy. When eggs were exposed to 75 Gy, 9.7% of larvae survived to the adult stage but emerged as deformed moths. At 100 and 125 Gy, 10.2 and 9.6% of larvae pupated, respectively, although no adult eclosion was recorded, whereas at 150 Gy, the larvae remained in mid-instar stage and eventually died. Gamma irradiation doses applied to inhibit potato sprouting could be also considered as a valuable control tool against potato tuber moth infestations.     

Effect of gamma irradiation on sperm utilization in twice-mated female Phthorimaea operculella Zeller (Lep., Gelechiidae)

The effects of the second mating on fecundity and fertility of potato tuber moth (PTM) Phthorimaea operculella (Zeller), when females were mated with 450 Gy-irradiated and normal males or vice versa, were studied. The percentage of eggs fertilized by sperm of the second mating (P₂ value) was 0.99, indicating that sperm transferred during the last mating were predominantly utilized in egg fertilization. Females, mated first with irradiated males, remated after 2 days, whereas those mated with normal males, remated after 3.3 days. Fecundity of twice-mated females was higher than those mated only once. Females started to lay their eggs 1.9 days after the first mating, regardless of the type of male. However, virgin females did not lay eggs at all. Duration of copulation varied from 102 to 117 min for normal and irradiated males, respectively. The present study elucidated important aspects of mating behaviour of PTM which could improve the efficiency of its control by the sterile insect technique.     

烟草潜叶蛾的过冷却点测定

为了明确烟草潜叶蛾的抗寒能力，对烟草潜叶蛾三龄幼虫、四龄幼虫、蛹的过冷却点进行了测定，并初步明确了不同龄期、不同寄主植物、冷驯化等因素对其过冷却点的影响。结果表明：不同龄期下过冷却点由低到高排列顺序为蛹、三龄幼虫、四龄幼虫，其中蛹的过冷却点显著低于三龄、四龄幼虫的过冷却点。以烟草和马铃薯为寄主的蛹和四龄幼虫的过冷却点没有显著差异。经过冷驯化处理的四龄幼虫过冷却点低于未经冷驯化的对照组，但差异不显著；经过冷驯化的蛹的过冷却点高于对照组。本研究有助于了解烟草潜叶蛾的抗寒性及其越冬分布区域。     

Cold tolerance characteristics of Korean population of potato tuber moth,Phthorimaea operculella (Zeller), (Lepidoptera: Gelechiidae)

Potato tuber moth (PTM), Phthorimaea operculella (Zeller), (Lepidoptera: Gelechiidae) is an invasive insect pest damaging solanaceous crops. We measured the supercooling point (SCP) and survival at low temperature of different development stages to determine which would be capable of overwintering in the Korean climate and adapting to low temperatures. The SCP ranges from ?23.8°C of the egg to ?16.8 of fourth instar larvae (L4). After short periods of low temperature acclimation in L3 (third instar larva), L4 and prepupae, only the prepupal stage showed a significant lowered SCP from ?20.78 to ?22.37°C. When exposed to different subzero temperature for two hours the egg turned out to be the most cold tolerant stage showing LT₅₀ of ?21.7°C followed by the pupal stage with ?15.89°C. One hundred percent mortality was observed when the larvae or adults were exposed to temperatures below ?15.1°C even for a period as short as 2 h. The results suggest that PTM pupae and egg would be the main overwintering stage in Korea where winter temperature does not drop below ?15°C.     

Susceptibility of potato tuber moth (Lepidoptera: Gelechiidae) to postharvest gamma irradiation

Gamma irradiation doses applied to inhibit potato sprouting were tested against potato tuber moth larval and pupal stages. Young larvae and pupae were more susceptible to irradiation injuries than older ones. When larvae of different ages were exposed to doses > or = 100 Gy, only 13-35% pupated, but no adult emergence was obtained. The exposure of 1-1.5- or 3-3.5-d-old pupae to 150 Gy induced high level of sterility and remarkable reduction in female mating ability and fecundity, whereas the reduction was less noticeable for 5-5.5-d-old pupae. Postharvest gamma irradiation of potatoes could be considered as an efficient control approach against potato tuber moth larval and pupal infestations.     

Resistance of wild Lycopersicon species to the potato moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae)

Abstract  Trichome-based host plant resistance of Lycopersicon species to potato moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae), was examined in a laboratory bioassay. Neonate P. operculella were placed on the foliage of accessions of L. hirsutum , L. hirsutum f. glabratum , L. pennellii , L. cheesmanii f. minor and L. esculentum for 48 h . At the end of this period, larval mortality, the numbers of larvae emigrating from, and mining into, the leaf surface were recorded as were leaf area and the densities of trichomes. Analysis by categorical logistic regression found accessions differed in levels of resistance to P. operculella ( P  < 0.001). Further analysis using generalised linear models showed mortality was associated with high densities of type VI and low densities of type V trichomes; emigration from the leaf was associated with high densities of type I and type VII trichomes; and the numbers of mines associated with low densities of type I and type VI trichomes and increased leaf area. Although results indicate that certain accessions of L. hirsutum and L. hirsutum f. glabratum may be most appropriate for inclusion in a breeding program aimed at introducing trichome-based host plant resistance of wild Lycopersicon species into the tomato, further research is necessary to fully understand the mechanisms.     

A potential threat to tomato,a congener crop to potato from invaded potato tuber moth,Phthorimaea operculella (Zeller)

Potato tuber moth (PTM) is a primary pest of potato which had invaded into Korea in 1968 and its distribution was restricted in the southern part of the peninsula. Possibly due to the climate change, its distribution expanded toward the Northern part of South Korea including Gyounggi and Gangwon province where tomato production is high. Host expansion and damage potential of PTM was evaluated on tomato, a congeneric crop of potato. Three commercial varieties of tomato (Dafnis, Bangul and Jujube) and a potato (Superior-Sumi) were subjected to PTM larvae. The results showed that host suitability of tomato to PTM was lower than potato, but PTM could completely develop and reproduce on tomato leaves or fruits. Development time was varied relative to tomato varieties and plant age. PTM showed lower performance on the leaves and fruits of cherry type tomatoes. Higher survival was observed in the large sized fruit of tomato varieties. This study showed substantial evidence that the invaded PTM could damage the tomato cultivation.     

马铃薯块茎蛾的交配行为

在温度为(24±2)℃、光周期为L∶D=14∶10、相对湿度为50%～70%环境条件下观察了马铃薯块茎蛾Phthorimaea operculella(Zeller)交配行为。结果表明,1～2日龄、3～4日龄成虫交配高峰期分别发生在进入暗期后的8.0～10.0h、6.5～8.0h内。两性交配率随日龄的增加显著下降。马铃薯块茎蛾雄成虫具有多次交配能力,在连续发生2次以上行为交配时会导致雄蛾有效交配率下降。雄蛾平均有效交配次数可达3.8次/头,最高达6次。增加雄性比例不会显著提高单雌产卵量,但将性比(♀:♂)由1∶1升至2∶1时即可显著降低单雌产卵量。     

马铃薯块茎蛾生物学、生态学与综合治理

马铃薯块茎蛾又称烟草潜叶蛾Phthorimaea operculella,起源于中美洲和南美洲北部地区,现已分布在亚洲、欧洲、北美洲、非洲等100多个国家,是茄科作物的世界性农业害虫,尤其对马铃薯有毁灭性的危害。目前,该虫在我国南方马铃薯产区普遍发生,尤其是在云南、四川、贵州等地区该害虫发生极为严重,且随着气候的变化该虫可能会扩散到其他马铃薯生产区。马铃薯块茎蛾主要进行两性生殖,少数孤雌生殖,其幼虫钻蛀叶片和薯块危害。初孵幼虫无性二态性,4龄幼虫、蛹和成虫均可依据外形特征进行雌雄区分。马铃薯块茎蛾发生世代数取决于当地的农业气候条件,年发生2~12代。马铃薯块茎蛾对温度有广泛的适应性,且在干燥炎热的年份该虫容易大爆发。马铃薯块茎蛾早期防控主要集中在种植抗性品种、深种、灌溉等农业防治措施上,但化学防治依然是马铃薯生产过程中防治马铃薯块茎蛾的主要方式,由于化学农药的广泛使用,该虫对有机磷类、拟除虫菊酯类等杀虫剂均产生了不同程度的抗性;为了减少化学农药的使用,延缓抗药性的发展,发现并筛选到多种对马铃薯块茎蛾具有防治作用的天敌昆虫和昆虫病原微生物。以(E4,Z7) 十三碳二烯基乙酸酯和(E4,Z7,Z10) 十三碳三烯基乙酸酯为主要成分的马铃薯块茎蛾性信息素在马铃薯块茎蛾监测和防治中也取得了较好的效果。桉树、皱叶薄荷等植物源化合物能够抑制马铃薯块茎蛾产卵;转基因抗虫马铃薯、遗传不育技术等绿色防控技术也成为了防控马铃薯块茎蛾的新方法。以往的研究发现使用单一生物防治手段很难达到理想的防控效果,集成与生物防控技术相容的化学物质、自然天敌和病原微生物等技术是有效控制马铃薯块茎蛾种群的重要趋势。本文系统综述了国内外马铃薯块茎蛾发生为害规律及综合防控技术研究进展,以期为马铃薯块茎蛾的持续治理提供参考依据。     

The toxicity of some medicinal plant extracts to the potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuber moth Phthorimaea operculella is a serious pest of potato both in the field and storage that makes great problem in storage. Farmers routinely rely on chemical insecticides that could be hazardous for human health and environment. Insecticide resistance of P. operculella has been reported all over the world, so botanical origin materials may serve as proper alternative materials for controlling the pest. Natural products are generally preferred because of they are less harmful to non-target organisms, eco-friendly and biodegradable. In the present study, ovicidal activity of essential oils (EOs) of basil, European pennyroyal, lavender, mint, oregano and savoury and oviposition-deterrent activity of methanolic extracts of fumitory, lavender, licorice and oregano were investigated on P. operculella. Probit analysis showed that EOs of Lavandula angustifolia revealed the highest activity (LC₅₀ value 0.4 μL/L air). Fumitory extract elicited the highest reduction in percentage of laying eggs. The results indicated that these medicinal plants could be effective for declining damage of P. operculella in storages.     

Efficacy of entomopathogenic nematodes against potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae) under laboratory conditions

The susceptibility of potato tuber moth, Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) to native and commercial strains of entomopathogenic nematodes (EPNs) was studied under laboratory conditions. Native strains of EPNs were collected from northeastern Iran and characterised as Steinernema feltiae and Heterorhabditis bacteriophora (FUM 7) using classic methods as well as analysis of internal transcribed spacer (ITS) and D2/D3 sequences of 28S genes. Plate assays were performed to evaluate the efficiency of five EPN strains belonging to four species including Steinernema carpocapsae (commercial strain), S. feltiae, Steinernem glaseri and H. bacteriophora (FUM 7 and commercial strains). This initial assessment with 0, 75, 150, 250, 375 and 500 IJs/ml concentrations showed that S. carpocapsae and H. bacteriophora caused the highest mortality in both larval and prepupal stages of P. operculella, PTM. Thereafter, these three strains (i.e. S. carpocapsae, H. bacteriophora FUM 7 and the commercial strains) were selected for complementary assays to determine the effects of soil type (loamy, loamy–sandy and sandy) on the virulence of EPNs against the second (L2) and fourth instar (L4) larvae as well as prepupa. A soil column assay was conducted using 500 and 2000 IJs in 2-ml distilled water. Mortality in the L2 larvae was not affected by the EPN strain or soil type, while there was a significant interactive effect of nematode strains and soil type on larval mortality. The results also showed that EPN strains have higher efficiency in lighter soils and caused higher mortality on early larvae than that in loamy soil. In L4 larvae, mortality of PTM was significantly influenced by nematode strain and applied concentrations of infective juveniles. The larval mortality induced by S. carpocapsae was higher than those caused either by a commercial or the FUM 7 strain of H. bacteriophora. Prepupa were the most susceptible stage.     

Susceptibility of Phthorimaea operculella Zeller (Lepidoptera; Gelechiidae) to its granulovirus PoGV with larval age

1 Granulovirus PoGV is a strong candidate to substitute for chemical insecticides in integrated pest management (IPM) of the potato tuber moth Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae). Generally, susceptibility to baculoviruses decreases with increasing larval age. For effective field applications, knowledge of the age‐related change in susceptibility is crucial. 2 The relative susceptibility of various instars of P. operculella larvae to PoGV was studied by leaf‐disc bioassays in the laboratory at 26 °C incubation temperature. The LC₅₀ increased from 4 × 10⁶ granules/mL for neonate larvae to 1.2 × 10⁷, 1.1 × 10⁸, 4.4 × 10⁸, and 4.2 × 10⁹ granules/mL, signifying resistance ratios of 3, 29, 110, and 1051, for 5, 6, 7, and 9‐day‐old larvae, respectively. 3 The relationship between log‐LC₅₀ values and log‐larval weight was significantly linear. A logistic function described significantly the relation between larval weights and physiological age measured in degree‐days (DD > 13.4 °C). Both functions allowed prediction of the activity ratio of PoGV for different larval ages by using temperature summation to express physiological age. 4 PoGV was found to be highly active against P. operculella larvae up to a physiological age of approximately 50 DD (>13.4 °C) (i.e. the first third of the total larval development time). Thereafter, the virus rapidly lost its activity against older larvae. Prospects for applying this knowledge in the field are discussed.     

Copulatory behaviour of the potato tuber moth, Phthorimaea operculella

ABSTRACT. Copulatory behaviour of the potato tuber moth, Phthorimaea operculella , was observed in a small glasshouse. The behavioural chain is started by the female 'calling'. Males responded to the female's sex pheromone by searching in her vicinity. When the males 'recognized' the female, they attempted copulation. This behaviour was released, however, by a wide variety of models, including dried whole male and female bodies, similarly sized rolls of paper with male or female wings attached, rolls of paper covered in wing scales, and even flat surfaces covered in wing scales (provided the surface was much larger than a moth). It is concluded that the mechanical stimulus from the scales is an important stimulus for evoking copulation.     

Establishment of Beauveria bassiana as a fungal endophyte in potato plants and its virulence against potato tuber moth,Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuber moth, Phthorimaea operculella, is the most damaging potato pest in the world and is difficult to control as the larvae are internal feeders in the foliage and tubers. Entomopathogenic fungi that colonize plants as endophytes have lethal and sublethal pathological effects on insect pests. We show that Beauveria bassiana colonizes the aerial parts of potato plants endophytically after inoculation through soil drenching. Endophytic B. bassiana persisted in potato foliage for more than 50 days postinoculation. Bioassays indicated that foliage of B. bassiana-inoculated potato plants were pathogenic against larvae of P. operculella. Sublethal experiments indicated that B. bassiana negatively affected the growth, development, and reproduction of P. operculella. Development experiments showed that the weight of P. operculella pupae reared on B. bassiana-colonized potato plants (4.25 mg) was significantly less than that of those reared on uninoculated control plants (8.89 mg). Compared with newly eclosed larvae fed on control plants, those fed on B. bassiana-inoculated plants had significantly lower survivorship, with only 17.8% developing to the adult stage. Oviposition of P. operculella females reared on B. bassiana endophytically colonized plants was significantly lower (35 eggs/female) than of those reared on uninoculated plants (115 eggs/female). This study demonstrates that endophytic B. bassiana can be a potential biological control agent for the control and management of P. operculella. Comparing pupal weights of P. operculella reared on potato plants inoculated with the B. bassiana strain GZGY-1-3 and on untreated control plants, pupae from the control plants were significantly heavier than those from treated plants.     

Behavior of newly hatched potato tuber moth larvae,Phthorimaea operculella Zell. (Lepidoptera: Gelechiidae), in relation to their host plants

A study was made of neonate larvae of Phthorimaea operculella.Host finding from soil-laid eggs and dispersal from hosts and nonhosts were first examined. Of first-instar larvae hatching from soil-laid eggs, 80% found the potato plant while roughly 50% found each of the other three plants (datura, tobacco, and tomato). Dispersal from potato, datura, and tobacco was very low, while on tomato it was higher and a high mortality was observed in the 24 h period. Dispersal from nonhost plants was high. Behavior on leaves of hosts and non-hosts is described and some host-plant specific behaviors are identified. Effects on behavior of some of the physical and chemical factors are described. Methylene dichloride extracts of potato leaf wax reduced locomotion rates and the number of turns during locomotion. Also methylene dichloride extract and, to a lesser extent, methanol extract caused biting behavior.     

Sterilisation of the potato moth, Phthorimaea operculella (Lepidoptera: Gelechiidae) by fumigation with thiotepa

The chemosterilant thiotepa was used in fumigation chambers for sterilisation of male and female potato moths. Its effectiveness was registered by recording egg production, egg hatch, longevity of moths, and mating frequency. Also studied was the effect on the persistence of the chemical of temperature, exposure time and concentration. The tests showed that it was possible to sterilise fully male and female moths with thiotepa without adverse effects on mating and longevity. Generally, males were more susceptible to sterilisation than females. No definite relationship was found between dosage and egg production, longevity and mating frequency of moths. The compound did not lose its sterilising activity when used successively up to five times during the same day or once weekly for a total of 4 wk. The sterilising activity was related to temperature, exposure time, concentration and rates of airflow of the circulatory fumigation chambers. Some reduction of fertility occurred when F, adults paired with untreated moths.     

Population biology of the potato tuber moth, Phthorimaea operculella (Lepidoptera: Gelechiidae), in two potato cropping systems in Israel

The life cycle, within-field distribution, crop damage and impact of natural enemies of the potato tuber moth, Phthorimaea operculella (Zeller) were investigated in two potato cropping systems. The two systems differed in soil type (sandy vs. loess) which in turn affected the choice of cultivars, irrigation programme, insecticide application method (ground vs. aerial), and planting and harvest times. From mid-April to the end of May, almost twice as many moths were caught in pheromone traps in sandy than in loess fields. Highest infestation of tubers was found before harvest, and infestation was greater in loess than in sandy fields. Larval densities in foliage and tubers were significantly higher at the margins of the fields than in the centre. A significant positive correlation was found between adult catch and larval infestation on foliage in sandy fields but not in loess. Tuber infestation in sand was positively correlated with foliage infestation. No such correlation was detected in loess. Five parasitic wasps emerged from P. operculella larvae collected from commercial fields and volunteer plants: Diadegma pulchripes (Kokujev) and Temelucha decorata, (Gravenhorst) (Ichneumonidae) and Bracon gelechiae Ashmead and two other unidentified Braconidae. The most abundant predators at the field site were Coccinella septempunctata Linnaeus (Coccinellidae), Chrysoperla carnea Stephens (Chrysopidae), Orius albidipennis (Reuter) (Anthocoridae) and four ant species (Formicidae). Parasitism rate reached 40% and predation was estimated at 79%. Results are discussed with regard to the development of an integrated pest management programme for this important pest.