Using high relative humidity and low air temperature as a long-term storage strategy for the predatory mite Neoseiulus californicus (Gamasida: Phytoseiidae)

The survival time of an indigenous Japanese strain of Neoseiulus californicus (McGregor) was investigated at high and low relative humidities (RHs) of approximately 100% and 80%, respectively, at an air temperature of 5 °C. Five life stages, larva, protonymph, deutonymph and unmated and mated adult female, were tested in 1.5-mL polypropylene vials, in which the RH was adjusted by either adding or omitting a water-saturated filter paper. The survival curves and median survival time (LT₅₀) were significantly different between high and low RHs, and the mean survival time (MST) was 1.6–2.3 times longer at high RH than that at low RH, except in larvae, in which tolerances to high RH and/or low air temperature were not well developed. At high RH, the MST of the mated adult females was 63.1 d and was 1.4 times longer than that of unmated adult females. These results indicate that the suitable water content in the body was probably maintained by increasing the RH at the low air temperature, which is considered to be a primary factor affecting the survival time of N. californicus. Moreover, the nutrient content in the body, such as eggs and male sperm in the mated adult females, could have positive effects on prolonging their survival time. These findings will help to construct an efficient long-term storage method for N. californicus.     

Rapid cold hardening response in the predatory mite Neoseiulus californicus

We investigated the rapid cold hardening (RCH) response in the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae). On direct exposure, ≤2 % of adult females survived ?10 °C for 2 h. However, when acclimatized first at 5 °C for 1 h, 75 % of females survived. RCH could also be induced by acclimatization at 30 °C for 2 h or anoxia (oxygen-free nitrogen) for 1–2 h. All immature stages showed enhanced survival when acclimatized at 5 °C for 2 h before exposure to ?10 °C. Acclimatization at 30 °C induced RCH only in eggs and deutonymphs, and anoxia was effective for eggs, larvae, and deutonymphs. The variability among immature stages may be attributed to the cost associated with the acclimatization treatments. Our findings suggest that RCH may promote the survival of N. californicus during unexpected changes in temperatures, and can be an important feature particularly when this natural enemy is introduced to non-native environments.     

Cold storage of the predatory mite Neoseiulus californicus is improved by pre-storage feeding on the diapausing spider mite Tetranychus urticae

Low air temperature accompanied with high humidity is effective for long-term cold storage of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae). To further improve this storage method, we investigated the effect of pre-storage nutrition on survival during storage and on post-storage quality in terms of survival, oviposition, and progeny viability. The predatory mite was fed from the egg to adult stage on the diapausing two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), non-diapausing spider mites, or Japanese pear pollen, Pyrus pyrifolia Nakai. Newly emerged N. californicus adult females and males were mated, and then both were stored at 7.5 °C and a vapor pressure deficit of 0.0 kPa for up to 75 days. Survival during storage and post-storage quality was significantly better with the diapausing spider mite diet than with the other diets. No effects on the survival or sex ratio of the progeny of the stored adults were observed, regardless of diet or storage duration. Providing diapausing spider mites as a pre-storage diet therefore significantly improves the long-term storage of N. californicus. We discuss the possibility that ingestion of the cryoprotectants, antioxidants, and energy reserves that are present in rich amounts in diapausing spider mites mitigates chilling injury.     

Evaluation of dry-adapted strains of the predatory mite Neoseiulus californicus for spider mite control on cucumber, strawberry and pepper

The goal of this study was to evaluate spider mite control efficacy of two dry-adapted strains of Neoseiulus californicus. Performance of these strains were compared to a commercial strain of Phytoseiulus persimilis on whole cucumber, pepper and strawberry plants infested with Tetranychus urticae at 50 +/- 5% RH. Under these dry conditions predators' performance was very different on each host plant. On cucumber, spider mite suppression was not attained by any of the three predators, plants 'burnt out' within 4 weeks of spider mite infestation. On strawberry, all predators satisfactorily suppressed spider mites yet they differed in short term efficacy and persistence. Phytoseiulus persimilis suppressed the spider mites more rapidly than did the BOKU and SI N. californicus strains. Both N. californicus strains persisted longer than did P. persimilis. The BOKU strain was superior to SI in population density reached, efficacy in spider mite suppression and persistence. On pepper, in the first 2 weeks of the experiment the BOKU strain was similar to P. persimilis and more efficacious in spider mite suppression than strain SI. Four weeks into the experiment the efficacy of P. persimilis dropped dramatically and was inferior to the SI and BOKU strains. Overall, mean predator density was highest on plants harbouring the BOKU strain, lowest on plants with P. persimilis and intermediate on plants with the SI strain. Implications for biocontrol of spider mites using phytoseiid species under dry conditions are discussed.     

Effect of temperature on life history of the predatory mite Amblyseius (Neoseiulus) californicus (Acari: Phytoseiidae)

Amblyseius (Neoseiulus) californicus is an indigenous mite in Japan that feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of A. californicus on a diet of eggs of Tetranychus urticae (red form). More than 97.3% of A. californicus eggs hatched and more than 81.6% of newly hatched larvae attained maturity at temperatures between 15 and 35 degrees C. Females oviposited at 37.5 degrees C, but no eggs hatched. At 40 degrees C, no females laid eggs. The lower threshold temperature from egg to oviposition was 10.3 degrees C and the thermal constant was 86.2 degree-days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between 21 and 28. At 25 degrees C, females laid a mean of 41.6 eggs during a mean oviposition period of 19.4 days. The intrinsic rates of natural increase (rm) were 0.173 at 20 degrees C, 0.274 at 25 degrees C and 0.340 at 30 degrees C.     

Effects of air temperature and water vapor pressure deficit on storage of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

To determine the optimum air temperature and water vapor pressure deficit (VPD) for the storage of the predatory mite, Neoseiulus californicus, 3-day-old mated females were stored at air temperatures of 0, 5, 10, or 15?°C and VPDs of 0.1, 0.3, or 0.5?kPa for 10, 20, or 30?days. At 10?°C and 0.1?kPa, 83?% of females survived after 30?days of storage; this percentage was the highest among all conditions. VPDs of 0.3 and 0.5?kPa regardless of air temperature, and an air temperature of 0?°C regardless of VPD were detrimental to the survival of the females during storage. Since the highest survival was observed at 10?°C and 0.1?kPa, the effect of the storage duration on the post-storage quality of the stored females and their progeny was investigated at 25?°C to evaluate the effectiveness of the storage condition. The oviposition ability of the stored females, hatchability, and sex ratio of their progeny were not affected even when the storage duration was extended to 30?days. Although a slight decrease in the survival during the immature stages of progeny was observed when the storage duration was ≥20?days, the population growth of N. californicus may not be affected when individuals stored in these conditions are applied to greenhouses and agricultural fields. The results indicate that mated N. californicus females can be stored at 10?°C and 0.1?kPa VPD for at least 30?days.     

Effect of hexythiazox and spiromesifen resistance on the life cycle of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae)

Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is one of the most important and effective predators of Tetranychus spp. (Acari: Tetranychidae). This study analyzed the effects of hexythiazox and spiromesifen resistance on biological characteristics of N. californicus. Pre-oviposition, oviposition, post-oviposition times, adult lifespan, total number of eggs laid per female, net reproductive rate (R₀), intrinsic rate of increase (r_m), doubling time (DT), mean generation time (T) and finite rate of increase (λ) were compared among three populations: 63.9-fold hexythiazox resistant (HEX14), 53.6-fold spiromesifen resistant (SPR13) and a susceptible base population. Pre-oviposition and oviposition times, mean number of eggs/female, adult lifespan, R₀ and r_m values were all significantly higher for the two resistant populations than for the susceptible population. Life tables of HEX14, SPR13 and the susceptible population showed that R₀ was 35.0, 26.5 and 19.4 (females/female generation), r_m was 0.35, 0.32 and 0.30 (females/female/day), DT was 1.92, 2.07 and 2.27 days, T was 9.8, 9.8 and 9.7 days, and λ was 1.43, 1.39 and 1.35 (individuals/female/day), respectively.     

巴氏新小绥螨对猎物搜寻能力的研究

巴氏新小绥螨Neoseiulus barkeri(Hughes)是一种多食性捕食螨,主要捕食叶螨和蓟马等。因其捕食范围广,捕食量相对较大,且易人工繁殖,因此,被广泛应用于农业生物防治中。本文利用温室的释放-回收实验研究了巴氏新小绥螨对截形叶螨Tetranychus truncatus和西花蓟马Frankliniella occidentalis(Pergande)的搜寻能力。实验共设3个处理:(1)叶螨为害植株与清洁植株;(2)蓟马虫害植株与清洁植株;(3)蓟马、叶螨混合为害植株与清洁植株。当捕食螨释放于清洁黄瓜植株和虫(螨)害黄瓜植株交替排列的六角结构的中心时,2种害虫(螨)不论是单独危害还是混合危害,巴氏新小绥螨回收比例随着时间的延长逐渐趋于平缓。释放后1 d之内,叶螨、蓟马及混合猎物处理中回收到的捕食螨分别占释放总量的65.25%±1.61%、62.75%±1.31%和81.75%±2.14%,并且虫(螨)害植株上回收到的捕食螨数量明显比清洁植株多,叶螨、蓟马及混合猎物危害植株回收的捕食螨量分别占释放总量的53.5%±5.6%、49.5%±3.6%和74.0%±2.7%。因此,巴氏新小绥螨对这2种猎物及其混合物均有较强的搜寻能力,能够有效定位作物中有猎物的植株。同时对利用一种捕食螨生物防治温室中同时发生的2种害虫(螨)的可能性进行了讨论。     

双尾新小绥螨的形态特征及捕食性功能

【目的】通过对新疆本地捕食螨双尾新小绥螨Neoseiulus bicaudus Wainstein的形态学特征观察及其对新疆农作物上两种重要害螨的捕食量测定,为该捕食螨的保护、研究、扩繁和释放提供理论基础。【方法】在实验室(26±1)℃,RH60%,16L︰8D条件下,借助显微成像系统观察其各个螨态形态特征及生物学习性;定量小室饲养技术对不同密度下对新疆两种重要害螨各螨态的捕食量进行研究。【结果】双尾新小绥螨有卵、幼螨、第一若螨、第二若螨和成螨5个螨态,嗜好阴暗条件,活动范围小,通过有性生殖进行繁殖,有多次交配行为,产卵方式为单产;单头双尾新小绥螨雌成螨每日对截形叶螨Tetranychus truncatus卵和幼螨的捕食量(106.8粒/日·雌和45.4头/日·雌)要显著大于土耳其斯坦叶螨Tetranychus turkestani(64.4粒/日·雌和39.4头/日·雌),而对两种叶螨的若螨和成螨捕食量无明显差异。【结论】本研究表明双尾新小绥螨对土耳其斯坦叶螨和截形叶螨的卵和幼螨的捕食较对若螨和成螨的效果好,对新疆害螨有一定控制能力。     

Impact of relative humidity and water availability on the life history of the predatory mite Amblyseius swirskii

The predatory mite Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) is currently used as an efficient biological control agent of thrips, whiteflies and spider mites, which are economically damaging pests of ornamental plants and vegetable crops grown in greenhouses and fields worldwide. Currently, the effects of relative humidity (RH) and water availability on the optimal growth of A. swirskii are unknown. Here, we test the combined effects of different levels of RH (33%, 53%, 73% and 92%) and water availability on the development and reproduction of male and female A. swirskii feeding on the dried fruit mite, Carpoglyphus lactis (Linnaeus). While eggs failed to hatch at 33% RH, the survival rates of the immature stages at?≥?53% RH increased solely in response to water availability and not due to changes in RH. Regarding growth and development, low RH extended the egg–adult duration and pre-oviposition period. We also found that the negative effects of low RH on fecundity were partially or completely eliminated when drinking water was available. For the life table parameters, the highest values of net reproductive rate (R₀) and intrinsic rate of natural increase (r) were achieved at the highest RH and when drinking water was available. Overall, water availability mitigated the negative effect of low RH on female reproduction, and female development was more sensitive to water availability than male development. Lastly, a comparison of similar research on A. swirskii suggested that water availability and RH are more influential on r than food source or temperature.

     

Rearing of coconut mite Aceria guerreronis and the predatory mite Neoseiulus baraki in the laboratory

A method was developed for the rearing of coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae), and its predatory mite Neoseiulus baraki (Athias-Henriot) (Acari: Phytoseiidae) on embryo culture seedlings of coconut (Cocos nucifera) in the laboratory. Seedlings in the ages of <2, 2–4 and 4–6 months were infested with 75 field-collected coconut mites and the population growth was determined up to six weeks after introduction. The populations of coconut mites increased exponentially up to five weeks after introduction and declined thereafter on seedlings of all ages with significant differences among the three groups of seedlings occurring over time. At week 5, a significantly higher mean number (±SE) of coconut mites (20,098 ± 3,465) was bred on 4–6-month-old seedlings than on smaller seedlings, and on the largest seedlings the numbers were highest at all time intervals, except at week 2. Neoseiulus baraki was reared on embryo culture seedlings of the three age groups infested with coconut mites, by introduction of five female deutonymphs and one male, three weeks after introducing coconut mites. Predator numbers progressed significantly over time, but the size of seedlings did not significantly influence the numbers. On all groups of seedlings, the mean number of N. baraki increased up to two weeks after introduction on to seedlings and then declined. Many coconut mites were successfully reared in the laboratory for a longer period by this method and it could also be used as an alternative method to rear N. baraki. Development of this method may contribute to the progress of studies on the biology and ecology of coconut mite and its interactions with natural enemies.     

Prey preference of the predatory mite Neoseiulus womersleyi Schicha is determined by spider mite webs

Abstract:  We experimentally verified a proximate cause for the preference of prey species by the predatory mite Neoseiulus womersleyi , which prefers the eggs of Amphitetranychus viennensis Zacher to those of Tetranychus urticae Koch. To separate the effects of spider mite eggs and spider mite webs on the prey preference of the predatory mite, we manipulated combinations of eggs and webs of the two prey species. The number of eggs consumed by adult female N. womersleyi was compared with respect to two factors: eggs of the same species under webs of the different species and eggs of different species under webs of the same species. The results revealed that the prey preference of N. womersleyi was determined by the webs, and not by the eggs.     

Effect of long-term feeding history on functional and numerical response of Neoseiulus californicus (Acari: Phytoseiidae)

The functional and numerical responses of the predatory mite Neoseiulus californicus to eggs and protonymphs of Tetranychus urticae were studied on excised strawberry leaflet discs under laboratory conditions (25 ± 1°C, 75–85% RH and 16L : 8D). Four strains of the phytoseiid were compared: three originated from a long-term mass-rearing with different food (T. urticae, Dermatophagoides farinae and Quercus spp. pollen) and under controlled conditions, while the fourth was directly collected from a natural environment and therefore considered a wild strain. The different nutritional histories affected the responses of N. californicus on tetranychids. On the whole, the wild strain gave better performance. When egg prey was administered this strain and the one mass-reared on two-spotted spider mites showed similar functional as well as numerical responses; on the contrary, when protonymphs were furnished, the wild strain did not differ from that mass-reared on pollen. The strain previously fed on house dust mites gave the worst performance and also showed the lowest percentages of females in the progeny. The functional responses obtained were predominantly type II curves. In all cases considered, no stored energy was allocated for reproduction and, with the exception of the wild strain on eggs, the prey was exploited less efficiently as the consumption increased. In spite of the differences evidenced in this experiment all strains were characterized by high predation and oviposition rates. Thus the results obtained suggest no drawbacks in the use of mass-reared N. californicus as biocontrol agents. © Rapid Science Ltd. 1998     

柑橘木虱及分泌物对胡瓜新小绥螨的吸引作用研究

在25℃温度条件下,在九里香(Murraya panicuata)嫩枝条上研究柑橘木虱Diaphorina citri Kuwayama混合虫态、卵、低龄若虫、高龄若虫、柑橘木虱分泌物对胡瓜新小绥螨Neoseiulus cucumeirs(Oudemans)雌螨的吸引作用,以探索与评价捕食螨对柑橘木虱各虫态及分泌物的趋向性。研究发现:1.柑橘木虱混合虫态对胡瓜新小绥螨的吸引作用在试验后第2小时经测验达到显著水平(P<0.05),第3小时达极显著水平(P<0.01),表明柑橘木虱混合虫态对胡瓜新小绥螨有很强的吸引作用;2.柑橘木虱卵对胡瓜新小绥螨雌成螨无吸引作用;3.试验开始后第1⁵小时在试验区胡瓜新小绥螨数量分别高于空白区25.00%、18.33%、13.33%、15.00%和23.33%,柑橘木虱低龄若虫对胡瓜新小绥螨有较强烈的吸引作用;4.柑橘木虱高龄若虫对胡瓜新小绥螨吸引作用在第1小时最高,第25小时在试验区胡瓜新小绥螨数量分别高于空白区25.00%、18.33%、13.33%、15.00%和23.33%,柑橘木虱低龄若虫对胡瓜新小绥螨有较强烈的吸引作用;4.柑橘木虱高龄若虫对胡瓜新小绥螨吸引作用在第1小时最高,第2³小时最低,第4小时开始回升,第5小时可达到51.67%。可见柑橘木虱高龄若虫对胡瓜新小绥螨有一定的吸引作用;5.柑橘木虱分泌物对胡瓜新小绥螨吸引作用在第1小时最高,试验区胡瓜新小绥螨数量高于空白区33.33%、胡瓜新小绥螨不能取食柑橘木虱分泌物,第2小时胡瓜新小绥螨向外逃跑的比率增加。但胡瓜新小绥螨在试验区数量仍高于试验区,柑橘木虱分泌物对胡瓜新小绥螨也有一定的吸引作用。本试验环境开放,模拟自然状态。在柑橘木虱混合虫态发生的情况下,胡瓜新小绥螨对其具备搜寻能力。     

Population dynamics of interacting predatory mites,Phytoseiulus persimilis and Neoseiulus californicus,held on detached bean leaves

The success of combined release of the predatory mitesPhytoseiulus persimilis and Neoseiulus californicus insuppression of spider mites may be related to the effects of the interactionsbetween the two predators on their population dynamics. We studied populationgrowth and persistence of the specialist P. persimilis andthe generalist N. californicus reared singly versus rearedin combination after simultaneous and successive predator introductions ondetached bean leaf arenas with abundant prey, Tetranychusurticae, and with diminishing prey. When reared singly with abundantprey, either predator population persisted at high densities to the end of theexperiment. In every predator combination system with abundant prey and variousinitial predator:predator ratios N. californicus displacedP. persimilis. When held singly with diminishing prey, thepopulation of P. persimilis grew initially faster than thepopulation of N. californicus but both species reachedsimilar population peaks. Irrespective whether reared singly or in combination,N. californicus persisted three to five times longer afterprey depletion than did P. persimilis. Regarding thecrucial interactions in the predator combination systems, we conclude thatintraguild predation was a stronger force than food competition and finallyresulted in the displacement of P. persimilis. Previousstudies showed that intraguild predation between the specialist P.persimilis and the generalist N. californicusisstrongly asymmetric favoring the generalist. We discuss the implications ofpotential interactions between P. persimilis andN. californicus to biological control of spider mites.     

The endosymbionts Wolbachia and Cardinium and their effects in three populations of the predatory mite Neoseiulus paspalivorus

Whereas endosymbiont-induced incompatibility is known to occur in various arthropod taxa, such as spider mites, insects and isopods, it has been rarely reported in plant-inhabiting predatory mites (Acari: Phytoseiidae). Recent cross-breeding studies with the phytoseiid mite Neoseiulus paspalivorus De Leon revealed a complete post-mating reproductive isolation between specimens collected from three geographic origins—Northeast Brazil (South America), Benin and Ghana (West Africa)—even though they are morphologically similar. We carried out a study to assess to what extent these populations exhibit genetic differences and whether endosymbionts are involved in the incompatibility. First, we used the mitochondrial cytochrome oxidase I (COI) gene to assess genetic diversity among the three populations. Second, we used a PCR-based method to check for the presence of Wolbachia and/or Cardinium in these populations, and we determined their phylogenetic relationships using specific primers for Wolbachia and Cardinium 16S rDNA genes. Third, we also conducted a test using an antibiotic (tetracycline) in an attempt to eliminate the symbionts and evaluate their effects on the reproductive compatibility of their host. Based on the DNA sequences of their COI genes, specimens of the three populations appear to be genetically similar. However, the 16S rDNA gene sequences of their associated endosymbionts differed among the three populations: the Benin and Brazil populations harbour different strains of Wolbachia symbionts, whereas the Ghana population harbours Cardinium symbionts. In response to antibiotic treatment females of each of the three populations became incompatible with untreated males of their own population, similar to that observed in crossings between females from one geographic population and males from another. Compatibility was restored in crosses involving uninfected Brazil females and uninfected Benin males, whereas the reciprocal crosses remained incompatible. Cardinium symbionts seem to be essential for oviposition in the Ghana population. It is concluded that their associated bacterial symbionts are the cause of the post-mating reproductive isolation previously observed among the three geographic populations. This insight is relevant to biological control of coconut mites for which N. paspalivorus is an effective predator, because introducing one geographic strain into the population of another (e.g. in field releases or mass cultures) may cause population growth depression.     

Mating duration and egg production of the predaceous mite Neoseiulus californicus (Acari: Phytoseiidae) vary with temperature

Effects of constant temperature on mating duration and total fecundity of Neoseiulus californicus females mated once were investigated at 18 °C, 25 °C, 30 °C, and 35 °C with a photoperiod of 16L:8D. Adult mites grown and maintained at 25 °C mated for 315.3 min on average and produced 46.1 eggs per female. These values varied significantly by temperature: 553.6 and 13.9 (18 °C), 261.2 and 26.6 (30 °C), and 253.6 and 23.9 (35 °C), respectively. Duration of copulation was negatively correlated with temperature. However, total egg production peaked at 25 °C and decreased at lower and higher temperatures. Reduced sperm transfer and/or survival rate of sperm in the female body may account for decreased egg production when temperatures are not optimal.     

Risk assessment of Cry toxins of Bacillus thuringiensis on the predatory mites Euseius concordis and Neoseiulus californicus (Acari: Phytoseiidae)

Genetically modified plants carrying Cry toxins of Bacillus thuringiensis (Bt) are widely used for pest control. Possible adverse effects as a result of the use of this control technique to non-target organisms is still a concern; however, few studies have addressed the effects of Bt crops on phytoseiid predatory mites. Phytoseiids are important for the natural control of phytophagous mites, but they can also feed on pollen, plant exudates, etc. Thus, phytoseiids may ingest Bt toxins through several pathways. In this paper, we evaluate the direct effect of Bt-toxins by feeding the predators on Bt cell suspensions, on solution of a Bt toxin and the tri-trophic effect by Bt expressed in transgenic plants. We present a method of conducting toxicological tests with Phytoseiidae which can be useful in studies of risk analysis of toxins to be expressed by genetically engineered plants. This method was used to evaluate the potential effect of ingestion of suspensions of Bt (1.25 × 10⁸ spores/ml) and of purified protein Cry1Ia12 (0.006 mg/ml and 0.018 mg/ml) on Euseius concordis, a predatory mite that develops and reproduces best on pollen. The effects of genetically modified Bollgard^® cotton, which carries the Cry1Ac protein, on Neoseiulus californicus, a selective predator that feeds more on spider mites than on pollen or insects, was determined by feeding them with Tetranychus urticae reared in Bollgard^® cotton and on the non-transgenic isoline. When E. concordis was fed with suspension of Bt isolate derived from product Dipel^® PM, no significant effects were detected. Similarly, Cry1Ia12 Bt toxin, at a concentration of 0.006 mg/ml, did not affect E. concordis. At a concentration of 0.018 mg/ml, however, the intake of this protein reduced the reproduction of E. concordis. There were no effects of Bollgard^® cotton on the biological traits and on the predatory capacity of N. californicus. Results indicate that the Cry toxins of B. thuringiensis studied, at the concentrations used in the field or expressed in transgenic plants, should not affect the predatory mites E. concordis and N. californicus.