Thrips Eggs Research Articles

Functional Response of Four Phytoseiid Mites to Eggs and First-Instar Larvae of Western Flower Thrips, Frankliniella occidentalis.

The predation capacity and functional responses of adult females of the phytoseiid mites Amblyseius largoensis (Muma), Proprioseiopsis lenis (Corpuz and Rimando), Paraphytoseius cracentis (Corpuz and Rimando), and Amblyseius swirskii (Athias-Henriot) were studied on eggs and first instars of the western flower thrips, Frankliniella occidentalis (Pergande), in the laboratory at 25 °C and 30 °C. At both temperatures, the functional response of all four phytoseiid mites was type II to first instars of the thrips. In contrast, when offered thrips eggs, the functional response was type III. At both temperatures tested, A. swirskii had the highest mean daily consumption of first-instar F. occidentalis, followed by A. largoensis, P. cracentis, and P. lenis. Amblyseius largoensis had the shortest handling time and the highest maximum attack rate when first-instar thrips were the prey. When fed on thrips eggs, A. largoensis had the highest mean daily consumption, followed by A. swirskii, P. cracentis, and P. lenis. On thrips eggs, A. swirskii showed the shortest handling time and highest maximum attack rate. Our findings indicate that all four phytoseiids had a better ability to prey on first-instar larvae of F. occidentalis compared to thrips eggs. At 25 and 30 °C, A. largoensis was the better predator on thrips larvae, whereas A. swirskii was superior in consuming eggs of F. occidentalis. Proprioseiopsis lenis was the inferior predator on both thrips larvae and eggs compared to the other phytoseiids tested.

Life table parameters of Amblyseius largoensis, Amblyseius swirskii and Proprioseiopsis lenis (Acari: Phytoseiidae) fed on eggs and larvae of Frankliniella occidentalis.

The immature development and reproduction of the predatory mites Amblyseius largoensis (Muma), Proprioseiopsis lenis (Corpuz and Rimando), and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were investigated using both thrips eggs and first instars of the western flower thrips, Frankliniella occidentalis Pergande, as prey in a controlled laboratory environment at 25°C and 60% relative humidity. When provided with thrips eggs as food, A. largoensis exhibited a notably shorter immature development period for both males (7.05 days) and females (6.51 days) as compared with A. swirskii (8.05 and 7.19 days, respectively) and P. lenis (8.10 days and 7.05 days, respectively). Amblyseius largoensis also displayed a higher oviposition rate (2.19 eggs/female/day) than A. swirskii and P. lenis (1.79 and 1.78 eggs/female/day, respectively). Moreover, it exhibited the highest fecundity (25.34 eggs/female), followed by P. lenis (24.23 eggs/female) and A. swirskii (22.86 eggs/female). These variations led to A. largoensis having the highest intrinsic rate of increase (rm) at 0.209, followed by A. swirskii at 0.188, and P. lenis at 0.165. However, when the predatory mites were provided with first instars of F. occidentalis, A. swirskii demonstrated a faster immature development period for both males (7.67 days) and females (7.59 days) as compared with P. lenis (9.00 days and 7.86 days, respectively) and A. largoensis (8.47 days and 8.61 days, respectively). While the oviposition rates of P. lenis (1.92 eggs/female/day) and A. swirskii (1.90 eggs/female/day) were similar when feeding on this prey, A. largoensis produced fewer eggs (1.83 eggs/female/day). Further, A. swirskii exhibited the highest fecundity (31.93 eggs/female), followed by A. largoensis (25.71 eggs/female) and P. lenis (23 eggs/female). Consequently, the intrinsic rate of increase (rm) on thrips first instars was highest in A. swirskii (0.190), followed by A. largoensis (0.186), and P. lenis (0.176). In summary, our findings indicate that in terms of life history parameters A. largoensis performs optimally when feeding on thrips eggs, whereas A. swirskii performs best when preying on the mobile first instars of the thrips. These insights into the dietary preferences and reproductive capabilities of the studied predatory mite species have important implications for their potential use as biological control agents against F. occidentalis in agricultural settings.

Egg Predation by Phytoseiid Predatory Mites: Is There Intraguild Predation Towards Predatory Bug Eggs?

Phytoseiid predatory mites are efficient biocontrol agents of important thrips pests, such as the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Until recently, it was believed that first instars, and to a lesser extent second instars, were the most vulnerable developmental stages of thrips to be attacked by phytoseiids. However, recent evidence showed that some phytoseiids can detect and prey upon thrips eggs inserted in the leaf tissue. As phytoseiid predatory mites often co-occur with other beneficial insects, such as mirid and anthocorid predatory bugs which also insert their eggs inside leaf material, this raises the question whether phytoseiid predatory mites may also feed on predatory bug eggs. Here we first tested the potential of Amblyseius swirskii Athias-Henriot, Transeius montdorensis Schicha, and Amblydromalus limonicus Garman and McGregor (Acari: Phytoseiidae) to kill eggs of F. occidentalis in leaf tissue. Secondly, we tested whether those phytoseiids were capable of killing eggs of Orius laevigatus Fieber (Hemiptera: Anthocoridae), Macrolophus pygmaeus Rambur and Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), three biocontrol agents that also insert their eggs inside plant tissue. Our results showed that A. swirskii and A. limonicus could kill thrips eggs, whereas T. montdorensis could not. Furthermore, we show that the presence of phytoseiid predatory mites does not affect the hatch rate of predatory bugs that insert their eggs inside leaves.

Life history trade-offs of thrips reared on fertilized and unfertilized Brazilian peppertree with respect to changes in plant terpenoid profiles

Mass rearing is a critical component of a successful biological control program and is strongly dependent on the diet agents consume. We investigated the impact of fertilizing the target Brazilian peppertree, Schinus terebinthifolia, on plant terpenoids and the phenology, fecundity, and morphometrics of the thrips agent, Pseudophilothrips ichini. Plants in 3.8 L pots were fertilized (24N-8P-16K) at one of three concentrations every two weeks: Low (0 g/L), Medium (1.8 g/L), or High (3.6 g/L). To examine fertilizer impacts on life history, cohorts of 20 thrips eggs were reared in containers on stem cuttings from the potted plants. Terpenoid profiles were characterized using gas chromatography-mass spectrometry from potted plants grown at each fertilizer level, half of which experienced 72 h of thrips feeding. The fewest thrips reached the pre-pupa on Low fertilizer plants, but those thrips developed the fastest, lived longer as adults, and laid more eggs. Thrips on plants at either Medium or High fertilizer levels took longer to develop, had shorter adult lifespans, laid fewer eggs, but adults were larger, and they produced potentially higher quality eggs. Differences in terpenoid profiles between damaged and undamaged Low fertilizer plants and life history trade-offs suggest fertilizing may have minimal impacts on thrips; however, fertilized plants grow faster and larger, thereby ensuring a reliable supply of host material for mass rearing. Moreover, these results suggest that although thrips may have reduced survival, they will perform well following field releases when fed wild, unfertilized Brazilian peppertrees.

Phytoseiid mites prey effectively on thrips eggs: Evidence from predation trials and molecular analyses

It is generally assumed that predation by phytoseiid mites (Acarina: Phytoseiidae) on thrips is mainly limited to the first and, to a lesser extent, the second thrips instars. Thrips eggs are imbedded in plant tissue and are supposed to be out of reach of most predators. Using a dual approach combining feeding trials with molecular gut content analysis, we confirmed that eggs of the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), can be vulnerable to attack by a subset of phytoseiid species. Of the five species investigated, the generalist predators Amblyseius largoensis and Amblyseius swirskii were shown to most readily feed on thrips eggs, followed by Neoseiulus californicus, which is classified as a selective predator of tetranychid mites. Neoseiulus longispinosus and Proprioseiopsis lenis did not or very rarely consume thrips eggs. As substantial reductions of hatching (up to 30%) were observed, predation on eggs should not be ignored when assessing the efficacy of phytoseiids as biological control agents against thrips.

Behavior of Montandoniola confusa Streito & Matocq (Hemiptera: Anthocoridae) preying upon gall-forming thrips Gynaikothrips ficorum Marchal (Thysanoptera: Phlaeothripidae)

The gall-forming thrips Gynaikothrips ficorum Marchal (Thysanoptera: Phlaeothripidae) is recorded in all regions where its host plant, Ficus microcarpa (Marchal) (Moraceae), has been cultivated as an urban and interior landscape plant species, including potted plants and bonsai. Similarly, the thrips predator Montandoniola confusa Streito & Matocq (Hemiptera: Anthocoridae) has generally followed the prey distribution. The gall induced by thrips degrades the plant foliage, and the thrips themselves can be annoying for people both outdoors and indoors. The galls, however, create a microcosm with all developmental stages of the thrips and its predator. In this study we present the first records of M. confusa in South America, document the species’ widespread concomitant occurrence across Brazil, and report our studies of three aspects of M. confusa predation upon the eggs, larvae/prepupae, and adults of G. ficorum thrips: (i) functional response of the predator adult female as a function of different densities of thrips eggs, larvae/prepupae and adults separately: (ii) predation on eggs by adult M. confusa with adult thrips present in the gall; and (iii) adult M. confusa prey preferences when all thrips stages occurred simultaneously in the gall. For all three thrips life stages tested, the predator exhibited a type II functional response. Despite the availability of different life stages in the gall, M. confusa adults are capable of preying upon all life stages of G. ficorum, predation was preferentially on thrips eggs, with an estimated ∼10-fold greater predation on eggs compared to larvae/prepupae and adult thrips. Egg predation was unaffected by the presence of defensive adult thrips in the gall under low densities (<30 eggs/gall) but when egg densities were greater than 30 eggs/gall, it was reduced when adult thrips were present. However, the relative number of thrips adults per gall did not statistically change the outcome.

Insecticidal effect of high carbon dioxide atmospheres on thrips eggs oviposited in plant tissue

Thrips are damaging crop pests, but their eggs are difficult to detect for farmers and agricultural inspectors. We investigated the insecticidal effects of an elevated carbon dioxide atmosphere on thrips eggs oviposited within plant tissues. Percent mortality of Frankliniella occidentalis (Pergande), Frankliniella intonsa (Trybom), Thrips tabaci Lindeman, and Thrips palmi Karny exposed to 60 % CO2 was evaluated at different temperatures (20, 25, 30, and 34 °C) and durations. Egg mortality of all four species increased with CO2 exposure duration at each temperature, and the time required to achieve 100 % mortality decreased as the temperature increased between 20–30 °C. Exposure to 60 % CO2 at 30 °C for 12 h is considered to be 100 % lethal to most thrips pests of fresh agricultural produce. Our findings suggested that CO2 treatment could be used to propagate thrips-free plants in horticultural nurseries.

Abundance of Thrips obscuratus (Crawford) (Thysanoptera: Thripidae) during wine grape flowering in different regions in New Zealand

As a first step in understanding the pest status of thrips in wine grapes in New Zealand, we aimed to determine the species composition of thrips in grape inflorescences in four grape-growing regions of the country (sampling grape cv. ‘Chardonnay’ from 18 growers) and to quantify their abundance. Of the regions, by far the largest numbers of thrips were recorded from Canterbury (mean number of thrips per inflorescence from the raw data=48.6, 9.3, 9.4 and 6.4 for Canterbury, Auckland, Hawke's Bay and Marlborough, respectively). Of a subsample of 15% (536 thrips) identified, all but one were New Zealand flower thrips females (NZFT, Thrips obscuratus). The largest numbers of thrips were measured on the windward sides of three out of four vineyards sampled. The presence of thrips eggs and larvae suggests that grape vines are breeding hosts for NZFT, but further research is now needed on the thrips’ life cycle and its distribution and numbers in New Zealand vineyards in order to determine the risk this potential pest presents to the wine industry.

Effect of temperature on life history traits of the predatory thrips, Scolothrips takahashii Priesner (Thysanoptera: Thripidae)

Scolothrips takahashii is an indigenous thrips in Japan that feeds on many spider mite species. To evaluate whether S. takahashii has potential as a biological control agent for spider mites, we investigated the development, survivorship and life-history parameters of S. takahashii on a diet of Tetranychus urticae (red form) eggs at different temperatures. More than 74% of thrips eggs hatched and more than 76% of newly hatched larvae attained maturity at 15–35°C. No females laid eggs at 37.5 or 40°C. The lower threshold temperature for development from egg to oviposition was 11.7°C and the thermal constant was calculated as 204.1 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 seven and ten. Mating was unnecessary to induce oviposition but unmated females produced only male progeny. At 25°C, females laid a mean of 90.5 eggs during a mean oviposition period of 17.8 days. The values for the intrinsic rate of natural increase (rm), one important life-history parameter, were 0.113 at 20°C, 0.195 at 25°C, and 0.246 at 30°C. These results suggest S. takahashii has considerable potential as a biological control agent against spider mites.

Enhanced fumigant toxicity of p-cymene against Frankliniella occidentalis by simultaneous application of elevated levels of carbon dioxide.

The fumigant toxicity of the essential oil component p-cymene was assessed against Western Flower Thrips, Frankliniella occidentalis. F occidentalis adult females, first- and second-instar larvae and eggs were exposed for 2, 24 and 48 h to combinations of three p-cymene doses and two carbon dioxide levels (ambient, 10%). Additional experiments were conducted on F occidentalis adult females with lower carbon dioxide levels (ambient, 2%, 4%, 6%) applied in combination with p-cymene. Combined applications of p-cymene and carbon dioxide were found to increase significantly the fumigant toxicity of p-cymene against both adult female and larval thrips, but not thrips eggs. An increase in exposure time also led to an increase in adult and larval mortalities in both the p-cymene alone and combined treatments. These results indicate that by combining applications of the essential oil component, p-cymene, with increased carbon dioxide, it may be possible to achieve toxicity levels similar to those of standard chemical fumigants.

Within–Tree Distribution of Pear Thrips (Thysanoptera: Thripidae) in Sugar Maple

Within–tree distribution of pear thrips, Taeniothrips inconsequens (Uzel), in Sugar maple, Acer saccharum Marsh., was determined in six nonflowering trees in 1990 and six flowering trees in 1992. During budburst, vegetative (1990) and flower (1992) buds were sampled from four cardinal quadrants, two canopy positions (inside and outside), and three crown levels (upper, middle, and lower) of sugar maples in a plantation in central Pennsylvania and examined for thrips eggs and adults. Almost all thrips adults were identified as T. inconsequens (94.9% in 1990 and 97.0% in 1992) and all eggs were likely to be from T. inconsequens because of their position in bud tissues and their morphology. Few larvae were present. Thrips eggs and adults were found in vegetative and flower buds throughout all levels, positions and quadrants. There were few significant differences in relation to any part of the tree in either year. In 1990 significantly more eggs (but not adults) were found in the middle level, compared with the lower and the upper levels. There was a significant interaction between height and quadrant for eggs (but not adults) in 1992. Within–tree distribution of pear thrips is likely to be affected by the synchrony between thrips emergence from ovelwintering sites and the timing of budburst in a particular position within the tree, and the distribution and density of flowers.

ADACTYLIDIUM SP. (ACARINA: PYEMOTIDAE, A NEW RECORD OF A PREDATORY MITE OF THRIPS EGGS IN PUERTO RICO

ADACTYLIDIUM SP. (ACARINA: PYEMOTIDAE, A NEW RECORD OF A PREDATORY MITE OF THRIPS EGGS IN PUERTO RICO