Duration Of Nymphal Stages Research Articles

Resistência induzida ao pulgão-do-algodoeiro em cultivares de algodão colorido

The aim of this study was to evaluate the resistance induced by chemical inducers on cultivars of colored cotton. The cotton was planted in pots and kept in a climate-controlled room (28±2oC daytime temperature, 25±2oC night temperature, 70±10 % R.H.; and 12 hours of photoperiod). Silicon and acibenzolar-S-methyl were applied to the plants that were offered to Aphis gossypii afterwards. The bioassays were conducted in a randomized design in a factorial arrangement, with three cultivars of cotton and two resistance inducers, with ten repetitions. The biological parameters observed were: ninfal mortality, duration of nymphal stage, and pre-reproductive, reproductive and post-reproductive periods, longevity and total number of nymphs produced. The lignin and phenol content in the leaves were quantified. The longest duration of the nymphal period, the lower number of nymphs produced, and the major mortality were observed in the ASM treatment. Silicon and ASM promoted an increase in lignin content in the cv. BRS Verde. Thus, the ASM application affected negatively biological parameters of A. gossypii, by increasing the lignin content in plants. The cv. BRS Verde is a better cutivar to be used, because it accumulated higher lignina and phenol contents.

The effect of temperature and light on embryogenesis and post-embryogenesis of the spider Eratigena atrica (Araneae, Agelenidae)

Embryogenesis and post-embryogenesis of spiders depend on several environmental factors including light and temperature. This study was aimed at evaluating the impact of different thermal and lighting conditions on embryonic and early post-embryonic development of Eratigena atrica. Embryos, larvae, nymphs I and II were incubated at constant temperatures of 12, 22, 25 and 32°C under three different light regimes: light, dark, light/dark. Extreme temperatures (12 and 32°C) significantly increased mortality of embryos (to 100%) and nymphs II, whereas larvae and nymphs I suffered reduced survival only at the lowest temperature. Moreover, the lowest temperature reduced the development rate of all stages. The impact of light conditions was less pronounced and more variable: constant light reduced the survival of nymphs I at lower temperatures, but increased that of larvae. Moreover, light increased the time of embryonic development and duration of nymphal stages, particularly at lower temperatures (12–22°C). Thus, the most optimal locations for spiders seem to be dark (though except larval stage) and warm (25°C) sites, where their development is fastest and mortality lowest.

Life-History Traits of Macrolophus pygmaeus with Different Prey Foods.

Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a generalist predatory mirid widely used in augmentative biological control of various insect pests in greenhouse tomato production in Europe, including the invasive tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera, Gelechiidae). However, its biocontrol efficacy often relies on the presence of alternative prey. The present study aimed at evaluating the effect of various prey foods (Ephestia kuehniella eggs, Bemisia tabaci nymphs, Tuta absoluta eggs and Macrosiphum euphorbiae nymphs) on some life history traits of M. pygmaeus. Both nymphal development and adult fertility of M. pygmaeus were significantly affected by prey food type, but not survival. Duration of nymphal stage was higher when M. pygmaeus fed on T. absoluta eggs compared to the other prey. Mean fertility of M. pygmaeus females was greatest when fed with B. tabaci nymphs, and was greater when offered M. euphorbiae aphids and E. kuehniella eggs than when offered T. absoluta eggs. Given the low quality of T. absoluta eggs, the efficacy of M. pygmaeus to control T. absoluta may be limited in the absence of other food sources. Experiments for assessing effectiveness of generalist predators should involve the possible impact of prey preference as well as a possible prey switching.

Changes in life history parameters of Rhopalosiphum maidis (Homoptera: Aphididae) under four different elevated temperature and CO2 combinations.

Biological characteristics of corn leaf aphid, Rhopalosiphum maidis (Fitch), on barley, Hordeum vulgare L., were examined for two generations under four different elevated temperature and CO2 combinations. The developmental duration for each life stage was significantly reduced under the elevated temperature (+4 degrees C). The elevated CO2 (700-750 microl/liter) reduced only the development time of fourth-instar nymph. The overall duration of nymphal stage was reduced in the second generation. Thus, the temperature was the dominant factor to development duration of corn leaf aphid. The fecundity of corn leaf aphid was significantly increased under the elevated temperature and CO2, as well as in the later generation. Elevated temperature and CO2 increased the number of alate production, which may enhance the aphid migration or dispersal and the spread of plant viruses. Corn leaf aphid had the highest intrinsic rate of increase under the elevated temperature and CO2 combination in the second generation. These results indicate that the combined effects of both elevated temperature and CO2 on aphid biology may exacerbate aphid damage on barley under the climate change in accompany with elevated temperature and CO2 level.

Characterization of antibiosis to the silverleaf whitefly Bemisia tabaci biotype B (Hemiptera: Aleyrodidae) in cowpea entries

The silverleaf whitefly, Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae), is considered one of the most important pests of cowpea (Vigna unguiculata L. Walp.), limiting the productivity of this crop worldwide. Chemical control is still the main strategy for the management of populations of this insect. However, due to the harmful effects of pesticides on the environment and to humans, less injurious alternatives have been investigated. Along this line, the use of resistant genotypes can be a valuable tool for the control of the silverleaf whitefly. In this paper, we investigate some biological aspects of B. tabaci biotype B confined on 14 genotypes of cowpea. We evaluated the incubation period, egg viability, duration of nymphal stages, total duration of the juvenile phase, instar mortality and total mortality of the immature stage. The genotype MNC 99-541 F21 exhibited antibiosis against the whitefly, prolonging the lifecycle of the insect. The genotypes Canapu, BRS-Urubuquara and TE97-304 G-4 also exhibited antibiosis, causing high nymphal mortality. These results may help in breeding programmes to develop cowpea lines with resistance to B. tabaci biotype B.

Variation in the number of nymphal instars in Nysius huttoni White (Hemiptera: Lygaeidae)

The number of nymphal instars of Nysius huttoni White was investigated at five constant temperatures (15, 20, 25, 30 and 35±0.5°C), one fluctuating (laboratory room conditions) temperature and three photoperiods (16-h, 12-h, and 8-h photophases) in the laboratory. Nymphs passed through four to six instars before they emerged as adults, individuals with five instars formed over 90% of the population, whereas those with four or six instars formed 4.2–5.8 and 1.6–2.9% respectively. Two nymphs were each recorded to pass through three and seven instars before emergence as adults. Both temperature and photoperiod affect the number of nymphal instars. Insects with four instars were more frequent at lower temperatures and those with six instars tended to be most frequent at higher temperatures. An 8-h short-day photoperiod resulted in more 4- and 6-instar types than other photoperiods. There was no obvious difference in the duration of nymphal stages of individuals with a maximum four, five, or six instars (P>0.05, t-test). This is the first report to show variation in the number of instars in a species of Lygaeidae. The results indicate a potential increase in survival of this adult-overwintering species, as more autumn generation nymphs in the field could reach the adult stage.

Reproductive Biology of Two Nontarget Insect Species, <I>Aphis gossypii</I> (Homoptera: Aphididae) and <I>Orius sauteri</I> (Hemiptera: Anthocoridae), on <I>Bt</I> and non-<I>Bt</I> Cotton Cultivars

Transgenic Bt cotton, engineered to continuously produce activated delta-endotoxins of the soil bacteria Bacillus thuringiensis, holds great promise in controlling Helicoverpa armigera and other lepidopteran pests. However, it also may impact the invertebrate community, which needs to be clarified. The effects of Bt cotton on two nontarget insects, Aphis gossypii and Orius sauteri, were assessed under semifield and laboratory conditions. Mean total duration of nymphal stages of A. gossypii was shorter (5.9 versus 6.3 d), and rm was higher (0.418 versus 0.394) on conventional Simian 3 (the most frequently planted non-Bt cotton in northern China) than on Bt transgenic NuCOTN 33B (the first Bt cotton commercially planted in China). Mean duration of fourth-instar O. sauteri was significantly longer on transgenic GK-12 (3.7 d) than on NuCOTN 33B (3.2 d), but no different from Simian 3. Mean total mortality was significantly lower on Simian 3 (3.7%) than on GK-12 (14.8%). During the fourth instar, the predator consumed a significantly higher number of prey on Simian 3 (202.3 prey) than on NuCOTN 33B (159.0), whereas the mean total number of A. gossypii prey consumed during the nymphal stage was significantly higher on Simian 3 (336.8 prey) and GK-12 (330.3 prey) than on NuCOTN 33B (275.7). No detrimental effects were detected on development (nymphs, adults, and progeny eggs), fecundity, longevity, and egg viability of O. sauteri on Bt cotton aphids compared with non-Bt cotton aphids. These results suggest that Bt cotton cultivars GK-12 and NuCOTN 33B have no direct effect on nontargets A. gossypii and O. sauteri. Germplasm divergence may account for the negative effects observed on A. gossypii and O. sauteri when reared on NuCOTN 33B or NuCOTN 33B-fed aphids. The biological meanings of the small difference observed between GK-12 and Simian 3 on survival of O. sauteri will require close monitoring over longer time periods.

Developmental Time of <I>Melanoplus sanguinipes</I> (Orthoptera: Acrididae) at High Latitudes

Rates of development of Melanoplus sanguinipes F. from Alaska were determined at eight constant temperatures between 21 and 42°C. Diurnally alternating temperatures were used to estimate rates of development at temperatures too low for nymphs to complete development under constant temperatures. Two previously published equations were fit to these data and used to predict developmental rates as a function of temperature. The first equation, nonlinear and only approaching zero rate of development asymptotically, was fit to the data from constant and alternating temperature treatments. The second equation, which included an intercept, was fit to the data from constant temperature treatments only. Estimated developmental times based on these equations were tested against observed developmental times in two fluctuating temperature regimes in growth chambers, and two seasons of field sampling. Elevation of body temperature of grasshoppers above ambient temperatures in the field was modeled as a linear function of solar irradiance, based on field measurements. The effect of behavioral thermoregulation on nymphal developmental times in the field was estimated using standard air temperatures and solar-adjusted temperatures. Rates of development under most of the constant temperature treatments were higher than any previously published for M. sanguinipes. Estimated rates of development in the field using air temperatures only were about one-half those using solar-adjusted temperatures. Observed developmental times in the field were 45 and 42 d in 2000 and 2002, respectively. Because of local adaptation and behavioral thermoregulation, duration of nymphal stages in M. sanguinipes is relatively independent of latitude.

Plant Phenology as a Guide in Timing Grasshopper Control Efforts on Montana Rangeland

Plant Phenology as a Guide in Timing Grasshopper Control Efforts on Montana Rangeland

Molting and Longevity of Oncometopia nigricans (Homoptera: Cicadellidae), a Suspected Vector of Lethal Yellowing of Coconut Palms, on Various Host Plants

Coconut and Veitchia palms along with periwinkle, lettuce, false aralia, ixora, hibiscus, and lantana were tested to determine the relationship of these locally grown plants to the biology of Oncometopia nigricans (Walker), a possible vector of lethal yellowing in coconut palms. Although the mortality of O. nigricans is generally high on coconut and Veitchia palms, some individuals can live 3 or more months on these 2 palms. This insect undergoes 5 molts and can complete its life cycle on coconut palm, ixora, periwinkle, lantana, and lettuce. The average duration of nymphal stages varies with different test plants, but was 54 days on leaf lettuce and 44 days on head lettuce. Lettuce plants are ideal for rearing O. nigricans colonies in the laboratory.

Some effects of crowding on the biology of Megoura viciae

SUMMARYCrowding Megour a viciae (Buckton) on bean plants affects both the nymphs and adults. Crowded nymphs show a low mortality, develop more rapidly to produce light adults after a series of synchronized moults: isolated nymphs show a high initial mortality, develop more slowly to heavier adults, the duration of nymphal stages being extremely variable, with no synchronization of moulting. Development is discussed in terms of both weight gain and linear growth rate.Crowding does not affect adult mortality but it does reduce the rate at which nymphs are produced. The significance of these findings in relation to the formation and maintenance of the aphid colony is considered, and possible controlling factors are discussed.

SIZE DIFFERENCES IN CICADAS FROM DIFFERENT PLANT COMMUNITIES

In 1952 Dr. R. A. Cumber published the only account of the nymphal life history of a New Zealand cicada, based on studies at the Phormium Research Laboratory at Paiaka in the Manawatu district of the common grass cicada Cicadetta muta (Fabr.), f or which, following Myers (1921), he used the name Melampsalta cruentata (Fabr.). As well as determining the number and duration of nymphal stages, Cumber investigated the variation in size of a sample of 143 males and 74 females collected during one season from his study area, a flax experimental plantation in which rows of Phormium plants were separated by mixed grass pasture. Owing to indications of bimodality in both sexes, Cumber next compared samples of fifth instar nymphs obtained froin beneath Phormium and from beneath pasture grass a few f eet away, finding highly significant differences between them, specimens of both sexes from beneath Phormium plants being more robust that those beneath pasture. He concluded that nymphs associated with Phormium roots are at a definite advantage over nymphs feeding on annual grasses.