#preoviposition

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Direct effect of Environment on Pest Population

●● Development & Development rates of Pests ●● Dispersal of Pests ●● Voltinism of Pests ●● Density of Pests ●● Composition of populations of Pests ●● Pest outbreaks Global warming could lead to an increase in pest insect populations, harming yields of staple crops like wheat, soybean, and corn. While warmer temperatures create longer growing seasons, and faster growth rates for plants, it also increases the metabolic rate and number of breeding cycles of insect populations. Insects that previously had only two breeding cycles per year could gain an additional cycle if warm growing seasons extend, causing a population boom. Temperate places and higher latitudes are more likely to experience a dramatic change in insect populations.

Temperature affects both the time of development as well as fecundity; consequently, the appearance and dynamics of insect populations in the field are dictated by ambient temperature. The effects of temperature on the melon thrips, Thrips palmi karny (Thysanoptera: Thripidae), preimaginal development, survival, fecundity, longevity of females and males and population growth were investigated indicating that the duration of egg, larval and pupal stages was significantly influenced by increased temperature. The egg to adult development period of T. Palmi declined from 35.7 to 9.6 days as the temperature increased from 16 to 31˚C. The development threshold temperature estimated was 13.91, 11.82, 9.36 and 10.45˚C for adult preoviposition period, total preoviposition period, female longevity, and male longevity, respectively. The thermal for competing the adult preovi position period, total preoviposition period, female longevity and male longevity were 29.3, 227.3, 454.6 and 344.8 degree days, respectively. Female longevity was found to be shortest at 31˚C (18.7 days) and longest at 16˚C(50.7 days). Fecundity was highest at 25˚C (64.2 eggs/female) and lowest at 16˚C (7.6). The optimal development temperature for T. Palmi in egg plant, Solanum melongena L. (Solanales: Solanaceae), ws determined to be 25˚C (Ramchandra Yadav and Niann-Tai Chang, 2014). The basic climate parameters, i.e. temperature and humidity, influence insects both directly and indirectly. The direct influence can be observed through limiting and stimulating the activity of larvae and adults, insects dispersal in the environment, phenology and growing length, as well as through the possibility of surviving in adverse weather conditions population genetics, etc. Indirect influence includes a climatic influence on environment where insects appear, such as influence on plant formations, plant phenology, food quality, predators, parasitoids and activity of entomopathogens. Insects as poikilothermic animals change activity depending on the temperature of the surrounding environment (Bale et al., 2002; Menéndez et al., 2007). Increasing the temperature to the thermal optima level causes acceleration of the insect metabolism. Hence, it directly influences their increased activity. In the temperate climate zone conditions, the average temperature increase is followed by i.a. more intensive and longer total day and night’s activity of imago of majority phytophagous species in forest environment, implied as feeding and mating, as well as time spent on finding proper place for laying eggs (Moore and Allard 2008; Netherer and Schopf 2010). It can also result in insects dispersion increase in the forest environment, as well as more frequent oviposition and possibility of colonising larger number of host plants (Parvatha Reddy, 2013). In higher temperature conditions, the development of egg, larva and pupa shortens, which is the characteristic phenomenon for large group of forest species (Szujecki, 1998). Faster development of pre-imaginal stages implies shorter time of exposure to adverse environmental conditions such as low temperature, too high or insufficient humidity, attacks of predators and parasitoids, and entomopathogen’s activity. It can result in reproductive success of many insect species. Temperature influence on a length of larval development has been observed under laboratorial conditions for two significant species of native foliophages: the nun moth, Lymantria monacha (L.) and the gypsy moth Lymantria dispar (L.) (Karolewski et al., 2007). In both cases, temperature increase has had an influence on reducing growth period, from egg phase to pupa. Different results have been obtained regarding larva survivability of both species. When the average environment temperature has increased, higher mortality has been observed for caterpillars of L. monacha. Whereas the survivability of L. dispar larvae has increased. These differences probably result from two different thermal optima for both species reflected in varied environmental preferences. The results of

the described experiment Present variety of climatic parameters influence on the insect development, even when closely related species are compared.

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On variation of preoviposition period in Utetheisa pulchella L. (Lep., Arctiidae)

http://dlvr.it/PSnCxN