AGRICULTURAL PEST MANAGEMENT
Year:2014 | Volume:1 | Issue:2|Papers Count:6

Characteristics such as rapid growth, longer longevity, shorter developmental time, higher fertility and larger body size are important criteria for selecting and initializing mass rearing of natural enemies. Oenopia conglobata contaminata (Menteries) (Col: Coccinellidae) is one of the major predators of insect pests in the orchards of Iran. The effect of five constant temperatures of 22.5, 25, 27.5, 30 and 32.5±1oC were investigated on the developmental rate of the predator by feeding on the green peach aphid, Myzus persicae (Sulzer) (Hem.: Aphididae), under laboratory conditions (55±5% RH and 16L: 8D h). The results showed that there were significant differences between the five temperatures in terms of developmental time. Total developmental times at above-mentioned temperatures were 24.02±0.4, 19.68±0.7, 17.15±0.33, 14.09±0.39 and 14.32±0.25 days respectively. Minimum survival rate was recorded for the first larval instar and maximum was for the third and fourth larval instars and pupa. The highest mortality rate was observed at 22,5 and 32,5oC. The lower temperature threshold and thermal constant for entire developmental time were estimated by using the simple linear regression model. The lower developmental thresholds of egg, larva, pupa and total immature stages were 9,99, 10,58, 9.63 and 8,48°C respectively and the thermal constant required at the above mentioned periods were 43,1, 163,93, 71,9 and 322,58 DD respectively. The results showed that 25 to 30oC are suitable temperatures for rearing this predator.

Pollen of different plants is supplementary or alternative food resource for most predator species. In this research, the effect of various diets was investigated on life table parameters of the predatory bug, Orius laevigatus (Fieber) at 26±2oC, 55±5% RH, and a photoperiod of 16:8 (L: D) h. Four diets including Anagasta kuehniella (Zeller) eggs plus corn pollen, A. kuehniella eggs plus sunflower pollen, A. kuehniella eggs plus red poppy pollen and A. kuehniella eggs (without pollen) were compared. The predators were separately reared on each diet for one generation and their offspring was used in the experiment. Newly hatched first instar nymphs of the predator were transferred individually to small plastic containers. The nymphs were separately reared on each diet. Newly emerged adults of the predator were paired in transparent plastic containers and fed separately on each diet. In all treatments, a piece of bean pod was used as oviposition substrate as well as a source of moisture to the insects. Number of eggs laid by females was recorded daily. The intrinsic rate of natural increase (rm) of O. laevigatus was significantly higher when A. kuehniella eggs plus corn pollen (0.1909 d-1) and A. kuehniella eggs plus sunflower pollen (0.1840 d-1) were served as diet compared to those estimated on A. kuehniella eggs plus red poppy pollen (0.1554 d-1) and A. kuehniella eggs alone (0.1626 d-1). The net reproductive rate (R0) of the predator ranged from 70.94 (♀/♀/generation) on A. kuehniella eggs plus corn pollen to 24.95 on A. kuehniella eggs plus red poppy. There were also significant differences in finite rate of increase (l), mean generation time (T) and doubling time (DT) in feeding on different diets. This study revealed that the corn and sunflower pollens increase the fecundity of O. laevigatus and can be used in mass rearing of this predator.

Predators when offered a choice between two or more prey types, often show a preference to one of them. Therefore, prey preference of natural enemies should be considered as one of the main criteria during the study of natural enemies efficiency. This experiment was conducted to determine the feeding preference of third and fourth instar larvae and females of H. variegata to D. noxia fed on different wheat cultivars including resistant (Omid), moderately resistant (Back cross) and susceptible (Sardari) varieties. Predator preference was analyzed using the Manly’s index of preference. Results showed that life stages of predator and host plant resistance influence prey preferences, in a way that older stages of H. variegata show the preference more tangibly. Based on collected data, female of H. variegata showed the highest, intermediate and the least preference to D. noxia on Omid, Back cross and Sardari cultivars, respectively. H. variegata females killed 73.89±1.06, 67.15±1.61 and 37.18±2.05 3rd instar nymphs of D. noxia during the experiment duration and preference index were 0.456±0.009, 0.379±0.013 and 0.165±0.018, respectively. The values of this index were 0.425±0.017, 0.372±0.013 and 0.202±0.016 for the 3rd instar larvae of ladybird. Results showed that H. variegata prefers Russian wheat aphids that feed on resistant cultivars. This tendency can be very important in developing integrated pest management programs of this species.

Codling moth is a serious pest of pome fruits in Iran. In order to timing chemical control, male adult emergence along with the time of larval activity were studied during 2008-2011 at a research orchard in Bavanat strict (Fars province). Delta-shape pheromone traps were used to determine male adult moth emergence. According to the data obtained from regional weather station and larval activity data, degree-day model was prepared. Calculations showed that 155, 720 and 1336 degree-days are required for egg eclosion at first, second and third generations respectively. On the basis of the data available by pheromone traps the measurement time was determined to be 9-14 May, 4-9 June and 2-7 August 2008 and 2-9 June, 7-11 July, and 11-16 August 2009 for the three generations of those years respectively. The larval emergence were determined in the same way for the next years as well. Based on this study, degree-days needed required for each event of codling moth life may be determined using daily reports of regional temperature data.

The potato tuber moth, Phthorimaea operculella Zeller is one of the most important pests of potato in temperate regions such as Iran. Since the damage of this pest dominantly occur in stores and the potato is one of the major sources of human food, safe methods in control of this pest is important. population responses to chemical compounds is very critical in insect management programs, therefore in this investigation sub-lethal concentrations (LC25) of essential oils of Lavandula angustifolia L. and Origanum vulgare Mill (0.30 and 0.25ml/l, respectively) were examined in terms of life-table parameters of P. operculella under laboratory condition at 26±1oC, 60±5% RH and a photoperiod of 16L: 8D. The values of rm were estimated to be 0.107±0.016, 0.101±0.017 and 0.104±0.008 in control, Lavander and Oregano treatments, respectively. In this parameter, there was no significant difference between control and Oregano treatment, but difference between control and Lavander treatment was significant. Life expectancy values of the pest in birth were estimated to be 27.38, 16.81 and 20.42 day in control, Lavander and Oregano treatments, respectively.

Tomato leaf miner, Tuta absoluta (Meyrick) (Lep: Gelechiidae) is one of the serious pests of tomato. With regards to its quick distribution in nearly all tomato fields in Iran as well as its destructive attributes, a study of its biological traits of T. absoluta is necessary. Furthermore, improvement of laboratory rearing methods is needed to set laboratory experiments as well as its mass production. In the present study, longevity and survival rate of immature stage of tomato leaf miner was investigated using leaf cuts of tomato plant cultivars including ATABAY, CLUSE and PRENSES under laboratory condition for three successive generations. The results indicated that, mean pre-adult developmental duration increased as generation increased. Maximum value of mean pre-adult developmental longevity was recorded on ATABAY cultivar. Maximum survival rate of eggs, larvae and pupae was related to the first, third and second generations on ATABAY, ATABAY and PRENSES cultivars respectively. The results showed that the development of tomato leaf miner can be affected by generation and tomato plant cultivar and these factors must be considered for toxicology, ecology assessments etc.