Search results for: Lipaphis erysimi

Authors: Ahmad-Ur-Rahman Saljoqi, Rahib Zada, Imtiaz Ali Khan, Iqbal Munir, Sadur-Rehman, Hazrat Jabir Alam Khan

Abstract:

Studies regarding the determination of population trend of Lipaphis erysimi (kalt.) and its associated natural enemies in different Brassica lines along with the effect of gamma radiation on their population were conducted at Agricultural Research Farm, Malakandher, Khyber Pakhtunkhwa Agricultural University Peshawar during spring 2006. Three different Brassica lines F6B3, F6B6 and F6B7 were used, which were replicated four times in Randomized Complete Block Design. The data revealed that aphid infestation invariably stated in all three varieties during last week of February 2006 (1st observation). The peak population of 4.39 aphids leaf-1 was s recorded during 2nd week of March and lowest population of 1.02 aphids leaf-1 was recorded during 5th week of March. The species of lady bird beetle (Coccinella septempunctata) and Syrphid fly (Syrphus balteatus) first appeared on 24th February with a mean number of 0.40 lady bird beetle leaf-1 and 0.87 Syrphid fly leaf-1, respectively. At the time when aphid population started to increase the peak population of C. septempunctata (0.70 lady bird beetle leaf- 1) and S. balteatus (1.04 syrphid fly leaf-1) was recorded on the 2nd week of March. Chrysoperla carnea appeared in the 1st week of March and their peak population was recorded during the 3rd week of March with mean population of 1.46 C. carnea leaf-1. Among all the Brassica lines, F6B7 showed comparatively more resistance as compared to F6B3 F6B6. F6B3 showed least resistance against L. erysimi, which was found to be the most susceptible cultivar. F6B7 was also found superior in terms of natural enemies. Maximum number of all natural enemies was recorded on this variety followed by F6B6. Lowest number of natural enemies was recorded in F6B3. No significant effect was recorded for the effect of gamma radiation on the population of aphids, natural enemies and on the varieties.

Keywords: Canola aphid, Lipaphis erysimi, natural enemies, brassica lines, gamma radiation.

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Authors: Nastaran Rezaei, Mohammad Saeed Mossadegh, Farhan Kocheyli, Khalil Talebi Jahromi, Aurang Kavousi

Abstract:

Integrated Pest Management (IPM) aims to combine biological and chemical strategies and measures, hence highlighting the study of acute toxicity and sub-lethal effects of pesticides comprehensively. The present research focused on the side effects of thiamethoxam and pirimicarb sub-lethal concentrations on demographic parameters of Diaeretiella rapae (McIntosh Laboratory) (Hymenoptera: Braconidae). Adult parasitoids were exposed to LC₂₅ of insecticides as well as distilled water as the control. The results showed that thiamethoxam adversely affected population parameters (r, λ, R₀, T), adults' longevity, females' oviposition period and mean fecundity, and a similar trend was obtained for pirimicarb with the exception of generation time (T), the latter did not significantly change compared to the control. The intrinsic rate of increase (r) in the control and those treated with pirimicarb and thiamethoxam were 0.2801, 0.2064, 0.1525 days^-1, respectively, and the sex ratio was biased toward females in all treatments. Furthermore, none of the insecticides influenced total pre-oviposition period (TPOP) and offspring emergence rate. In general, these results indicated that both insecticides potentially distort the demographic parameters of the parasitoid even at sub-lethal concentrations, and then they should not be considered for IPM program in the presence of D. rapae.

Keywords: Diaeretiella rapae, Lipaphis erysimi, life-table study, pirimicarb, thiamethoxam.

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