Effect of Temperature and Relative Humidity on the Population Density of the Whitefly Parasitoid on Some Vegetable Crops Under Field Conditions.

2015 ◽  
Vol 4 (2) ◽  
pp. 87-92 ◽  
Author(s):  
Gamini Sahu ◽  
Surendra K. Gautam ◽  
Aditi N. Poddar

Root knot nematodes (Meloidogyne species) are major pests of vegetable crops causing serious losses in quantity and quality of crop yield. This study involves an assessment of their suitable hosts on the basis of variations in their population densities and body sizes in different vegetable crop plants under field conditions. A random survey of root knot nematode infestation in vegetable crops was conducted in 9 villages of Abhanpur block, Chhattisgarh state, Central India, from January 2012 to March 2012.  Diseased plants were identified on the basis of above ground symptoms and soil and root samples collected by digging. Extraction of nematodes was done by Cobb’s sieving and decantation method and Baerman’s funnel technique. Identification was done microscopically by morphological examination of perineal patterns of female nematodes. Body sizes were measured by using an eyepiece/ocular micrometer. Twenty nine percent of the total farm area surveyed suffered from root knot nematode attack. Among the several genera of vegetable crop plants surveyed, Lycopersicon esculentum, Dolichos lablab, Solanum melongena, Momordica charantia, Daucus carota,Capsicum annum,Cucumis sativus had root galls. Three species of root knot nematodes Meloidogyne incognita, M. javanica, M. areneria were identified from the above hosts and a comparative morphometric analysis of the body, head and neck size ratios of females were done. Non-significant body and head size variations existing between the females from D. lablab, S. melongena, C. annum, D. carota, L. esculentum showed that all the crops are equally susceptible to root knot nematode attack.  However, on the basis of nematode population density, D. carrota appears to be the best suitable host of the Meloidogyne species other than L. esculentum and S. melongena.


1996 ◽  
Vol 10 (2) ◽  
pp. 253-257 ◽  
Author(s):  
Joan A. Dusky ◽  
William M. Stall

Imazethapyr was evaluated PRE and POST in five lettuce types and chicory under Florida field conditions. The relative sensitivity of leafy crop vigor (most sensitive to most tolerant) to imazethapyr PRE, based on 20% inhibition determined using regression analysis, was as follows: Boston > bibb > crisphead > romaine > leaf > escarole > endive. Leafy crop injury increased as the rate of imazethapyr applied POST increased, with all leafy crops responding in a similar manner. Surfactant addition increased imazethapyr phytotoxicity. Imazethapyr PRE treatments at 0.067 kg ai/ha provided greater than 80% control of livid amaranth, common purslane, flatsedge, and common lambsquarters. Imazethapyr POST at 0.067 kg/ha, with surfactant provided control greater than 85% of all weed species. Greater than 85% spiny amaranth control was provided by imazethapyr POST at 0.017 kg/ha. Use of surfactant with imazethapyr did not improve spiny amaranth control over imazethapyr with no surfactant. POST treatments did not decrease leafy crop yield compared with the hand-weeded check. Imazethapyr applied PRE reduced crop yield compared to the POST treatments and the hand-weeded control.


2005 ◽  
Vol 7 (3) ◽  
pp. 75-90 ◽  
Author(s):  
Suman Kashyap ◽  
Satyawati Sharma ◽  
Padma Vasudevan

2007 ◽  
Vol 38 (1) ◽  
pp. 81-93 ◽  
Author(s):  
Joseph Hermann ◽  
Steve Hoff ◽  
Claudia Muñoz-Zanzi ◽  
Kyoung-Jin Yoon ◽  
Michael Roof ◽  
...  

2020 ◽  
Author(s):  
Lei Qin ◽  
Qiang Sun ◽  
Jiani Shao ◽  
Yang Chen ◽  
Xiaomei Zhang ◽  
...  

Abstract Background: The effects of temperature and humidity on the epidemic growth of coronavirus disease 2019 (COVID-19)remains unclear.Methods: Daily scatter plots between the epidemic growth rate (GR) and average temperature (AT) or average relative humidity (ARH) were presented with curve fitting through the “loess” method. The heterogeneity across days and provinces were calculated to assess the necessity of using a longitudinal model. Fixed effect models with polynomial terms were developed to quantify the relationship between variations in the GR and AT or ARH.Results: An increased AT dramatically reduced the GR when the AT was lower than −5°C, the GR was moderately reduced when the AT ranged from −5°C to 15°C, and the GR increased when the AT exceeded 15°C. An increasedARH increased theGR when the ARH was lower than 72% and reduced theGR when the ARH exceeded 72%.Conclusions: High temperatures and low humidity may reduce the GR of the COVID-19 epidemic. The temperature and humidity curves were not linearly associated with the COVID-19 GR.


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