Cass B.N.,University of Arizona |
Yallouz R.,Newe Ya'ar Research Center |
Bondy E.C.,University of Arizona |
Mozes-Daube N.,Newe Ya'ar Research Center |
And 5 more authors.
Microbial Ecology | Year: 2015
A new heritable bacterial association can bring a fresh set of molecular capabilities, providing an insect host with an almost instantaneous genome extension. Increasingly acknowledged as agents of rapid evolution, inherited microbes remain underappreciated players in pest management programs. A Rickettsia bacterium was tracked sweeping through populations of an invasive whitefly provisionally described as the “B” or “MEAM1” of the Bemisia tabaci species complex, in the southwestern USA. In this population, Rickettsia provides strong fitness benefits and distorts whitefly sex ratios under laboratory conditions. In contrast, whiteflies in Israel show few apparent fitness benefits from Rickettsia under laboratory conditions, only slightly decreasing development time. A survey of B. tabaci B samples revealed the distribution of Rickettsia across the cotton-growing regions of Israel and the USA. Thirteen sites from Israel and 22 sites from the USA were sampled. Across the USA, Rickettsia frequencies were heterogeneous among regions, but were generally very high, whereas in Israel, the infection rates were lower and declining. The distinct outcomes of Rickettsia infection in these two countries conform to previously reported phenotypic differences. Intermediate frequencies in some areas in both countries may indicate a cost to infection in certain environments or that the frequencies are in flux. This suggests underlying geographic differences in the interactions between bacterial symbionts and this serious agricultural pest. © 2015, Springer Science+Business Media New York.
Asher J.B.,Katif Research Center |
Yosef B.B.,Katif Research Center |
Volinsky R.,Katif Research Center
Biosystems Engineering | Year: 2013
The Penmane-Monteith (PM) equation is the best-known approach to estimate evapotranspiration from meteorological data on a daily basis. Limited information is available on an hourly basis, mostly because of the requirement for the parameterization of aerodynamic and canopy resistance (ra and rc, respectively), which are difficult to estimate. The objectives of this study were a) to develop a new remote sensing approach to estimate rc and ra from the output of an infrared radiometric system; b) to include rc and ra in the PM equation to calculate evapotranspiration (ET) for irrigation scheduling; and c) to formulate a numerical model that solves the changes in soil water profile with time using a onedimensional Richards' equation (RE). The integration of the time-dependent changes in the soil water profile provided the effect of irrigation on soil water balance. Infrared radiometers and a conventional meteorological system were stationed on top of a linear move irrigation system. The output signals were collected remotely in a personal computer (PC) that was equipped with specific code to solve the PM equation for ra and rc, which were then used to calculate the water requirement of the plants. The software used the actual ET as a boundary condition for the instantaneous calculations of the soil water balance components based on the hydraulic properties of the soil in Western Negev, Israel. Currently, all components that are required to improve irrigation management are controlled remotely, including the automatic data collection, models, hardware and software. © 2012 IAgrE.
Horowitz A.R.,Agricultural Research Organisation |
Horowitz A.R.,Katif Research Center |
Ishaaya I.,Agricultural Research Organisation
Pest Management Science | Year: 2014
BACKGROUND: The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a key pest in many agricultural crops, including vegetables, ornamentals and field crops. B. tabaci is known for its genetic diversity, which is expressed in a complex of biotypes or, as recently suggested, a complex of distinct cryptic species. The biotypes are largely differentiated on the basis of biochemical or molecular polymorphism and differ in characteristics such as host plant range, attraction by natural enemies, secondary symbionts and expression of insecticide resistance. An extensive survey of B. tabaci biotypes and their impact on insecticide resistance was conducted from 2003 to 2012 in cotton fields and other crops from several locations in Israel. RESULTS: Two biotypes of B. tabaci, B and Q, were identified, and some differences in the biotype dynamics were recorded from different areas. In northern Israel from 2003 to 2007, a higher proportion of the B biotype was consistently found in early season. However, by the end of the season a definite rise of the Q biotype was sampled, ranging from 60 to 100%, along with high resistance to the insect growth regulator (IGR) pyriproxyfen and to a lesser extent to the neonicotinoid insecticides. In fields located in the central part of Israel, the Q biotype was predominant throughout the seasons, with high resistance to pyriproxyfen. Since 2009, a significant shift in the biotype ratios has been observed: the B biotype has come to predominate over the Q biotype ranging up to 90% or more in most fields. At the same time, resistance to the IGR pyriproxyfen was reduced considerably. CONCLUSION: The possible reasons for the change in the dynamics of B. tabaci biotypes, and its implications for resistance management, are discussed. Strong B. tabaci resistance to pyriproxyfen in Israel has been associated with the Q rather than with the B biotype. The B biotype is more competitive than the Q biotype under untreated conditions. Reduction in the acreage of cotton fields during recent years, along with a decrease in insecticide use, especially pyriproxyfen, has resulted in the expansion of the B biotype. © 2014 Society of Chemical Industry.