Inter-seasonal population dynamics and cultural management of Helicoverpa spp. in a Central Queensland cropping system

A strategic trap cropping program targeting Helicoverpa spp. on cotton was developed and implemented in the Emerald irrigation area of Central Queensland beginning in the winter of 1997. Growers were advised to plant 1% of total cropping area to a trap crop of chickpea (Cicer arietinum) in winter and pigeon pea (Cajanus cajan) in summer. The population dynamics of Helicoverpa spp. in relation to the Emerald cropping system was studied over a 3-year period (August 1996–July 1999) to provide a framework for testing the validity of key assumptions underlying the trap cropping strategy and optimising the implementation of the program. The population dynamics study showed continuous production of Helicoverpa pupae (moths) in the crop production system during each calendar year. The pattern of pupae production was consistent with cycling of Helicoverpa populations between irrigation and rainfed cropping components of the system. Spring rainfall and the availability of host plant resources is shown to impact on the population dynamics of Helicoverpa in the cropping system and its pest status on early-season cotton. Performance and potential impact of the trap crops are discussed within the context of host plant availability and resource bottlenecks. It is shown that the impact of the trap crops on abundance of Helicoverpa spp. early in the growing season could not be distinguished from that of naturally occurring host plant resource bottlenecks in spring most likely as a result of suboptimal timing of trap crop destruction. The potential contribution of cultural control tactics to integrated pest management of Helicoverpa spp. in cropping systems is discussed

Neutron diffraction study of superconducting RESr(2)Cu(3-x)M(x)O(z) (M=Re,W)

Superconductivity has recently been reported in RESr(2)CU(2.85)Re(0.15)O(x) (RE = Y,Tb,Dy,Ho,Er and Tm) and RESr(2)Cu(2.80)W(0.20)O(x) (RE = Y, Dy, Ho and Er) with T-c ranging from 22 to 41 K. Room temperature powder neutron diffraction studies have been carried out for obtaining structural parameters and their relation with superconductivity in these materials. Reitveld refinements were carried out adopting the space groups P4/mmm (tetragonal). Occupancy of the rare earths is less than 1 indicating vacancy at the rare earth sites. Cu(2)-O distance in RESr(2)Cu(3-x)M(x)O(z) (M = Re and W) is smaller than that of REBa(2)Cu(3)O(7-delta) which is consistent with the smaller ionic radius of Sr2+. Our studies show that the M-cations (Re or W) occupy the Cu(1) chain site

Neutron diffraction study of superconducting RESr<SUB>2</SUB>Cu<SUB>3&#8722;x</SUB>M<SUB>x</SUB>O<SUB>z</SUB> (M = Re, W)

Superconductivity has recently been reported in RESr<SUB>2</SUB>Cu<SUB>2.85</SUB>Re<SUB>0.15</SUB>O<SUB>z</SUB> (RE = Y, Tb, Dy, Ho, Er and Tm) and RESr<SUB>2</SUB>Cu<SUB>2.80</SUB>W<SUB>0.20</SUB>O<SUB>z</SUB> (RE = Y, Dy, Ho and Er) with T<SUB>c</SUB> ranging from 22 to 41 K. Room temperature powder neutron diffraction studies have been carried out for obtaining structural parameters and their relation with superconductivity in these materials. Reitveld refinements were carried out adopting the space groups P4/mmm (tetragonal). Occupancy of the rare earths is less than 1 indicating vacancy at the rare earth sites. Cu(2)-O distance in RESr<SUB>2</SUB>Cu<SUB>3&#8722;x</SUB>M<SUB>x</SUB>O<SUB>z</SUB> (M = Re and W) is smaller than that of REBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7&#8722;&#948;</SUB> which is consistent with the smaller ionic radius of Sr<SUP>2+</SUP>. Our studies show that the M-cations (Re or W) occupy the Cu(1) chain site

Effect of row covers on silverleaf whitefly (Homoptera: Aleyrodidae) population densities and crop yield in zucchini

The use of a row cover effectively reduced silverleaf whitefly, Bemisia tabaci Biotype B, densities in a field zucchini crop. The trial assessed yields and quality of zucchini under floating row covers where silverleaf whitefly had been introduced or not introduced, and with those in open plots where whitefly were introduced. Floating row covers increased temperature and humidity compared with the uncovered treatment. Total and average fruit weight and percent marketable fruit were less (P<0.05) under row covers with silverleaf whitefly present. Floating row covers may provide an effective alternative to pesticide use in small-scale cucurbit production