Alfalfa Insect Update: 2021 Growing Season

Alfalfa weevils (AW) and fall armyworms (FAW) were newsmakers for very different reasons during the 2021 alfalfa growing season. An AW control failure with a pyrethroid in Kentucky drew attention to practices to manage insecticide resistance. A regional outbreak of FAWs resulted in significant damage to alfalfa and grasses along with a reminder of the unpredictable nature and difficult detection of this pest. While there are several effective FAW control options, it is challenging is to detect infestations in time to act

Cowpea Aphids: Where Did They Come From, Will They Be Back?

Clearly, something was unusual back in March when large numbers of very dark aphids were found covering stems and tips in Logan, Marion, and Barren counties. They were the cowpea aphid or black legume aphid (Aphis craccivora), a sap-feeding insect known to occur in at least 28 states scattered over the US and into Canada. The cowpea aphid is the only black aphid found infesting alfalfa. Winged or wingless adults are usually shiny black, while the smaller nymphs are dull gray to black. Usually. they are lined along stems or clustered in the expanding leaf tips

An Integrated Pest Management IPM Approach in Alfalfa Production Systems

Alfalfa lends itself to an integrated pest management (IPM) approach for alfalfa weevils and potato leafhoppers, the two key insect pests of the crop. Both species live in most alfalfa fields every summer. However, alfalfa can tolerate low levels of their feeding without costly yield or quality loss

Membrane solitons in eight-dimensional hyper-Kaehler backgrounds

We derive the BPS equations satisfied by lump solitons in $(2+1)$-dimensional sigma models with toric 8-dimensional hyper-K\"ahler (${HK}_8$) target spaces and check they preserve 1/2 of the supersymmetry. We show how these solitons are realised in M theory as M2-branes wrapping holomorphic 2-cycles in the \bE^{1,2}\times {HK}_8 background. Using the $\kappa$-symmetry of a probe M2-brane in this background we determine the supersymmetry they preserve, and note that there is a discrepancy in the fraction of supersymmetry preserved by these solitons as viewed from the low energy effective sigma model description of the M2-brane dynamics or the full M theory. Toric ${HK}_8$ manifolds are dual to a Hanany-Witten setup of D3-branes suspended between 5-branes. In this picture the lumps correspond to vortices of the three dimensional ${\mathcal N}=3$ or ${\mathcal N}=4$ theory.Comment: 12+1 pages. LaTex. v2: Typos corrected and references adde

Blister Beetles in Alfalfa

Blister beetles are Iong cylindrical beetles that may be black, gray, yellow and brown striped, black with gray margins on the wing covers or black with a red head. These insects are usually found feeding in clusters on alfalfa. They can cause severe sickness and sometimes death when livestock especially horses eat the live or dead beetles. They are usually not found in alfalfa in mid-July and early August which translates to the third or fourth cutting. Blister beetles (black ones, gray margined ones, and yellow striped ones) were collected in very noticeable numbers in several central Kentucky alfalfa fields this past summer. The most commonly found species is the margined blister beetle. This insect has a black head and body with a gray margin around the wing covers. They range in size from 3/4 to 1 inch. Other species that are also found but do not seem as common include the red-headed blister beetle, the striped blister beetle and the black blister beetle. When found in alfalfa, blister beetles are usually on the very tops of the plants and most often found feeding on the blossoms. Timely harvest, before bloom occurs, is useful in preventing the attraction of these beetles to the field

Maxwell Chern-Simons Solitons from Type IIB String Theory

We study various three-dimensional supersymmetric Maxwell Chern-Simons solitons by using type IIB brane configurations. We give a systematic classification of soliton spectra such as topological BPS vortices and nontopological vortices in $\mathcal{N}=2,3$ supersymmetric Maxwell Chern-Simons system via the branes of type IIB string theory. We identify the brane configurations with the soliton spectra of the field theory and obtain a nice agreement with field theory aspects. We also discuss possible brane constructions for BPS domain wall solutions.Comment: 23 pages, Latex, 4 figures; (q_1,q_2)-string convention changed, minor correction

Kappa-mechanism excitation of retrograde mixed modes in rotating B-type stars

I examine the stability of retrograde mixed modes in rotating B-type stars. These modes can be regarded as a hybrid between the Rossby modes that arise from conservation of vorticity, and the Poincare modes that are gravity waves modified by the Coriolis force. Using a non-adiabatic pulsation code based around the traditional approximation, I find that the modes are unstable in mid- to late-B type stars, due to the same iron-bump opacity mechanism usually associated with SPB and $\beta$ Cep stars. At one half of the critical rotation rate, the instability for $m=1...4$ modes spans the spectral types B4 to A0. Inertial-frame periods of the unstable modes range from 100 days down to a fraction of a day, while normalized growth rates can reach in excess of $10^{-5}$. I discuss the relevance of these findings to SPB and pulsating Be stars, and to the putative Maia class of variable star. I also outline some of the questions raised by this discovery of a wholly-new class of pulsational instability in early-type stars.Comment: 11 pages, 6 figures, accepted by MNRA

Axion-Dilaton Cosmology and Dark Energy

We discuss a class of flat FRW cosmological models based on D=4 axion-dilaton gravity universally coupled to cosmological background fluids. In particular, we investigate the possibility of recurrent acceleration, which was recently shown to be generically realized in a wide class of axion-dilaton models, but in absence of cosmological background fluids. We observe that, once we impose the existence of radiation -and matter- dominated earlier stages of cosmic evolution, the axion-dilaton dynamics is altered significantly with respect to the case of pure axion-dilaton gravity. During the matter dominated epoch the scalar fields remain either frozen, due to the large expansion rate, or enter a cosmological scaling regime. In both cases, oscillations of the effective equation of state around the acceleration boundary value are impossible. Models which enter an oscillatory stage in the low redshift regime, on the other hand, are disfavored by observations. We also comment on the viability of the axion-dilaton system as a candidate for dynamical dark energy. In a certain subclass of models, an intermediate scaling regime is succeeded by eternal acceleration. We also briefly discuss the issue of dependence on initial conditions.Comment: 28 pages, 11 figure

On a possible new R^2 theory of supergravity

We consider a new MacDowell-Mansouri R^2-type of supergravity theory, an extension of conformal supergravity, based on the superalgebra Osp(1|8). Invariance under local symmetries with negative Weyl weight is achieved by imposing chirality-duality and double-duality constraints on curvatures, along with the usual constraint of vanishing supertorsion. An analysis of the remaining gauge symmetries shows that those with vanishing Weyl weight are invariances of the action at the linearized level. For the symmetries with positive Weyl weight we find that invariance of the action would require further modifications of the transformation rules. This conclusion is supported by a kinematical analysis of the closure of the gauge algebra.Comment: 52 pages, Late