Biological control ecology of Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae) on Myzus persicae (Sulzer) (Hemiptera: Aphididae) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Sciences (Entomology) at Massey University, Palmerston North, New Zealand

Content removed from thesis due to copyright reasons: Khatri, D., He, X. Z., & Wang, Q. (2017) Effective biological control depends on life history strategies of both parasitoid and its host : evidence from Aphidius colemani-Myzus persicae system. Jounal of Economic Entomology, 110(2), 400-406. doi:10.1093/jee/tow324; Khatri, D., He, X. Z., & Wang, Q. (2016). Trade-off between fitness gain and cost determines profitability of a peach aphid parasitoid. Journal of Economic Entomology, 109(4), 1539-1544. doi:10.1093/jee/tow105The solitary and koinobiont endoparasitoid, Aphidius colemani Viereck, is produced commercially for biological control of green peach aphid Myzus persicae (Sulzer) and cotton aphid Aphis gossypii Glover around the world. However, its production cost is still high and biological control efficiency is still uncertain, probably due to the lack of knowledge on its biological control ecology. To fill the knowledge gap, I investigated the biological control ecology of the A. colemani-M. persicae system. My results show that most emergence and reproductive activities of A. colemani occur during the photophase. After emergence, both sexes need about 2 hours for sex maturation, but once sexually mature, age of neither sex has any significant effect on mating success. Food supply to adult females is essential to mating success. The mating behavioural sequence is similar to that of many other braconid parasitoids. My findings suggest that A. colemani is an effective biological control agent of M. persicae because reproductive outputs of the parasitoid are twice as high as the aphid, the parasitoid reaches the maximum lifetime reproductive potential about a week earlier than the aphid, and parasitised aphids contribute little to their population growth and make limited damage to plants. The parasitoid prefers to attack larger hosts but such preference is counterbalanced by greater defensive ability of larger hosts, resulting in similar parasitism rate on hosts of all ages. As a result, parasitising mid-aged hosts allows A. colemani females to gain maximum fitness in developmental period, body size and parasitism of their progeny. Finally, my study confirms that A. colemani has a Type II functional response. However, it can still successfully control M. persicae regardless of pest density probably because parasitoid density has significantly more effect than host density on parasitoid reproductive fitness and the low mutual interference among the searching parasitoids encourages aggregation of the parasitoids on host patches of high density. The present study provides basic knowledge on the biology of A. colemani for development of effective measures for laboratory handling, rearing, and field release, and brings insight into the success of aphid biological control programmes using the parasitoid augmentation approach

Linearized iterative least-squares (LIL): A parameter fitting algorithm for component separation in multifrequency CMB experiments such as Planck

We present an efficient algorithm for the least squares parameter fitting optimized for component separation in multi-frequency CMB experiments. We sidestep some of the problems associated with non-linear optimization by taking advantage of the quasi-linear nature of the foreground model. We demonstrate our algorithm, linearized iterative least-squares (LIL), on the publicly available Planck sky model FFP6 simulations and compare our result with the other algorithms. We work at full Planck resolution and show that degrading the resolution of all channels to that of the lowest frequency channel is not necessary. Finally we present results for the publicly available Planck data. Our algorithm is extremely fast, fitting 6 parameters to 7 lowest Planck channels at full resolution (50 million pixels) in less than 160 CPU-minutes (or few minutes running in parallel on few tens of cores). LIL is therefore easily scalable to future experiments which may have even higher resolution and more frequency channels. We also naturally propagate the uncertainties in different parameters due to noise in the maps as well as degeneracies between the parameters to the final errors on the parameters using Fisher matrix. One indirect application of LIL could be a front-end for Bayesian parameter fitting to find the maximum of the likelihood to be used as the starting point for the Gibbs sampling. We show for rare components, such as the carbon-monoxide emission, present in small fraction of sky, the optimal approach should combine parameter fitting with model selection. LIL may also be useful in other astrophysical applications which satisfy the quasi-linearity criteria.Comment: Accepted versio

A coarse-grained biophysical model of sequence evolution and the population size dependence of the speciation rate.

Speciation is fundamental to understanding the huge diversity of life on Earth. Although still controversial, empirical evidence suggests that the rate of speciation is larger for smaller populations. Here, we explore a biophysical model of speciation by developing a simple coarse-grained theory of transcription factor-DNA binding and how their co-evolution in two geographically isolated lineages leads to incompatibilities. To develop a tractable analytical theory, we derive a Smoluchowski equation for the dynamics of binding energy evolution that accounts for the fact that natural selection acts on phenotypes, but variation arises from mutations in sequences; the Smoluchowski equation includes selection due to both gradients in fitness and gradients in sequence entropy, which is the logarithm of the number of sequences that correspond to a particular binding energy. This simple consideration predicts that smaller populations develop incompatibilities more quickly in the weak mutation regime; this trend arises as sequence entropy poises smaller populations closer to incompatible regions of phenotype space. These results suggest that a generic coarse-grained approach to evolutionary stochastic dynamics allows realistic modelling at the phenotypic level

Midline Household Survey Results: Rupandehi, Nepal

This report summarizes the main findings from the household midline survey conducted in seven villages of the district of Rupandehi, one of CCAFS site, in Nepal in July 2019. The household survey revisited the 135 households of the 2012 CCAFS baseline survey and used the same standardized household survey tools. The Open Data Kit (ODK) software was used for the data collection. The results show that the majority of households in Rupandehi produce a variety of crops, among which rice, wheat and mustard. Many farmers also rear livestock such as cows, buffalo, chicken, oxen and goat. All members of the family typically engage in the on-farm agricultural work but men are more likely to be also involved in off-farm activities. Households members derive their income from a variety of sources, the main one being payments from the government or other projects/programs. This is followed by remittances and income from businesses as the main alternative income sources for many households. Moreover, most of the farmers have made changes in their agricultural practices since the baseline. Many have introduced higher-yielding crop varieties or have stopped keeping one or more types of animals on the farm. In terms of food security, the majority of the households surveyed in Rupandehi district are food secure throughout the entire year. The households mostly obtain their food directly from their farms. However, some of the households purchase food from other sources, especially during the month of June, July and August. Most farmers are small landholders, almost 75% of the households’ land sizes are marginal (< 1 ha), followed by a minority of smallholders owning between 1 and 2 ha of land. 98% of the households indicated buying seeds and inorganic fertilizers whereas 95% of households reported the purchase of pesticides and insecticides. 70% of households also recorded the purchase of veterinary medicine. According to the survey, television, cell phone and bicycle are the most common assets in the area. Internet access is also common in many households. Women are mostly involved in crops cultivation, mainly vegetables and cereals along with rearing livestock. The farmers have shifted towards higher-yielding and better-quality varieties of rice, and wheat. The survey findings indicate that farmers are well aware of agricultural innovations and tend to use new crop varieties