Root-lesion nematodes (Pratylenchus thornei and P. neglectus): A review of recent progress in managing a significant pest of grain crops in northern Australia

Two species of root-lesion nematode (predominantly Pratylenchus thornei but also P. neglectus) are widespread pathogens of wheat and other crops in Australia's northern grain belt, a subtropical region with deep, fertile clay soils and a summer-dominant rainfall pattern. Losses in grain yield from P. thornei can be as high as 70% for intolerant wheat cultivars. This review focuses on research which has led to the development of effective integrated management programs for these nematodes. It highlights the importance of correct identification in managing Pratylenchus species, reviews the plant breeding work done in developing tolerant and resistant cultivars, outlines the methods used to screen for tolerance and resistance, and discusses how planned crop sequencing with tolerant and partially resistant wheat cultivars, together with crops such as sorghum, sunflower, millets and canaryseed, can be used to reduce nematode populations and limit crop damage. The declining levels of soil organic matter in cropped soils are also discussed with reference to their effect on soil health and biological suppression of root-lesion nematodes.

Influence of food supplementation on the fitness of two biological control agents: a predatory nabid bug and a bollworm pupal parasitoid

Many arthropod predators and parasitoids exhibit either stage-specific or lifetime omnivory, in that they include extra-floral nectar, floral nectar, honeydew or pollen in their immature and/or adult diet. Access to these plant-derived foods can enhance pest suppression by increasing both the individual fitness and local density of natural enemies. Commercial products such as Amino-Feed®, Envirofeast®, and Pred-Feed® can be applied to crops to act as artificial-plant-derived foods. In laboratory and glasshouse experiments we examined the influence of carbohydrate and protein rich Amino-Feed UV® or Amino-Feed, respectively, on the fitness of a predatory nabid bug Nabis kinbergii Reuter (Hemiptera: Nabidae) and bollworm pupal parasitoid Ichneumon promissorius (Erichson) (Hymenoptera: Ichneumonidae). Under the chosen conditions, the provision of either wet or dry residues of Amino-Feed UV had no discernable effect on immediate or longer-term survival and immature development times of N. kinbergii. In contrast, the provision of honey, Amino-Feed plus extrafloral nectar, and extrafloral nectar alone had a marked effect on the longevity of I. promissorius, indicating that they were limited by at least carbohydrates as an energy source, but probably not protein. Compared with a water only diet, the provision of Amino-Feed plus extrafloral nectar increased the longevity of males and females of I. promissorius by 3.0- and 2.4-fold, respectively. Not only did female parasitoids live longer when provided food, but the total number of eggs laid and timing of deposition was affected by diet under the chosen conditions. Notably, females in the water and honey treatments deposited greater numbers of eggs earlier in the trial, but this trend was unable to be sustained over their lifetime. Egg numbers in these treatments subsequently fell below the levels achieved by females in the Amino-Feed plus extrafloral nectar and cotton extrafloral nectar only treatments. Furthermore, there were times when the inclusion of the Amino-Feed was beneficial compared with cotton extrafloral nectar only. Artificial food supplements and plant-derived foods are worthy of further investigation because they have potential to improve the ecosystem service of biological pest control in targeted agroecosystems by providing natural enemies with an alternative source of nutrition, particularly during periods of prey/host scarcity.