A comparison of alternative plant mixes for conservation bio-control by native beneficial arthropods in vegetable cropping systems in Queensland Australia.

Cucurbit crops host a range of serious sap-sucking insect pests, including silverleaf whitefly (SLW) and aphids, which potentially represent considerable risk to the Australian horticulture industry. These pests are extremely polyphagous with a wide host range. Chemical control is made difficult due to resistance and pollution, and other side-effects are associated with insecticide use. Consequently, there is much interest in maximising the role of biological control in the management of these sap-sucking insect pests. This study aimed to evaluate companion cropping alongside cucurbit crops in a tropical setting as a means to increase the populations of beneficial insects and spiders so as to control the major sap-sucking insect pests. The Population of beneficial and harmful insects, with a focus on SLW and aphids, and other invertebrates were sampled weekly oil four different crops which could be used for habitat manipulation: Goodbug Mix (GBM; a proprietary seed Mixture including self-sowing annual and perennial herbaceous flower species); lablab (Lablab purpureus L. Sweet); lucerne (Medicago sativa L.); and niger (Guizotia abyssinica (L.f.) Cass.). Lablab hosted the highest numbers of beneficial insects (larvae and adults of lacewing (Mallada signata (Schneider)), ladybird beetles (Coccinella transversalis Fabricius) and spiders) while GBM hosted the highest numbers of European bees (Apis mellifera Linnaeus) and spiders. Lucerne and niger showed little promise in hosting beneficial insects, but lucerne hosted significantly more spiders (double the numbers) than niger. Lucerne hosted significantly more of the harmful insect species of aphids (Aphis gossypii (Glover)) and Myzus persicae (Sulzer)) and heliothis (Heliothis armigera Hubner). Niger hosted significantly more vegetable weevils (Listroderes difficillis (Germar)) than the other three species. Therefore, lablab and GBM appear to be viable options to grow within cucurbits or as field boundary crops to attract and increase beneficial insects and spiders for the control of sap-sucking insect pests. Use of these bio-control strategies affords the opportunity to minimise pesticide usage and the risks associated with pollution

Aerated water irrigation (oxygation) benefits to pineapple yield, water use efficiency and crop health

Pineapple roots need adequate oxygen to function, sustaining growth and yield. The crop is susceptible to soil saturation caused by natural rainfall or irrigation, or even with drip irrigation that creates sustained wetting fronts. Drip and subsurface drip irrigation can develop sustained wetting fronts, particularly in low permeability soils, predisposing plant roots to a low oxygen environment. We evaluated the use of aerated irrigation water “oxygation”, employing Mazzei air injectors which mix air with irrigation (12% air by volume of water) in-line, increasing oxygen concentration in the irrigation water stream. The effect of this treatment was evident in growth, development, and leaf gas exchange parameters. Total fruit yield increased by 44 and 26% whereas industry yield increased by 11 and 6% due to oxygation compared to the control and no irrigation, respectively. High yield was associated with an increase in fruit size and not the number of fruits produced. Phytophthora to the control (4.9%), and without irrigation treatment (10.5%) suggesting that reasonable management of Phytophthora, which is one of the major pathological problems for pineapple production in Australia and elsewhere, can be addressed through aerated water irrigation. Oxygation responses were mediated through root and soil processes involving greater root biomass, root respiration, increased microbial diversity and enhanced soil aeration status

Supplying vegetables to Asian cities: is there a case for peri-urban production?

PRISI; IFPRI3DSG

Genotypic variation for root pulling resistance in potato and its relationship with yield under water deficit stress

An extensively distributed root system may reduce the probability of crop failure during periods of restricted water supply . A quantitative measure of root distribution in the soil profile, i .e . pulling resistance of roots (PR), was tested at two moderately droughted tropical field sites . A total of 250 genotypes were evaluated for PR, 45 days after planting and for tuber yield at harvest at separate sites and years . The need to use genotypes adapted to a specific location for comparisons, across sites or seasons was shown by the results of a random analysis of variance model partitioning across site-season, location, and year effects for PR and tuber yield . A combined PR and growth analysis on 31 early-maturing clones, 7 of which had tubers at the time of sampling, gave significant correlations between PR and root length, dry weight of pulled and residual roots, plant height, number of stems, and in the case of the 7 genotypes with tubers, tuberlet weight and number . A regression model to predict PR based on growth analysis data is presented . Neither tuberlet weight nor number contributed significantly to the prediction once root characters and vigour-related characters were incorporated . Variation for PR among clones was significant and the means ranged from 0 kg/plant to 37 kg/plant during the 3 trials . High PR was evident in both early and late maturing clones . Drought resistance (DR), defined as high yielding ability and high PR under water deficit conditions, of the clones Huinkul and MS-35.22 .R was superior to that of the high-yielding and adapted LT-7 check, while moderate levels of DR were confirmed for the clones BR-63 .15, Cruza 27, Haille, and MEX-21 . Tuber yield and PR under moderate drought were significantly correlated (r = 0 .569***), which suggests that the PR method can be utilized to assist in the selection of high-yielding, drought resistant, potato genotypes adapted to tropics

Pyriproxyfen controls silverleaf whitefly, Bemisia tabaci (Gennadius), biotype B (Homoptera: Aleyrodidae) (SLW) better than buprofezin in bitter melons Momordica charantia L. (Cucurbitaceae)

To improve compatibility between chemical and biological controls, the use of selective insecticides such as insect growth regulators (IGRs) is crucial. In cucurbits, the use of pyriproxyfen (an IGR) has been shown by others to be an effective method of reducing the number of sap-sucking insects, especially silverleaf whitefly, Bemisia tabaci (Gennadius) Biotype B (SLW). Therefore, we compared pyriproxyfen and buprofezin (an IGR) with that of no treatment (control) in a bitter melon crop for the control of populations of SLW and for their effects on fruit production. Pyriproxyfen controlled SLW and tended to have heavier fruits than the control treatment and reduced the abundance of nymphs and exuvia. Buprofezin showed no evidence in controlling SLW compared with the pyriproxyfen and control treatments. Neither pyriproxyfen nor buprofezin had any effect on the number of harvested fruit or overall fruit yield, but the average weight per fruit was higher than the control treatment. Pyriproxyfen was effective in controlling whitefly populations in bitter melons, and both pyriproxyfen and buprofezin may have the potential to increase yield. Their longer-term use may increase predation by natural enemies as they are species-specific and could favour build up of natural enemies of SLW. Thus, the judicious use of pyriproxyfen may provide an effective alternative to broad-spectrum insecticides in small-scale cucurbit production

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

Comparative metabolic and ionomic profiling of two cultivars of Stevia rebaudiana Bert. (Bertoni) grown under salinity stress

This study provides a comprehensive investigation on the impact of increasing NaCl concentrations on hydroponically grown Stevia rebaudiana cultivars (Shoutian-2 and Fengtian). Growth parameters including plant height, biomass and physiological responses including osmotic potential were measured. In addition, the levels of steviol glycosides, elements and primary metabolites were measured and statistically evaluated. The cultivar Fengtian grew faster, accumulated less Na+ and compatible organic solutes, and more K+ in the leaves, as compared to the cv. Shoutian-2. Metabolite analysis identified 81 differentially accumulated metabolites, indicating an alteration in the metabolite phenotype of both cultivars upon exposure to salinity A general increase in many amino acids, amines, sugars and sugar phosphates with a concurrent decrease in most organic acids; including tricarboxylic acid (TCA) cycle intermediates, was observed. In the more salt tolerant cv. Fengtian, the levels of hexose phosphates and metabolites involved in cellular protection increased in response to salinity. These metabolites remained unchanged in the sensitive cv. Shoutian-2. Interestingly, salt treatment notably increased the rebaudioside A concentration by 53% while at the same time stevioside decreased by 38% in Fengtian which has important implications for controlling the relative amounts of reboudioside A and stevioside. The findings of this study leads to the conclusion that mild salinity stress can increase the yield of sweetener compounds, which is dependent on the cultivar and the level of salinity stress