Chitosan Pesticides for Control Aphids (Aphis craccivora) on High Population in Long Bean (Vigna sesquipedalis) Cultivation

Pesticides with chitosan as an alternative are still relevant for aphids which are important pesticides in vegetable crops. This research was conducted to see the effect of several types of pesticides with chitosan active ingredients, the concentration of pesticides, and interactions between types of pesticides and concentrations of aphids on long bean plants. The study used factorial methods with randomized block designs. The first factor was the type of pesticide made from chitosan, which consisted of control (JO), pure chitosan (Jl), soft guard (J2), super biovit (13). The second factor was the concentration of pesticides that consisted of 0.1% (Kl), 0.3% (K2), and 1% (K3). There were 48 experimental units consisting of 12 treatment combinations and 4 replications. Data were analysed using Analysis of variance (ANOVA), and comparison between averages using Duncan Multiple Range Test (DMRT). The results showed the effect of the treatment was single or there was no interaction between the types of pesticides made from chitosan with an active concentration in all parameters of observation. Furthermore, the effect of the type of pesticide with active chitosan was significantly different only on the average aphid population I and 3 days after the first application. Whereas pesticides made from active chitosan soft guard type tended to control the aphid population higher than other types of pesticides, then the effect of pesticide concentration was not significantly different from all parameters. However, the concentration of 1% indicated to inhibit the population of aphids higher than other concentrations. The high early aphid population, the behaviour of aphid colonies, the application method, and the nature of the active ingredient of chitosan were thought to be factors that reduce the ability of pesticides to control aphids on long bean plants.

PLOT SIZE, NUMBER OF TREATMENTS AND REPLICATES AND EXPERIMENTAL PRECISION IN BUCKWHEAT

ABSTRACT The objective of this work was to determine the optimal plot size to evaluate the fresh weight in buckwheat (Fagopyrum esculentum Moench) of the IPR91-Baili and IPR92-Altar cultivars, in scenarios formed by combinations of numbers of treatments, numbers of replicates, and levels of experimental precision. Sixteen uniformity trials (blank experiments) were carried out, eight with cultivar IPR91-Baili and eight with cultivar IPR92-Altar. The trials were performed in eight sowing dates. The fresh weight was evaluated in 576 basic experimental units (BEU) of 1 m x 1 m (36 BEU per trial). The soil heterogeneity index of Smith (1938) was estimated. The plot size was determined by the method of Hatheway (1961) in scenarios formed by combinations of i treatments (i = 5, 10, 15, and 20), r replicates (r = 3, 4, 5, 6, 7, and 8), and d precision levels (d = 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, and 20%). To evaluate the fresh weight in buckwheat of the IPR91-Baili and IPR92-Altar cultivars, in experiments under completely randomized and randomized block designs, with 5 to 20 treatments and eight replicates, plots of 8 m3of useful area are sufficient to identify significant differences between treatments, at 5% probability level, of 15% of the overall mean of the experiment.

Adaptation of New Rice High Yielding Varieties on New Constructed Irrigated Rice Field Affected by Sea Water Intrusion in West Tanjung Jabung District, Jambi

Assessment adaptation of several new superior rice varieties on new rice fields affected by seawater intrusion was carried out in Tungkal Ilir Subdistrict, West Tanjung Jabung District, from April to October 2018. The study applied randomized block designs (RBD) with four replications. The treatments consisted of four new rice high yielding varities suitable for tidal/swamps areas namely Inpara 3, Inpara 8, Inpara 9, and Inpari 34 Salin Agritan, and one local rice variety (Londo) as control. Three stems seedlings per clump were planted at the age of 21-25 days, using a 4:1 Legowo planting system. Fertilizer application consisted of basic fertilizer (1.0 Mg ha-1 of lime, 2.5 Mg ha-1 of manure, and 75 kg ha-1 of urea) and supplementary fertilizer (SP-36 150 kg ha-1 and KCl 125 kg ha-1),. Urea supplementation is given based on observations with a leaf color chart (LCC). The results of the study showed that the four new rice HYVs were more adapted as compared to the local rice variety. The performance of the tested new rice HYVs showed quite a good growth appearance and productivity. The highest production was obtained in Inpari 34 Salin Agritan variety 2.85 Mg ha-1, while Inpara 3, Inpara 8, and Inpara 9 ranged between 2.0 and 2.1 Mg ha-1, while the local variety’s productivity was 1.9 Mg ha-1.

Challenges in chemical management of soybean looper (Chrysodeixis includes) using several insecticides

Soybean looper, Chrysodeixis includens (Walker, [1858]) (Lepidoptera: Noctuidae), is the most important caterpillar pest in Brazil due to its high tolerance to insecticides and control failures that have been reported in fields. Based on this, we assessed the performance of several insecticides against C. includens on soybean over three seasons (2014, 2015, and 2016), performing four experiments in southern Brazil. Experiments I / 2014, II / 2015, III / 2016 were carried in completely randomized block designs with eight insecticides. Experiment IV / 2016 was arranged in completely randomized block design in an 8 x 2 factorial arrangement, eight insecticides x two spraying time. Mortality of small (< 1.5 cm) and large (> 1.5 cm) soybean looper larvae was assessed with a vertical beat cloth, sampling in each plot 1.0 m2 at 3, 7 and 10 days after spray. Percentage of defoliation injury was assessed visually comparing to a scale of soybean leaf injury in experiment IV / 2016. Data were subjected to one-way (type I SS) analysis of variance (ANOVA) using the general linear models. The insecticides indoxacarb and chlorfenapyr had consistently high mortality upon small and large larvae of C. includens. Spinosyn, spinosad and spinetoram insecticides showed higher effect over small larvae (< 1.5 cm) than large (> 1.5 cm). Number of spraying was significant for spinetoram and indoxacarb that increased mortality of large larvae (from 4.50 to 2.75 and from 3.75 to 0.87 larvae m-2, respectively) and reduced defoliation injury significantly (from 22.5% to 9.3% and from 14.5% to 3.3%, respectively) with two applications. The treatment chlorfluazuron+acephate showed low defoliation injury in 2016 but did not affect larval density. Chlorfenapyr showed reduced defoliation (3.0%) and low larvae density (1.37 larvae m-2) with only one application. Spinosyns have satisfactory control of small larvae and indoxacarb and chlorfenapyr show high mortality of both sizes, small and large larvae. Therefore, we recommend that 7 days from the first one, a second application should be considered for indoxacarb, and spinetoram to achieve higher mortality. Considering our results, we demonstrate that the satisfactory control of soybean looper larvae is difficult to achieve with most chemical insecticides. It needs a more accurate management strategy of C. includens in soybeans.

Heterosis and combining ability in crosses between two groups of open-pollinated maize populations

The rapid expansion of corn in Brazil indicates the need to explore new sources of germplasm. Thus, the wider use of local germplasm, and the introduction of exotic ones seem to be an advisable strategy to achieve higher levels of yield and adaptability. The objective of this work was to generate information about the potential of two groups of populations (NAP - exotic; HG - local) and their heterotic pattern in hybrid combinations for the synthesis of new populations. Populations and hybrids were evaluated in complete randomized block designs with four replications, in two locations, and three yield traits were studied (GY - grain yield, EY - ear yield, SW - specific weight). The basic strategy was the selection of one HG population as base for the incorporation of each exotic population. The expected yield gain of the best combinations varied from 1 to 22%. Average heterosis for grain yield was 34.5%.