Author(s): Berta Catingan-Ratilla and Victor P. Briones

Abstract

Application of nitrogen fertilizer up to 90 kg/ha with 30 kg each of P2O5 and K2O did not remarkably affect the growth and yield parameters of flint corn. However, visual observation indicated that fertilization resulted in the development of sturdier corn plants with darker green and broader leaves. It likewise promoted earlier initiation of reproductive stage and hence, maturity. Row spacing at 50 cm resulted in the highest leaf area index, stover and grain yields. Increase in row spacing from 50 to 75 or 100 cm markedly reduced these parameters. Significantly interaction effects of nitrogen level and row spacing were observed on stover yield only.

Keywords : Flint corn. Nitrogen level. Row spacing. Growth. Yield.

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Author(s): Paz Saladaga-Eronico and Rodolfo G. Escalada

Abstract

Generally, no significant differences in agronomic characters and yield components of sweet potato were observed using either the traditional methods or the recommended practice of planting. Varying the number of cutting per hill significantly influenced only the fresh vine weight of Kaimay, BNAS-51 and Samar Big Yellow sweet potato varieties. Plants that developed from one cutting per hill produced heavier herbage than the other treatments. Root yield was likewise not markedly affected by the number of cuttings per hill although the varieties, Kaimay obtained the highest value in yield and nearly all yield components.

Keywords : Sweet potato. Traditional methods of planting. Recommended practice. Varietal characteristics. Agronomic characters. Yield components

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Author(s): Emmanuel M. Cabia and Eduardo Paningbatan

Abstract

Date of planting significantly influenced growth and development of corn. Corn first planted on the last week of April and those planted 3 and 5 weeks later (May 16 and May 29) exhibited superior growth and ear yields over those planted 7 and 9 weeks later (June 12 and June 27). Relative to the highest total ear yield obtained (3.65 tons/ha), the mean reduction in ear yield of plants in the latter treatments was 60.55% representing a three-fifth decrease in this parameter. This was due to the very wet conditions during the early growth stages which affected crop establishment and consequently, yield performance.

Keywords : Corn. Aquic Eutropept. Date of planting. Growth. Yield.

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Author(s): Nestor L. Pido and Liwayway M. Engle

Abstract

Inherent variations were observed in the lead shape of sweet potato cultivars Kinabakab and UPLB Acc. 624 and in the root skin pigmentation of BNAS-51 cultivar. Doses of 2000 and 3000 rads produced wrinkled and deformed leaves in vM1 plants of all three cultivars with the latter dose giving the higher percentage of aberrant leaves and plants with such leaves. Among the cultivars, Kinabakab apparently has the most radiosensitive leaf shape and leaf rugosity. Only Kinabakab had some vM2 plants which retained the wrinkled leaves observed in vM1 plants. The same cultivar exhibited the highest mortality of cuttings obtained from vM1 plants which showed wrinkled and deformed leaves. One Kinabakab vM2 plant treated with 3000 rads produced a secondary branch that was an apparent genetic variant. Vine length at maturity and internode length of vM2 plants of the three cultivars were not significantly affected by various doses of gamma radiation.

Keywords : Sweet potato. Gamma radiation. Varietal characteristics. Inherent variation. Induced variation. Aberrant leaves. Mortality.

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Author(s): Gracia B. Bajit and Ruben M. Gapasin

Abstract

The morphological characteristics of sweet potato cultivars which are resistant and susceptible to Sphaceloma batatas Saw.were determined. Susceptible cultivars have thinner cuticle, more stomates in the leaves, and more lenticles in the petioles and stems than resistant cultivars.
The scab pathogen had longer incubation period, lower infection frequency and smaller lesions in resistant than in susceptible cultivars.
Highly significant positive correlation was found between thickness of cuticle and incubation period as well as between number of stomates and lenticels, and infection frequency.

Keywords : : Sweet potato. Sphaceloma batatas Saw. Cuticle. Stomates. Lenticels. Incubation period. Infection frequency. Lesion diameter.

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Author: Manuel K. Palomar

Abstract

Adults and nymphs of the taro planthopper, Tarophagus Proserpina Kirk., were equally efficient in transmitting taro feathery mosaic disease. Both the minimum acquisition feeding period and minimum inoculation feeding period were about 5 min. A single insect could induce the disease in a healthy plant and percentage infection increased as the number of insects was also increased. Starving the insects for 1-6 hours prior to acquisition feeding produced more infected plants than shorter or longer starvation periods. Infective insects could transmit the disease until death and most individuals transmitted the pathogen intermittently.

Keywords : Pathogens-vector relationship. Taro feathery mosaic disease. Tarophagus Proserpina Kirk.

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Author(s): Tita L. Cayme and Dely P. Gapasin

Abstract

The total developmental period of the coconut spider mite, Oligonychus velascoi Rimando was 6.3 and 6.9 days for those reared on detached and undetached leaflets, respectively. The slight difference observed in the life cycle of mites using the two rearing methods indicates that both techniques are satisfactory for rearing spider mites.
Of the 30 plant species tested, only proved to be alternate hosts of the coconut spider mite, namely: bunga de China, Adonidia merrilli Becc.; pugahan, Caryota cumingii Lodd.; and buri palm, Corypha elata Roxb. However, longer life cyle and higher mortality were observed in spider mites reared on these alternate host plants than is those reared on coconut. Natural enemies included two coccinellid beetles and a phytoseeid mite.

Keywords : Coconut spider mite (Oligonychus velascoi Rimando). Biology. Host range. Natural enemies.

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