Late-season Plant Research Articles

Comparative Efficacy of <i>Tephrosia vogelii</i> and <i>Moringa oleifera</i> against Insect Pests of Watermelon (C<i>itrullus lanatus</i> Thumb)

Despite the fact that synthetic insecticides are fast acting, they constitute environmental hazard thereby necessitating the use of ecologically based alternative such as plant based insecticide. This experiment was conducted during the late and early planting seasons of 2011 to determine the insecticidal efficacy of Tephrosia vogelii and Moringa oleifera extracts at three tested concentrations (5, 10 and 20% v/v) against insect pests of watermelon. The experiment was set up in a randomized complete block design with three replicates. The results showed that M. oleifera extracts had 62% reduction of Phyllotreta cruciferae compared with T. vogelii which had 45% control. However, T. vogelii extracts had 64% control of Diabrotica undecimpunctata and Bactrocera curcubitea but M. olefera extracts had 50% control. The plant extracts proved effective against studied insects when compared with untreated plots. However, the effectiveness of the two plants extracts were concentration dependent. Therefore, the two plant extracts can be used in the control of insect pests of the watermelon

Comparative Efficacy of <i>Tephrosia vogelii</i> and <i>Moringa oleifera</i> against Insect Pests of Watermelon (C<i>itrullus lanatus</i> Thumb)

Despite the fact that synthetic insecticides are fast acting, they constitute environmental hazard thereby necessitating the use of ecologically based alternative such as plant based insecticide. This experiment was conducted during the late and early planting seasons of 2011 to determine the insecticidal efficacy of Tephrosia vogelii and Moringa oleifera extracts at three tested concentrations (5, 10 and 20% v/v) against insect pests of watermelon. The experiment was set up in a randomized complete block design with three replicates. The results showed that M. oleifera extracts had 62% reduction of Phyllotreta cruciferae compared with T. vogelii which had 45% control. However, T. vogelii extracts had 64% control of Diabrotica undecimpunctata and Bactrocera curcubitea but M. olefera extracts had 50% control. The plant extracts proved effective against studied insects when compared with untreated plots. However, the effectiveness of the two plants extracts were concentration dependent. Therefore, the two plant extracts can be used in the control of insect pests of the watermelon

Male bumble bees are important pollinators of a late-blooming plant

Differences in the pollinator performance of flower visitor sexes are rarely considered. In bumble bees, males differ from workers in morphology and behaviour in ways that may affect their contribution to pollination. We compared the abundance, foraging behaviour, and pollen transfer ability of worker and male bumble bees on late-blooming Gentiana parryi (Gentianaceae) in subalpine meadows of the Colorado Rocky Mountains. Male bees mostly outnumbered female workers throughout blooming of the gentian. Males and workers foraged similarly, though individual males were more faithful to small foraging areas than workers. During single flower visits, males and workers caused similar levels of pollen deposition and seed production, yet female bees left fewer pollen grains in anthers to be transferred to other stigmas in the plant population. Overall, male bumble bees are common and capable pollinators of G. parryi and in some years and sites could be more important than workers. Male bumble bees may be important but unrecognized pollinators of other late-season plant species, and animal sexes may differ in their pollinator performance in other systems.

Parameterization of temperature sensitivity of spring phenology and its application in explaining diverse phenological responses to temperature change.

Existing evidence of plant phenological change to temperature increase demonstrates that the phenological responsiveness is greater at warmer locations and in early-season plant species. Explanations of these findings are scarce and not settled. Some studies suggest considering phenology as one functional trait within a plant's life history strategy. In this study, we adapt an existing phenological model to derive a generalized sensitivity in space (SpaceSens) model for calculating temperature sensitivity of spring plant phenophases across species and locations. The SpaceSens model have three parameters, including the temperature at the onset date of phenophases (Tp), base temperature threshold (Tb) and the length of period (L) used to calculate the mean temperature when performing regression analysis between phenology and temperature. A case study on first leaf date of 20 plant species from eastern China shows that the change of Tp and Tb among different species accounts for interspecific difference in temperature sensitivity. Moreover, lower Tp at lower latitude is the main reason why spring phenological responsiveness is greater there. These results suggest that spring phenophases of more responsive, early-season plants (especially in low latitude) will probably continue to diverge from the other late-season plants with temperatures warming in the future.

Comparative Efficacy of <i>Tephrosia vogelii</i> and <i>Moringa oleifera</i> against Insect Pests of Watermelon (C<i>itrullus lanatus</i> Thumb)

Despite the fact that synthetic insecticides are fast acting, they constitute environmental hazard thereby necessitating the use of ecologically based alternative such as plant based insecticide. This experiment was conducted during the late and early planting seasons of 2011 to determine the insecticidal efficacy of Tephrosia vogelii and Moringa oleifera extracts at three tested concentrations (5, 10 and 20% v/v) against insect pests of watermelon. The experiment was set up in a randomized complete block design with three replicates. The results showed that M. oleifera extracts had 62% reduction of Phyllotreta cruciferae compared with T. vogelii which had 45% control. However, T. vogelii extracts had 64% control of Diabrotica undecimpunctata and Bactrocera curcubitea but M. olefera extracts had 50% control. The plant extracts proved effective against studied insects when compared with untreated plots. However, the effectiveness of the two plants extracts were concentration dependent. Therefore, the two plant extracts can be used in the control of insect pests of the watermelon

Comparative Efficacy of <i>Tephrosia vogelii</i> and <i>Moringa oleifera</i> against Insect Pests of Watermelon (C<i>itrullus lanatus</i> Thumb)

Despite the fact that synthetic insecticides are fast acting, they constitute environmental hazard thereby necessitating the use of ecologically based alternative such as plant based insecticide. This experiment was conducted during the late and early planting seasons of 2011 to determine the insecticidal efficacy of Tephrosia vogelii and Moringa oleifera extracts at three tested concentrations (5, 10 and 20% v/v) against insect pests of watermelon. The experiment was set up in a randomized complete block design with three replicates. The results showed that M. oleifera extracts had 62% reduction of Phyllotreta cruciferae compared with T. vogelii which had 45% control. However, T. vogelii extracts had 64% control of Diabrotica undecimpunctata and Bactrocera curcubitea but M. olefera extracts had 50% control. The plant extracts proved effective against studied insects when compared with untreated plots. However, the effectiveness of the two plants extracts were concentration dependent. Therefore, the two plant extracts can be used in the control of insect pests of the watermelon

Variations in Stem Borer Infestation and Damage in Three Maize (<i>Zea mays</i> L.) Types in Southern Guinea Savanna and Rainforest Zones of Nigeria

The effects of location, maize types and borer control with carbofuran (Furadan 3G®) on the severity of maize stem borer infestation and damage was investigated in the late maize planting season of 2011. Treatments were laid out in randomized complete block design using a split-slip-plot factorial arrangement. Whole plot factor consisted of two locations (Southern Guinea Savanna and Rainforest agro-ecological zones of Nigeria), subplot factor consisted of 1.5 kg a.i.ha-1 and 0.0 kg a.i.ha-1 of carbofuran, while the sub-sub-plot factor comprised of three endosperm types of maize (flint, pop and sweet corn). Stem borer infestation (quantified by dead heart count and larval population per plant) and damage (quantified by %lodged stem, %bored internodes, %bored ears, number of exit holes, number of stem borer cavities and number of damaged seeds per plant) as well as yield were compared. Results revealed that borer infestation and damage were significantly higher (P 0.05) location × carbofuran × maize type and location × maize type effect was detected. However, significant (P < 0.05) location × carbofuran and carbofuran × maize type interaction effects were observed. We conclude that in both agro ecologies, flint corn was more tolerant of borer attack while sweet corn was more susceptible compared to either flint or popcorn. In addition, carbofuran at 1.5 kg a.i.ha-1 can significantly reduce stem borer population in the three maize types.

Daily soil surface CO2 flux during non-flooded periods in flood-irrigated rice rotations

Carbon dioxide (CO2) emitted from the soil, as a result of root and microorganism respiration, is a major process in the global carbon cycle. Since CO2 production is dependent on oxygen availability, prolonged saturated soil conditions in rice (Oryza sativa) can decrease the quantity of soil carbon released in the form of CO2 over time. At present, a deficiency exists in the scientific literature on soil surface CO2 flux in well-established, flood-irrigated rice systems, which are flooded for approximately 3 months a year during the rice growth period. Plenty of studies have examined soil surface CO2 flux in dryland cropping systems and methane emissions in paddy-grown rice, but flood-irrigated rice does not easily fall into either of these categories due to the cyclic nature of seasonal flooding. Therefore, this is the first study to examine daily soil surface CO2 flux during non-flooded periods in well-established, flood-irrigated rice rotations. For a comprehensive analysis, soil surface CO2 flux was measured for 2 years on 10 different rice-based rotations, which had been managed using conventional tillage or no-tillage for 10 and 11 years. Rotations included continuous rice and various combinations of rice rotated with soybean (Glycine max), corn (Zea mays), and/or winter wheat (Triticum aestivum) and were located on a silt-loam soil in the Mississippi River Delta region of Arkansas in the USA. Results showed that 7 of the 16 measurement dates differed in daily soil surface CO2 flux among tillage and/or crop rotations. However, these differences were determined to be from crop maturity, in relation to early- or late-season planting, instead of patterns of long-term flood irrigation. Years that rice was grown reduced the cumulative CO2 emissions, but substantial differences over time were minimized in rotations with soybean or corn. Findings from this experiment are valuable in the scientific understanding of carbon gas cycling in rice-based cropping systems because the aerobic periods between flooding were evaluated, which is the time period often ignored when examining carbon gas emissions in rice. Overall, this study provides evidence that the commonly used rice-based cropping systems reach a somewhat equilibrium state in daily CO2 fluxes over time, regardless of the frequency in periodic soil saturation.

Variation and Heritability of Sixteen Characters in West African Okra, Abelmoschus Caillei (A. Chev.) Stevels

Abstract Genotypic and phenotypic variances, genotypic and phenotypic coefficients of variation, heritability and genetic advance were estimated for 16 agronomical characters in West African okra for two seasons, using 25 West African okra lines of diverse origin. Considerable differences were observed for some characters in the two seasons. Number of days to flowering, number of leaves at flowering, plant height at flowering and number of pods at branches showed seasonal differences. The estimates of genotypic coefficients of variation (gcv) in the two seasons were close in many cases. The gcv values ranged from 1.41 for number of days to flowering in the early season to 68.63 for number of branches per plant in the late season planting. Heritability estimates ranged from 5.02% for number of leaves at flowering in the early season to 99.54% for weight of matured pod during the early season. This study highlighted the significance of genotype-environment interaction in the breeding programmes of West African okra. The relatively large genotypic coefficient of variation, heritability estimates and genetic advance for number of pods at stem, number of pods per plant, number of branches per plant, weight of matured pods and seed yield per plant, were indicative of likely effectiveness of selection for such characters.

Flea beetle (Chrysomelidae: Alticinae) species composition and abundance in different cruciferous oilseed crops and the potential for a trap crop system

Flea beetles are significant insect pests of cruciferous oilseed crops in northern Europe. A two-year small-scale field experiment was performed to determine the species complex and abundance of flea beetles (Chrysomelidae: Alticinae) associated with eight cruciferous oilseed plants: Brassica juncea (L.) Czern., Brassica napus L. var. oleifera subvar. annua, Brassica nigra (L.) Koch, Brassica rapa L. var. oleifera subvar. annua, Camelina sativa (L.) Crantz, Eruca sativa Mill., Raphanus sativus L. spp. oleifera (DC) Metzg. and Sinapis alba L. Their relative attractiveness to flea beetles was compared to assess their potential for use within a trap crop system for spring oilseed rape. Adults of six species of flea beetles were found on the test plants. Phyllotreta undulata Kutsch. was the most abundant species followed by Phyllotreta nigripes (Fabr.), Phyllotreta nemorum L. and Phyllotreta vittata (=striolata) (Fabr.), while Phyllotreta atra (Fabr.) and Chaetocnema concinna Marsh. were occasionally present. The species composition of flea beetles on seven of the investigated plant species was fairly similar but differed significantly on C. sativa. The flea beetle species discriminated between the tested host plants, with a general gradient in attraction from E. sativa > B. juncea > B. nigra > R. sativus > S. alba > B. rapa > B. napus through to C. sativa. Brassica juncea and B. nigra developed faster and at early growth stages were more attractive to overwintered adult flea beetles than B. napus and therefore had potential as trap plants to protect spring rape. R. sativus and E. sativa, despite their development rate being slower than B. napus were also more attractive to flea beetles. Thus, further experiments with a complex of attractive early season and late-season plant species (multiple trap crops) should be undertaken.

Early planting and hand sorting effectively controls seed-borne fungi in farm-retained bean seed

Home-saved bean (Phaseolus vulgaris L.) seed can be hand-sorted to remove discoloured seed, thereby reducing the level of contamination by certain seed-borne fungi and improving seed germination. In this study, the effect of planting date on the infection and discolouration of bean seed by seed-borne fungi was investigated in order to improve the quality of hand-sorted, farm-retained bean seeds used by resource poor smallholder farmers. The germination quality and level of seed-borne fungi in hand-sorted first-generation bean seed harvested from an early-, mid- and late-summer season planted crop was therefore assessed. The highest percentage of discoloured seed (68%) was obtained from the mid-summer season planting. Non-discoloured seed from early- and late-season plantings had significantly (p&lt;0.001) higher normal germination (82% and 77%, respectively) than that from the mid-season planting date (58%). Irrespective of planting date, unsorted seed and discoloured seed had higher levels of infection by Fusarium spp. and Phaeoisariopsis spp. than the non-discoloured seed. Removal of discoloured seed by hand sorting eliminated Rhizoctonia spp. from all seed lots. Farmers can eliminate this pathogen by simply removing discoloured seed. Non-discoloured seed from the early-planted crop had the lowest level of infection by Fusarium spp. and Phaeoisariopsis spp. The results indicate that planting date is an important consideration in improving the quality of hand-sorted farm-retained bean seed.

Camelina (Camelina sativa) Tolerance to Selected Preemergence Herbicides

Camelina is an emerging oilseed crop suitable for biofuel production in dryland cropping systems of the northwestern United States. Currently, camelina growers have limited herbicide options available for weed control. Tolerance of camelina to PRE applications of quinclorac,S-metolachlor, dimethenamid-P, pendimethalin, and pyroxasulfone was evaluated at two locations (Kalispell in 2009 and 2010, and Huntley in 2010 and 2011) in Montana. Susceptibility to each herbicide was determined at three different rates. Quinclorac applied PRE at 280 to 840 g ai ha−1did not significantly injure camelina, and had no negative effect on plant density, biomass, flowering, and yield at either location.S-Metolachlor at 1,060 to 2,140 g ai ha−1caused less than 20% injury to camelina, with no reductions in plant density, biomass, and yield compared with the nontreated check. Dimethenamid-P applied at 630 g ai ha−1did not affect camelina density, biomass, flowering, and yield; however, at the 1,260 g ha−1rate, injury was as high as 60% (in the coarse-textured Kalispell soil), and plant density and yield were reduced as much as 50 and 31%, respectively, in addition to delayed flowering. Despite causing some visual injury to camelina, crop yield was not reduced by pendimethalin at the 1,060 or 2,130 g ai ha−1rate. Pyroxasulfone caused significant crop injury, stand loss, and yield reductions, and thus does not appear to be a viable option for weed control in camelina. Camelina plants that exhibited early-season injury showed robust growth and compensatory abilities, with lack of significant effect of herbicides on late-season plant height and biomass at least in one of the two locations. On the baseis of this research, quinclorac was the safest of all herbicides tested in camelina. Dimethenamid-P,S-metolachlor, and pendimethalin also may have an acceptable level of crop safety at lower use rates for possible registration in camelina.

English

Pumpkin (Cucurbita pepo L.) young leaves and vines are consumed as vegetables among the rural dwellers in Southwest Nigeria. It is a cheap source of protein, vitamins, fibres and antioxidants in their diet. Due to the intensive cultivation of available lands which affects the nutrient status of most soils and their productivity, the need to apply fertilizer on pumpkin became pertinent. Therefore, nitrogen, phosphorus and potassium (NPK) fertilizer influence on biomass accumulation in pumpkin was investigated for two consecutive seasons in 2010 at the Research Farm of Obafemi Awolowo University, Ile-Ife, Nigeria. NPK (15:15:15) compound fertilizer was applied at the rates of (0, 50, 100, 150, 200 and 250 kg ha-1) to C. pepo at 2 weeks after planting (WAP). At 8 WAP, the following morpho-physiological traits: vine length, vine diameter, number of internodes, internodes length, vine weight, number of leaves, total fresh and dry biomass assessed were significantly influenced by season and fertilizer effects. The combined analysis of variance (ANOVA) results showed that the effects of season (S) and fertilizer (F) are significant effect on all the traits. Season effect showed that the early season was better (p = 0.05) while the application of fertilizer beyond 100 kg of NPK per hectare was not statistically beneficial for biomass yield and its components. However, the significant S X F interaction on the total dry matter fitted well into a quadratic equation with significant R2 values. The response curves showed higher response to fertilizer in the early than late planting season and a maximum biomass yield was attained at the application of 205 kg and 244 kg ha-1 of NPK (15-15-15) for early and late season cultivations, respectively. Key words: Biomass, nitrogen, phosphorus and potassium (NPK) fertilizer, pumpkin, dry matter, morpho-physiological trait, quadratic equation.

Evaluation of 15 Varieties of Okra (Abelmoschus esculentus(L.) Moench to Field Infestation by Flea Beetles (Podagricaspp.)

The study evaluated 15 okra varieties to field infestation by flea beetles, Podagrica spp., in the early and late planting seasons of 2009, at the Teaching and Research Farm, Federal University of Agriculture, Abeokuta, Nigeria (7°15′N 3°25′E), located in a sub-humid zone. The experiment was arranged in a split plot design, with three replicates. The main plot consisted of spraying regime (sprayed and unsprayed) while the sub-plot consisted of 15 okra varieties: V-35, V2-Oyo, V45-2, NH99/28, NH99/DA NH88/1-8-16-2, Enugu1, Osadep:purple Tall, LD88/1-8-5-2, LD88/1-8-16-2, Ola99/13, Ola3 Local, Olak2005, Short Mouth and Dajofolowo1. Lambda-cyhalothrin was sprayed to the appropriate plots weekly. The results showed that in both early and late seasons, sprayed okra had significantly (P < 0.05) lower number of flea beetles, lower leaf damage per plant, lower number of holes per leaf, wider stem girth, higher total plant dry biomass, higher number of pods compared with unsprayed okra. The sprayed okra had significantly (P < 0.05) higher shoot dry biomass, higher root dry weight, higher total plant dry biomass, wider pods and higher pod weight in the early planting season compared with the late season. Varieties with leaf pubescence, namely NH99/DA, V-35 and Dajofolowo1, had the lowest flea beetle population, leaf damage per plant and number of holes per leaf compared to glaborous varieties. Likewise, the okra varieties NH99/28, V-35 and Dajofolowo1 which have thorny pods had no pod damage at all in both early and late planting seasons. LD88/1-8-5-2 had the highest number of pods per plant, whereas okra variety Ola99/13 had significantly (P < 0.05) higher pod weight during early planting. There was no significant difference in okra pods weight in all varieties evaluated in the late planting season.

EVALUATION OF NATIVE SOAP (BLACK SOAP) FOR THE CONTROL OF MAJOR INSECT PESTS AND YIELD OF COWPEA (VIGNA UNGUICULATA (L.) WALP) IN ABRAKA, DELTA STATE

The experiments were carried out during the early and late planting seasons on a public land adjacent to Campus 2, Delta State University, Abraka, Nigeria. The study evaluated native soap at 1, 2 and 3 percent concentrations for insecticidal property in the control of cowpea insect pests, namely cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. It also assessed influence of control on cowpea yield. The result showed that native soap at 3% concentrations significantly reduced (P<0.05) A. craccivora in the early season. M. sjostedti damage, thrip population, Maruca damage and pod sucking bug were generally low in this season. In the late season, colonies of A. craccivora were reduced at 1 and 2% concentrations. Similarly, all the tested concentrations checked flower thrips. Maruca damage was slightly suppressed at 1 and 2% native soap concentrations. The control plots had the highest population of sucking bugs suggesting that native soap had effect on bugs. Yields were 1,355.90kg ha-1, 1105.20kg ha-1 and 919.80kg ha-1 for 3%, 2% and 1% soap concentration respectively in the early season. Late season grain yield were 570.80kg ha-1, 510.10kg ha-1 and 358.90kg ha-1 for 3%, 1% and 2% respectively. Based on the high yields, particularly in the early season, the study suggests that native soap can be an effective insecticide against cowpea insect pests, and could form component of the integrated pest management. It was however, observed in the field that native soap caused delay and reduction in copious cowpea flowering. Eliminating this factor could be necessary to increase the efficacy of soap in the management of cowpea insect pests.

OBSERVATIONS OF THE INSECT COMPLEX OF COWPEA (VIGNA UNGUICULATA (WALP) IN ABRAKA, A NON-COWPEA GROWING AREA, SOUTHERN NIGERIA.

The Sudan Savannah, the drier northern Nigeria is the major belt for the cultivation of cowpea (Vigna unguiculata (L) Walp. The West and East of southern Nigeria, however, began its cultivation recently. The crop constitutes a main food for many Nigerians and because of this, the crop performance and all factors which are constraints to its production are being studied. Cowpea was cultivated in Abraka, a non-major cowpea cultivation region, during the early and late planting seasons of 2005 to study the insect pests spectrum (insect complex) which decimate the crop. Their relative abundance were also determined. The results indicated that in the early season, there were 8 insect orders; 25 families and 37 species. Coleoptera had the highest species 11, with relative abundance of 29.6%. Others were heteroptera, 8 species (21.6%), diptera, 5 species (13.5%), homoptera, 4 species (10.8%), orthoptera, 3 species (8.1%), hymenoptera, 3 species (8.1%), lepidoptera, 2 species (5.4%) and thysanoptera, 1 specie (2.7%). During the late season, coleoptera were the highest, 10 species (28.6%). Others were heteroptera, 9 species (25.7%), diptera, 4 species (11.4%), homoptera, 4 species (11.1%), orthoptera, 3 species (8.6%), hymenoptera, 2 species (5.7%), lepidoptera, 2 species (5.7%) and thysanoptera, 1 specie (2.9%). Ootheca mutabilis Sahl, Aphis craccivora Koch, Megalurothrips sjostedti Trybom, Maruca vitrata Fab and coreid bugs such as Clavigralla tomentosicollis Stal, Anoplocnemis curvipes Fab, C. shadabi, Aspavia armigera Fab, Nezara virudula L, Mirperus jaculus Thunb were the commonest major insect pests on cowpea at Abraka. More insect species occurred in the early season than late in the study area.

Agro-economic assessment of the response of maize varieties to the prevailing moisture stress of late season planting in South Western Nigeria

The growth, development and yield of two maize varieties: TZSR-W and TZESR-W were monitored in two agro-economic trials during the 2006 and 2007 late planting seasons in Nigeria. Results obtained, which were similar for both years showed that TZSR-W (a late maturing variety) was significantly superior to variety TZESR-W (early maturing) in terms of plant height and leaf area. In terms of grain yield and growth analysis parameters (LAR and RLGR), TZESR-W was superior to TZSR-W. The yearly dry season was observed to have set in at the time of tarselling and silking in cultivar TZSR-W, whereas cultivar TZESR-W was well into grain filling. The additional labour requirement for weeding of TZSR-W before full maturity was attained also made it costlier to produce. The value of yield advantage of TZESR-W averaged aboutN31, 440.00 (US$209.6) per hectare. Early maturing maize variety therefore appears to have the potentials for the development of high seed yield and economic value under the prevailing environmental condition that characterized the late season planting in South West Zone of Nigeria. Key words: Agro-economic, yield advantage, economic value.

Evaluation of neem seed extract for the control of major field pests of cowpea (&lt;i&gt;Vigna unguiculata&lt;/i&gt; L. Walp) under calendar and monitored sprays

Cowpea growers sometimes apply chemicals as many as 8-10 times to control insect pests during the growing season. Calendar sprays at 7 days' intervals (CA.S7) carried out 5 times and 10 days' intervals (CA.S10) carried out 4 times and monitored spray (MOS) carried out only when insect infestation/damage reached or exceeded the action threshold were studied to find out their effect on major insect pests and yield of cowpea - whether there were differences in the number of insect pests and grain yield. The insect pests studied were the cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs under the application of 5% aqueous extract of neem seed kernel extract (NSKE). The trials were conducted during the early and late planting seasons in Abraka, on a piece of land half a kilometre to Campus 2, Delta State University, Nigeria. The results indicated that calendar sprays significantly controlled A. craccivora colonies compared to control in the early season. Population of other major insect pests was generally low. During the late season, the various NSKE treatments effectively controlled A. craccivora. No significant difference among the treatments in their effect on the other major insect pests. Grain yields were high in both seasons and a significant difference did not exist among the calendar and monitored spray treatments. Three main things are obvious from this study: (1) neem seed kernel extract is effective in the control of cowpea insect pests, especially A. craccivora, (2) Grain yields were similar in calendar and monitor sprays. (3) spraying every 10 days for 4 times and monitoring insect pest damage/infestation before spraying reduced the number of chemical application.Keywords: Cowpea, insect pests, neem extract, calendar and monitored sprays.

Evaluation of native soap (local black soap) for the control of major insect pests and yield of cowpea (Vigna unguiculata (L) WALP in ASABA, Southern Nigeria

Three concentrations of native soap namely 1, 2 and 3 percent were evaluated for the control of four major insect pests and yield of cowpea. The insect pests studied were the cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. The experiments were conducted in the early and late planting seasons in the Teaching and Research Farms of the Agronomy Department, Asaba Campus, Delta State University, southern Nigeria. Effect of chemicals on insect pests indicated that M. sjostedti damage was prevented at all the tested soap concentrations. Similarly, at 2% concentration, Maruca population was reduced in the early season. During the late season, all the tested soap concentrations effectively controlled A. craccivora and pod sucking bugs. At 1% concentration, M. sjostedti was effectively checked. On grain yield, the figures suggested that native soap was an insecticide for pest control in cowpea production. In particular, 2% and 1% concentrations gave cowpea yield of 570.00kg ha -1 and 547.90kg ha -1 respectively in the early season. It was observed however, that during the study, native soap had an inhibitory property by delaying and reducing copious flowering in cowpea. In the late season, yield were relatively low in all the soap treatments due to very low rain. The study suggests that (1) native soap is an effective bio-pesticide against cowpea insect pests (2) more grain yield could be obtained if the inhibitory factor in native soap is removed; local cowpea growers may prefer it to synthetic chemicals, since this could save cost and pose less hazards to health.

Optimizing &lt;I&gt;Helicoverpa zea&lt;/I&gt; (Lepidoptera: Noctuidae) Insecticidal Efficacy in Minnesota Sweet Corn: A Logistic Regression to Assess Timing Parameters

Late-season plantings of sweet corn in Minnesota result in an abundant supply of silking corn, Zea mays L., throughout August to early September that is highly attractive to the corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). During a 10-yr period, 1997-2006, insecticide efficacy trials were conducted in late-planted sweet corn in Minnesota for management of H. zea. These data were used to develop a logistic regression model to identify the variables and interactions that most influenced efficacy (proportion control) of late-instar H. zea. The pyrethroid lambdacyhalothrin (0.028 kg [AI]/ha) is a commonly used insecticide in sweet corn and was therefore chosen for use in parameter evaluation. Three variables were found to be significant (alpha = 0.05), the percentage of plants silking at the time of the first insecticide application, the interval between the first and second insecticide applications, and the interval between the last insecticide application and harvest. Odds ratio estimates indicated that as the percentage of plants silking at the time of first application increased, control of H. zea increased. As the interval between the first and second insecticide application increased, control of H. zea decreased. Finally, as the interval between the last insecticide application and harvest increased, control of H. zea increased. An additional timing trial was conducted in 2007 by using lambda-cyhalothrin, to evaluate the impact of the percentage of plants silking at the first application. The results indicated no significant differences in efficacy against late-instar H. zea at 0, 50, 90, and 100% of plants silking at the first application (regimes of five or more sprays). The implications of these effects are discussed within the context of current integrated pest management programs for late-planted sweet corn in the upper midwestern United States.