Lowest Number Of Adults Research Articles

Fly larvicidal activity in the faeces of cattle and pigs treated with endectocide products.

Bioassays were conducted to study the effect of a single therapeutic dose of injectable ivermectin, doramectin or moxidectin given to cattle and pigs and excreted in their faeces, against larvae of the housefly, Musca domestica L. (Diptera: Muscidae). Five cattle were treated with each of the test products. Cattle faecal samples were collected before treatment and on days 1, 2, 3, 6, 10, 16, 20, 23 and 28 after treatment. Three groups of pigs, each comprising 12-14 pregnant sows and gilts, were used in the experiment. Pig faeces was collected from each group before treatment and on days 1, 3, 5, 7, 9, 11, 13, 15 and 20 after treatment. Thirty, first-stage larvae were placed into 100 g of faeces. Five replicates were examined for each time-point and for each endectocide group. Evaluation was based on the number of larvae surviving to adult emergence. Low numbers of adults emerged from samples taken from cattle 1 day after treatment, indicating that ivermectin and doramectin were rapidly excreted in the faeces and affected the development of the house fly. A larvicidal effect of both drugs in cattle faeces was present for a period of about 3-4 weeks and lasted a few days longer in cattle treated with doramectin than with ivermectin. In cattle, the larvicidal activity of moxidectin was first observed in faecal samples collected 2 days post-treatment; however, it killed fewer larvae than the other two drugs. The larvicidal effect of moxidectin subsequently decreased. Ivermectin and doramectin exhibited a pronounced larvicidal effect against the house fly in the faeces of pigs. The effect of doramectin was of longer duration. Moxidectin gave the weakest larvicidal effect in pig faeces. The main difference between the results obtained for the two livestock species is that peak toxicity occurred relatively later and for a shorter duration in pig than in cattle faeces.

Bemisia tabaci (Homoptera: Aleyrodidae) biotype B colonization on okra- and normal-leaf upland cotton strains and cultivars.

We compared smooth-leaf okra- and normal-leaf upland cotton (Gossypium hirsutum L.) strains and cultivars for susceptibility to colonization by Bemisia tabaci (Gennadius) biotype B. Experiments were conducted at seven field sites, five at Holtville, CA, and two at Maricopa, AZ, during 1996-2000. Okra-leaf strains and cultivars, as a group, had lower numbers of adults, eggs, and nymphs compared with normal-leaf strains and cultivars indicating the potential of okra-leaf genetic traits for reducing colonization by B. tabaci. Results also suggest that okra-leaf shape may provide less favorable micro-environmental conditions for the habitat of B. tabaci because of more open canopy as evidenced by higher leaf perimeter to leaf area ratio. The okra-leaf cultivar 'Siokra L-23' appears to have genetic traits that should be examined further as a source of B. tabaci resistance.

Cash Transfer Programs with Income Multipliers: PROCAMPO in Mexico

Cash transfer programs create multiplier effects when recipients put the money they receive to work to generate further incomes. When this is the case, the ultimate income effects are multiples of the amounts transferred. We analyze the PROCAMPO program in Mexico that was introduced to compensate farmers for the anticipated negative effect of NAFTA on the prices of basic crops. The transfer rules and the timing of the panel data collected allow unique control of biases in this impact analysis. We find that the multiplier among ejido sector recipients is in the range 1.5–2.6. Multipliers are higher for households with medium and large farms, low numbers of adults in the household, nonindigenous backgrounds, and located in the Center and Gulf regions. High multipliers reflect income opportunities that had remained unrealized due to liquidity constraints that are relaxed by the transfers. Opportunities come from the asset endowments that these households received through the land reform, particularly irrigated land, and they are enhanced by access to technical assistance.

Efeito da temperatura na maturação ovariana e longevidade de Anastrepha fraterculus (Wied.) (Diptera: Tephritidae)

Na Região Sul do Brasil, a incidência de Anastrepha fraterculus (Wied.) flutua durante o ano, sendo que no inverno não são detectados adultos quando se utilizam métodos convencionais de coleta. Com o uso de armadilhas especiais capturaram-se adultos, ainda que, em número muito reduzido. Duas hipóteses são sugeridas para o seu aumento populacional após o inverno, nas regiões produtoras de frutíferas: a) repovoamento da região na primavera por populações circunvizinhas; e b) regulação metabólica diferencial no desenvolvimento de alguns indivíduos que conseguem sobreviver ao período crítico. A segunda hipótese foi testada no presente trabalho, analisando-se a influência de quatro temperaturas (9, 13, 20 e 25ºC) constantes sobre a maturação ovariana e sobre a longevidade das fêmeas dessa espécie. Apenas a 25 e 20ºC ocorreu amadurecimento ovariano. A expectativa de vida foi maior nas temperaturas intermediárias (20 e 13ºC) que nas temperaturas extremas (25 e 9ºC). A relação entre maturação ovariana e longevidade foi observada a 25 e 20ºC, sendo que a 25ºC o amadurecimento ovariano foi mais rápido, mas a expectativa de vida menor. Não se pode, portanto, descartar a hipótese de regulação do desenvolvimento como mecanismo populacional em A. fraterculus para repovoamento da região nos meses subseqüentes ao inverno.

Adubação e inseticidas no controle de Empoasca kraemeri e Bemisia tabaci, em cultivares de feijoeiro semeados no inverno

Vários fatores influenciam a produtividade da cultura do feijoeiro, dentre estes podem ser citados as pragas, merecendo destaque, a cigarrinha verde, Empoasca kraemeri Ross & Moore (Hemiptera: Cicadellidae) e principalmente a mosca branca, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), que prejudica o feijoeiro pela transmissão do vírus do mosaico dourado. Este trabalho avalia o efeito de cultivares de feijoeiro, adubação e inseticidas nas populações de E. kraemeri e B. tabaci na época de semeadura "de inverno". Os genótipos utilizados foram IAPAR MD-806, IAPAR MD-808, IAC-Carioca e Bolinha. Avaliaram-se, dos 7 aos 56 dias após emergência das plantas, o número de ninfas e adultos de cigarrinha verde e mosca branca, percentual de ataque de cigarrinha e número de plantas com sintomas de mosaico dourado. Na colheita, foram avaliados o número e peso de vagens por planta, o número de grãos por planta e peso de grãos (kg ha-1). Os danos de cigarrinha verde e os sintomas de mosaico dourado foram menos intensos em IAPAR MD-806 e IAPAR MD-808 em relação ao Bolinha e IAC-Carioca. A adubação não influenciou o número médio de adultos de cigarrinha verde nos genótipos de feijoeiro. As aplicações de inseticidas e adubo proporcionaram menores números médios de adultos de mosca branca nos genótipos de feijoeiro quando avaliados em conjunto aos 56 dias após emergência das plantas.

Bemisia argentifolii Adult, Nymph and Egg Densities and Egg Distribution on Selected Upland Cottons

Five upland cotton, Gossypium hirsutum L., cultivars, Deltapine (DPL) 50, 5415 and 5432, Fibermax 832 and Siokra L23, were studied in relation to silverleaf whitefly, Bemisia argentifolii Bellows and Perring, oviposition and colonization. Deltapine 5415 and 5432 had the highest numbers of eggs and nymphs and Siokra L-23 the lowest. Siokra L-23 also had the lowest number of adults compared to the other four cultivars. Over 75% of eggs were oviposited on leaf surfaces between veins and 23% were oviposited in veins that were ≤4 cells wide. Few eggs were found on veins that were five or more cells wide. No eggs were inserted into leaf stomata.

Comparative persistent efficacy of doramectin, ivermectin and fenbendazole against natural nematode infections in cattle

A study was conducted in Argentina, to investigate the period of protection of a single injection of doramectin administered subcutaneously (SC) at 200 μg kg −1 (1 ml/50 kg) compared with single treatments of ivermectin (200 μg kg −1 SC) and fenbendazole (5 mg kg −1 PO), against field infections of gastrointestinal parasites of cattle. Eighty-three animals were selected and ranked on the basis of serial fecal egg counts (e.p.g.'s). From this group, three animals were slaughtered before treatment and their lungs, abomasum, small and large intestines, were processed for parasite counts and identification. The remaining 80 animals were allocated in ranked groups of four to a control or one of three treated groups. Animals of the four groups were grazed together in the same pasture for the duration of the study. Treatments were administered on Day 0. Individual fecal samples were collected at weekly intervals for the first 49 days post-treatment and twice a week from Day 52 to Day 84 (end of study). At each collection day fecal samples were pooled for coprocultures. On Day 28 and 56, two animals from each group, previously identified on Day 0, were killed and their parasite burdens determined. The duration of protection of a single injection of doramectin was longer than ivermectin or fenbendazole treatment. On Day 56, the total number of parasites found in doramectin-treated animals was significantly ( P < 0.05) lower than parasite burdens found in either ivermectin- or fenbendazole-treated animals. The longer persistent activity of doramectin was expressed by the lower number of adults and L 4 stages of Ostertagia ostertagi. Data from this experiment demonstrated the limitations of using fecal egg counts to evaluate the persistent efficacy of anthelmintics. The duration of activity of doramectin was demonstrated more accurately by parasite counts in cattle from each group since decreasing e.p.g.'s were seen in non-medicated animals without changes in total parasite burdens.

Walnut Husk Fly (Diptera: Tephritidae) Pest-Free and Preovipositional Periods and Adult Emergence for Stone Fruits Exported to New Zealand

Walnut husk fly, Rhagoletis completa Cresson, adults were trapped in two of nine trap locations in walnuts in five counties in the San Joaquin Valley of California before the end of the pest-free period, 1 July 1992. Highest numbers of adults were collected in walnuts from 19 August through 8 October after early-season, midseason, and most late-season stone fruit cultivars had been harvested. Lowest numbers of adults were trapped in Kern County locations in the southern region of the San Joaquin Valley. Laboratory behavioral studies showed that earliest ovipositional punctures in walnuts occurred 9 d after and eggs were laid 11 d after adult emergence. The preovipositional period will reduce the risk of stone fruit infestations during atypical years when adults emerge before 1 July. Adults emerged from pupae reared in the previous year from peaches, nectarines, and walnuts, but no adults emerged from plums. The biological risk for accidental introductions of walnut husk fly into New Zealand through shipments of stone fruits from California is negligible.

Effects of alternating temperatures onAcarus siro L. (Acari: Acaridae)

Fecundity, longevity and survival to adulthood ofAcarus siro (L.) at constant and alternating temperatures were compared. Both fecundity and longevity were affected by alternating temperatures but the effect of the frequency of alternations was not significant. Significantly higher fecundity and longer life spans were recorded at constant temperatures of 14 and 21°C than at 28°C or at alternating temperature regimes. Alternating temperature regimes in comparison to constant regimes did not significantly change the number of males and females surviving to adulthood or the sex ratio. However, the lowest number of adults surviving was recorded when temperatures were changed every 12 h and the highest at a constant temperature of 14°C.

Larval drift of Chironomidae (Diptera) in a North Florida stream

The Orthocladiinae and Chironomini dominated the numbers of drifting larvae captured in Turkey Creek, Florida, during 1979 and 1980. Polypedilum outnumbered all other taxa and seasonal peaks occurred in Polypedilum aviceps Townes. Polypedilum illinoense (Malloch) was subject to catastrophic drift. Current speed was not correlated with numbers of drifting larvae, but net placement was correlated for some taxa. Low numbers of adults and pupae were captured in the drift. Drifting egg masses, larval instars I, and pupal exuviae were abundant in Turkey Creek.