California Agriculture - All Issues

Thin sheets of polyethylene are used extensively to cover strawberry beds by southern California growers who report that covered beds have less fruit rot, cleaner fruit, and in many instances earlier production when compared with uncovered beds. Varying degrees of weed control are also realized.

Abstract: A 1959 technical report described the results of a study of the effects of feeding irradiated bacon and fruit compote to male and female rats on longevity, relative to a non-irradiated control diet. No differences were found in brain cholesterol/phospholipid ratios or in glycerophospholipid fatty acids between the 2 diets.

Phytophthora parasitica was isolated from an unusual type of crown rot. Plants successfully inoculated showed a brown rot of the crown and a red-brown cortical rot of roots near the crown. Inoculation of green fruit produced a firm brown rot not seen in the field. The low incidence of the disease suggests that rotation will provide adequate control.

The use of wind-breaks in orchards was studied. Similar observations were carried out on early horticultural crops such as strawberry and potato, and on field crops such as rye, wheat, sugar-beet, and maize.Net profits of 10-45 % with apple and 12-162 % with pear were calculated, if the wind-breaks were 4-6 h away (h = height of the wind-break). The analysis showed that wind-breaking had an important influence on fruit-setting. Higher mean temperature and humidity in sheltered places may favour pollination and fertilization. Therefore, the recommendation to plant more wind-breaks than usual should be accompanied by advice on planting of wind-break trees coming into leaf before blossom time.Strawberries yielded significantly more and were much more profitable in sheltered areas. With early potato, higher revenues were obtained only by promoting earliness, perhaps through 'hothouse' conditions in the sheltered zone.Smaller increases in yield were found for field crops in a zone of nearby 10 h away from the wind-break. | ITBON studie

The use of wind-breaks in orchards was studied. Similar observations were carried out on early horticultural crops such as strawberry and potato, and on field crops such as rye, wheat, sugar-beet, and maize.Net profits of 10-45 % with apple and 12-162 % with pear were calculated, if the wind-breaks were 4-6 h away (h = height of the wind-break). The analysis showed that wind-breaking had an important influence on fruit-setting. Higher mean temperature and humidity in sheltered places may favour pollination and fertilization. Therefore, the recommendation to plant more wind-breaks than usual should be accompanied by advice on planting of wind-break trees coming into leaf before blossom time.Strawberries yielded significantly more and were much more profitable in sheltered areas. With early potato, higher revenues were obtained only by promoting earliness, perhaps through 'hothouse' conditions in the sheltered zone.Smaller increases in yield were found for field crops in a zone of nearby 10 h away from the wind-break.

The preharvest and harvest drop of apples often causes considerable losses to the fruit growers. The early summer varieties are especially liable to drop, but dropping is also found to be a common occurrence among many autumn and certain winter varieties. In a few varieties, such as Filippa, the fall may be quite rapid. In most varieties, however, it happens graduelly increasing during the time the apples approach their full maturity. On the other hand we also know apple varieties, which keep their fruits well after reaching maturity. This is the case e.g. with Huvitus and Lobo, which are grown as standard varieties in Finland. Spraying with growth regulating substances in order to delay the preharvest drop of apples has been a common practice especially in the USA and Canada. The chemical first used for this purpose was α-naphthaleneacetic acid. However, in this respect great progress was made when EDGERTON and HOFFMAN (4) found that 2,4,5-trichlorophenoxypropionic acid (2,4,5-TP) was an ideal chemical for the control of the preharvest drop of Mclntosh apples. Later such sprays have been applied succesfully to several apple varieties (3, 5, 10, 11, 12). In 1958 experiments for controlling the preharvest and harvest drops of some apple varieties with 2,4,5-TP were made at the Department of Horticulture, Piikkiö. The following varieties were tested: Bergius, Sävstaholm, Melba, Atlas, Wealthy, Åkerö and Antonovka. The applications were given 21—33 days before the harvest, both by dilute (20 ppm) and by concentrate (80 ppm) sprays. Furthermore the effect of Tween 20 (polyoxyethylene sorbitan monolaurate) on 2,4,5-TP was studied. Tween 20 has been used as an additive to increase the effect of α-naphthaleneacetic acid in the thinning of apples (7). The results are shown in Tables 1 and 2, and in Figs. 1 and 2. 2,4,5-TP has proved very effective in delaying preharvest and harvest drops in all the varieties mentioned here. The concentraded sprays (80 ppm) have been superior to the diluted (20 ppm) applications. A concentration of 80 ppm did not result in picking difficulties at harvest. Despite the higher concentration, the low volume application supplied only about 50 per cent of the 2,4,5-TP applied per tree in the dilute spray. The additive Tween 20 in concentrations of 0.125 and 0.25 per cent increased the effect of 2,4,5-TP in the Wealthy and Antonovka varieties, whereas on the Åkerö variety it did not have any marked effect. In all the varieties mentioned the application of 2,4,5-TP resulted in a better colour of the apples. This was particularly pronounced in the Melba and Atlas apples. The treated Antonovka apples were also decidedly more yellow at harvest time than the apples from the check trees. | Edellä on selvitetty 2,4,5-triklorfenoksipropionihapon (2,4,5-TP) vaikutusta omenien putoamisen vähentämiseksi ennen sadonkorjuuta ja sen aikana. Ainetta kokeiltiin lajikkeilla Bergius, Sävstaholm, Melba, Atlas, Wealthy, Åkerö ja Antonovka. Käsittely suoritettiin 21—33 päivää ennen sadonkorjuuta. Kokeissa selvitettiin myös Tween 20-valmisteen (polyoksietyleeni sorbitan monolauraatin) vaikutusta 2,4,5-TP:n tehoon. Edelleen verrattiin toisiinsa paineruiskun ja sumuruiskun käyttöä 2,4,5-TP-käsittelyssä. Kokeista saadut tulokset on esitetty taulukoissa 1 ja 2 sekä kuvissa 1 ja 2. 2,4,5-TP on tehokkaasti vähentänyt omenien putoamista kaikista kokeiltavina olleista lajikkeista. Sillä on ollut verrattain pitkäaikainen vaikutus. Tween 20:n yhdistäminen 2,4,5-TP:en on parantanut viimeksi mainitun tehoa. Käytettäessä ruiskutukseen sumuruiskua ja 80 ppm:n väkevyyttä on saatu parempi tulos kuin paineruiskua ja 20 ppm:n väkevyyttä käyttäen. Sumuruiskulla ruiskutettaessa on 2,4,5-TP:ä käytetty n. 50 % vähemmän puuta kohti verrattuna paineruiskulla suoritettuun käsittelyyn. 2,4,5-TP on parantanut kaikkien kokeissa olleiden lajikkeiden omenien väriä.

O presente ensaio, realizado com a var. bourbon de Coffea arabica, além de dar informações sôbre a produção dos cafeeiros protegidos dos insetos polinizadores, permitiu também averiguar o comportamento de várias espécies de abelhas e obter outras informações correlatas. Constatou-se, assim, que o néctar da flor é ainda abundante mesmo 24 horas após a antese e que o teor de açúcar do néctar é elevado, da ordem de 38%, em média. Apis mellifera foi a espécie mais freqüentemente encontrada coletando o néctar e o pólen. Em dias chuvosos, muitas das abelhas dessa espécie apenas coletam o pólen. Das abelhas indígenas, somente Plebéia sp. e Nannotrigona (Na.) testaceicomis e Melipona quadrifasciata foram encontradas colhendo o pólen. Com tempo bom, as abelhas visitam as flôres do café em grande número, tendo-se notado que A. mellifera ocorre com maior freqüência em horas próximas do meio dia, à temperatura de 30 a 32°C. As abelhas Plebeia sp. e N. (Na.) testaceicomis iniciam o vôo mais tarde que a A. mellifera. Em observações realizadas no decurso de 24 horas verificou-se que uma abelha européia trabalhou num território de 13m x 6m, enquanto outras abelhas marcadas não foram vistas novamente. As observações feitas indicaram também que as abelhas grandes, como A. mellifera e Melipona quadrifasciata, são mais eficientes do que as pequenas como polinizadoras do cafeeiro. Em flores mais velhas, com a base da corola já desprendida, encontraram-se as abelhas menores, lambendo diretamente os nectários. As espécies de meliponíneos Plebeia sp., Tetragona (Tetragonisca) jaty, N. (Na.) testaceicomis e Trigona (Trigona) ruficrus, foram vistas muitas vêzes alcançando os nectários através de cortes feitos na base das corolas por Trigona (Trigona) hyalinata. Observações adicionais mostraram que as abelhas M. quadrifasciata e Cephalotrigona capitata, bem como A. mellifera, dão preferência as flôres de exemplares oriundos de Coffea Dewevrei, que são maiores do que as do café Bourbon e têm perfume mais intenso. Apesar da ocorrência dos insetos colhendo néctar e pólen, os dados de produção de café cereja não mostraram diferenças significativas entre as plantas protegidas e sem proteção. Notou-se apenas uma tendência, em cinco dos seis anos analisados, de serem maiores as produções das plantas sem proteção e, portanto, visitadas por insetos. Os dados de frutificação obtidos indicaram, também, melhor pegamento dos frutos nas plantas sem proteção. Nestes cafeeiros as porcentagens de sementes moca mostraram-se significativamente maiores, enquanto as porcentagens de sementes concha, embora também maiores, não se mostraram significativas. A quantidade de frutos com lojas sem sementes e o tamanho das sementes não diferiram nos dois tratamentos. A influência das abelhas na polinização do cafeeiro deve, pois, ser pràticamente limitada às espécies autoestéreis de Coffea. Os dados aqui obtidos indicam que o papel desempenhado pelos insetos em promover maior polinização e aumento de produção dos cafeeiros da var. bourbon, é de importância secundária. | The diploid species of Coffea so far investigated, are self sterile, while tetraploid C. arabica, besides being self-fertile, is an almost completely autogamous species. Natural crossing in this species is promoted either by wind or by insects while gravity probably only plays a limited role. The trial here discussed was established to study the effect of certain native and also of the European honey bee in the promotion of the pollination in C. arabica var. bourbon, and also to test their influence on the yield of coffee. As it was difficult to specifically determine the effects of only this group of insects, the data represent the total effect on coffee yield and seed characteristics, of the exclusion of all pollinating insects. A group of 135 coffee "hills", each with four seedlings, and planted in 15 rows of 9 "hills" each, was used for this purpose. A row consisted of two plots of three "hills" each, besides the borders. One "hill" in each plot was always covered with muslin cloth as shown in figure 1. The trial comprised 26 replications. About 20 meters away from the trial, 15 beehives were established, basically of the following species: Nannotrigona (Scaptotrigona) sp., Tetragona (Tetragonisca) jaty, Melipona quadrifasciata anthidioides, Plebeia sp. and Nannotrigona (Na.) testaceicomis. In the course of the experiment, the species Melipona Scutellaria and Cephalotrigona capitata were added. There was an apiary of honey bees (A. mellifera) at about 700 meters from the experiment. The muslin protections to exclude insects were palced one day before the opening of the flowers and removed, some 10 to 15 days later, when all flowers bad dried corolla?. These treatments were repeated every year from 1951 to 1956, in order to collect information on the yield of each of the "hills" and also on the seed types produced and their size. During 1953, 1954 and 1955, data were also collected concerning the percentage of fruit set and seed types based on a certain number of previously counted flowers. It was noticed that the nectar of the coffee flowers was still abundant even 24 hours after anthesis; its sugar content was about 38%. Apis mellifera was the species most frequently found visiting the Bourbon flowers. Among the native bees, the Plebeia sp. and Nannotrigona (Na.) testaceicomis were found in higher numbers, collecting mainly pollen. During rainy weather, nearly half of the A. mellifera bees present was seen collecting only pollen. On sunny days a large number of bees was observed visiting the coffee flowers, A. mellifera being found in larger numbers at about 12 a.m., at temperatures of 30 to 32°C. The Plebeia sp. and N. (Na.) testaceicornis start their flights later than A. mellifera. Of several A mellifera bees marked, only one was seen four times during 24 hours in an area of 13m x 6m. The inconstancy of these bees may be due to the short duration of the coffee flowering period. According to the data obtained, large bees, as A. mellifera and Melipona quadrifasciata were more efficient to promote pollination than the small ones. Plebeia sp., Tetragonisca (Te.) jaty and N. (Na.) testaceicornis were found on older flowers collecting nectar from the base of the displaced and almost dried corolla tubes. The meliponin bees Plebeia sp., N. (Na.) testaceicomis, Tr. (Tr.) ruficrus were sometimes frequently seen taking nectar through the slit like holes made near the base of corolla tubes by Tr. (Tr.) hyalinata and by the wasp Brachygastra augustii. Additional observation indicated that A. mellifera and the native bees M. quadrifasciata, Cephalotrigona capitata prefer the larger and more scented flowers of Coffea Dewevrei hybrids, found farther away from lhe Bourbon trial. N. (Scaptotrigona) sp. although present in strong colonies, was seen only once on coffee flowers. In spite of the large number of insects collecting nectar and pollen on Bourbon coffee flowers, the yield data here presented do not show significant differences between the protected trees in comparison with the control, without any protection. In these plants only a certain tendency towards a higher production was observed, during four of the six consecutive years. This effect may be the result of an intensified liberation of pollen, simply due to insect contacts,the pollen then being transported by wind. The somewhat lower yield of the protected plants may also be the result of the reduction of light due to the use of muslin protection which remained on the trees for about 10 to 15 days after each coffee blossoming, 3 to 4 times every year. The data on fruit setting, also indicate a higher percentage in the unprotected trees. The percentage of peaberry (²) seeds was significantly higher in the covered plants. The percentage of "elephant" (³) seeds was also higher, but not significantly, in this same group of plants. The causes of these abnormalities are not yet well understood. There were no differences in the amount of empty seeds and in the size of the beans in both groups of plants. The influence of bees on coffee pollination must be restricted nearly only to the diploid self-sterile species of Coffea. The results here presented for C. arabica var. bourbon indicate that the role played by insects in promoting pollination and increasing the yield, seem to be of secondary importance for this variety of coffee.