Two experiments were conducted to evaluate the effectiveness of three nematicides in the control of nematodes that affect plantain (Musa acuminata x M. balbisiana, AAB): one at the Corozal Agricultural Substation and the other at the Gurabo Substation. The results show that all of the three doses of Dasanit 15G. Mobcap 10G, and Furadan 10G tested were effective in controlling nematodes, increasing yield, and extending the useful life of the plantation so that three crops were harvested without renovating the plantation.
Five Lacknau plantain clones were tested in the field against yellow sigatoka (Mycosphaerella musicola), the corm weevil (Cosmopolites sordidus) and nematodes (Radopholus similis), and for yield and fruit processing quality. These plantains retained 10 or more functional leaves even without a foliar spraying program at bunch-shooting. At harvest, however, the number of useful leaves was drastically reduced. This condition was not totally related to sigatoka damage but to a rather faster rate of senescence occurring in unsprayed as well as sprayed leaves. These clones, without soil granular pesticides, recorded 4.5 cavities per rhizome and yielded 51.6 t/ha of fruits, 11 to 23 t/ha more than Maricongo in the plant crop. The application of carbamate based insecticide-nematicide compounds to corm weevil-resistant plantains reduced insect damage but did not increase yields. All Lacknau clones were susceptible to the burrowing nematode. Fried flattened slices and chips prepared from Lacknau mature green fruits were rated as acceptable. However, 59% of the tasters preferred fried slices from Lacknau over those of Maricongo, and 90% chose the Maricongo chips.
The burrowing nematode, Radopholus similis, and the black weevil, Cosmopolites sordidus, are the most important economic pests of plantain, Musa acuminata x M. balbisiana, AAB, in Puerto Rico. Research carried out by this Station has demonstrated that chemical control of nematodes increases plantain production and the useful life of the plantation. Similar results have not been obtained with the black weevil even when research has been conducted toward this goal. Several nematicide-insecticides for the control of both pests have been tested. At the Fortuna Substation five pesticides were evaluated: Carbofuran 5G and 10G, Fensulfothion 15G, Ethoprop 10G, and Aldicarb 10G. Carbofuran 5G was evaluated at the rate of 42 g/plant applied every 4 months. The other pesticides were evaluated at 56 g/plant applied every 6 months. At the Corozal Substation Aldicarb 10G was evaluated at 4 doses (10, 15, 30, 45 g/plant) applied every 4 and 6 months. Carbofuran 10G at 56 g/plant applied every 6 months was included for comparison. At the Fortuna Substation, where only one crop was harvested with no significant differences in yields, the majority of the pesticide treatments controlled the nematodes. The black weevil was controlled only with Aldicarb, Ethoprop, and Fensulfothion. At Corozal, where two crops were harvested, all treatments were significantly better than the control; with the control of nematodes and weevils there was an increase in yield and suckers. The most effective doses and frequencies for the control of both pests were Aldicarb 10G at the rate of 30 and 45 g/plant applied every 4 months and at 30 g applied every 6 months.
Two experiments were conducted, one each at Utuado and Corozal, to evaluate the effect of a soil spray and a seed treatment with the systemic nematicide-insecticide Oxamyl L and soil treatments of Phenamiphos 15G for the control of the nematode Pratylenchus coffeae (Zimmerman) Filip. Sehuur-Stekh. and the white-grub, Diaprepes abbreviates (L.), in yam (Dioscorea rotundata Poir). The soil was sprayed at the base of the plant with a 20 ml automatic applicator (Spot Gun). At Utuado, two doses of oxamyl, 0.3 ml (7,410 µg a.i./ml) and 0.6 ml (1 5,297 ug a.i./ml) per plant applied every two months were evaluated alone and in combination with a seed immersion in 2,400 p/m a.i. of oxamyl/15 min. Also seed immersion was evaluated when combined with foliar sprays of Oxamyil L (4.68 l/ha every 15 and 60 days). At Corozal soil spray of Oxamyil L [0.6 and 0.9 ml (23,700 µg a.i./ml)/plant], 0.3 and 0.6 ml/plant plus seed treatment (2400 p/m a.i./15 min), Oxamyil L sprayed at 4.68 l/ha/15 days and soil treatments of Phenamiphos (0.64, 0.93 and 1.27 g/plant) were evaluated. Harvested tubers were classified in quality categories based on the cortical dry-rot damage caused by P. coffeae: high (0-25%), medium (26-50%) and poor (51-100%); and based on perforations made by the larvae of D. abbreviates: tunneled (tubers with one or more perforations) and marketable (high and medium quality tubers without tunnels). Significant yield increases (P = 0.01) of high quality yams over the control were obtained at both locations with all Oxamyil L treatments. Highest yields were obtained at Utuado with 0.3 ml/plant combined with seed immersion and with 0.6 ml/plant without seed treatment. An increase from 0.6 to 0.9 ml of Oxamyil L did not increase yields significantly at Corozal. At Utuado there was no significant reduction in tunneled yams attributable to foliar spray or soil treatments. Infestation of D. abbreviates at Corozal was very low.
Two field trials were performed to evaluate oxamyl 24 L for control of nematodes and increase yields of high quality yam tubers, Dioscorea rotundata Poir. The nematicide was tested as a seedpiece immersion, furrow and foliar treatment, as well as combinations of foliar with seedpiece and furrow treatments. Significant increases on yield of high quality yams were obtained by controlling nematodes with the combination of the foliar and seedpiece treatments and with the seedpiece treatment alone. Oxamyl 24 L, if registered for use in yams in Puerto Rico, can provide the farmer an effective alternative to the presently authorized granular nematicide aldicarb 10G.
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