Chemical Control of Sufetula anania on Pineapple (Ananas comosus MD-2)

Abstract

In a commercial pineapple farm, two successive experiments were conducted to evaluate the effect of Rynaxypyr 20SC, Nemacur® 40EC and Mocap® 72EC on Sufetula anania control. In a block with the same propagative material and planting age, that was located at the edge of the mountain, where the pressure of the pest is greater, the experiments were established. The experiments were run in a Complete block design with three treatments and eight replicates. Each repetition was a terrace of 15 beds wide and 10-15 m long with 2000-2500 plants. In the first trial the following products were evaluated: Rynaxypyr 20SC 120 ml ha-1, Rynaxypyr 20SC at 80 ml ha-1 and Nemacur® 40EC 8 L ha-1, each one plus 3 L of Agrex® F and all in 3750 L of water per hectare applied with spray boom, 68 days after planting. A second application was made on the same terraces, 33 days after the first application, but rotating the products. The treatment repetitions that ended with the highest pest incidence and pressure (Nemacur® 40EC 8 L ha-1) was applied with Rynaxypyr 20SC at 100 ml ha-1, those of Rynaxypyr 20SC at 80 ml ha-1 were treated with Nemacur® 40EC at 10 L ha-1 and those of Rynaxypyr 20SC at 120 ml ha-1 were applied with Mocap® 72EC at 10 L ha-1, each one of them, plus 3 L of Agrex® F and all in 3750 L of water per hectare applied with spray boom. To determine the performance of the products in pest control, monitoring was carried out in the first test, pre-application at 0, 10, 15, 23 and 31 days after the application and in the second, at 11, 18, 25 and 33 days after products were applied. In both tests, on the external line of the bed at the bottom of the terrace (border with mountain), 5 plants distributed along it were removed with a shovel and examined for the presence of Sufetula anania. Once the plants were examined, they were planted again and marked with colored spray paint, so that in the next sampling the evaluated plant was the neighbor and so on for the next samplings for both tests. That is, in each evaluation, there were 3 treatments (products) with 8 repetitions (8 terraces) and 5 plants on each terrace, for a total of 40 plants in each treatment and evaluation. In the first test, pre-treatment application (0 days), no differences were observed in the incidence (P= 0.4725) nor the number (P= 0.3831) of Sufetula anania by plant. The Sufetula anania incidence varied between 32.5 and 42.5% which means that from the 40 plants evaluated in each treatment between 13 and 17 had at least one larva present. The number of larvae oscillated between 1.2 and 1.7 by plant among treatments. Ten days after the treatments were applied, the incidence of root larvae differed (P= 0.0002) among products, being lower in plants treated with Rynaxypyr 20SC at 120 ml ha-1 with 2.5%. Fifteen days after application, an even lower incidence of the pest was observed with all the products, but it increased, in all, after 23 days of application. The number of larvae per plant followed the same trend with reductions of 99 and 97% in the period of 10-15 days for the rate of 120 and 80-ml ha-1 of Rynaxypyr, respectively, then the population began to increase. In the plants applied with Nemacur®, the population was diminished (P< 0.0001) by 87, 84 and 79% for the periods of 10-15, 10-23 and 10-31 days after its application, respectively. In the second test, a 95% reduction (P< 0.0001) in the incidence was observed 11 days after applying Rynaxypyr 20SC at 100 ml ha-1 remaining such effect up to 25 days, and 92% (P= 0.0006) with the application of Mocap® 72EC at 10 L ha-1 remaining the effect up to the 33 days post application. In the plants treated with Nemacur® 40EC at 10 L ha-1 an 89% decrease was found 18 days after its application. Rynaxypyr 20SC at 100 ml ha-1 reduced (P< 0.0001) the number of root larvae by plant by 96% 11 days after application, which remained low until 25 days after application. A very similar behavior was observed in the plants applied with Mocap® 72EC at 10 L ha-1 where the reduction (P= 0.0004) was 94% at 11 days after application, remaining low with 0.02 per plant up to 25 days after application. In the plants treated with Nemacur® 40EC at 10 L ha-1 a reduction of 90% was observed 18 days after application, such reduction was maintained up to 25 days and then started to increase. The results obtained show that Rynaxypyr 20SC was effective in controlling pineapple root larvae and that a rate of 120 ml per hectare should be used at high incidences and high population levels. Additionally, the effect of Mocap® 72EC in controlling the pest was confirmed and it was found that Nemacur® 40EC is another option for its control when both are used at the maximum rate registered on the label.