Abstract
The destructive nature of maize fall armyworm has triggered the importation of plenty of plant protection products onto the Ghanaian agrochemical marketplace. These imported chemicals sold at market places sometimes are unregistered for use in the Ghanaian environment. Thus, some importers do not do due diligence in testing the chemical agronomically to ascertain its mode of action and also being not harmful to beneficial insect species in the Ghanaian environment. It was in this view that three Ampligo concentrations or rates (0 ml/ha, 200 ml/ha, and 240 ml/ha) were tested against FAW on maize that were sown at a spacing of 60 cm × 60 cm. Treatments applied to maize were arranged in a randomised complete block design and replicated three times. Ampligo rates caused a very significant ( p < 0.05) reduction in FAW at 21 and 28 days after maize emergence. The damage to maize leaf on treated maize plot was significantly ( p < 0.05) different from that on the untreated. Thus, damage of FAW was more visible on maize leaves on control plots compared to the treated ones. A significantly ( p < 0.05) positive correlation existed between damage rating and FAW number. Furthermore, the Ampligo rates correlated negatively to FAW density at p = 0.014 at 21 days after emergence. Also, FAW infestation did not impact maize grain yield. The study, therefore, concluded that Ampligo pesticide falls in low-risk plant protection product category with a very potent active ingredient that reduces FAW populations. We recommend that Ampligo should be applied between 14 and 21 days after emergence; two applications at one-week interval at 200 ml/ha are sufficient to sustain maize for the whole cropping season.
Highlights
Study Area Location and Description. e study was carried out at the Biotechnology and Nuclear Agriculture Research Institute (BNARI) of the Ghana Atomic Energy Commission (GAEC) research farm (5°40′21′′N, 0°13′00′′W), located in the Ga East Municipality of the Greater Accra Region of Ghana. e location of the trial field was selected based on previous history. e site had previously been cropped to maize without controlling fall armyworm (FAW) infestation
FAW Number, Number of Egg Batches, and FAW Density against Sampling Days. ere was a general decline in the average number of fall armyworms (FAW) for all three treatments evaluated during the trial. us, the number of FAW sampled over the period was on the rise from the initial population on the first day of sampling and began showing a decrease in number 14 days after first Ampligo application (Figure 1(a)). is decline in FAW continued after the second application, which saw the larvae decreasing to zero at 28 days and rising marginally at 35 days
The effect of the two Ampligo rates did not emerge for yields, it did emerge for number of FAW and damage incidence. us, the rates of 200 and 240 ml/ha reduced damage incidence in treated maize compared to the nontreated
Summary
Soil and Climate Characteristics of the Study Area. E soils of the study area belong to the savannah Ochrosols subgroup, which is characterised by very shallow, reddish brown, and brown concretionary, medium to light textured soil belying directly over sandstone, or quartzite or schists [43]. E physical and chemical properties of soils in the study area are described in the work of Frimpong et al [44]. Rainfall of the study area is reported to be low and erratic. This informed our decision to grow maize crops under drip irrigation in the minor season of the coastal savannah environment.
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