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The aim of this study was to determine the damage in Brachiaria ruziziensis (Germain & Edvard) according to the density of and exposure time to adults of Mahanarva spectabilis (Distant, 1909) (Hemiptera:Cercopidae). Each plant was kept with 0, 12, 18, or 24 adults of M. spectabilis for five or ten days. Then, the insects were removed from the plant, and the following parameters were evaluated: content and loss of chlorophyll, visual damage score, shoot dry mass, and the capability for regrowth. In fact, plants exposed to the highest level of infestation for 10 days showed an 80.97% loss of chlorophyll, which is 25% higher than that shown by the plants exposed for five days. The damage score also increased with infestation levels. In the levels of 12 and 18 adults per plant, the damage score increased with increasing time of exposure. The dry mass content was higher in plants exposed to 24 insects for 10 days, suggesting that the attack of spittlebugs caused premature drying of the plant. These effects caused significant reduction in the number of tillers of infested plants. Our results indicate that exposure to adults of M. spectabilis causes significant damage and affects the development and persistence of B. ruziziensis plants.

The damage caused by spittlebugs varies according to the species of grass, and the losses can reach alarming levels. Measures for population control are currently restricted to the use of resistant grasses and the diversification of pastures. Therefore, alternative control measures are necessary, such as the use of botanical insecticides. The aim of this study was to evaluate the insecticidal activities of thymol, carvacrol, eugenol, cinnamaldehyde, and trans-anethole on Mahanarva spectabilis eggs, nymphs, and adults under laboratory conditions. In the egg tests, treatments with eugenol, carvacrol, and thymol showed the highest mortalities, presenting efficiencies higher than 85% after 48 h of application. In the nymph tests, the treatments with thymol and carvacrol at 2.5% and eugenol at 2.0% and 2.5% showed intermediate efficiencies, with values above 61%. The highest mortality was observed in the treatment with trans-anethole at 2.5%, with an efficiency of 95%. In the tests with adults, only treatment with trans-anethole at 2.5% obtained an efficiency reaching 90%; in the other treatments, the efficiency did not exceed 51%. These results showed that, at these concentrations, trans-anethole presents a high rate of insecticidal activity on M. spectabilis nymphs and adults and, therefore, is recommended as a potential natural insecticide for the control of this pest.

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The performance and preference of Mahanarva spectabilis (Distant) for feeding on different forage species were evaluated. The survival and duration of the nymphal period, longevity and fertility of adults, and food preferences (free choice) of adults of M. spectabilis were evaluated in a greenhouse trial, and food preferences of adults were also evaluated in laboratory tests without a choice of host plant. In the field, the numbers of plants with spittle masses were evaluated by forage sampling. Lower levels of nymph survival were observed in the greenhouse on Molasses grass, Jaraguá, Tanzânia, and Makueni. The duration of the nymphal period did not differ significantly on different forage species; however, the longevity and fertility of adults were significantly lower on Cynodon and Brachiaria decumbens Stapf. In the free-choice preference test, adult insects were attracted most strongly to B. decumbens and Jaraguá, with intermediate attraction to Brachiaria brizantha (Hochst ex A. Rich) Stapf and Pioneiro. In the test without host choice, insects exhibited lower excretion rates on Tanzânia, Cynodon, Jaraguá, B. brizantha, and Molasses grass, and those fed on Cynodon, Jaraguá, Molasses grass, and Makueni also exhibited reduced body mass. In the field, Pioneiro had the highest number of spittle masses, followed by Roxo de Botucatu. Thus, Molasses grass, Tanzânia, Makueni, and Jaraguá plants are less suitable food sources for M. spectabilis nymphs and adults. Additionally, although Jaraguá was less favorable to nymphs, it attracted food-seeking adults; hence, these plants have potential for use in control of M. spectabilis.

The aim of this study was to determine the damage caused by adult Mahanarva spectabilis (Distant, 1909) (Hemiptera: Cercopidae) on Brachiaria ruziziensis (Germain & Evard) under field conditions. A total of 0, 4, 8, 12, or 16 M. spectabilis adults per plot were maintained for 6 days. Thereafter, the insects were removed from the plant, and the following parameters were evaluated: chlorophyll content, damage score, dry as well as fresh weights, percentage of shoots' dry matter, and the forage's ability to regrow. The chlorophyll content was significantly reduced; the damage score and percentage of dry matter in plants increased depending on the increased insect infestation density after 6 days of exposure. In contrast, no change was observed on the B. ruziziensis fresh and dry weights as well as the regrowth capacity depending on the M. spectabilis infestation densities. Attacks by 8 adult M. spectabilis per clump of B. ruziziensis with an average of 80 tillers for 6 days were sufficient to reduce the chlorophyll content and the functional plant loss index. This density can be a reference for spittlebug integrated management in Brachiaria.

The aim of this study was to determine the favorable constant temperature range for Mahanarva spectabilis (Distant) (Hemiptera: Cercopidae) development as well as to generate geographic distribution maps of this insect pest for future climate scenarios. M. spectabilis eggs were reared on two host plants (Brachiaria ruziziensis (Germain and Edvard) and Pennisetum purpureum (Schumach)), with individual plants kept at temperatures of 16, 20, 24, 28, and 32°C. Nymphal stage duration, nymphal survival, adult longevity, and egg production were recorded for each temperature*host plant combination. Using the favorable temperature ranges for M. spectabilis development, it was possible to generate geographic distribution. Nymphal survival was highest at 24.4°C, with estimates of 44 and 8% on Pennisetum and Brachiaria, respectively. Nymphal stage duration was greater on Brachiaria than on Pennisetum at 20 and 24°C but equal at 28°C. Egg production was higher on Pennisetum at 24 and 28°C than at 20°C, and adult longevity on Pennisetum was higher at 28°C than at 20°C, whereas adult longevity at 24°C did not differ from that at 20 and 28°C. With these results, it was possible to predict a reduction in M. spectabilis densities in most regions of Brazil in future climate scenarios.

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