The aim of this study was to evaluate the quality of starch produced by plants that suffer damage caused by M. fryanus, analyzed by colorimetric and morphological indices. Colorimetric data were composed of luminosity indices, “a” and “b” chroma coordinates and darkening index. For morphological data, the perimeter and area of starch granules extracted from cassava roots were analyzed. The variables were summarized in a principal component analysis and the axes scores retained for interpretation were correlated with the damage caused by the M. fryanus. From these analyses and observing the main effects, linear regression models for the variables were determined, according to the level of damage caused by the pest. The damage caused by M. fryanus in the roots strongly influenced the indices related to starch colorimetry, hence, under conditions of greater damage, the tendency of the chroma coordinates to vary toward red and yellow was observed and a decrease in starch luminosity occurred, inversely proportional to the increase in darkening. Similar to what was observed in the colorimetric data, a drop in the size of starch granules was noted in the roots, which suffered greater damage from the pest.

The damage caused by insect pests in plants can considerably affect their development and crop yield. It can also cause the activation of biochemical defense mechanisms in the plant, combined with the production of reactive oxygen species. The levels of these oxygen molecules are controlled by antioxidant enzymes and this mechanism is an important plant defense process. The aim of this study is to learn the effect of feeding by the stink bug, Diceraeus melacanthus, on the growth of corn plants and on the activity of the antioxidant enzyme peroxidase (POD) and catalase (CAT). The study was carried out in a greenhouse, in a completely randomized design, with a 2 × 4 factorial block and five replications. The first factor was composed of plants with and without the presence of the bug and the second factor was composed the age of corn plants, two, four, six, and eight days after emergence. Corn seedlings infested with the stink bug were negatively influenced in terms of plant height, root mass and increasing in activity of the POD enzyme was 84% higher in plants infested at 8th DAE. The CAT enzyme activity was not detected in the samples. The stink bug feeding affected the growth of the corn seedlings. The analysis of the POD enzyme could be a valuable tool to quantify the stress caused by the stink bug in futures studies.

The insect attack is one of the main factors responsible for the loss of corn grain stored after harvest, thus sustainable strategies such as natural extracts can be used as cheap methods of control. This study evaluated the effects caused by Spathodea campanulata nectar extracts on the maize weevil Sitophilus zeamais to the preference test and mortality was used completely randomized design with 10 replications and treatments solutions of 0, 5, 10, 30 to 50% nectar under study. He noted that the preference index was lower in the first 3 hours of evaluation and the highest concentration of extract (50%), resulting in a possible repellent effect, but with the potential loss in subsequent evaluations. Already mortality was increased from the concentration of 30%, but the number of dead insects was low, indicating low efficiency. However, the percentage of perforated grains was reduced at the highest concentration and decreasing interfering insect feeding.