Juvenile hormone analogs (JHA) are known to interfere with growth and biosynthesis of insects with potential for insecticide action. However, there has been comparatively few data on morphological effects of JHA on insect organs. To determine pyriproxyfen effects on Aedes aegypti larvae, we conducted toxicity, behavioral bioassays and assessed ultrastructural effects of pyriproxyfen on midgut cells. A. aegypti larvae were exposed in aqueous solution of pyriproxyfen LC₅₀ concentrations and evaluated for 24 h. This study fulfilled the toxic prevalence of pyriproxyfen to A. aegypti larvae (LC₅₀ = 8.2 mg L⁻¹). Behavioral observations confirmed that pyriproxyfen treatment significantly changes swimming behavior of larvae, limiting its displacement and speed. The pyriproxyfen causes remarkable histopathological and cytotoxic alterations in the midgut of larvae. Histopathological study reveals presence of cytoplasmic vacuolization and damage to brush border of the digestive cells. The main salient lesions of cytotoxic effects are occurrence of cell debris released into the midgut lumen, cytoplasm rich in lipid droplets, autophagosomes, disorganized microvilli and deformed mitochondria. Data suggest that pyriproxyfen can be used to help to control and eradicate this insect vector.

Deficit irrigation has great significance for sustainable cultivation of cotton in water scarce arid regions, but this technique creates drought situation that induces stress adaptive changes in cotton plants due to indeterminate growth habit. In the present experiment, the impact of drought stress on assimilates partitioning associated vegetative and reproductive development, and yield quality attributes of cotton were examined under desert conditions. Four levels of drip irrigation including 100, 80, 60, and 40% replenishment of depleted water from field capacity were applied to develop drought stress regimes during two growing seasons (2015 and 2016). Results revealed that under limited water supplies, plant’s preference for allocation of photo-assimilates was roots > leaves > fruits that substantially increased root–shoot ratio and hampered reproductive growth. Consequently, boll density (m⁻²), fresh boll weight and lint yield (kg ha⁻¹) were significantly reduced. An obvious change in partitioning of assimilates inside stressed bolls was observed that indicated relatively more accumulation in seeds than fiber, thus reducing the fiber quality. In addition, decreased starch, oil, and protein contents in seeds of stressed plants markedly reduced 100 seeds weight and also the vigor. Later, seed quality confirmatory tests of subsequent years (2016 and 2017) showed significant reduction in emergence counts (m⁻²) and seedling biomasses of seeds harvested from deficit drip irrigated cotton. These results suggest that deficit irrigation could necessarily be an appropriate yield optimization and water saving technique for cotton in desert environment but, for the best quality fiber and cottonseeds, full irrigation should be preferred.