There is always a silent war between plants and herbivorous insects that we are rarely privy to. In this silent war, chemicals act as both weapons and messengers. Insect-plant co-evolution is going on for millions of years. Plants always look for new strategies to avoid insect pests and insects, in turn, are always ready to develop counter adaptations. This intricate interaction has led to the development of a number of plant defensive traits and the counter adaptive features in insects as well. Both plants and insects have developed morphological and biochemical defensive traits to dodge each other’s strategies. However, biochemical interactions are considered more important and effective than morphological ones because of their dynamic nature. Some of the plant defensive traits evolved during this evolution include toxic furanocoumarins, toxic amino acids, trichomes, lignin and latex. Since there is an increasing focus on improving crop production through safe and sustainable means by reducing the reliance on pesticides, it is highly important to understand the plant defensive traits against insect herbivory. It is equally important to understand the adaptations by insect pests to these defensive traits in order to develop and deploy management strategies to outsmart the insect pests. Here we discuss the plant defense traits against insect herbivory, their induction by elicitors and/or insect damage, and the counter adaptation by insect pests.

Nickel-oxide nanoparticles (NiO NPs) using aqueous Rauvolfia serpentine leaf extract were tested against Callosobruchus maculatus. Synthesis of NiO NPs was confirmed by various physiochemical methods such as UV-visible spectroscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy etc. The sharp and strong reflections (111, 200, 220, 311 and 222 crystal planes) of the monoclinic phase and cubic NiO NPs were observed. The crystallite sizes varied in Scherrer's and W–H plots from 9.42 (20 ml) to 4.89 nm (15 ml) and 20.0 nm (10 ml) to 10.12nm (15 ml), respectively. The highest strain was observed in 15 ml (93.8 × 10⁻⁴) and the lowest (37.9 × 10⁻⁴) in 20ml extract. The C. maculatus on black gram seeds with 5, 10, 20 and 40ppm NiO NPs showed decreased fecundity and an increased developmental period in a dose-dependent manner. The longevity of the insect did not differ significantly. Seed germination was significantly reduced at 40ppm (79.12%)

Chlorpyriphos is one of the major organophosphorus pesticides used widely to control a range of insect pests across several crops. This insecticide is hazardous to the environment and toxic to mammals, thus, it is essential to remove the same from the environment. Similarly, use of polythene is also increasing day by day. Therefore, it is highly important to identify ways to degrade chlorpyriphos and other pesticides from the environment. We studied the degradation of chlorpyriphos and polyethylene by Citrus mealybug (Planococcus citri) bacterial endosymbionts such as Bacillus licheniformis, Pseudomonas cereus, Pseudomonas putida and Bacillus subtilis. This investigation revealed that bacterial endosymbionts use the polythene as a source of carbon and solubilize them by their enzymatic machinery. The degradation of polyethylene by endosymbionts showed a significant reduction in weight of polyethylene sheet after 15, 30 and 45 days of treatment. The SEM images showed localized degradation of the polyethylene around the bacterial cells in the biofilm. Further, the tensile strength (percentage elongation) was significantly reduced after 45 days of incubation. The weight of paraffin wax showed significant reduction in B. cereus. A significant reduction in total amount of chlorpyriphos in soil was observed at an interval of 7, 14 and 21 days after treatment by the bacterial isolates. Among the bacteria, B. cereus and P. putida were found to be most effective. The results from this study show that endosymbionts can be significantly implicated in degrading chlorpyriphos and polyethylene from the environment.

To better understand the elicitor induced defense in wine grapes against Drosophila suzukii (Matsumura), two varieties, Pinot Noir and Chardonnay, were sprayed with jasmonic acid (JA) and salicylic acid (SA). Total phenols, total flavonoids, total tannins and total soluble sugars were quantified. Oviposition preference by D. suzukii in response to JA and SA applications were also studied. Behavioral response of D. suzukii to various sugars was recorded. The effect of flavonoids (gallic acid, catechin, quercetin at 100 and 500 ppm) on mortality of D. suzukii was also studied in CAFE assay. Our results showed that JA and SA application significantly affected phenol, flavonoid and tannin contents of grapes. Reduced injury was observed in treated plants; this reduction was more pronounced in Chardonnay than Pinot Noir. The number of eggs laid by D. suzukii females was lower in JA and SA-treated plants; this reduction was more pronounced under no-choice conditions than under choice conditions. In prandial behavior, sucrose solution (5%), glucose solution (5%), fructose solution (5%), sucrose (5%) + yeast (5%) solutions and yeast solutions (5%) showed higher attraction of D. suzukii females compared to control treatments. Among flavonoids, catechin (100 ppm) showed higher mortality of D. suzukii than rest of the treatments. The results of this study can be used for developing management strategies of D. suzukii in wine grapes and related crops.

Ladakh (Jammu and Kashmir) is the coldest arid region of India, where apricot is a major fruit grown across the region. In recent years, severe infestation by the defoliating caterpillar, brown-tail moth, Euproctis chrysorrhoea (L.) (Lepidoptera: Lymantriidae), on apricot trees has been reported in and around the Batalik sector. During field surveys, dead larvae of the brown-tail moth infected with a nucleopolyhedrovirus (NPV) were found. Electron microscopic studies revealed the typical baculovirus occlusion bodies (OBs) with polyhedral structures. Under a scanning electron microscope (SEM), the OBs of Euproctis NPV appeared to have crystalline structures of variable shapes and sizes which varied from 1.016 to 1.596 μm. Most of the OBs were tetrahedral and few were of hexagonal in shape. The transmission electron microscope (TEM) images of the OBs revealed the tetrahedral shape. The leaf disc bioassay showed the LC₅₀ of 1 × 10⁴ OBs/ml against second instar larvae of Euproctis chrysorrhoea. The 95% fiducial limits ranged from 1.416 to 2.887. This is the first report of NPV from the brown-tail moth in India from the Ladakh region. NPV being safe and environmentally friendly could be an ideal component for the integrated pest management (IPM) approach to controlling the pest.

The giant willow aphid (GWA), Tuberolachnus salignus (Gmelin) was reported for the first time from the cold arid region of Ladakh, India. The identification of GWA was done based on morphological and molecular characterization. The important morphological characters of GWA are grayish-golden color, covered with numerous fine hairs with a large dark brown tubercle in the center of the back. GWA is a serious pest of willow and poplar trees. There is a need to study the biology and host selection behavior of this pest to develop effective management strategies.