Attraction of the biocontrol agent, Lema praeusta, towards two Commelinaceae weed volatiles

Abstract

Two Commelinaceae weeds, Commelina benghalensis L. and Murdannia nudiflora (L.) Brenan, are abundant in rice fields of India. Larvae and adults of Lema praeusta (Fab.) (Coleoptera: Chrysomelidae) voraciously consume these two weeds. Synthetic herbicides are applied to control both weeds, but applications of these substances have harmful effects in environment and beneficial organisms. So, it is necessary to use native biocontrol agent to control these weeds. Hence, an attempt has been made to find volatile organic compounds (VOCs) from both weeds causing attraction of L. praeusta. Behavioural responses of L. praeusta towards volatile blends from undamaged (UD), insect‐damaged (ID: plants after 6 or 48 hr of continuous insect feeding) and mechanically damaged (MD) plants were conducted by Y‐tube olfactometer bioassays. Benzyl alcohol was predominant in VOCs of UD plants and M. nudiflora after 48 hr of insect feeding. Benzyl alcohol and cuminaldehyde were both predominant in VOCs of C. benghalensis after 48 hr of insect feeding. Females were more attracted towards volatile blends from plants after 48 hr of insect feeding compared to undamaged plants. Females showed attraction towards a synthetic blend of seven compounds—7.28 µg (Z)‐3‐hexen‐1‐ol, 0.93 µg trans‐isolimonene, 19.18 µg benzyl alcohol, 0.16 µg undecane, 1.07 µg 1‐nonanol, 1.23 µg 1‐undecanol and 0.47 µg 1‐eicosene resembling the amounts released by C. benghalensis after 48 hr of insect feeding during 1 hr or a synthetic blend of six compounds—18.10 µg benzyl alcohol, 0.25 µg undecane, 0.56 µg 1‐nonanol, 1.37 µg 1‐undecanol, 0.35 µg 1‐eicosene and 2.19 µg phytol resembling the amounts released by M. nudiflora after 48 hr of insect feeding during 1 hr. This study concludes that both blends could be used to attract the biocontrol agent during early vegetative period of these two weeds, which could lead to eradication of weeds from rice fields.

Semiochemicals from Trichosanthes anguina (Cucurbitaceae) plants influence behavior in Diaphania indica

“…Implicating feeding by caterpillars of D. indica resulted in qualitative as well as quantitative changes in VOCs among volatiles of insect-damaged plants in comparison to volatiles of undamaged plants. 29,35 Methyl salicylate was detected as HIPVs in ID MNS and ID BAR plants but not in ID POLO plants. Nerol was an unique HIPV in ID MNS plants.…”

“…The results of the present study on the olfactory responses of D. indica adults revealed that virgin females and gravid females had similar behavioral response to volatiles of undamaged T. anguina plants, which indicates that the response to host plant volatiles is not associated with the physiological state (mating status) of the female. 30,35,39 Therefore, we used virgin D. indica females throughout the olfactory bioassays. However, olfactory responses of virgin and gravid females could be different when volatiles from undamaged plants were tested against volatiles from conspecific-damaged plants.…”

“…43 The behavioral responses of D. indica in all olfactometer bioassays were analyzed with a chi-square test (H 0 : P = 50%). 35,38 3 RESULTS…”

“…Damage by an insect on its host plants results in the changes of total amounts of VOCs compared to undamaged plants, and some novel herbivore-induced plant volatiles (HIPVs) that are emitted by insect-damaged plants. [35][36][37][38][39] Therefore, it is necessary to observe the role of HIPVs from T. anguina plants in the behavior of adult D. indica. In addition, the composition of VOCs varies between undamaged plants and jasmonic acid (JA) treated plants as application of JA plays an important role in plant defense by emitting VOCs, which repel an insect herbivore to feed on its host plant.…”

The Role of Green Gram Plant Volatile Blends in the Behavior of Arctiid Moth, Spilosoma obliqua

“…For the treatment of mechanical damage (MD), 10 leaves of a plant were wounded twice with hole punches (each hole 0.5 cm), and volatile blends were collected without delay after wounding. An experimental plant was positioned in a closed glass dome (4 L) with Te on base having a small opening for passing the stem of plant (Das et al 2021) (Supplementary Fig. S1).…”