Variation in damage to cotton affecting larval feeding preference of Spodoptera littoralis

Abstract

Feeding experiments with larvae of Spodoptera littoralis were performed with leaves from cotton plants subjected to damage and from undamaged plants. In the experiments, four different time intervals (1, 3, 7, and 14 days) after damage induction and two different levels (high and low) of herbivore damage were tested. Seven days after damage induction larvae fed less on the young top leaves from damaged plants for both levels of damage. At the high damage level, the larvae fed less on leaves from the damaged plants after just three days, and this effect still remained 14 days after damage infliction. When mature leaves from the middle of the plant were compared, no difference between treatments was observed. Two plant sizes were tested, small plants with 4–5 true leaves and large plants with 8–10 true leaves. In small plants the induced changes affecting larval feeding were found mainly in the youngest leaf at the top of the plant, while in large plants the induced effects were found in both the youngest and the second youngest leaves. In plants subjected to artificial damage, larvae fed less on top leaves of the damaged plants when compared to leaves from undamaged plants. When leaves from plants that had been artificially damaged were directly compared with leaves from plants damaged by herbivores, larvae fed more on the youngest leaves from artificially damaged plants when the plants were large. In small plants no significant difference was found when comparing artificial and herbivore damage.

Increased Sulfur Precursors and Volatiles Production by the Leek Allium porrum in Response to Specialist Insect Attack

“…Under our study conditions, no response was observed after damages involving a small number of caterpillars or attacks of short duration. Similar findings have been reported in cotton Gossypium hirsutum in which the induced response to attack by Spodoptera littoralis depends on the extent of damage (Anderson et al, 2001). In Brassica napus, the increase in concentration of glucobrassicine (but not the other 13 glucosinolates analyzed) depends on the intensity of the damage inflicted by Delia floralis larvae (Hopkins et al, 1998).…”

“…Similar findings have been observed in tobacco in which the peak increase of nicotine production occurs 7Y8 d after the beginning of the attack (Baldwin, 1989). In cotton, attack by S. littoralis induces a strong response 5Y10 d after the beginning of the attack but not after only 1Y3 d (Anderson and Alborn, 1999;Anderson et al, 2001). Previously attacked leeks may present higher precursor levels than neverattacked plants for a long time after injury.…”

Timing of induced resistance in a clonal plant network

“…The strength of induced resistance decreased gradually with time in our system, which corroborates earlier studies on non-clonal plants (Stout et al 1996;Anderson et al 2001;Agrell et al 2003;Alves et al 2007). One of the four genotypes used in this study, however, showed a prolonged strong decrease in palatability after defense induction, indicating differences in defense timing between the selected genotypes in this study.…”

Attraction of Spodoptera frugiperda Larvae to Volatiles from Herbivore-Damaged Maize Seedlings

“…Host plant location and acceptance behaviors toward damaged plants are partially decoupled in other lepidopterans. Studies on related noctuid caterpillars in other plants indicate that larvae tend to move away from herbivore-damaged or induced plant tissues, if they move at all on the plant (McAuslane and Alborn, 2000; Anderson et al, 2001). Female Trichoplusia ni moths orient toward herbivore-damaged rather than undamaged plants, but preferentially oviposit on undamaged plants when given a choice (Landolt, 1993(Landolt, , 2001.…”