Physiological Responses of Cotton to Two‐Spotted Spider Mite Damage

Abstract

Bondada et al. (1995) studied T. urticae damage to cotton grown in the field and found alterations to the sto-Spider mites are important pests of cotton (Gossypium hirsutum matal apparatus and internal damage to the mesophyll L.), capable of dramatically affecting growth, yield, and fiber quality. This study investigated the physiological response of cotton leaves to cells, which resulted in declining photosynthesis in paralfeeding damage by the two-spotted spider mite (Tetranychus urticae lel with declining stomatal conductance and transpira-Koch) in two experiments in the field over two seasons. Mite colonies tion. However, studies of the relationship between the initially established and developed in the basal areas of leaves, where density of mites on leaves and effects on the photosynthe leaf blade joins the petiole. These infestations caused rapid and thetic rate of cotton leaves in the field are limited. Many severe reductions in photosynthetic rate, stomatal conductance, tranother studies on the impact of spider mites on host plants spiration, transpiration efficiency (TE), and chlorophyll content. In such as peach [Prunus persicae (L.) Batsch], almond basal areas, a peak of 68 adult female mites per leaf caused photosyn-(Prunus dulcis Mill.), apple (Malus domestic Borkh), thesis to decline to zero, while undamaged leaves averaged 33 mol tomato (Lycopersicon esculentum Mill.), strawberry (Fra-CO 2 m Ϫ2 s Ϫ1 . Differences in plant responses to mites occurred between garia ananassa Duch.), and peppermint (Mentha piperita seasons despite similar infestation levels, possibly related to later timing of infestation and harder leaves in the second season. Compen-L.) have recorded both reduced leaf photosynthesis and sation for mite damage was not apparent at the leaf level, since photo-transpiration rates (Hall and Ferree, 1975; Poskuta et synthesis was reduced on undamaged portions of damaged leaves. al., 1975; DeAngelis et al., 1983; Youngman et al., 1986; The sequence of mite damage events on the undamaged leaf portions Youngman and Barnes, 1986; Hare and Youngman, was determined to be: first, reduction of stomatal conductance; second, 1987; Royalty and Perring, 1989; Mobley and Marini, reduction of transpiration; third, reduction of photosynthetic rate; and 1990; Nihoul et al., 1992). Reductions in photosynthesis finally, reduction of transpiration efficiency. At the leaf level, the have been shown to result from decreased stomatal openoverall effect of mite damage on photosynthesis was greater thaning and increased mesophyll resistance (Welter, 1989). expected because undamaged areas surrounding those visibly dam-However, the order in which these changes occur and aged were also affected.how this varies with different mite densities and intensity of damage has not been clarified previously.A further limitation of the above studies was that A.A. Reddall and L.J. Wilson, CSIRO Plant Industry and Australian Cotton CRC, Locked Bag 59, Narrabri NSW 2390, Australia; V.O.

Contradictions in host plant resistance to pests: spider mite (Tetranychus urticae Koch) behaviour undermines the potential resistance of smooth‐leaved cotton (Gossypium hirsutum L.)

“…Leaf physiological variables and mite abundance were measured as described by Reddall et al 35 Briefly, photosynthesis, stomatal conductance, transpiration and intercellular CO 2 content were measured with a LI‐6400 (Lincoln, NE) portable photosynthesis system, with a clear leaf chamber covering an area of 6 cm 2 . Measurements were made around midday on clear, sunny days, and leaves were held perpendicular to the sun.…”

“…Data were analysed and presented in SPAD units. Basal (near the junction with the petiole) and distal (near the leaf edge furthest from the petiole junction) leaf positions were distinguished for gas exchange and chlorophyll measurements to allow for differences in mite distribution between smooth and hairy isolines, as described previously 35. Adult female mites per leaf were counted, and the percentage leaf area damaged by mites was assessed on the same leaves used for gas exchange measurements.…”

“…The percentage of leaf area damaged by mites was estimated visually 32. The percentage or area with low or ‘light’ damage, where the leaf showed the pale yellow mottling typical of a short period of mite feeding, was estimated separately from that of extreme or ‘heavy’ damage, where the leaf showed the dark red‐brown scarred areas typical of prolonged mite feeding 35…”

Spray stability of self-assembled filaments for delivery

“…These mites feed on the undersides of leaves, which are the major sites of photosynthesis [40–41], but spraying is applied to the tops of leaves, which can limit efficacy. Pesticidal efficacy required high doses of > 200 ppm of BFN, and so only OB filomicelles formulations could be tested.…”

Photosynthetic Response of Cotton to Spider Mite Damage: Interaction with Light and Compensatory Mechanisms

“…However, spider mites are mesophyll feeders, and their mode of action is fundamentally different from that of the herbivores investigated in the previous studies, which were predominantly defoliators or cause shedding of reproductive structures. Reddall et al (2004) found no evidence of increased photosynthetic rate in undamaged portions of mite‐infested leaves in the upper canopy, but the possibility of compensation in lower leaves was not reported. Spider mite damage can result in reduced leaf size, internode length, and plant height, and if damage is severe, loss of upper leaves (Reddall, 2000).…”