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Clarifying the amount of pest damage that can be tolerated without justifying insecticidal control will be useful in reducing insecticide use and in development of integrated pest management (IPM) systems. This study investigated the ability of irrigated, high-yielding cotton (Gossypium hirsutum L.) to recover from artificially applied damage simulating that of early season insect pests. Six experiments were done across five cotton-growing seasons. Damage included defoliation, terminal damage, and flower bud removal in a range of timings, combinations, and intensities. Crop yield was unaffected by defoliation applied before first flower buds appeared, even when 100% of true leaves were removed on three occasions (Nodes 2, 4, and 6). Crop maturity was affected by sustained high levels of leaf loss with a peak delay of 10 d after 100% defoliation three times. Up to three light tip damage events or one heavy damage event had no effect on yield and only a slight effect on crop maturity (, COTTON IS ATTACKED by a range of insect pests, some of which are prevalent through the early portion of the growing cycle, such as tobacco thrips (Thrips tabaci Lindeman), tomato [...]

The objective of this study was to assess the ability of cotton (Gossypium hirsutum L.) crops to recover after early-season damage by thrips (Thysanoptera). Such information may help clarify the actual need to control thrips. Ten experiments, resulting from the combination of two to four sites per season and three seasons, were carried out in commercial crops in the irrigation area of northwest New South Wales, Australia. Two treatments were compared: unprotected crops and crops protected with aldicarb{2-methyl-2-(methylthio)propanal O-[(methylamino)carbonyl]oxime} at sowing. Early season thrips communities were dominated by Thrips tabaci Lindeman, which accounted for 52 to 100% of the total phytophagous thrips present in the crops. Insecticide treatment consistently reduced the number of larval thrips compared with the unprotected crops. Number of larval thrips per plant ranged from 0 to 24. Thrips reduced crop leaf area in six experiments, dry matter production in four experiments, and yield in two experiments. Maximum differences in leaf area and dry weight between treatments were found about 40 d after sowing. In all cases, crops damaged by thrips recovered well and reached leaf areas and dry weights similar to protected crops after about 60 to 80 d after sowing. On average, protected crops reached maturity 3 d earlier than crops damaged by thrips, but differences were not statistically significant. Despite large reductions in early growth, yield reductions due to thrips were found in only two experiments. The magnitude of the reduction in yield in those experiments (11%) contrasts with the magnitude of the reduction in growth (about 40%) and highlights the ability of the cotton crop to recover after early season damage by thrips., Young cotton crops host a range of insect pests, including thrips (Thysanoptera) (Hearn and Fitt, 1992). Common species of phytophagous thrips in high-input cotton cropping systems include Thrips tabaci and [...]

Foliar pests can affect reproductive allocation in plants. Depending on bow spider mites (Tetranychus urticae Koch) affect dry matter partitioning in cotton (Gossypium hirsutum L.), yield losses in infested crops could be similar, greater, or lower don expected from growth reduction. In this paper, we analyzed the effects of mite infestations initiated at three stages during the crop cycle on the yield, growth and dry matter partitioning of cotton. Normal- and okra-leaf types, which am known to differ in their responses to mites, were compared in two experiments. Lint yield losses were significant end were greatest for the earliest mute infestations. Reduced Shoot dry matter and reduced harvest index (lint yield/shoot dry matter) both contributed to these yield reductions. Yield losses were less severe in the okra-leaf cultivar than in its normal-leaf counterpart; this was in part due to a more favorable partitioning to key yield components in the former. to both experiments, reduced lint fraction [g lint [(g seed cotton).sup.-1] contributed to the lower harvest index of damaged crops. Reductions in both fruit number per unit shoot dry matter and seed cotton mass per fruit also contributed to reductions in harvest index of damaged crops. Despite the observed reductions in harvest index and some of its components, allometric analysis showed that mites did not affect partitioning to reproductive organs even in the more severely infested treatments. Rather, the low harvest index of mite-infested crops was the result of small plant sm. We conclude that mite effects on cotton growth and yield could be modelled by taking into account their primary effect on radiation-use efficiency and leaf senescence. Explicit modelling of the effects of mites on dry matter partitioning may not be necessary., Spider mites (Acari: Tetranychidae) can severely reduce cotton lint yield (Wilson, 1993, and references cited therein). Mite effects on yield are primarily related to reduction in shoot growth which is, [...]

Two-spotted spider mites Tetranychus urdow Kock) are important pests of cotton (Gossypium hirsutum L.). The effects of mites on cotton photosynthesis have been investigated at the leaf and cytological levels but not at the canopy level. Our objective was to quantify the effects of timing and intensity of infestation by mites on cotton radiation-use efficiency (RUE). Leaf area, light interception, RUE, canopy temperature, and leaf nitrogen concentration (LNC) were assessed during two growing seasons in crops artificially infested with miles between 59 and 127 d after sowing. Normal and okra-leaf cultivars were compared. A mite index (MI = natural log of the area under the curve of mite number vs thermal time) was used to quantify the cumulative effects of mites on RUE, LNC, and canopy temperature. Crop growth reduction due to mites was greater in early- than in late-infested crops. Growth reduction was primarily due to reductions in RUE, but in the more severe treatments accelerated leaf senescence and, henca, reduced light interception also contributed to reductions in crop growth. At a given date, infested okra-leaf crop usually had greater RUE than their normal-leaf counterparts. Both plant types, however, responded similarly to a given level of mite infestation. The ability of the okra-leaf cultivar to maintain greater RUE Levels can be attributed, therefore, to its relative inhospitality for the development of mite colonies rather than to an intrinsically greater capacity to maintain photosynthesis under mite damage. Canopy temperature, LNC, and RUE showed a similar, biphasic pattern of response to MI. In the first phase, response variables were almost unaffected by mites. In the second phase, there was a marked decline in RUE and LNC and a marked increase in canopy temperature with increasing MI. These results suggest (i) some degree of compensatory photosynthesis at low to moderate levels of mite infestation, and (ii) reductions in RUE of mite-infested cotton crops involved alterations in both canopy gas diffusion and metabolic activity. Quantitative relationships between RUE and MI were developed that could be used to link mite and crop growth models., Spider mites (Acari: Tetranychidae) are important secondary pests in cotton cropping systems which rely heavily on use of insecticides for the control of primary pests (Hearn and Fitt, 1992). While [...]

The presence of distinct evolutionary lineages within herbivorous pest insect taxa requires close attention. Scientific understanding, biosecurity planning and practice, and pest management decision‐making each suffer when such situations remain poorly understood. The pest bug Nezara viridula Linnaeus has been recorded from numerous host plants and has two globally distributed mitochondrial (mtDNA) lineages. These mtDNA lineages co‐occur in few locations globally, and the consequences of their divergence and recent secondary contact have not been assessed. We present evidence that both mtDNA lineages of N. viridula are present in Australia and their haplotype groups have a mostly separate distribution from one another. The north‐western population has only Asian mtDNA haplotypes, and the population with an eastern distribution is characterized mostly by European mtDNA haplotypes. Haplotypes of both lineages were detected together at only one site in the north of eastern Australia, and microsatellite data indicate that this secondary contact has resulted in mating across the lineages. Admixture and the movement of mtDNA haplotypes outside of this limited area of overlap has not, however, been extensive. Some degree of mating incompatibility or differences in the climatic requirements and tolerances of the two lineages, and perhaps a combination of these influences, might limit introgression and the movement of individuals, but this needs to be tested. This work provides the foundation for further ecological investigation of the lineages of N. viridula, particularly the consequences of admixture on the ecology of this widespread pest. We propose that for now, the Asian and European lineages of N. viridula would best be investigated as subspecies, so that "pure" and admixed populations of this bug can each be considered directly with respect to management and research priorities. [ABSTRACT FROM AUTHOR]

This study investigated the olfactory responses of 3 thrips species [ Frankliniella schultzei Trybom, F. occidentalis Pergrande and Thrips tabaci Lindeman (Thysanoptera: Thripidae)] to cotton seedlings [ Gossypium hirsutum L. (Malvales: Malvaceae)] simultaneously damaged by different combinations of herbivores. Cotton seedlings were damaged by foliar feeding Tetranychus urticae Koch (Trombidiforms: Tetranychidae), Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), Aphis gossypii Glover (Hemiptera: Aphididae) or root feeding Tenebrio molitor L. (Coleoptera: Tenebrionidae). Thrips responses to plants simultaneously damaged by 2 species of herbivore were additive and equivalent to the sum of the responses of thrips to plants damaged by single herbivore species feeding alone. For example, F. occidentalis was attracted to T. urticae damaged plants but more attracted to undamaged plants than to plants damaged by H. armigera. Plants simultaneously damaged by low densities of T. urticae and H. armigera repelled F. occidentalis but as T. urticae density increased relative to H. armigera density, F. occidentalis attraction to coinfested plants increased proportionally. Thrips tabaci did not discriminate between undamaged plants and plants damaged by H. armigera but were attracted to plants damaged by T. urticae alone or simultaneously damaged by T. urticae and H. armigera. Olfactometer assays showed that simultaneous feeding by 2 herbivores on a plant can affect predator-prey interactions. Attraction of F. occidentalis to plants damaged by its T. urticae prey was reduced when the plant was simultaneously damaged by H. armigera, T. molitor, or A. gossypii and F. schultzei was more attracted to plants simultaneously damaged by T. urticae and H. armigera than to plants damaged by T. urticae alone. We conclude that plant responses to feeding by 1 species of herbivore are affected by responses to feeding by other herbivores. These plant-mediated interactions between herbivore complexes affect the behavioral responses of thrips which vary between species and are highly context dependent. [ABSTRACT FROM AUTHOR]

Cotton pest management in the Australian cotton industry was highly pesticide reliant from its inception in the early 1960s until the late 1990s. Aphids were controlled effectively over this period either co-incidentally by compounds applied against Helicoverpa spp. or by targeted applications of dimethoate/omethoate or pirimicarb in the late 1990s. By cotton season 1999-2000, after this prolonged period of selection, the cotton aphid Aphis gossypii Glover showed resistance to pirimicarb and cross resistance to dimethoate/omethoate as well as resistance to older organophosphates (profenofos, chlorpyrifos-methyl, chlorpyrifos-ethyl) targeted against Helicoverpa spp.. No new chemical controls were available so effective control required development of an insecticide resistance management (IRM) strategy incorporated with integrated pest management (IPM) strategies designed to maximalise any known selective disadvantage for resistant individuals. The IRM component emphasised rotation between insecticide mode of action (MOA) groups and limited the number of applications of any MOA. The IPM component incorporated farm hygiene to reduce overwinter hosts for resistant aphids, conserved natural enemies and incorporated effective use of pest sampling and thresholds. The aphid management strategy was fluid, evolving and adapting as new knowledge, new resistance and further IPM or IRM tactics became available. For instance, in 2007-2008 resistance was detected in aphids to the neonicotinoids resulting in field failures. Detection of neonicotinoid resistance required modifications to the aphid management strategy to address prolonged selection by both neonicotinoid seed treatments and foliar applications. The strategy also considered the need to manage concurrent pest species to mitigate the risk that insecticides sprayed against those pests would coincidently cause aphid outbreaks or select for resistance in aphids. The integrated strategy has now almost completely recovered susceptibility to IPM friendly pirimicarb and resistance to neonicotinoid insecticides has declined dramatically. [ABSTRACT FROM AUTHOR]

Thrips ( Thysanoptera: Thripidae) are important pests of seedling cotton and their damage can delay crop maturity and/or reduce yield. Plant resistance to thrips in cotton would reduce the need to treat crops with insecticides for their control. This would support integrated pest management strategies by reducing the risk of selecting insecticide resistance in concomitant pests and of disrupting the natural enemy complex. Traits that reduce thrips abundance in cotton are poorly understood, but dense leaf hairs and high gossypol content are implicated to negatively affect thrips. Furthermore, some diploid cottons are resistant against thrips. Thrips abundance and damage on a range of Gossypium ( Malvaceae) genotypes including hairy leaf, smooth leaf (glabrous), okra leaf shape, and diploid species was evaluated over four crop seasons. Thrips were significantly less abundant and they caused less damage on diploid cotton genotypes from Gossypium arboreum L. ( BM13H, Roseum A256), Gossypium thurberi Tod. ( GOS5310), and Gossypium trilobum (Moc. & Sess. ex DC.) Skov. ( GOS5332) than on the standard commercial Gossypium hirsutum L. cv. Sicot 71. There was no significant relationship between thrips abundance or damage and leaf hairiness, leaf hardness, or leaf shape, though conclusions about the value of these traits must be made cautiously as they are confounded across genotypes that differ in a range of traits simultaneously. The diploid cottons had a lower damage per thrips ratio, indicating that they are more tolerant of thrips feeding damage and thus could be valuable sources of host plant resistance to thrips. [ABSTRACT FROM AUTHOR]

We investigated the responses of 3 thrips species, Frankliniella schultzei Trybom, F. occidentalis Pergrande, and Thrips tabaci Lindeman (Thysanoptera: Thripidae) to herbivore-damaged and undamaged cotton seedlings ( Gossypium hirsutum L. [Malvales: Malvaceae]) at a range of time intervals following damage by adult Tetranychus urticae (Koch), adult T. ludeni (Zacher) (Acari: Tetranychidae) or Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae in olfactometer assays. The intensity/frequency of the response of thrips to herbivore-induced plants decreased with time and ultimately disappeared in all cases; however, the rate at which the response declined was related to the herbivore species that inflicted the damage. All 3 species of thrips were attracted to plants damaged by T. urticae for longer than they were to plants damaged by T. ludeni. The duration for which damaged plants remained attractive was also affected by the degree of damage inflicted on cotton seedlings. For example, F. schultzei was attracted to plants damaged by a higher density of two-spotted spider mites (100/plant) for much longer than to plants damaged by a lower density of these mites (50/plant). The results reinforce previous studies that demonstrate that arrangement of variables influences the responses of thrips to their herbivore-induced cotton host plants. Results also show that these responses are variable in time following herbivore damage to cotton plants, which further demonstrates how difficult it is to generalize about the functional significance of these interactions. [ABSTRACT FROM AUTHOR]

In a glasshouse trial with potted cotton plants grown from thiamethoxam-treated seed, neither 2.76 g a.i./kg seed (Cruiser®) nor 5.52 g a.i./kg seed ( Cruiser Extreme®) protected plants from neonicotinoid-resistant A phis gossypii Glover, 1877. Against susceptible A . gossypii each treatment was highly effective, providing control of >90% for 42 days. Continued use of either thiamethoxam treatment against resistant A . gossypii will select for resistant phenotypes and probably restrict the useful life of the neonicotinoid insecticides against this pest. In a separate trial, side-dressing of cotton seed with phorate 200 g/kg ( Thimet®) effectively provided plants with protection from susceptible A . gossypii. The insecticidal activity of phorate-treated plants against pirimicarb-resistant A . gossypii was not statistically different to untreated plants ( P > 0.05). To maintain the effectiveness of pirimicarb in the Australian cotton integrated pest management strategy, the use of phorate as an alternative pre-germination treatment to thiamethoxam for aphid control must be managed. We recommend that the first foliar spray applied to cotton treated with phorate at planting should not be pirimicarb or any other insecticide affected by insensitive cholinesterase ( ACE1) type resistance. [ABSTRACT FROM AUTHOR]

BACKGROUND The twospotted spider mite ( Tetranychus urticae Koch) is an important pest of cotton. This pest has a broad host range, but when changing between hosts an initial decline in fitness often occurs. This is usually followed by an increase in fitness after rapid adaptation to the new host, usually within five generations. RESULTS The generality of this adaptive response was tested by assessing elements of fitness when mites were reared on a host to which they were adapted ( Gossypium hirsutum L. cv. Sicot 71) or on a new host, Gossypium arboreum L. (accession BM13H). In a first experiment, mites reared on the new host for ten generations showed declining immature survival compared with those reared on the adapted host. In a second experiment, the intrinsic capacity for increase of mites cultured on the new host for six generations was significantly lower than that of mites cultured on the adapted host for six generations and then transferred to the new host. Hence, exposure to the new host for six or ten generations resulted in declining fitness. CONCLUSION This 'negative adaptation' indicates robust antibiosis traits in G. arboreum accession BM13H, which therefore have value in developing mite-resistant G. hirsutum cultivars. © 2014 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Two-spotted spider mites ( Tetranychus urticae Koch) oviposit near leaf veins or in leaf folds on the undersides of cotton ( Gossypium hirsutum L.) leaves where the humid boundary layer offers protection from desiccation. The authors predicted that the boundary layer of glabrous cotton leaves should be shallower than that of hairy leaves, providing some resistance to mites. The dynamics of mite populations, leaf damage, leaf gas exchange and crop yield on two leaf hair isolines (smooth versus hairy) in two genetic backgrounds was assessed. Mite colonies developed faster on the hairy leaf isolines, but leaf damage per mite was higher in smooth leaf isolines, indicating more intense damage. A 50% reduction in photosynthesis on the hairy isolines required 1.8 times more mites than smooth leaves. The yield of cotton was reduced in + mite treatments, but the magnitude of reduction was similar for hairy and smooth isolines. Paradoxically, the relative inhospitality of glabrous leaves may have induced mites to concentrate in protected leaf sections, causing more localised and more severe damage, negating the yield benefits from fewer mites. These results highlight interactions between leaf microenvironment, pest behaviour and plant productivity that may have implications for other instances of plant resistance. Copyright © 2010 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Cotton or melon aphid, Aphis gossypii Glover, is an important pest of cotton, and recently the neonicotinoid group of insecticides has provided a key option for control where they are used as seed treatments and foliar sprays. Here we document for the first time in Australian cotton, resistance to three neonicotinoids (acetamiprid, clothianidin and thiamethoxam) in A. gossypii via diagnostic discriminating concentration assays that were also associated with field control failure. Subsequent full log dose probit analysis on strains with discriminating dose survivors confirmed acetamiprid, clothianidin and thiamethoxam resistance at 6.4-, 10- and 22-fold, respectively. Further laboratory pressuring of strains caused acetamiprid resistance to significantly increase to 22-fold but resistance factors to clothianidin and thiamethoxam were unchanged. Clearly there is a need to reduce overall neonicotinoid selection to prevent or slow any increase in neonicotinoid resistance. An effective method to contain resistance would be to move away from the more persistent neonicotinoid seed dressings to either organophosphate or carbamate-based products and to limit the use of neonicotinoid foliar sprays. [ABSTRACT FROM AUTHOR]

The effects of production practices on the relative abundance of springtails (Collembola) in irrigated cotton fields of northern New South Wales (NSW) were studied over 2 yr to examine effects of farm management on these decomposer organisms. Pitfall trapping and soil core extraction was undertaken in both pseudoreplicated plots within whole fields on cotton farms and on experimental replicate plots of Envirofeast cotton and Lucerne. The relative abundance of surface-active springtails in cotton rows and densities of soil species from the rhizosphere were calculated. Twenty-three species of Collembola were collected from 5 fields, 19 in pitfall traps, and 11 in soil cores. Five species, Setogaster sp., Proisotoma minuta, Entomobrya unostrigata, Entomobrya multifasciata grp, and Lepidobrya sp. were numerically dominant on the ground at 86-96% of individuals and Mesaphorura sp., Folsomides parvulus, and Hemisotoma thermophila grp dominant in the soil. Native grassland samples contained 15 species of which a probable 10 were native and 8 were not found in cotton. Nineteen species of the 24 species identified from cotton were predominantly fungal feeders. Highest catches of Collembola occurred after flowering and soil Collembola increased with depth and during cotton growth on unsprayed plots but decreased on sprayed plots. Surface soil moistures affected daily catch rates with decomposing residues, crop stage, predator abundance, and season as secondary factors. Insecticide (endosulfan, pyrethroid, carbamate, and organophosphate) and predator effects were either negligible or unclear depending on the factor involved. Springtails appear to be predominately food limited during times of adequate soil moisture in cotton fields., (© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)