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Insect derivatives represent an important innovation in specialty crop risk management. An active over-the-counter market in insect derivatives will require a transparent pricing method. This paper develops an econometric model of the spatio-temporal process underlying a particular insect population and develops a pricing model based on this process. We show that insect derivatives can play an important risk management role in mitigating B. tabaci (whitefly) damage in cotton. Beyond developing a new risk management instrument, the key methodological contribution of this paper lies in pricing derivatives with stochastic properties in both space and time dimensions. Copyright 2008, Oxford University Press.

We used brightfield electron microscopy (BEM), differential interference con- trast microscopy (DICM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM) to investigate the stylet pathways of Bemisia tabaci during nymphal feeding behavior in cotton leaves beginning with penetration of the abaxial leaf surface and ending with stylets in sieve tubes in phloem tissues. Most nymphal stylets within salivary sheaths penetrating leaf tissues made complex turns and developed more than one salivary sheath branch before ending in sieve tubes. The external morphology of the salivary sheaths and their routes between and through leaf cells are described during the present study. Results showed the presence of the stylet within the sieve tubes. B. tabaci nymphs may remove stylets and feed in different sieve tubes. Ten short movies showing the progression of the stylet penetrations from adaxial surface to the sieve tubes are attached to Figures 8-15. The report and movies can be viewed from the internet. Download the movies to a local drive in your computer first for fast upload. The movies are posted on the website http://www.ars.usda.gov/Services/docs.htm?docid=14629. The movies can be used as a teaching aid in biology classes.

An outbreak of the sweetpotato whitefly, Bemisia tabaci (Gennadius), biotype B occurred in the Imperial Valley, California in 1991. The insects destroyed melon crops and seriously damaged other vegetables, ornamentals and row crops. As a result of the need for sampling technology, we developed a whitefly trap (named the CC trap) that could be left in the field for extended time periods. We used the traps to monitor populations of B. tabaci adults during year-round samplings from 1996 to 2002 to study variations in the weekly trap catches of the insect. The greatest number of B. tabaci adults was recorded in 1996, followed by a continuing annual decrease in trap catches each year through 2002. The overall decline of B. tabaci is attributed in part to the adoption of an integrated pest management (IPM) program initiated in 1992 and reduced melon hectares from 1996 to 2002. Other factors may also have contributed to the population reductions. Seasonally, B. tabaci trap catches decreased during the late summer and fall concurrent with decreasing minimum tempera- tures that are suggested to be a significant factor affecting seasonal activity and reproduction.

We examined the patterns of male pink bollworm (PBW), Pectinophora gossypiella (Saunders), moth catches in gossyplure-baited traps over a 15-year period from 1989 to 2003 in the Imperial Valley, California, USA. Monitoring was conducted during periods when different pink bollworm areawide control strategies were being used. Numbers of male pink bollworm moths caught in gossyplure-baited traps progressively decreased each year from 1990 to 1994 during short-season cotton production. High numbers of male moths caught in traps from 1995 to 1997 may have been related to moth migrations from the large cotton acreages grown in the Mexicali Valley bordering the Imperial Valley. Transgenic Bollgard® (Bt) cotton was planted in 3% of the cotton area in 1996 and thereafter in 80%–94% of the cotton area from 1997 to 2003. Pink bollworm moth trap catches were significantly lower from 1998 to 2003 than catches in 1995 to 1997, except for 1999. The trapping results suggested that Bt cotton had significant input on reduction of pink bollworm populations, confirming results of other investigators and providing additional documentation on the benefits of the Bt cotton culture.

Scirtothrips dorsalis (Hood) (Thysanoptera: Thripidae) is a recently identified invasive pest to the Caribbean and poses a significant threat to agriculture and trade in the region. Methods are needed to detect the presence and to monitor populations of this pest so that it can be effectively managed. Three different CC trap base colors (blue, yellow, and white) with or without dichlorvos as a killing agent, and a newly developed and named the Blue-D trap were studied in Taiwan and St. Vincent for attraction and capture of S. dorsalis. In lemons in Taiwan, mean numbers of S. dorsalis caught in Blue-D traps were greater compared with dichlorvos cube modified CC traps. In St. Vincent chili pepper plantings, the Blue-D traps caught more Thrips palmi (Karny), Frankliniella sp., and Microcephalothrips abdominalis (Crawford) than dichlorvos cube modified CC traps. More Frankliniella intonsa (Trybom), Megalurothrips usitatus (Bagnall), T. palmi, Frankliniella sp., and M. abdominalis were caught in blue and white base CC traps than yellow base CC traps. Average captures per CC trap per week were 0.07 and 0.02-0.09 S. dorsalis in Taiwan and St. Vincent, respectively. There were no differences in S. dorsalis captures in white, blue, or yellow base CC traps. The average weekly S. dorsalis catch for yellow sticky card traps was 19.8. CC traps can be used for detection of S. dorsali and collecting intact S. dorsalis for taxonomic and genetic determinations when a few of the species are found in a large commercial production area. Yellow sticky traps can be used for monitoring S. dorsalis populations. A combination detecting system of visual observation, yellow sticky traps, and CC traps may be an effective S. dorsalis population detecting and monitoring system.

Various trap types were evaluated for catching western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and hoverflies (Diptera: Syrphidae). More western flower thrips were attracted to blue (458-nm peak reflectance) sticky card traps compared with yellow (560 nm) or white sticky card traps. Blue light-emitting diodes (LEDs; 465-nm peak emission) increased the efficacy of blue sticky card traps for catching western flower thrips. Numbers of western flower thrips caught on blue flat rectangular card traps were increased 2.0–2.5 times when cards were equipped with blue LEDs. Hoverflies adults are pollinators, and larvae are natural enemies of aphids and other pest insects. Hoverfly adults were attracted to blue sticky card traps. Nylon screen cages effectively excluded the hoverflies from the blue sticky card traps.

Insects in a commercial poinsettia (Euphorbia pulcherrima) greenhouse were monitored with yellow sticky card (YC) traps and YC equipped with 530-nm lime green light-emitting diodes (LED-YC) traps from 3 June to 25 Nov. 2002. Pest insects were: dark-winged fungus gnat (Bradysia coprophila), sweet potato whitefly (Bemisia tabaci) biotype B (= B. argentifolii), western flower thrips (Frankliniella occidentalis) and leafhopper (Empoasca sp.). Natural enemies were: minute pirate bug (Orius tristicolor), parasitic wasps (Hymenoptera), and rove beetles (Staphylinidae). Over the 24 weeks of the experiment, LED-YC traps captured more dark-winged fungus gnats, sweet potato whiteflies, leafhoppers, and rove beetles compared with YC traps. Capture of western flower thrips, minute pirate bugs, and parasitic wasps were not significantly increased on the YC traps equipped with LEDs. The results indicate that the LED-YC traps attract three major pest insects in poinsettia greenhouses and do not catch more beneficial, minute pirate bugs and parasitic wasps, but may catch significant number of rove beetles. The results suggest that LED-YC traps may be useful to monitor and reduce pest populations in greenhouses.

Equipping the standard plastic cup trap, also known as the CC trap, with lime-green light-emitting diodes (LED-plastic cup trap) increased its efficacy for catching Bemisia tabaci by 100%. Few Eretmocerus eremicus Rose and Zolnerowich and Encarsia formosa Gahan were caught in LED-plastic cup traps. The LED-plastic cup traps are less expensive than yellow sticky card traps for monitoring adult whiteflies in greenhouse crop production systems and are more compatible with whitefly parasitoids releases for Bemisia nymph control.

Size and weight measurements were made for all the life stages of Bemisia tabaci (Gennadius) B biotype from field grown cotton (Gossypium hirsutum L.) and cantaloupe (Cucumis melo L., var. cantalupensis) in Phoenix, AZ and Fargo, ND, USA in 2000 and 2001. Nymphal volumes were derived from the measurements. The average nymphal volume increase for settled 1 st to the late 4th instar was exponential. The greatest increase in body volume occurred during development from the 3rd to early 4th instar. Nymphs on cotton leaves were wider, but not longer compared with those on cantaloupe. Ventral and dorsal depth ratios of nymphal bodies from 1 st to late 4th instars from cantaloupe leaves were significantly greater compared with those from cotton leaves. During nymphal development from 1st to 4th instar, the average (from the two host species) ventral body half volume increased by nearly 51 times compared with an increase of 28 times for the dorsal body half volume. Adult female and male average lengths, from heads to wing tips, were 1 126 µm and 953 µm, respectively. Average adult female and male weights were 39 and 17 µg, respectively. Average widths, lengths, and weights of eggs from cotton and cantaloupe were, 99 µm, 197 µm, and 0.8 µg, respectively. Average widths, lengths, and weights for exuviae of non-parasitized nymphs from both cotton and cantaloupe were 492 µm, 673 µm, and 1.20 µg, respectively; and widths, lengths, and weights of parasitized nymph exuviae were 452 µm, 665 µm, and 3.62 µg, respectively. Both exuviae from non-parasitized and parasitized nymphs from cotton leaves were wider, longer, and heavier than those from cantaloupe leaves. © 2017 Wiley. All rights reserved.

Studies were conducted in 1994 and 1995 to examine the effects of a range of action thresholds for managing Bemisia tabaci (Gennadius) Biotype B (= B. argentifolii Bellows & Perring) with insecticides in cotton on populations of arthropod predators in Imperial Valley, CA, and Maricopa, AZ. Application of insecticides significantly reduced population densities of spiders, Geocoris punctipes (Say), G. pallens (Stal), Orius tristicolor (White), Nabis alternatus Parshley, Zelus renardii Kolenati, Hippodamia convergens Guerin-Meneville, Spanogonicus albofasciatus (Reuter), Drapetis sp., and Chrysoperla carnea Stephens in one or both years and sites compared with untreated controls. Use of higher B. tabaci thresholds conserved some species and groups relative to lower thresholds. Stepwise regression analyses indicated that reductions in predator populations were generally influenced more strongly by the timing of the first insecticide application than by the total number of sprays necessary to maintain suppression of the pest below any given action threshold. A predation index, which weights the importance of each predator species based on their known frequency of predation on B. tabaci and another key pest, Pectinophora gossypiella (Saunders), was developed and analyzed. Patterns were similar to results based on changes in abundance alone, but the index generally revealed less severe effects of insecticides on overall predator function. The current action threshold for conventional insecticidal control of B. tabaci in Arizona and southern California is five adults per leaf. Results here suggest that predator conservation may be enhanced by raising the initial threshold to delay the first application or initially using more selective materials such as insect growth regulators.

We compared smooth-leaf okra- and normal-leaf upland cotton (Gossypium hirsutum L.) strains and cultivars for susceptibility to colonization by Bemisia tabaci (Gennadius) biotype B. Experiments were conducted at seven field sites, five at Holtville, CA, and two at Maricopa, AZ, during 1996-2000. Okra-leaf strains and cultivars, as a group, had lower numbers of adults, eggs, and nymphs compared with normal-leaf strains and cultivars indicating the potential of okra-leaf genetic traits for reducing colonization by B. tabaci. Results also suggest that okra-leaf shape may provide less favorable micro-environmental conditions for the habitat of B. tabaci because of more open canopy as evidenced by higher leaf perimeter to leaf area ratio. The okra-leaf cultivar 'Siokra L-23' appears to have genetic traits that should be examined further as a source of B. tabaci resistance.

Silverleaf whitefly, Bemisia argentifolii Bellows & Perring, adults and nymphs feed on the phloem tissue of host plant leaves. Infested leaves were rapidly fixed to prevent the insects from withdrawing their mouthparts. The adult stylet bundle enters the labial groove of the labium between the first and second segments and is completely contained within the labium except during feeding. Stylet length is equal to the combined length of labial segments 2, 3, and 4. Stylet penetration can be determined by examining the position that the stylet enters the labial groove. The physical force necessary for adult stylet penetration is derived from changes in the position of the whitefly head during feeding. The head is bent over the labium, which is attached to the leaf surface, forcing the stylet bundle down the labial groove and into the host tissue. Nymphal stylet lengths were found to be longer than previously reported, and of sufficient length to reach the phloem tissue in cotton and hibiscus leaves from essentially any position on the abaxial leaf surface.

The relationships between leaf trichome densities, leaf age, and sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype B, infestations of 13 upland cotton, Gossypium hirsutum L., cultivars were investigated in 1990 and 2000. Stoneville 474 supported higher numbers of B. tabaci biotype B eggs, nymphs and adults, and also had higher numbers of stellate trichomes on abaxial leaf surfaces compared with other cotton cultivars. Siokra L-23, in general, had fewer stellate trichomes and also fewer whiteflies. However, the positive trichome–whitefly density relationships were affected by the ages of leaves from different main stem cotton nodes. The youngest leaves on main stem node 1 below the terminal for all cultivars had higher numbers of stellate trichomes but fewer whiteflies compared with older leaves.

Adult whitefly Bemisia argentifolii Bellows & Perring trap (CC trap) catches were compared with suction type trap catches. CC trap catches were significantly correlated to the suction trap catches. Higher numbers of B. argentifolii adults were caught in CC traps oriented toward an untreated, B. argentifolii-infested, cotton field as compared with traps oriented toward Bermuda grass fields, farm roads, or fallow areas. CC trap catches at five heights above ground (from 0 to 120 cm) were significantly related to each other in choice and no-choice studies. CC trap catches were low in the Imperial and Palo Verde Valleys from late October to early June each of 1996, 1997, and 1998. Trap catches increased with increasing seasonal air temperatures and host availability. Trap catches were adversely affected by wind and rain. Abrupt trap catch increases of 40- to 50-fold for 1–2 d in late June to early July followed by abrupt decreases in adult catches suggest migrating activity of adults from other nearb...

We compared Bemisia argentifolii Bellows & Perring colonization on Stoneville (ST) 474 and Deltapine (DPL) 5415 cottons, Gossypium hirsutum L., in the field. We also examined leaf trichome density, leaf age, and leaf morphological characteristics as possible factors influencing cultivar host selection. The increased numbers of all B. argentifolii life stages on ST 474 in the field appeared to be related to the higher trichome density on abaxial leaf surfaces compared with DPL 5415. In both cultivars, leaves from node number 1 below the terminals were smaller and had higher vascular bundle densities and numbers of lysigenous glands than older, larger leaves. Younger leaves also had smaller leaf areole areas, more terminal vein endings per unit leaf area, and shorter distances from abaxial leaf surfaces to minor vein phloem tissues compared with older leaves. These younger leaf morphological characteristics may contribute to the higher B. argentifolii densities on younger leaves. In the laboratory, electronically monitored adult females and visually monitored settled first and fourth instars preferred to probe into secondary and tertiary leaf veins as compared with main and primary leaf veins.

Five upland cotton, Gossypium hirsutum L., cultivars, Deltapine (DPL) 50, 5415 and 5432, Fibermax 832 and Siokra L23, were studied in relation to silverleaf whitefly, Bemisia argentifolii Bellows and Perring, oviposition and colonization. Deltapine 5415 and 5432 had the highest numbers of eggs and nymphs and Siokra L-23 the lowest. Siokra L-23 also had the lowest number of adults compared to the other four cultivars. Over 75% of eggs were oviposited on leaf surfaces between veins and 23% were oviposited in veins that were ≤4 cells wide. Few eggs were found on veins that were five or more cells wide. No eggs were inserted into leaf stomata.

In plant-insect interaction experiments, a clip cage is frequently used to isolate insects or other small pests on a leaf. Clip cage effects on the physiology of the leaf could possibly confound experimental results. Our objective was to quantitate the effects of an insect clip cage of the type typically used for small pests such as whiteflies (Bemisia sp.), aphids (Aphis sp.) and mites (Urticae sp.) on the photosynthetic traits of cotton (Gossypium hirsutum L. cv. Coker 100A-glandless) and muskmelon (Cucumis melo L. cv. Imperial 45) leaves. Clip cages that enclosed 11.3 cm 2 of both the abaxial and adaxial sides of a leaf were attached to young fully expanded leaves. For the leaf tissue within the clip cage, incident radiation was decreased and leaf temperature was increased. After 24 h, chlorophyll content of tissue within the clip cage was significantly increased compared with noncaged-control samples taken from the opposite half of the same leaf. Three days after clip cages were attached to leaves, compared with controls, the tissue within the cage had a lower light-saturated, steady-state CO 2 exchange rate (CER) and leaf soluble protein content. The cage effect on CER and soluble protein could be explained, at least in part, by decreased light-saturated initial Rubisco activity for leaf tissue within the clip cage. We conclude that the clip cages caused physiological and biochemical alterations of leaves that could alter insect nutrition. Thus, it is suggested that clip cage effects on leaf physiology and microenvironment must be considered when interpreting results of plant-insect interaction experiments.

A study of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) midgut structures and contents was conducted using scanning and transmission electron microscopy. The larval midgut was enclosed by a peritrophic membrane that seemed to be composed of two layers. Numerous bacteria were found throughout the lumen of the midgut, and because the midgut does not open to the hindgut, we hypothesized that the bacteria may serve to decompose the residues occurring in the midgut lumen. Few yeast cells were present in the larval midgut. The visual observations suggest that the concentration of bacteria were much lower in adult midguts than in larval midguts. However, many yeast cells were observed in the lumen of the adult midgut. No obvious peritrophic membrane was observed in electron micrographs of the adult midgut compared with the larval midgut. The results suggest different modes of food residue disposal.

Action thresholds for whiteflies, Bemisia argentifolii Bellows & Perring on cotton, Gossypium hirsutum L., are being developed to determine the whitefly densities at which cotton should be treated with insecticides to prevent lint yield losses. However, the effects action threshold treatments have on cotton photosynthesis have not been determined. Changes in the photosynthetic rate of cotton can be used to assess damage to cotton early in the season before lint is harvested. In this study photosynthetic rates and stomatal conductance of cotton treated at 4 different action thresholds for whiteflies were measured 12 times during July and August 1995 in the Imperial Valley of California using a portable photosynthesis system. Action thresholds were 2.5, 5, 10, and 20 adults per leaf. Untreated control plots were also used for comparison in a 5 × 5 Latin square design. Adult, egg, and nymphal whitefly densities on untreated cotton were significantly higher than those on all other treatments. In general, no differences in densities of any stage were seen among the 2.5, 5, and 10 treatments. Densities from the 20 treatment were variable. Photosynthetic rates of untreated cotton leaves were usually significantly lower compared with those of 2.5, 5, and 10 treatments. In general, no significant differences in photosynthetic rates were seen among the 2.5, 5, and 10 treatments. Photosynthetic rates of leaves from the 20 treatment were significantly lower and higher than leaves from the other treatments and the untreated control, respectively, on some dates. In general, no significant differences were detected in stomatal conductance among the 2.5, 5, and 10 treatments, and results were similar to those seen with photosynthesis. Based on photosynthetic rates and stomatal conductance, measurable physiological damage to cotton leaves occurs between action thresholds of 10–20 adult whiteflies per leaf.

Field studies were conducted during 1993 and 1994 in the Imperial Valley, California and Maricopa, Arizona to examine relationships between densities of Bemisia tabaci (Gennadius) populations and cotton (Gossypium hirsutum L.) yields, and to estimate economic injury levels (EILs) for pest management application. Populations of B. tabaci were manipulated by applying different numbers of insecticide applications in replicated plots. Resulting insect populations and cotton lint yields were used to develop damage functions and to estimate EILs for all life stages in relation to variable cotton prices, insecticide costs, and pest control efficacy. Economic injury levels declined with increasing cotton prices and increased as the cost of control increased, however, these changes were relatively small, based on typical ranges in price and control costs. In contrast, the efficacy of control provided by insecticide applications had a large influence on EILs, with lower efficacies being associated with higher injury levels. We developed a multiple regression model that accounted for the dynamic changes in the EIL in relation to crop price, control costs, control efficacy, and potential yield. Based on average prices and reasonable control costs and efficacy, EILs ranged from 5.9–15.2 adults/leaf, 6.1–19.8 eggs cm−2, and 1.7–4.7 nymphs cm−2 of leaf area. Additional research is needed to more closely relate the costs of control to the suppression of insect populations, and to define economic thresholds that will enable pest managers to maintain pest populations below EILs.

Honeydew secretion by nymphal field populations of silverleaf whitefly, Bemisia argentifolii Bellows & Perring, on cotton was documented during 10-, 14-, or 24-h periods in the Imperial Valley, California. Honeydew drops were collected on water-sensitive paper by placing 5th main stem node leaves inside open-ended plastic bags with strips of paper. Honeydew drops were also collected directly on open-ended plastic bags placed on leaves, and honeydew sugars were analyzed using gradient anion-exchange high performance liquid chromatography. No consistent diurnal patterns of honeydew drop secretion emerged, but on 1 of the 4 d drop numbers were higher in the morning (0500-1100 hours) than in the afternoon and evening (1500-1900 hours), and drops were collected throughout one 24-h period. On 3 of the 4 d, higher quantities of honeydew sugars were collected in the morning (0500 hours) than in the evening (1500-1900 hours). Quantities and percentages of honeydew sugars ranked as follows: trehalulose > melezitose > sucrose > fructose > glucose. This ranking, with minor exceptions, did not change during the day (0500-1900 hours). Trehalulose accounted for approximately 30% of the total sugar mass in the honeydew. Honeydew sugar secretion and composition did not show a clear or consistent relationship with either leaf water potentials or temperatures.

This study revealed strong evidence that nymphs of the silverleaf whitefly, Bemisia argentifolii Bellows and Perring, are obligate feeders on vascular bundles and that there are large differences between different host plants as to the availability of vascular bundles to silverleaf whitefly nymphs. The relationship between nymphs and leaf vascular bundles was studied using 1) leaf sectioning and 2) techniques of leaf clearing of intact leaves. A geometric model is presented of the feeding relationship of vascular bundle-using homopterans. The relative abundance of vascular bundles was examined in six species of host plants that varied from highly preferred to tolerably acceptable. Included in order of acceptance were cantaloupe, cotton, hibiscus, broccoli, lantana and lettuce. The length of vascular bundle per 1.0 mm 2 of leaf surface ranged from about 10 mm in cantaloupe to 2.8 mm in lettuce. Salivary sheaths were found to connect with vascular bundles in 100% of the intact nymphs examined by the staining and clearing technique. However only 64% of those examined by the sectioning technique appeared to be connected to vascular bundles. This indicates that the sectioning technique leads to a high rate of error, causing an underestimation of the importance of direct contact with vascular bundles. About 50% of epidermal stylet penetrations were through epidermal cells ; the remaining 50% went through intercellular junctions. On cotton leaves, the distance between the point of labial contact with the leaf surface and the nearest point of the vascular bundle rarely exceeded 60 μm. Our studies show that while 50% of lettuce leaf-surface was beyond 60 μm of a vascular bundle, only 10% of cantaloupe leaf surface area was outside of the 60 μm range. In cotton, mean distance from labium to the nearest point of the vascular bundle was 40.9 μm (SEM = 2.66, N = 50, range 0-80 μm). Over 98% of all salivary sheaths went to minor veins (78% to single-filament vascular bundles, nearly 20% to double filament bundles). Fewer than 2% went to bundles with 3 or more filaments.

In irrigated desert areas of the southwestern USA, fruiting of cotton (Gossypium hirsutum L.) typically peaks in July. Water management during the fruiting period can influence cotton lint yields. This study tested the hypothesis that small frequent irrigations during the July peak fruiting stage would increase fruit set and yields compared with the same amount of water applied less frequently. During 3 yr under a short-season production system, irrigation intervals of 5-d with 42 mm of water applied at each of six irrigations increased lint yield by 5 to 11% compared with irrigation intervals of 10- and 15-d with 81 and 130 mm of water applied at each of three and two irrigations, respectively. Average stomatal conductance of 1989 and 1991 was higher for the 5-d-irrigation interval than for 10- or 15-d intervals. For 1990 and 1991 average leaf water potentials were higher and average leaf temperatures were lower for the 5-d-irrigation interval than for the other two irrigation intervals. The results show that with the same amount of water conventionally applied through furrow irrigation, small frequent irrigations during cotton fruiting were effective in reducing water deficit during critical growth stages and increasing lint production. The small frequent irrigations did not increase soil salt content in the top 15 cm of soil after 3 yr of study.

Bemisia argentifolii Bellows & Perring preferred cantaloupe, Cucumis melo var. contalupensis L. , to cotton, Gossypium hirsutum L. , broccoli, Brassica oleracea Var. botrytis L. , and lettuce, Lactuca sativa var. capitata L. , in 1992 and 1993 in field and greenhouse studies. In the absence of cantaloupe, B. argentifolii preferred cotton to broccoli and lettuce, respectively. More eggs and fewer nymphs were found on broccoli than on cotton in the field. Differences in relative abundance of vascular bundles per unit of leaf area among the four plant species may partly account for differences in oviposition site selection. Vascular bundle volume per unit of leaf tissue volume was 50% greater in cantaloupe than in cotton and broccoli, which in turn had significantly greater volumes than lettuce. Field studies showed that most B. argentifolii on cotton and cantaloupe leaves were found on lower leaf surfaces. Distances from upper and lower leaf surfaces to the nearest vascular bundles in cotton leaves were 131and 60 µm, respectively. This distribution favors oviposition and feeding on the lower surface of a leaf. Leaf structure, positive effect of gravity,and negative effect of light affected oviposition site preferences in laboratory studies.

Pink bolloworm (Pectinophora gossypiella Saunders), and associated secondary insect pests have dramatically reduced cotton (Gossypium hirsutum L.) production in the Imperial Valley of California, resulting in mandated short-season cotton production practices. Application of a a chemical defoliant and/or a growth regulator in August or September is an important component of the short-season system. Studies were conducted to determine the effectiveness of various chemical defoliants on cotton lint yield, leaf abscission, and reduction of late-season fruiting forms under a short-season production system in the Imperial Valley (...)

Cotton (Gossypium hirsutum L.) growers use significant quantities of insecticides to control pink bollworm (PBW), Pectinophora gossypiella (Saunders). The germplasm line WC-12NL (nectariless, okra leaf, and early maturing) and «Deltapine 61» (nectaried, normal leaf, and later maturing) were grown at Maricopa, AZ, and Brawley, CA, for three seasons. Irrigation water was terminated and plots were defoliated earlier than normal, a practice that favored the early-maturing line. Insecticides were applied as needed, based on PBW egg infestations of cotton bolls. The major objective was to determine whether insecticide use can be reduced or eliminated by growing WC-12NL

After ethephon and thidiazuron were applied in late season to small plots of Upland cotton ( Gossypium hirsutum L.) to terminate fruiting chemically, the numbers of green bolls and pink bollworm, Pectinophora gossypiella (Saunders), diapausing larval populations, and yields were determined. Tests were conducted during 1985 and 1986 on the Maricopa Agricultural Center, Maricopa, Ariz., and on the Irrigated Desert Research Station, Brawley, Calif. Also, at Brawley in both years, we determined the combined effects of early irrigation cut-off and chemical termination. Results show that rates of 1.12 kg (AI)/ha of ethephon or higher and rates of 0.056 or 0.112 kg (AI)/ha of thidiazuron were needed for effective termination of cotton fruiting as indicated by reductions in number of green bolls. These rates of each chemical also reduced the number of squares and blooms after treatment, and sequential applications resulted in greater reductions than a single application. Last irrigation in mid-July resulted in reduced yields. However, irrigation cut-off in late July or early August resulted in yields as high as when the last irrigation was in September. Yields were not reduced by chemical termination treatments except by thidiazuron at Brawley in 1986, when last irrigation was in mid-July. Diapausing pink bollworm larval populations were reduced by chemical termination treatments and early irrigation termination.

(...) Results indicated that cotton plants stems were high in NRA relative to leaf blades, except at the seedling stage. Samples taken from 35 cultivars and breeding lines in the same year under the same environmental conditions showed that the petiole NRA was high at the early flower bud stage. The petiole's average contribution of 52% of the total NRA of the top mature leaf indicates that petiole NRA may be useful as an indicator of N metabolism at the early flower bud stage of development

During 1996, 1997, and 1999, studies were conducted in cotton, sugar beets, alfalfa, yardlong bean, and peanut fields to compare insect catches in CC traps equipped with different trap base colors. The studies were conducted in southwestern United States, China, and India. The nine colors, white, rum, red, yellow, lime green, spring green, woodland green (dark green), true blue, and black, varied in spectral reflectance in the visible (400–700 nm) and near-infrared (700–1050 nm) portions of spectrum. Lime green, yellow, and spring green were the three most attractive trap base colors for silverleaf whitefly, Bemisia argentifolii Bellows & Perring, and leafhopper, Empoasca spp. adults. The three trap base colors were moderately high in the green, yellow, and orange spectral regions (490–600 nm), resembling the spectral reflectance curve of the abaxial (underleaf) surfaces of green cotton leaves. True blue and white were the most attractive trap base colors for western flower thrips, Frankliniella occidentalis (Pergande), adults. The true blue and white trap bases were moderately high in the blue spectral region (400–480 nm).

A whitefly trap recently developed by Chu and Henneberry was tested in a cantaloupe field at the University of Arizona Maricopa Agricultural Center in 1995. The trap was compared with a 3 × 5-inch yellow sticky card trap, a commercial dome trap, and the leaf-turn sampling method. Results showed that the new whitefly trap effectively caught adults in cantaloupes. Numbers of adults increased as whitefly adult population densities increased during the season. Numbers of adults caught by the new whitefly trap were comparable to numbers of adults caught with the commercial dome trap and to a lesser extent the counts of adults determined by leaf-turn sampling method. Results with the new trap were not comparable to adults caught with yellow sticky card traps.

Germination of fruit of common lambsquarters(Chenopodium albumL.) from three out of four sources was enhanced by 9 to 41% by removal of the fruit coat, and by 21% by washing the fruit for 70 h. Brown-black seed germinated more rapidly than the black and brown seed after washing for 70 h. The washing treatment appeared to remove some unknown inhibitors. After washing, seed germination was found to be positively correlated with seed size.

Greenhouse studies were conducted to determine the potential of nitrate reductase activity (NRA) as an indicator of the change of N concentration of cotton (Gossypium hirsutum L.) shoots. The results showed that cotton petiole in vivo NRA was not significantly different from NRA in leaf blades during vegetative growth (...)

To investigate fertilizer injury to potatoes under field conditions, a three year study from 1979 to 1981 was undertaken in Central New York. The study was carried out on a well drained Howard gravelly silt loam; pH 6.6–6.8 with high organic matter (6.1–6.4%) and cation exchange capacity (CEC) of 13.4–14.9. When applied at a normal rate equivalent to 1,685 kg/ha of 10-15–15-1.2 the blended fertilizer containing urea N did not significantly reduce the tuber yield compared to ammoniated fertilizer and blended fertilizer containing ammonium nitrate (AN). However, when it was placed in contact with the seedpiece, the urea delayed emergence and early growth of the plant. Fertilizers containing urea-diammonium phosphate (DAP) and ureatriple superphosphate (TSP), applied at higher than normal rates and placed in contact with the seedpiece, significantly delayed emergence and reduced tuber yield.

Nitrate reduction on a leaf fresh weight basis was measured in common lambsquarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.) in individual leaves as a function of the photosynthetic photon flux density (PPFD) under which the plants were grown. Common lambsquarters had greater rates of nitrate reduction than did redroot pigweed regardless of leaf age or PPFD and responded to a significantly greater degree when PPFD was increased, with a proportionately greater increase in nitrate reduction among younger leaves.