Feeding and maturation by soybean looper (Lepidoptera: Noctuidae) larvae on soybean affected by weed, fungus, and nematode pests

Feeding and maturation by the soybean looper, Pseudoplusia includens (Walker) (Lepidoptera: Noctuidae), were investigated in a 2-yr study on \u27Davis\u27 soybean, Glycine max (L.) Merr., grown alone and combined with the weed hemp sesbania, Sesbania exaltata (Raf.) Rybd. ex. A. W. Hill, the root-knot nematode, Meloidogyne incognita (Kofoid & White) Chitwood, and the charcoal rot fungus, Macrophomina phaseolina (Tassi) Goid. Of the three pests, hemp sesbania had the greatest effects on plant growth and insect feeding and maturation. When fed foliage from soybean stressed by hemp sesbania, soybean looper larvae remained longer in feeding stages, consumed more foliage, and showed altered weight gain compared with larvae fed control foliage. Results suggest that nutrient(s) critical for proper development of larvae may have been limited in weed-stressed soybean foliage. Less dramatic results were observed when larvae fed on foliage from soybean with roots colonized by the charcoal rot fungus. Such larvae consumed more foliage, weighed more, and showed a slight increase in larval feeding period, but only in 1 yr of the study. Colonization of soybean roots by the root-knot nematode had no consistent effects on either the soybean host or insect

Rice and other cereals

On a worldwide basis, rice is consumed daily by more people than any other single food crop. The economic value of losses, even minor ones such as those caused by the stem rot and leaf scald fungi, translate into millions of dollars on a global basis. Minimizing losses sustained from major agricultural pest species such as nematodes will remain a major responsibility of plant protection scientists. The challenge will be to employ traditional pest management strategies and tactics including the use of pesticides, in an environmentally responsible manner. At the same time, agricultural production systems must be developed that employ the most current technologies available, exploit biological competition among microorganisms for the suppression of pathogens, and focus on long-term crop sustainability instead of short-term profitability. Management of nematodes of barley, oat, and rye relies heavily on the use of resistant cultivars

Influence of plant-parasitic nematodes on growth of St. Augustine and centipede turfgrasses

During the spring, summer and fall (May-November) of 2011 and 2012, 100 residential lawns in East Baton Rouge Parish, LA, were sampled to document the incidence and abundance of plant-parasitic nematode communities. Genera of nematodes associated with St. Augustine and centipede turfgrasses included Criconemella, Helicotylenchus, Meloidogyne, Pratylenchus, Tylenchorhynchus, and Tylenchus. Damage potentials of Meloidogyne incognita and Pratylenchus zeae individually were evaluated in subsequent greenhouse trials. Across nematode infestation levels of 200 and 2,000 individuals, reductions in final plant weight below controls for St. Augustine and centipede averaged 24% and 28%, respectively, for M. incognita and 37.0% and 39.3% for P. zeae; indicating that overall, P. zeae was more damaging to both turfgrasses than M. incognita

The elusive search for reniform nematode resistance in cotton

The reniform nematode (Rotylenchulus reniformis Linford and Oliveira) has emerged as the most important plant-parasitic nematode of cotton in the United States cotton belt. Success in the development of reniform nematode-resistant upland cotton cultivars (Gossypium hirsutum L.) has not been realized despite over three decades of breeding efforts. Research approaches ranging from conventional breeding to triple species hybrids to marker-assisted selection have been employed to introgress reniform nematode resistance from other species of cotton into upland cultivars. Reniform nematode-resistant breeding lines derived from G. longicalyx were developed in 2007. However, these breeding lines displayed stunting symptoms and a hypersensitive response to reniform nematode infection. Subsequent breeding efforts focused on G. barbadense, G. aridum, G. armoreanum, and other species that have a high level of resistance to reniform nematode. Marker-assisted selection has greatly improved screening of reniform nematode-resistant lines. The use of advanced molecular techniques such as CRISPER-Cas9 systems and alternative ways such as delivery of suitable cry proteins and specific double-stranded RNA to nematodes will assist in developing resistant cultivars of cotton. In spite of the efforts of cotton breeders and nematologists, successes are limited only to the development of reniform nematode-resistant breeding lines. In this article, we provide an overview of the approaches employed to develop reniform nematode-resistant upland cotton cultivars in the past, progress to date, major obstacles, and some promising future research activity

Influence of soil nutrients on reproduction and pathogenicity of rotylenchulus reniformis on cotton

Greenhouse and field studies were conducted to evaluate the effect of soil nutrients on reniform nematode (Rotylenchulus reniformis) reproduction and pathogenicity on cotton (Gossypium hirsutum). Initial greenhouse studies examined phosphorus (P) and potassium (K) at very low (10 or 44 mg kg -1) and high (50 or 123 mg kg-1) levels, respectively. Phosphorus produced significant increases in plant height and shoot and root dry weights as well as significant reductions in numbers of nematodes in soil and eggs from roots. Subsequent greenhouse studies evaluated increasing levels of P (10, 20, 35, 60, and 73 mg kg-1), K (44, 70, 106, 123, and 153 mg kg-1), and sulfur (S) at 3, 12, 20, 40, and 50 mg kg-1 on cotton growth and nematode reproduction. Phosphorus significantly increased plant height at 15 and 30 d and shoot and root weights at 60 d. Potassium and S had no effect on plant growth with the exception of the highest level of S, which significantly reduced plant height and shoot dry weights. Overall, as P level increased, reproduction of the reniform nematode decreased. Potassium and S, irrespective of level, had no effect on densities of eggs or soil stages of the nematode. Field trials with cotton included combinations of P at 44.8 or 112 kg ha-1 and S at 5.6 or 22.4 kg ha-1 with or without 1, 3-dichloropropene at 28.1 L ha-1. Nematicide application significantly reduced nematode population density at mid-season and harvest in 2011 and at planting in 2012. In both 2011 and 2012, management of soil nutrients did not significantly influence nematode reproduction. In both years, seed cotton yield was significantly increased with nematicide, but not with supplemental nutrients

Evaluation of damage potential of urban turf-associated nematode communities under microplot conditions and influence of soil type on nematode reproduction

Two full-season microplot experiments were conducted to evaluate the damage potential of a plant-parasitic nematode community on St. Augustine and centipede turfgrasses grown in three soil types and to assess the influence of soil type on reproduction of the nematode populations comprising the community. Genera of nematodes associated with both turfgrasses included Criconemella, Helicotylenchus, Meloidogyne, Pratylenchus, Tylenchorynchus, and Tylenchus spp. In 2012, nematodes did not cause significant damage to either turfgrass, but soil type affected plant growth parameters. In 2013, there was significant nematode-related injury to both turfgrasses, but there were no significant effects of soil type on plant growth parameters

The influence of soil texture on reproduction and pathogenicity of rotylenchulus reniformis on cotton

Sixty-day duration studies were conducted under greenhouse conditions to evaluate the influence of three soil textures on reproduction and pathogenicity of three isolates of Rotylenchulus reniformis on Phytogen 375WF, Stoneville 5288B2F, and Stoneville LA887 cotton. Soil with clay content of 25.9% had a significant negative effect on reproduction of the nematode on all three cultivars. Soil texture had a significant main effect on heights of Stoneville 5288B2F and Phytogen 375WF plants. Across the cotton cultivars, there were significant differences in reproduction among the three isolates of reniform nematode. Overall, the Avoyelles isolate reached the highest population density. There was significant soil texture by reniform isolate interaction that affected population density of the nematode only for Phytogen 375WF

Identification and haplotype designation of Meloidogyne spp. of Arkansas using molecular diagnostics

In this study, polymerase chain reaction (PCR) and DNA sequencing analysis were performed to identify Meloidogyne species present in Arkansas. A total of 106 soil and root samples from 36 of the 75 counties were collected, of which 79 contained root-knot nematodes. To identify species, PCR was performed using primers C2F3/1108 to amplify a region of mitochondrial DNA (mtDNA) of root-knot nematodes. Additionally, M. incognita specific primers were designed to confirm speciation, as M. incognita was the most abundant species that was identified in 54 of the 79 samples. Other species found in this survey were M. marylandi, M. haplanaria, M. hapla, M. arenaria, and M. partityla. Haplotype designation was performed for each species based on nucleotide variation. With a limited number of samples, this study designated distinct mtDNA haplotypes of Meloidogyne spp. endemic in Arkansas. Unlike previous reports, M. javanica and M. graminis were not detected from any of the samples collected during this study