Meta-analysis of the field efficacy of seed- and soil-applied nematicides on Meloidogyne incognita and Rotylenchulus reniformis across the U. S. Cotton Belt

Meta-analysis was used to compare yield protection and nematode suppression provided by two, seed- and two, soil-applied nematicides against Meloidogyne incognita and Rotylenchulus reniformis on cotton across three years and several trial locations in the United States Cotton Belt. Nematicides consisted of thiodicarb- and fluopyram-treated seed, aldicarb and fluopyram applied in-furrow and combinations of the seed treatments and soil-applied fluopyram. The nematicides had no effect on nematode reproduction or root infection but had a significant impact on seed cotton yield response (¯D) with an average increase of 176 and 197 kg/ha relative to the nontreated control in M. incognita and R. reniformis infested fields, respectively. However, because of significant variation in yield protection and nematode suppression by nematicides, five or six moderator variables [cultivar resistance (M. incognita only), nematode infestation level, nematicide treatment, application method, trial location, and growing season] were used depending on nematode species. In M. incognita infested fields, greater yield protection was observed with nematicides applied in-furrow and seed-applied + in-furrow than solo seed-applied nematicide applications. Most notably of these in-furrow nematicides were aldicarb and fluopyram (>131 g/ha) with or without a seed-applied nematicide compared to thiodicarb. In R. reniformis infested fields, moderator variables provided no further explanation of the variation in yield response by nematicides. Furthermore, moderator variables provided little explanation of the variation in nematode suppression by nematicides in M. incognita and R. reniformis infested fields. The limited explanation by the moderator variables on the field efficacy of nematicides in M. incognita and R. reniformis infested fields demonstrates the difficulty of managing these pathogens with nonfumigant nematicides across the U. S. Cotton Belt.

Tarnished Plant Bug (Heteroptera: Miridae) Behavioral Responses to Chemical Insecticides

The tarnished plant bug (Lygus lineolaris Palisot de Beauvois) is the dominant insect pest of cotton (Gossypium hirsutum L.) in the Mid-South Cotton Belt. This is partly due to the fact that this pest has developed resistance to most insecticides used for control. Laboratory experiments were conducted during 2014 and 2015 to study the behavioral response of tarnished plant bug nymphs to several classes of insecticides. Twenty third-instar nymphs were placed in individual dishes divided into four quadrants with five green bean pieces in each quadrant (10 treated and 10 untreated green beans in each dish). Dishes were checked at 1, 4, 8, and 24 h. Tarnished plant bug nymphs appeared to avoid green beans treated with IGR, pyrethroid, organophosphate, or carbamate insecticides, while there appeared to be an attraction to green bean pieces treated with sulfoxamine and pyridine carboxamide insecticides. No relationship was observed with neonicotinoid insecticides within 24 h.

Performance of Tank Mix Partners with Isoxaflutole Across the Cotton Belt

BASF Corporation has developed P-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor-resistant cotton and soybean that will allow growers to use isoxaflutole in future weed management programs. In 2019 and 2020, a multi-state research project was conducted non-crop to examine weed control following isoxaflutole applied preemergence alone and with a number of tank mix partners at high and low labeled rates. At 28 DAT, Palmer amaranth was controlled ≥95% at 6 of 7 locations with isoxaflutole plus the high rate of diuron or fluridone. These same combinations provided the greatest control 42 DAT at 4 of 7 locations. Where large crabgrass was present, isoxaflutole plus the high rate of diuron, fluridone, pendimethalin, or S-metolachlor or isoxaflutole plus the low rate of fluometuron controlled large crabgrass ≥95% in 2 of 3 locations 28 DAT. In 2 of 3 locations, isoxaflutole plus the high rate of pendimethalin or S-metolachlor improved large crabgrass control 42 DAT when compared to isoxaflutole alone. At 21 DAT, morningglory was controlled ≥95% at all locations with isoxaflutole plus the high rate of diuron and at 3 of 4 locations with isoxaflutole plus the high rate of fluometuron. At 42 DAT at all locations, isoxaflutole plus diuron or fluridone and isoxaflutole plus the high rate of fluometuron improved morningglory control compared to isoxaflutole alone. These results suggest that isoxaflutole applied preemergence alone or in tank mixture is efficacious on a number of cross-spectrum annual weeds in cotton and extended weed control may be achieved when isoxaflutole is tank mixed with a number of soil residual herbicides.

CHEMICAL SOIL FERTILITY DIAGNOSIS FOR COTTON CROPPING IN NORTHERN COTE D'IVOIRE

The work was conducted in the north of Cote d’Ivoire, central pivot cotton production savannah area, to make the diagnosis of soil fertility for cotton cropping. Cotton cropping, the mainstay of the savannah's economy, suffered from low productivity in relation to the soils chemical properties. Prior cultivation, soils samples were collected at a depth of 0 to 30 cm, collecting 32 simple samples to generate a complete sample. The samples were sent to the soil laboratory to measure the pH unities, CEC, nitrogen, phosphorus, potassium, calcium, magnesium, sodium, iron, zinc, copper and manganese contents. In order to facilitate the interpretation of analysis results, the nutrients critical level recommended for optimum production of cotton were used. Results showed that soils had pH ranging from 4.4 to 6.4. On the other hand, the need to add nitrogen, magnesium and phosphorus to the soils and to augment the low carbon, calcium and potassium content. There is the need to search for fertilizer formulations with nitrogen, magnesium phosphorus and calcium for the Cote d'Ivoire cotton belt.

Genome analysis of cotton leafroll dwarf virus reveals variability in the silencing suppressor protein, genotypes and genomic recombinants in the USA

Cotton leafroll dwarf virus (CLRDV) is an emerging virus in cotton production in Georgia and several other Southeastern states in the USA. To better understand the genetic diversity of the virus population, the near complete genome sequences of six isolates from Georgia and one from Alabama were determined. The isolates sequenced were 5,866 nucleotides with seven open reading frames (ORFs). The isolates from Georgia were >94% identical with other isolates from the USA and South America. In the silencing suppressor protein (P0), at amino acid position 72, the isolates from Georgia and Alabama had a valine (V), similar to resistant-breaking ‘atypical’ genotypes in South America, while the Texas isolate had isoleucine (I), similar to the more aggressive ‘typical’ genotypes of CLRDV. At position 120, arginine (R) is unique to Georgia and China isolates, but absent in Alabama, Texas and South American isolates. Ten potential recombinant events were detected in the isolates sequenced. An increased understanding of CLRDV population structure and genetic diversity will help develop management strategies for CLRDV in the USA cotton belt.

Detection and characterization of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 causing Fusarium wilt of cotton seedlings in New Mexico, USA

Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. vasinfectum (Atk.) W.C. Snyder & H.N. Hans (FOV), is one of the most destructive diseases in cotton (Gossypium spp.) worldwide. FOV race 4 (FOV4) is a highly virulent nominal race of this pathogen and is a significant threat to cotton production in the western and southwestern US and potentially the entire Cotton Belt. A field survey in three southern counties of New Mexico was conducted in 619 cotton fields in 2018-2020 to identify FOV4. From 132 samples of cotton plants that exhibited wilt symptoms, Fusarium spp. were the most frequently isolated group of fungal species with an isolation frequency of 57.4%. Eighty-four Fusarium spp. isolates were subsequently characterized by a DNA sequence analysis of three genes, EF-1α, PHO and BT encoding for translation elongation factor, phosphate permease and β-tubulin, respectively. Forty-two isolates were identified to be FOV4 from 10 cotton fields and confirmed with a positive 500 bp fragment that is diagnostic for FOV4. Twenty-six (62%) of the 42 FOV4 isolates were T type and the remainder (38%) were Null type with and without a Tfo1 insertion in PHO, respectively; and each FOV4-infested field contained the same FOV4 genotype. Ten representative FOV4 isolates with one each from the 10 FOV4-infested fields were evaluated for their pathogenicity on resistant Pima PHY 841 RF and susceptible Upland PHY 725 RF at 7, 14, 21, and 28 days post inoculation under temperature-controlled conditions at 21-22°C. Based on disease severity rating (DSR), mortality rate (MR) and the area under the disease progress curve (AUDPC) value, all the 10 isolates were pathogenic to both cotton cultivars and differed in virulence in that four isolates of the T genotype as a whole were more virulent than the six isolates of the N genotype. PHY 841 RF had significantly higher levels of resistance than PHY 725 RF to all FOV4 isolates. The results provide the first comprehensive account of the occurrence, distribution and virulence of FOV4 in cotton production in New Mexico and will be useful in developing an effective strategy to manage FW in both the state of New Mexico and entire southwestern Cotton Belt.

Reniform nematode (Rotylenchulus reniformis) and its interactions with cotton (Gossypium hirsutum).

The reniform nematode, Rotylenchulus reniformis, is a major economic factor limiting cotton (Gossypium hirsutum) production in the USA. Across the United States cotton belt, 0.1-5.0% of the cotton crop is lost to the reniform nematode (RN) annually. This chapter discusses the economic importance, geographical distribution, host range, damage symptoms, biology and life cycle, interactions with other nematodes and pathogens, recommended integrated management, and management optimization of the reniform nematode (R. reniformis). Future research requirements are also mentioned.