Seedling Disease
- Steps to prepare for seedling disease
- First step: Where possible, plant a high-quality seed with a strong, documented, germination rate.
- It is difficult, if not impossible to recover when a poor quality seed is planted.
- Second step: Plant under conditions that result in rapid, uniform germination and vigorous growth.
- Cool, and wet soils, or planting just ahead of cold rain, can slow germination and plant growth.
- This gives the fungal pathogens, “the bad guys”, the chances to play catch-up with the cotton seeds and seedlings, infect and then damage them.
- Third step: Ensure that the seeds are well-protected with a fungicide seed treatment.
- All commercial seed will come pre-treated with a “base” fungicide package.
- The base package varies among different seed companies but is always composed of a mix of three-to-four fungicides that have proven efficacy against common pathogens like Rhizoctonia, Pythium, and Fusarium.
- From Bob Kemerait’s recent studies, about four-out-of-five years, the use of the “base” fungicide treatment alone results in stands and yields similar to where additional fungicide seed-treatments or in-furrow fungicides are applied. However, investment in extra “insurance” with additional seed treatments or in-furrow fungicides may be beneficial.
- You are most likely to observe a benefit from “extra” treatments where the risk of seeding disease is elevated, such as when planting into cool and wet soils or conservation tillage.
- Additional seed protection may also be beneficial when planting at reduced seeding rates or where seed-quality is thought to be an issue.
- First step: Where possible, plant a high-quality seed with a strong, documented, germination rate.
- Protecting seeds and seedlings from death and loss of vigor is an important task for growers.
- You can use additional seed-treatments or in-furrow
applications to compliment the performance of base seed-treatments and to further protect against seedling diseases. - “Extra” fungicide seed-treatments are more convenient to use.
- In-furrow fungicides may be more effective as they can be used to treat the seed and the soil surrounding the seed as well.
Nematodes
- You can minimize damage from southern root-knot nematodes by
- planting a root-knot nematode variety.
- fumigating with Telone II
- using Velum Total (14-18 fl oz/A) or AgLogic 15G (6-7 lb/A) in-furrow at planting
- using one of several seed treatment nematicides.
- You can apply Vydate C-LV or Return XL at the 5th-to-7th true-leaf stage to compliment the earlier nematicide treatments.
- There are currently no commercial varieties with resistance to the reniform, Columbia lance, or sting nematodes.
- It is important to use nematicides to protect your crop.
Thrips
- A preventive insecticide should be used at planting for thrips control. UGA
- Positive yield responses are consistently observed in UGA research when an at-plant insecticide is used for thrips control.
- At-plant insecticide options include:
- in-furrow granule applications of aldicarb
- in-furrow liquid applications of imidacloprid or acephate
- commercial seed treatments of imidacloprid, thiamethoxam, and acephate.
- Imidacloprid seed treatment is the most common at-plant insecticide used.
- In-furrow applications of aldicarb, imidacloprid, and acephate tend to provide greater residual control of thrips compared with the commercial seed treatments.
- We encourage you to take advantage of the Thrips Infestation Predictor for Cotton.
- This web-based tool will predict thrips risk by planting date by geographic location and can be found at https://climate.ncsu.edu/CottonTIP.
- Thrips infestations are significantly lower in reduced tillage systems compared with conventional tillage. In general, the more cover on the soil surface the greater the reduction in thrips.
- Seedlings are most sensitive to yield loss during early developmental stages.
- 1-2 leaf cotton is at greater risk to yield loss from excessive thrips injury compared with 3-4 leaf cotton.
- Once cotton reaches the 4-leaf stage and is growing rapidly, thrips are rarely an economic pest.
- A rapidly growing seedling can better tolerate thrips feeding. Conversely, seedlings that are growing slowly from cool temperatures or some other stress are more susceptible to thrips.
- Scout for thrips and thrips injury early. Use thresholds and only make foliar applications when necessary.
- Optimal timing for supplemental insecticide applications (when needed) is the 1-leaf stage.
Silverleaf Whitefly (SLWF)
- Our mild winter is setting us up for a lot of whitefly activity this year so start preparing now.
- Variety Selection:
- hairy leaf cotton is preferred by SLWF compared with smooth leaf cotton.
- There is a direct correlation of SLWF infestations in cotton based on the degree of leaf hairiness. (I know because I pulled the leaves and counted the dang things)
- Risk of SLWF is greatest on hairy varieties > light hairy > semi-smooth > smooth varieties.
- Smooth leaf varieties are the least preferred by SLWF.
- Plant Smooth Leaf Varieties if possible
- Planting Date:
- The risk of SLWF problems increases as planting dates are delayed.
- SLWF completes a generation in about 2 weeks during summer months and populations can increase rapidly.
- The impact of SLWF on yield is dependent on the growth stage of cotton when SLWF infest the crop.
- Potential yield loss is greater when infestations appear during squaring or early bloom compared with late bloom.
- The duration or time of control required to protect yield and quality from SLWF is also dependent upon the planting date.
- April and early May planted cotton is at lower risk for SLWF problems compared with late May and June planted cotton.
- Avoid Late Planting
- Location (proximity of SLWF infested crops):
- Spring vegetable and melon crops are a source of SLWF infesting cotton.
- In the fall cotton is a source of SLWF infesting fall vegetables.
- The nearness of cotton to a SLWF infested field increases the risk of SLWF.
- Minimize Planting Cotton Next to SLWF Infested Crops.
- If planting cotton near SLWF infested crops, be sure to avoid late planting and use a smooth leaf variety.
- Destroy SLWF host crops immediately after harvest; this includes vegetable and melon crops in the spring and cotton (timely defoliation and harvest) and other crops in the fall.