General Information

Mepichlor 4.2 is a Arysta LifeScience Corporation product which is equivalent to PIX® Plant Regulator. Mepichlor 4.2 is a foliar applied plant regulator. It allows the grower to manage the cotton plant for short-season production leading to reduced risk of yield and quality loss due to delayed and prolonged harvest. Benefits derived from the use of Mepichlor 4.2 include increased early boll retention and/or larger bolls, reduced plant height which provides a more open canopy, less boll rot, improved defoliation, less trash and lower ginning costs, better harvest efficiency and a darker leaf color. These benefits can provide for earlier maturity and often result in improved yields.

Early Application of Mepichlor 4.2
Growers may use low-rate multiple applications, or higher, less frequent dosages which provide maximum flexibility under a wide range of growing conditions. Mepichlor 4.2 should not be applied to plants under stress. If stress is alleviated, plants should be evaluated for vegetative growth before additional applications are made. Mepichlor 4.2 may be tank mixed with insecticides/miticides when application timing coincide. (See RESTRICTIONS AND LIMITATIONS.)

Fields should be carefully scouted. Mepichlor 4.2 should not be applied if plants are under any form of stress. In the absence of stress, a maximum of five low rate applications can be made each season. The first application can be applied at the matchhead square stage. The rate and timing of subsequent applications depend on growing conditions and desired benefits. Under good growing conditions, additional treatments of 2-4 fl.oz./acre can be made at 7-14 day intervals. Higher rates of Mepichlor 4.2 (1/4 - 3/4 pt./acre) should be used if vegetative growth becomes excessive or a greater degree of height control is desired. Do not use more than a total of 48 fl. oz. of Mepichlor 4.2 per acre in a growing season.

If significant loss of squares and/or young bolls has occurred earlier due to insect pressure or other stresses, but now these stresses have been alleviated, the need for Mepichlor 4.2 is increased - excess vegetative growth is likely because of poor fruit load.

Late Season Application of Mepichlor 4.2
Late application of Mepichlor 4.2 (approximately during the fourth to sixth week of blooming) can provide certain benefits to cotton. However, it should not and does not substitute for early season use, the time of the greatest benefit from the use of Mepichlor 4.2. Late season application can lead to one or more of the following: reduction in late season vegetative growth or regrowth after cutout or defoliation, more complete and manageable cutout, better defoliation, earlier maturity and reduction in trash and lower ginning costs. Some of these effects may favorably influence the yield potential and fiber quality. A late season application of Mepichlor 4.2 should be applied only if fields are not drought or nutrient stressed; that is, those fields likely to experience additional vegetative growth or regrowth. However, fields that are very rank and extremely vigorous due to a combination of poor boll load and excellent growing conditions may not respond as much as desired to late season applications at the suggested rates.

Timing for Late Season Applications
A. On fields where cotton cuts out and then starts regrowth: apply when regrowth begins, as evidenced by new leaves in the terminal and stem elongation. This would often, but not always, be in the period of 5-6 weeks after the first bloom.

B. On fields where cotton never completely cuts out, apply Mepichlor 4.2 when there are 4-6 nodes above the white flower (NAWF). Measure NAWF by counting the number of mainstem nodes from the first position white bloom (the one closest to the mainstem) to the terminal. Count the node with the first position white bloom as zero and the last node in the terminal, which is counted, should have a leaf at least the size of a quarter. Generally, the NAWF first reaches 4-6 during the fourth to sixth week of bloom. During this time period, the NAWF should be decreasing about one node every 5-6 days - if its rate of decrease is less, this means that the plant is not cutting out soon enough (the crop is too vigorous). If the fifth week of bloom arrives and NAWF is still above 5-6, apply Mepichlor 4.2.

Use Rate for Late Season Application
Mepichlor 4.2 should be applied at a rate between 1/2 pint to 1 1/2 pints per acre. Use the lower rate range on cotton with only moderate additional growth potential, and the higher rate range on fields likely to continue vigorous growth. Total seasonal use per season (early plus late application) must not exceed 3 pints per acre.

Thorough coverage is required

Areas other than California:
Ground Application – Use a minimum of 2 gallons of water per acre.
Aerial Application – Use a minimum of 2 gallons/acre.

California Only:
Ground Application – Use a minimum of 5 gallons/acre.
Aerial Application – Use a minimum of 5 gallons/acre.

Use a minimum total oil volume of 2 pints/acre for ultra low volume (ULV) aerial application. Application in oil is permitted only in AL, AR, FL, GA, LA, MO, MS, NC, OK, SC, TN and TX. Use a nonphytotoxic oil concentrate which contains either a petroleum or vegetable oil base, contains only EPA-exempt ingredients, provides good mixing quality in the jar test (see “Compatibility” section), and has been used successfully in your locality. The oil diluent should contain emulsifiers which provide good mixing quality. If the oil does not contain an emulsifier, one must be added during mixing at a volume equal to 3% of the final volume of the mixing tank. Do not apply Mepichlor 4.2 as ULV without using emulsifiers. If using a vegetable oil based product, only highly refined concentrates should be used.

Mix under constant agitation. Pour one-half of the required volume of oil into the spray tank, followed by the emulsifier (if the oil does not already contain one) at approximately 3% of the final spray tank volume, and then pour in the Mepichlor 4.2 while the remainder of the oil is added. Constant, moderate agitation is required during and after mixing and during application.

Avoiding spray drift at the application site is the responsibility of the applicator. The interaction of many equipment-and-weather-related factors determine the potential for spray drift. The applicator and the grower are responsible for considering all these factors when making decisions.

The following drift management requirements must be followed to avoid off-target drift movement from aerial applications to agricultural field crops. These requirements do not apply to forestry applications, public health uses or to applications using dry formulations.
- The distance of the outer most nozzles on the boom must not exceed 3/4 the length of the wingspan or rotor.
- Nozzles must always point backward parallel with the air stream and never be pointed downwards more than 45 degrees.

Where states have more stringent regulations, they should be observed.

INFORMATION ON DROPLET SIZE: The most effective way to reduce drift potential is to apply large droplets. The best drift management strategy is to apply the largest droplets that provide sufficient coverage and control. Applying larger droplets reduces drift potential, but will not prevent drift if applications are made improperly, or under unfavorable environmental conditions (see Wind, Temperature and Humidity, and Temperature Inversions).

The use of a high quality, EPA-exempt surfactant will enhance the uptake of Mepichlor 4.2 into the plant. Therefore, the use of a surfactant allows applications made as little as 4 hours prior to rainfall to be effective. Without a surfactant, the product should be used at least 8 hours prior to expected rainfall.

Mepichlor 4.2 is water based, and is compatible with most insecticides and miticides. If compatibility is in doubt, perform a jar test to check for compatibility. Mepichlor 4.2 can be used with foliar fertilizers if your prior experience shows the combination is compatible and will not injure cotton under your conditions. Caution should be used when applying with foliar fertilizers under conditions of extreme heat.

- Insect or mite damage to Mepichlor 4.2 treated crops can lead to yield decreases or other undesirable effects.
- Do not apply Mepichlor 4.2 to cotton that is under stress. If using low rate multiple applications, discontinue use until your crop has overcome any stress.
- Do not apply more than 48 fl. oz. of Mepichlor 4.2 per acre per season. The sum of all products and formulations containing mepiquat chloride must not exceed 0.132 pounds (60 grams) of mepiquat chloride per acre per season.
- Do not apply Mepichlor 4.2 within 30 days of harvest.
- Do not graze or feed cotton forage to livestock.
- Mepichlor 4.2 contains a dye and effectiveness is not related to the color of the spray solution.
- Do not tank mix with other products other than those mentioned under “COMPATIBILITY”.
- Do not plant another crop within 75 days after last treatment.

Limitations, Restrictions, and Exceptions


- Use these instructions when you want to maintain maximum flexibility in plant regulation treatments.


Fifth Application:
- (If needed): 7 – 14 days later, or when regrowth occurs.

- Use the higher rate if previous application was not made or if growing conditions favor excessive growth.

Pre-Harvest Interval

30 days

Restricted Entry Interval

12 hours