Control Mint Nematode

CONTROL OF MINT NEMATODE WITH VYDATE

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Mint nematodes are very sensitive to Vydate, and foliar as well as soil applications are generally effective for control. Dipping foliage into a Vydate solution (equivalent to 2 lb a.i./A) for 30 sec reduced populations 80% (90 days after treatment) when treatments were made 10 days before, at the same time, or 30 days after nematodes were added to pots. A second application 10 days later reduced populations an additional 15% (Jatala and Jensen, 1974).

Few studies have been conducted on the efficacy of Vydate on control of mint nematode in the field, but those completed also indicate dramatic improvement of mint performance. Late spring applications at 1/2, 1, or 1 1/2 GPA significantly increased oil yield by an average of 60%, but there was no difference between these rates. In addition, two and three applications of 1/2 GPA did not increase yield more than a single application (Table 1)(Pinkerton and Jensen, 1983).

Table 1. Effect of Vydate 2L application rate (GPA - gallons per acre) on oil yield in field severely infested (1400/quart soil) with mint nematode (Longidorus elongatus). Modified from Pinkerton and Jensen, 1983).

Treatment Oil Yield (lb/A)

               Check                                                        28 a (4)
               1/2 GPA - once (1)                                      43 b
               1/2 GPA - twice (2)                                     39 b
               1/2 GPA - three times (3)                            48 b
               1 GPA                                                        47 b
               1 1/2 GPA                                                   48 b

(1) Appication on May 19, 1977.
(2) Appliction on May 19 and June 2, 1977.
(3) Application on May 19, June 2 and June 16, 1977.
(4) Means followed by the same letter are not significantly different.
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Table 2. Effect of Vydate 2L application time on hay yield (lb fresh hay/4m²) in a field severely infested with the mint nematode (Longidorus elongatus). (Modified from Pinkerton and Jensen, 1983).

Treatment

Check

Ľ GPA

˝ GPA

1 GPA

Fall

5.1

6.0

6.1

5.6

Winter

6.6

8.3

10.0

Spring

9.4

9.7

7.9

Fall & Spring

11.2

11.5

14.1

Fall & Winter

3.9

10.2

12.8

Winter & Spring

12.2

10.6

10.9

Applications in winter (late February) or spring (mid-June) tended to provide greater increases in hay yield than fall (mid-November) treatments. Split applications at fall and spring, fall and winter, or winter and spring were equal to each other in performance and superior to a single application. In most instances, rates of 1/4 to 1 GPA provided equal control (Table 2).

After effective treatment, the suppressed nematode activity permits plants to regrow a vigorous root system with greater branching and deeper penetration of the soil. This rejuvenated root system is more effective at taking up water and nutrients, culminating in increased yields of hay and oil. However, this healthier root system is also an excellent environment for rapid growth of the remaining population. This accounts for the observation of higher nematode densities in late summer and the potential need for subsequent treatments to maintain stand vigor. Noticeable plant responses after treatment include taller and more vigorous foliage which is darker green in color (Pinkerton and Jensen, 1983).