Cotton Insect Pests
Cotton Insect Scouting Methods
|Insect Species||Scouting Method|
|Thrips||Primarily a pest of seedling cotton, 4th leaf stage
Examine whole seedlings for presence of thrips, concentrating on undersides of leaves and in terminal area.
Alternatively, pull seedling plants and beat vigorously over a sheet of white paper or shallow box and count number of thrips dislodged. Record counts as number of thrips per 100 seedling plants.
|Cutworms||Walk over field noting presence and frequency of cutworm damaged plants or skips due to active cutworm infestation. Note relative amount of field infested. Record average number of cutworms and number of cutworm damaged plants per 10 feet of row in infested areas. Determine and record average plant stand density.|
|Walk either along or across rows and scout visually for presence of plant bugs. Primarily adults are of concern at this time. Make observations at several areas in the field and record counts as average number of plant bugs per 10 feet of row.|
|Pheromone traps are the most important component of boll weevil eradication programs and eradication maintenance programs. Growers should take special care to avoid mechanical damage to pheromone traps placed around fields.|
|Even one boll weevil is one too many in an area that is in the last stages of a boll weevil eradication program or an eradication maintenance program. Check for adult boll weevils in open blooms and examine flared squares for boll weevil egg laying punctures. Fallen squares can also be examined for the presence of boll weevil larvae or pupae. Immediately report any detection of either adult boll weevils or squares containing egg laying punctures or immature boll weevils to boll weevil eradication personnel!|
|Adult plant bugs are best quantified by using a 15
inch diameter sweep net. Take several 25 sweep samples per field
and record results as average number of plant bugs per 100 sweeps.
Because adult plant bugs are very mobile and easily flushed, it is
important to space sweeps widely apart and more quickly down the
row while sweeping.
Plant bug nymphs must be sampled by spreading a 3 ft ground cloth between two adjacent rows, vigorously beating plants over the cloth, and counting the number of nymphs that are dislodged onto the cloth. Take several such samples per field and record counts as average number of plant bugs per 6 feet of row.
During the period between square initiation and early bloom, it is also important to monitor percent square retention. Conduct counts by examining 100 potential first and/or second position square sites and counting the number of missing squares, as indicated by the presence of an abscission scar. On plants with more than 5 fruiting branches such counts should be limited to potential fruiting positions on the 5 uppermost fruiting branches.
|Randomly select individual plants and examine carefully
for presence of eggs or small (less than 1/2 inch long) larvae. Concentrate
scouting primarily on the terminal area and the upper 8 to 12 inches
of the plant. Eggs are usually deposited in the terminal bud or on
the upper surface of newly expanded leaves, but also be sure to check
for presence on eggs on outer square bracts. Look for small larvae
feeding in the terminal bud or inside developing squares. Record
counts as percent of plants that are infested, noting age structure
of insects present (example: 10% eggs, 12% larvae less than 1/2 inch).
In many cases, especially where resistant tobacco budworm occurs,
it may be necessary to note and record more specific information
on age of eggs and small larvae.
|Beet Armyworm||Beet armyworms lay eggs in clusters on undersides of leaves. Newly hatched larvae remain at the oviposition site for several days feeding on the underside of the leaf but leaving the translucent upper epidermis intact. This creates small windowpane like areas, referred to as 'hits'. Scout for beet armyworms by counting the number of 'hits' observed on a given length of row at several locations in the field. Examine any hit areas that are detected to verify presence of larvae and to note age of larvae and signs of parasitism or predation. Also include any unhatched egg masses that may be detected in the count. Record counts as average number of 'hits' per 100 feet of row. Note that initial populations are usually greatest around field edges and along field drainage ditches. A ground cloth is sometimes used to quantify extremely high populations of larvae.|
|Fall Armyworm||Like beet armyworm, fall armyworm lays its eggs in masses, usually on undersides of leaves. However, young larvae tend to disperse soon after hatching. Infestations usually develop deep within the plant canopy. Small larvae often feed on bracts of lower bolls, but large larvae bore directly into bolls near their base. Scout for fall armyworms by randomly selecting large, lower bolls and examining inside bracts for feeding and presence of small larvae (large larvae that have already bored into bolls cannot be effectively controlled and should be counted separately). Also examine randomly selected blooms for presence of fall armyworm larvae. Record counts as number of larvae per 100 bolls and/or number of larvae per 100 blooms.|
|Aphids||When scouting for aphids, it is important to note any additional stress factors that may be affecting the crop and to be aware of predators, parasites, and pathogens that may be affecting the aphid population. Scout by randomly selecting fully expanded leaves (4th or 5th leaf below terminal is often used) and counting the number of aphids present. Record counts as average number of aphids per leaf. Also be sure to note the general distribution of the aphid infestations within the field and the degree of honeydew present.|
|Whiteflies||Scout for whiteflies by examining plant terminals and undersides of upper leaves for presence of adults and/or immatures. Record counts as percent of terminals infested.|
|Loopers||Loopers are occasional, late season pests that cause damage by premature defoliation. Loopers populations can be quantified by using a ground cloth to determine number of larvae per foot of row. Treatment decisions involving loopers must consider number of insects present, remaining time until crop maturity and potential for excessive premature defoliation. Estimated percent defoliation is often used as a criteria for assessing looper infestations.|
|Spider Mites||Randomly select individual plants and examine the 5th leaf below the terminal for the presence of mites. Record counts as percent of plants infested.|