Southeastern U.S. Vegetable Crop Handbook - 2023 - 114

or a combination of 20 CPB larvae and/or adults per 10 plants.
Insecticide sprays should be made after most egg masses have
hatched, but before larvae become large. CPB have developed
resistance to many different insecticides, so knowledge of the
resistance status of populations is essential in choosing which
insecticides to use.
Tomato Fruitworm: The tomato fruitworm, also known as the
corn earworm and cotton bollworm, is potentially the most damaging
pest of tomato. However, there are many insecticides that
provide excellent control. The key to controlling this insect is to
ensure that there is a toxic pesticide residue on the plant during
egg laying periods so that larvae are killed shortly after hatching,
because larvae feed on leaf tissue for only a short time before
boring into fruit. Tomato fruitworm moth activity can be monitored
with pheromone traps and serves as a measure of the adult
population within an area. Corn that is in the silking stage is a
preferred host of fruitworm, but when corn silks begins to dry,
moths will switch egg laying to other hosts, including tomato.
Armyworms: At least three species of armyworms are potential
pests of tomato, including the beet armyworm, southern armyworm
and yellowstriped armyworm. Infestations are usually
sporadic in the more northern regions of the southeastern US,
but are an annual problem in more southern areasw. In contrast
to tomato fruitworm, armyworms will also feed extensively on
foliage as well as fruit, and the presence of feeding damage on
leaves can help differentiate between fruitworm and armyworm
damage. Beet armyworm is notorious for exhibiting resistance to
a wide range of insecticides, but the recent registration of newer
insecticides has greatly aided the management of this pest.
Tomato Pinworm: The tomato pinworm is more common in the
southern compared with northern regions of the southeast, but
late-season infestations are common in northern areas. Moths lay
eggs on foliage, and larvae feed within leaves, creating blotchy
mines. As larvae increase in age they bore into stems and/or
fruit. The use of pheromone-based mating disruption is an effective
control method. Initiate mating disruption at the first sign of
mines on foliage. Numerous insecticides also control pinworm.
Stink Bugs: The green and brown stink bug can be important
direct pests of tomato, but they are sporadic in occurrence. Stink
bugs are most common in smaller fields (i.e., 5 acres or less)
that are surrounded by weedy borders, or fields that are adjacent
to soybeans. In fact, chemical control of stink bugs is often not
necessary in fields that do not fit the previous description. Unfortunately,
there is not a good sampling method to assess population
densities before damage occurs, and preventive strategies
are used. Depending on the surrounding habitat and abundance
of stink bugs within an area, one to three applications of an insecticide
are necessary to prevent damage.
Thrips: Thrips can cause direct damage to tomato fruit by their
feeding or oviposition scars on small fruits, and are also indirect
pests of tomato due to their ability to transmit tomato spotted
wilt virus (TSWV). The tobacco thrips and western flower thrips
are vectors of tomato spotted wilt virus. The majority of virus
114
infections are the result of primary spread (thrips transmitting
the virus from surrounding weeds directly to tomatoes), and insecticides
do not kill thrips quickly enough to prevent inoculation.
However, an aggressive early insecticide control program
early in the season (3 to 4 weeks after transplanting) and the
use of reflective mulches have helped to reduce the incidence of
TSWV in tomatoes. Thrips can also cause direct damage to tomato
fruit. This is the result of thrips feeding and/or laying eggs
in small fruits before stamens are shed from flowers. This damage
appears as small dimples in fruit. Sample thrips in tomato
flowers by placing a white index card below flowers and tapping
the flowers with a finger. An average of 1 thrips per flower has
worked well as a treatment threshold level.
Whiteflies: The greenhouse whitefly and silverleaf whitefly can
both infest tomatoes in the southeast. Generally, the silverleaf
whitefly is more common in the southern region and the greenhouse
whitefly is more common in the northern region of the
southeast. Once whitefly populations of either species become
established on a crop, they are very difficult to control. Therefore,
preventive control is usually necessary for effective, season-long
management. Preventive control can be achieved with
soil-applied systemic insecticides or the application of other insecticides
when populations are low.
Mites: Mites have become an increasingly important problem on
tomatoes and other vegetables grown in the southeast. Twospotted
spider mite is the most common mite pest, but the broad mite
and carmine spider mite can also infest tomatoes. Mites overwinter
on weeds and move into tomatoes in the spring as weeds
die. Mites can also move from other crops (including other
tomato fields) into tomatoes throughout the season. Localized
infestations can be spot treated, but thorough coverage of foliage
is important. Mites can be sampled by using a sample of 10
leaflets (terminal leaflet on a leaf from the upper one-third of the
plant), from a minimum of 5 sample sites per field. When mites
reach an average of 2 mites/leaflet, a miticide should be applied.
Note that certain pesticides, such as pyrethroids and some neonictinoids,
aggravate mite populations and can lead to high mite
densities.
DISEASE MANAGEMENT
A. Keinath, Plant Pathologist, Clemson University and R.
A. Melanson, Extension Plant Pathologist, Mississippi State
University
Accurate diagnosis is necessary for effective disease management.
Incorporate appropriate and effective cultural practices
and pesticides, as detailed in the Disease Management section,
in a season-long integrated disease management program.
Soil-borne Diseases (bacterial wilt, Fusarium wilt, southern
blight, etc.): Several soil-borne bacterial, fungal, and oomycete
pathogens can significantly affect tomatoes. Many are difficult to
manage when fields become infested. When possible, use resistant
varieties or rootstocks. Limited fumigants and fungicides are
available for some diseases. Pathogens can be spread via move2023
Vegetable Crop Handbook for Southeastern United States
Southeastern U.S. Vegetable Crop Handbook - 2023

Table of Contents for the Digital Edition of Southeastern U.S. Vegetable Crop Handbook - 2023
