The primary diseases of garden mums are bacterial leaf spot, septoria leaf spot, Pythium, and Botrytis.
Bacterial Leaf Spot
Bacterial leaf spot (Pseudomonas cichorii) is favored by moisture
on the leaves, high humidity, high temperature, and growing susceptible
cultivars. Symptoms include dark-brown to black lesions covering half of
the leaf. The disease typically begins on lower leaves and spreads upward,
often on one side of the plant.
Septoria Leaf Spot
Septoria leaf spot (Septoria chrysanthemella) causes small
yellow spots on the foliage that later turn dark brown or black. In advanced
stages, the leaves may turn completely yellow and fall off or remain attached
to the stem. The disease is spread by splashing water, so overhead watering
should be avoided.
Pythium
Pythium is a root rot disease that is present in most
media. The disease causes browning and death of the roots accompanied by
wilting of the foliage, especially during the day. Avoid conditions which
stress the plant and damage the root system such as over watering, high
soluble salts, or cool medium temperature.
Botrytis
Botrytis can infect leaves and flowers under high humidity
conditions. Avoid overhead watering and space plants far enough apart for
good air circulation.
The primary pests of garden mums are aphids, leaf miners, spider mites, thrips, and caterpillars.
Aphids
Green peach aphids, melon aphids, and chrysanthemum aphids are common
pests of garden mums. Aphids feed on young terminal growth and flower buds
prior to opening using piercing-sucking mouthparts causing plant stunting,
wilting, leaf yellowing, and leaf curl. A by-product of feeding is a sticky
honeydew that serves as a medium for black sooty mold.
Leaf Miners
Chrysanthemum and serpentine leaf miners are the common leaf miner species
that infest garden mums. Adult females puncture the leaf surface and lay
eggs inside the leaf. The eggs hatch into larvae that tunnel between the
upper and lower leaf surfaces causing white, twisting mines that disfigure
the leaves and reduce marketability.
Spider Mites
The two-spotted spider mite is the most common mite species that infest
garden mums. Spider mites feed on the underside of leaves by sucking plant
sap. Damage appears as tiny yellow speckles on the upper leaf surface. Severe
mite damage can cause leaf drop. Mites are favored by dry warm conditions.
Thrips
The common flower thrip and western flower thrip are the two most common
thrips infesting garden mums. Thrips feed on young leaves and flowers using
rasping-sucking mouthparts. Feeding on leaves causes a silvery-appearance
while damage to flowers causes deformed flower buds, bud abortion, or streaking
of petals.
Caterpillars
A number of caterpillars are pests on garden mums including beet armyworm,
cabbage looper, fall armyworm, corn earworm, and European corn borer. Caterpillars
can feed on almost all of the aboveground portions of the plant including
leaves, stems, and flowers. Adult female moths lay eggs on plant parts which
emerge as larvae to begin feeding. Adults generally migrate to garden mums
when they are placed outdoors.
Specific control measures for insect and disease problems on garden mums can be found in the Extension Circular ANR-500A, Alabama Pest Management Handbook--Volume 1, and Extension Circular ANR-500B, Alabama Pest Management Handbook--Volume 2 or contact your county Extension agent.
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A knowledge of the costs involved in garden mum production is essential for making decisions on the optimum number of plants to produce and how to establish prices. Costs of production can be classified as either variable or fixed. Variable costs are incurred directly during the production of the crop including pots, plants, medium, and chemicals. These items are usually easy to allocate to a specific crop. Fixed costs are incurred whether or not the crop is produced including salaries, depreciation, insurance, and taxes. These items may be more difficult to allocate to a specific crop. Because garden mums are often produced outdoors, fixed costs may be allocated as a percentage based on actual use of a piece of equipment or as a percent of sales.
Despite the best production practices, a certain percent of the crop will not be marketable. The cost of inputs for unmarketable plants should be taken into account. This is often done by adjusting the variable costs using a shrinkage factor. Adding the total variable costs adjusted for shrinkage and the total fixed cost provides a total cost of production. Profitability of the crop is then related to the price received.