Determining whether a sick tomato plant has a pest or disease problem is challenging, and sometimes it’s a combination of the two. Organic gardeners can attack tomato plant problems with a number of effective natural controls.
Tomato Hornworm
One of the most notorious tomato pests is the tomato hornworm. These voracious caterpillars can quickly defoliate an entire plant, but gardeners can handpick them at dusk, their favorite feeding time. Although the barbed horn on the caterpillar looks treacherous, these caterpillars don’t sting. Nevertheless, gardeners may wear gloves to avoid any skin irritation from handling insects. Drop the caterpillars into a bucket of soapy water, and dispose.
Squeamish gardeners can avoid handpicking entirely by attracting parasitic wasps to the garden. Gardeners can plant nectar-rich plants, like sweet alyssum, to attract the wasps that lay their eggs on hornworms and other caterpillars. Leave any caterpillar donning the white eggs on the plant, as feeding will slow, and soon a new generation of wasps will hatch from the parasitized body.
Fusarium and Verticillium
These soil-borne diseases with the hard-to-pronounce names are the reason gardeners see the “VFN” acronym on tomato plants at the nursery. These tomato hybrids are bred to resist these fungi, which causes yellowing and plant death. Gardeners who crave heirloom tomatoes must practice a three-year crop rotation to prevent fungi from building in the soil. Include potatoes and peppers in the rotation plan.
Tomato Wilt
Plants affected with the tomato spotted wilt virus may exhibit slow growth, spotty leaves, or yellow blemishes on the fruits. Gardeners must discard these plants, as there isn’t a cure for tomato wilt. Prevent this disease by controlling the vector that spreads it, the western flower thrip. Weedy patches draw thrips, so deny the pest its habitat. Control thrips with insect soap and diatomaceous earth.
Tomato Blight
Blight is more common in humid climates in the hottest months of summer. The fungal disease may appear first as brown patches on lower leaves, as the fungal spores can spread when water splashes soil onto leaves. Prevent the spread of disease by using organic mulch under the tomato plants. Space the plants properly to encourage air circulation, and water using drip irrigation rather than an overhead sprinkler.
Tomato Rot
An ugly, shrunken black spot on the end of an otherwise healthy looking tomato looks like a disease, but is actually a problem that relates to poor cultural practices. Blossom end rot occurs when irregular watering practices deny the developing tomato of calcium. Excessive nitrogen is also sometimes to blame. Prevent tomato rot by watering regularly through dry periods, and by using a balanced organic tomato fertilizer with a 5-10-10 ratio of nitrogen, phosphorus, and potassium.
Source:
ColoradoStateUniversity Cooperative Extension
Jamie McIntosh - Jamie has written hundreds of garden articles for the web, and is your guide to Flowers on About.com.
