Explorando e Identificando Enfermedades en Tomates

Ah scouting and identifying diseases and early blight the hector ya bacterial diseases and late blight can cause serious problems in tomato plantings make sure you scout for diseases once a week during July and August it is very helpful to pay attention to tom cast it will help you predict when conditions are right for diseases like early blight and septoria you can also use blake cast for late blight and remember to in order to determine if you have a problem and before it gets out of control once a week select 10 plants at random evenly spread across the field note any trouble spots like wet areas or the edges of the field but don't focus on just those areas I examined the upper and make sure to look at the for each plant I examined five leaves across the canopy for disease symptoms make sure to look at the leaves close to the ground, in the middle and at the canopy of the plant note which diseases are present and what percentage of the leaf is affected it is important to scout each cultivar Separate and see which ones have been affected in some cases you will need to check the lets look at some common problems and their symptoms the symptoms of early blight are easy to distinguish because they have this shape like woodside or concentric rings it is a regularly shaped ring that is usually dark brown with some lighter coloration there is often a yellow halo around the lesion stem lesions occur at any age initially they are small dark and slightly sunken they then enlarge and form concentric rings the fruit may darken with hard, sunken spots usually at the point of stem attachment it can affect the whole upper portion of the fruit fruit can be infected at the green or mature stage through growth cracks and wounds and often drop before maturity foliar symptoms of bacterial spot include black spots on the leaves which often have a yellow halo similar lesions will be seen on the underside of the leaf the spots frequently form dead areas on the leaves speckle and bacterial spot are most clearly distinguished by the development of the symptoms on the fruit bacterial spot lesions are slightly Raised but are usually much smaller than Bacterial speck lesions are very superficial and do not crack and scaly as with bacterial spot. Bacterial spot can be easily confused with the two. They often can be oversodden with soil. Tomatoes often start at the soil level and work their way up the plant. Heavily infected leaves will yellow, dry up, and drop. This defoliation will result in fruit burn. Small, circular, water-soaked spots, one- sixteenth to one-eighth of an inch in diameter, appear on the undersides of older leaves. The centers of the spots are gray or burnt and the spots have a dark brown margin. As the spots mature, they increase to about a quarter of an inch in diameter and may coalesce. In the centers of the spots, there are many dark brown, lump-like structures called mushroom bodies Late blight can develop on all parts of the plant and can quickly kill tomatoes and potatoes in as little as 14 days. Think of the famine as a Potato leaves will show The spots often appear first toward the top of the plant canopy from spores that travel on wind currents and thunderstorms, but can occur throughout the canopy. The lesions may appear greasy, especially when wet. In humid conditions, a downy white growth usually develops near the margins of the leaf spots on the undersides of leaves. The best time to see these white spores is in the early morning when there is still dew on the leaves. If you are unsure, grab a few leaves and incubate overnight on your counter in a container with a damp paper towel and see if spores develop. Late blight causes the fruit to have a chorea-like appearance. Usually near where the fruit meets the stem of the plant, these lesions will look sunken and have indistinct margins. Stem lesions of late blight are similar to leaf symptoms, initially appearing as greasy or water-soaked marks that quickly turn brown and dry. and the White rot or white mode typically starts in a leaf axil where a bloom drops and becomes lodged providing a nutrient source or on damaged stems the pathogen does not infect healthy tissue until after it has colonized dead or aging parts such as on flowers or leaves the lesions initially have a waterlogged appearance and gradually enlarge to cover the stem older lesions will become discolored and when environmental conditions favor the pathogen a dense white mycelium will develop on the surface of the lesions and large black sclerosi will develop on the outer surface of leaf mode and gray mold are often a problem in greenhouses and high tunnels where airflow is limited and humidity is high on the upper sides of leaves the lesions are yellow this is a characteristic population of the mode on the underside of an olive green or brown colored tomato leaf on susceptible varieties under certain conditions severe defoliation can occur it is not always possible to tell what the problem is At each site, be sure to ask your local Extension educator or send a sample to the Penn State Plant Diagnostics Lab to confirm what the problem is if you are unfamiliar with it.