This morning we looked a Spaghetti Squash in the southern part of the county that is showing symptoms of downy mildew. We were able to get back to the office and confirm both downy and powdery mildew. We usually see powdery on the upper side of the leaf and downy on the lower side. With downy, the yellowing will stay within the veins, and powdery will cross over the veins.
Underside of leaf
Microscope – PM (left) DM (right)
Here is some information from UGA Extension Pathologist Dr. Bhabesh Dutta:
These observations indicate that inoculum of downy mildew is currently in GA and under favorable conditions (cool and wet conditions) potential disease outbreak in cucurbit can occur. I would suggest our cucurbit growers to look for the downy mildew symptoms in their fields and start applying protective spray of below stated fungicides.
Watermelon: Rotation (foliar application) with Orondis+Bravo/Manzate;
Please do not use bravo after fruit set.
Other cucurbits: Ranman+Bravo; Previcur flex+Bravo
If Orondis was used as a soil application, please do not use it as foliar (use restriction according to label).
If Orondis was not used as a soil application, foliar application can be done for controlling downy mildew.
Plants are now in for the Thomas County 4-H tomato fundraiser. The money goes to help pay for summer camp fees. You can buy single plants or flats. Info below:
We have a few vegetables planted in the county this fall. Here is Brandon Barnes with some bare ground broccoli that was transplanted back in October. This variety is Emerald Crown which is a mid-season variety in Georgia and North Carolina. The heads are coming on now, and some will probably be ready to pick in a week to ten days. The overall plants and color look good across the field. He has a pivot in this field, and we want to make sure we’re putting on an inch more or less of water each week.
Caterpillars are a common insect pest of cole crops. We have been checking for diamond back moths which is part of the cabbageworm complex. Populations are low in the field right now which is good since management is a challenge with resistance. When scouting, we note the ‘window pane’ effect that is common from diamondback moth feeding.
Some disease is showing up but not causing real problems. Alternaria is usually observed with concentric ring on a leaf. Another pathogen we may check for is black rot, which is a bacteria in the Xanthamonus genera. Below is a photo of black rot in red cabbage. With black rot you generally see yellowing at the leaf margin, and you will see ‘black veins’ running through the yellow/necrotic area through the light. Lesions are usually characteristic of V-shape. Upcoming cool nights will hold back the bacterium. So far, a good fungicide program has proved to be effective.
Black Rot of red cabbage
We sure have quite a bit more vegetable crops planted this season. I’ve been looking a lots of different vegetable set ups. Here is Brandon Barnes who has squash, egg plants and peppers planted this year. He has done a very good job. They picked Yellow Straightneck and Zucchini squash last week.
Downy mildew has not been as much of a concern with the dry weather the past 2 weeks, but with rain and increase humidity we need to be aware of it moving again. Downy mildew was found in Echols County a few weeks ago when it was still raining and had cooler temperatures. New UGA Extension Vegetable Pathologist Dr. Bhabesh Dutta has this information on downy mildew of cucurbit.
“Downy mildew of squash has been detected in Georgia. These observations indicate that inoculum of downy mildew is currently in GA and under favorable conditions (cool and wet conditions) can be a potential problem in cucurbits. I would suggest our cucurbit growers to look for the downy mildew symptoms in their fields and start applying protective spray of stated fungicides.”
Downy Mildew on Cucumber
Here are some collards planted at the Thomas / Colquitt County line. This field was planted a few weeks ago and growers are checking for diamondback moths. We were already seeing some moths in buds. Looking for diamondback moths, we also noticed larger plants were flowering or bolting. Bolting is the term used to describe premature flowering in vegetables making them unable to use. Cold spells or changes in day length cause bolting to occur. We are not exactly sure what set off the run to seed in this field, but unfortunately, the crop cannot be used. Bolting can occur in annual and biennial crops.
Frost damage on cabbage
Pitting from frost damage
After our meeting yesterday, I met with Colquitt Agent Amber Arrington to look at some vegetables hit hard by freezing temperatures. Here is some cabbage just above the Thomas/Colquitt line that was direct seeded last month. Some fields were hit harder than others. This field had a better stand and more plants not killed by frost. To check for damage, we looked at the buds and also cut laterally into the stem. If pitting is present in the stem, the plant is likely too injured to come out of injury. Sometimes the pitting comes from the knife, so it can be hard to tell. This field was direct seeded to save money on transplanting costs which was the biggest issue here. The drawback is the risk with weed control and freezing temperatures. Injury may also depend on the cold acclimation plants get prior to freezing temperatures.
Here is also some Emerald Crown broccoli hit by frost. This field of broccoli was planted later than the others and the only one didn’t get cut. The heads are not salvageable now and will not be able to be cut.
Emerald Crown Broccoli -Frost Damage
Pepper Weevil frass on seeds
Coming back from our area wheat meeting Wednesday, Colquitt County Ag Agent Amber Arrington and I stopped in Pavo to look at some bell peppers where Tim Flanders had found pepper weevils. These beetles get inside the fruit as it is developing and oviposit. Once eggs hatch, the larvae feed on the seeds. This problem is first noticed by observing spots where peppers are aborted. Aborted peppers is not necessarily ID feature of weevils since the plant can abort fruit during dry conditions. Cracking open smaller fruit reveals black frass from larvae (Above).
We found a few larvae and pupae. Here is a photo of a pupae taken by Amber Arrington:
Pepper Weevil Pupae
At this point, all growers can do is use pyrethroids to knock down adult weevils. UGA Extension Vegetable Entomologist Dr. Stormy Sparks says they are typically long lived as adults. They can overwinter here during a mild winter. A hard winter like last year would knock them back.
Pepper weevils are usually imported. They also reproduce on nightshade. If you have a gap between planting bell peppers, weevils do not do well with heat.
Dr. Sparks advises if planting in Spring to start with clean transplants. If you have a history of pepper weevils, make an insecticide application before they reproduce. They reporudce on buds and fruit, but prefer buds. Make application when you see buds. Prior to reproduction, they feed on leaves. Once the eggs are laid, there is nothing you can do until adults come. Systemic products mostly travel through xylem, but fruit is fed through phloem.
Pumpkins are really difficult to grow here because our disease and insect pressure is so strong at normal planting time. Here are some that have been flowering for a few weeks and first we saw flowers dropping. It turns out that these are male flowers with the long stems. It blooms for a day. The female flowers have shorter stems and come out usually a week after. With the heat this weekend, likely caused us to lose some flowers. For now, we need to watch for the female flowers and make sure those are not dropping. They have a 1-2 inch stem with a swollen base were pumpkin is forming.
We also have to be aggressive with disease prevention. Here is some early signs of downy mildew. There are some resistance concerns we need to be aware of with downy mildew in curcubits. Here is an update from Hunt Sanders, Disease Management Specialist in UGA Department of Plant Pathology:
“Based on what we are seeing in our cucumber trials this year, we may be experiencing some fungicide resistance problems in downy mildew of cucumber this fall. Some plots that have been sprayed with a Ranman/ Zampro rotation have a great deal more downy mildew in them than we are used to. We are using an older cucumber variety in these trials with no downy mildew resistance, but we still should not be seeing the level of disease severity in these plots that we are seeing. The trial in question is an industry trial with different fungicide rotations which makes it hard to determine which product (Ranman or Zampro) might be experiencing a problem. We have initiated a follow up fungicide screening trial that will help clear up what we are currently seeing. Results from the screening trial should be available in 3-4 weeks. Until that time all we know is that we are seeing increased levels of downy mildew in plots that were sprayed with a Ranman/Zampro rotation. I have been in contact with Dr. Langston about current downy mildew recommendations and
Downy Mildew – Pumpkin
we both want to stress how important it is to tank-mix products that contain mancozeb or chlorothalonil with the products Ranman or Zampro. In the current environment it is critical that your growers tank-mix these products. If you have a grower that experiences an outbreak of downy mildew that he cannot control with the current fungicide recommendations please contact me and I will investigate the situation.”
Folks were able to get some things done last week before rain Friday. Here are some bell peppers transplanted into plastic with drip irrigation. We’ve already had some nutsedge come up through the plastic. One way to distinguish yellow and purple nutsedge is by the tip of the leaf blade. Yellow nutsedge will taper off at the tip where purple will be more rounded. Also, the yellow nutsedge tubers are more sweet to the taste compared to purple (not that I eat them regularly, but that taste is still in my mouth after Seminole Agent, Rome Ethredge made me eat some one day while he was teaching me the difference). In the situation here, a good control option would be a directed spray application of Sandea (halosulfuron). Check the Sandea label for specific instructions about timing and rate.