We are blessed in Georgia to have ample rainfall and mostly mild temperatures. These conditions make Georgia a great place to grow a vegetable garden. You can provide fresh produce for your family basically year round. Late summer to early fall is a great time to grow both warm and cool season crops, but it can be quite challenging.
We can often avoid pest populations and diseases by planting crops in a certain window. Some examples are planting squash and other cucurbits early to avoid diseases, or planting southern peas late to avoid cowpea curculio. When we plant in late summer or early fall we have to take into consideration that both insect pests and plant pathogens will be abundant. Insects and diseases are usually what limits our late season production of warm season crops.
Planting varieties that have resistance to diseases is essential this time or year. Powdery mildew and downy mildew can destroy cucurbits fairly rapidly. Only plant varieties with resistance to both of the mildews as well as resistance to several viruses
Like most viruses, the viruses that affect cucurbits are insect vectored. This means they enter the plant as a result of insect feeding. Insects like whiteflies and aphids feed on the underside of the leaf so they are not easy to detect. Both of these pests can also transmit viruses as they feed. Whiteflies in particular love leafy greens, cabbage and kale.
If you are adventurous you still have time to produce things like peas, beans, squash and cucumbers. Most of these crops require around two months to mature. With a first frost date in mid to late November you should have plenty of time to make a few more of these vegetables before the cold. If you are planning on growing cool season crops like cabbage, collards, turnips, kale, spinach, broccoli, or cauliflower now is the time to start the seed indoors. Most people opt for direct seeding of these plants, but planting transplants is a good way to insure uniformity.
There are no great insecticides or fungicides to combat these late season insects and diseases. To achieve acceptable levels of control coverage is critical. Use protectant fungicides to keep leaves free of disease. Once a disease like powdery mildew (squash) or cercospora leaf spot (turnips) get started it is hard to control. Insecticide options are limited for homeowners. There are only two products that are effective against both aphids and whiteflies, unless you decide to use an insecticidal soap.
Growing crops in late summer and early fall can be challenging but it can also be rewarding. I hope this information will help you produce late summer squash and keep turnips free of disease. As always contact your County Agent if you have questions