A MA grower has reported adult flea beetles, which appear to be Redheaded Flea Beetles (cranberry flea beetle) feeding on foliage of mums. Shiny black beetles are about 3/16 -1/4” long with a reddish head (in good light). Antennae are light colored near the head and dark near the tips. Adults feed primarily on young foliage (mostly at night), chewing holes and causing leaf spot damage primarily on the upper surface of the foliage.
Various scenarios can take place when growing mums during these very hot days. Here are a few tips to think about.
If plants are drying out quickly during these very high temperatures, and plants are being watered and fertilized more frequently, growers are advised to reduce fertilizer to 200 ppm (constant feed) and use plain water once a week. This will help to lower risk of high soluble salts. High soluble salts can lead to root injury and Pythium root rot.
Two-spotted spider mites (TSSM) can develop quickly during hot dry weather like we have been having recently. Although we have not seen outbreaks yet this season, it is important to monitor for mites and treat when populations are low if using biological controls. Also, it is important to prevent outbreaks of two-spotted mite infestations prior to fall to minimize infestations next spring.
Expect production areas with black fiber cloth to get hot, again this weekend. Garden mums, flowering cabbage and kale may exhibit signs of wilting during extended periods of 90 plus degree temperatures. Plants wilt when the soil is dry, but wilting will also occur in hot weather which may cause plants to be stressed, or if the roots are damage from a root disease such as Pythium, even if the soil is saturated with water. When the roots stop functioning the plants will show signs of stress by wilting.
Feeding injury caused by Four-lined plant bug is showing up on Shasta daisies, Gentiana and other perennials. Retail customers may confuse the damage with disease. Feeding damage appears as spotting on the upper leaf surface. The adult is greenish yellow with 4 black lines running down the back and about 1/4 in long. The immature stage is bright red or orange with black spots on the segment behind the head. As they mature, a yellow stripe appears on each side of the wing pads. They feed for about 6 weeks and plants often outgrow the damage.